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471 Cards in this Set
- Front
- Back
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Cell membrane: what defines the boundary between ICF and ECF?
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Lipid bilayer
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T or F in a cell membrane the lipid bilayer which is selectively permeable.
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True
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in a cell membrane what contains membrane-spanning transport proteins?
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Lipid bilayer
(exposed to both ICF and ECF) -channel proteins -carrier proteins |
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in a cell membrane what maintains chemical gradients?
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lipid bilayer
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what are the 2 types of movement across the cell membrane?
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diffusion
active transport |
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which movement across the cell membrane is a passive process?
a. diffusion b. active transport |
a. diffusion
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which movement across the cell membrane follows a gradient?
a. diffusion b. active transport |
a. diffusion
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which movement across the cell membrane increases entropy of system?
a. diffusion b. active transport |
a. diffusion
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which movement across the cell membrane system approaches equilibrium?
a. diffusion b. active transport |
a. diffusion
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which movement across the cell membrane active process?
a. diffusion b. active transport |
b. active transport
requires E input |
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which movement across the cell membrane requires an E input?
a. diffusion b. active transport |
b. active transport
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which movement across the cell membrane occurs against a gradient?
a. diffusion b. active transport |
b. active transport
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which movement across the cell membrane decreases entropy of system?
a. diffusion b. active transport |
b. active transport
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which movement across the cell membrane does the system move farther from equilibrium?
a. diffusion b. active transport |
b. active transport
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what is the equation for the rate of diffusion?
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diffusion velocity= Δd/Δt
diffusion velocity= distance traveled per unit time |
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T or F diffusion across a membrane is a dynamic process
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true
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diffusion across biological membranes are governed by Fick's Law which means what?
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-substances will diffuse from area of high substrate to an area of low substrate
-at given temp, diffusion rate is proportional to: surface area of membrane, permeability of membrane, and substrate difference (gradient) across membrane |
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diffusion across biological membranes are governed by what law?
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Fick's law
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what type of diffusion is directly through the lipid bilayer?
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simple diffusion
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what are some small lipid-soluble non-poplar molecules found in simple diffusion?
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gases (O2, CO2, N2)
steroids, alcohols,etc. |
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what type of diffusion is sometimes considered to be facilitated diffusion?
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simple diffusion through a transmembrane protein channels
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simple diffusion through a transmembrane protein channels what are some of its small in-soluble molecules?
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ions, amino acids, H20, urea, some antibiotics
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what are some properties of protein channels?
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1. selectivity filters
-size exclusion -position of charged amino acid residues 2. gating -non-gated channels -voltage-gated channels -ligand-gated channels -mechanically-gated channels 3. channel configuration -closed -open -inactivated |
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what property of protein channels: pore size excludes overly large or bulky molecules?
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selectivity filters
-size exclusion eg: Na+ channel = 0.3nm |
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what property of protein channels: e.g. Na+ channel negatively charged. pulls Na+ away from hydrating H20 molecules and through pore. repels negatively charged molecules?
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selectivity filters
- position of charged amino acid residues |
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what property of protein channels: e.g. K+ channel not charged. hydrated K+ ions can pass. excludes larger hydrated Na+ ions
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selectivity filters
- position of charged amino acid residues |
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which gating mechanism in protein channels can be always open?
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non-gated (resting, leak) channels
e.g. K+ leak channel |
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which gating mechanism in protein channels change conformation based on membrane potential?
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voltage-gated channels
e.g. voltage-gated Na+ channels |
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which gating mechanism in protein channels open when ligand binds?
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ligand-gated channels
e.g. ionotropic ACH receptor |
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which gating mechanism in protein channels have some which are voltage-regulated? (not: voltage-gated channels)
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ligand-gated (chemically gated) channels
e.g. NMDA receptor |
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which gating mechanism in protein channels: would you find a K+ leak channel?
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non-gated (resting, leak,) channel
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which gating mechanism in protein channels would you find a ionotropic ACH receptor?
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ligand-gated (or chemically gated) channels
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which gating mechanism in protein channels would you find a NMDA receptor?
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ligand-gated (or chemically gated) channels
(voltage regulated) |
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which gating mechanism in protein channels open in response to membrane stretching/deformation?
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mechanically-gated (or stretch-activated) channels
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in a the protein channels what are the 3 types of configurations?
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closed
open inactivated |
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which protein channel configuration is the default state for many ion channels?
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closed
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which protein channel configuration is poised to open in response to stimulus?
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closed
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which protein channel configuration ions may diffuse freely through channel?
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open (activated)
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which protein channel configuration channels is closed and incapable or opening?
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inactivated
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which protein channel configuration only some channels have this configuration?
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inactivated
e.g. voltage-gated Na+ channel |
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which protein channel configuration are voltage-gated Na+ channel
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inactivated
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which type of diffusion is assisted by transmembrane carrier proteins
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facilitated diffusion
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T or F in facilitated diffusion the diffusing molecules binds to carrier proteins
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True
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in facilitated diffusion how does the diffusion kinetics differ from simple diffusion?
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diffusion rate limited at high solute concentrations (V max)
property of carrier protein kinetics |
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what are the steps of facilitated diffusion when it is assisted by transmembrane carrier proteins?
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1. diffusing molecule binds carrier protein
2. binding induces conformation change in carrier protein --> molecule is internalized 3. molecule diffuses into cytosol |
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what are some factors which affect net diffusion rate across membrane?
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magnitude of chemical gradient
magnitude of electrical gradient magnitude of pressure gradient |
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which factor which affects net diffusion rate across membrane: net diffusion of solute into cell a
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magnitude of chemical gradient
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which factor which affects net diffusion rate across membrane: voltage potential determined using Nernst equation.
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magnitude of electrical gradient
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which factor which affects net diffusion rate across membrane: molecules will move from high pressure to low pressure
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magnitude of pressure gradient
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movement of H20 (or other solvent) across a semi-permeable membrane is called
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osmosis
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what is free E available to move water molecules?
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Water potential (Ψ)
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Ψ stands for what in reference to osmosis?
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water potential
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what is the Greek symbol which stands for water potential?
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Ψ
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what interaction of 2 factors determine water potential?
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Ψ= Ψπ + Ψp
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what is the greek symbol which stands for osmotic potential?
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Ψπ
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Ψπ stands for what in reference to osmosis?
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osmotic potential
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T or F osmotic potential decreases with increasing [solute]
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True
tends from 0 to (-) |
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what is the greek symbol which stands for pressure potential?
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Ψp
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Ψp stands for what in reference to osmosis?
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pressure potential
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T or F pressure potential results from 0 to (-)
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False
pressure potential results from (+) to (-) and osmotic potential tends from 0 to (-) |
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assuming there is no pressure net diffusion of H20 occurs from what area of ______ water potential-->____ water potential.
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high water potential ---> low water potential
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assuming there is no pressure net diffusion of H20 occurs from what area _____ [solute]--> ____ [solute]
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low [solute]-->high [solute]
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net diffusion of H20 occurs from what area _____ osmotic potential ---> _____ osmotic potential
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high osmotic potential ---> low osmotic potential
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what pressure is required to completely oppose osmosis (no net diffusion of H20)
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osmotic pressure of solution
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T or F osmotic pressure is dependent on mass (not number) of particles per unit volume of solution.
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False
osmotic pressure is dependent on NUMBER (not MASS) of particles per unit volume of solution. |
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T or F the average kinetic energies are the same for large and small particles.
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True
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1 osmole= what?
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weight (in grams) per 1 mole of osmotically active solute
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when osmolality = measure of number of particles in a solution what equals its weight (in grams) per 1 mole of osmotically active solute?
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1 osmole
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when osmolality = measure of number of particles in a solution for chemical compounds # of osmoles per unit weight= what?
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# of dissociated particles per 1 mole compound
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when osmolality = measure of number of particles in a solution, the MW of glucose = 180 g/mol; therefore 180g glucose which = how many osmoles?
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1
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the MW of NaCl = 58.5 g/mol; therefore 58.5g NaCl = how many osmoles?
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2
therefore 1 osmole of NaCl = 29.25 |
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when osmolality = # osmoles per kg water the normal osmolality of ECF/ICF = how many milliosmoles per kg of water?
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300
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T or F the total osmotic pressure of body is calculated from osmolaity
|
True
1mOsm/L= 19.3 mmHg |
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when osmolality = # osmoles per kg water measured osmotic pressure = ____ times a theoretical value?
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0.93
this is b/c not all disassociated particles act as osmotically active solutes |
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when osmolarity = # osmoles per liter water, it can be used for what?
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to dilute solutes
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T or F osmolarity is slighly less accurate that osmolality
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True
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which is more practical for most clinical and physiological applications
a. osmolarity b. osmolality |
a. osmolarity
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what are the 2 types of active transport across the biological membrane?
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Primary active transport
secondary active transport |
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which type of active transport has energy provided directly by ATP hydrolysis?
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Primary active transport
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which type of active transport has energy provided indirectly via chemical gradients?
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secondary active transport
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what types of pumps might you find in primary active transport?
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Na+-K+ pump
Ca2+ pump H+ pump bioenergetic of primary active transport |
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what types of co-transporters might you find in secondary active transport?
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symporter
antiporter |
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active transport of one molecule is coupled to transport of another is called?
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co-transporters
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which primary active transport pump is the most highly studied active transporter?
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Na+-K+ pump
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Na+-K+ pump pumps how many Na+---> outside cell and how many K+---> inside the cell
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3Na+
2K+ |
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Na+-K+ pump pumps 3 Na+ ---> where in the cell and 2 K+----> where in the cell
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Na+-----> outside the cell
K+ ------> inside the cell |
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the sodium potassium pump uses 1 ATP to produce what?
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1 ADP+ 1Pi
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in Na+ K+ pump which multimeric carrier protein carries out ion transport and ATP hydrolysis?
a. large alpha subunit b. large beta subunit c. small alpha subunit d. small beta subunit |
a. large alpha subunit
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in Na+ K+ pump which multimeric carrier protein inside portion has 3 Na+ receptor sites?
a. large alpha subunit b. large beta subunit c. small alpha subunit d. small beta subunit |
a. large alpha subunit
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in Na+ K+ pump which multimeric carrier protein outside portion has 2 K+ receptor sites?
a. large alpha subunit b. large beta subunit c. small alpha subunit d. small beta subunit |
a. large alpha subunit
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in Na+ K+ pump which multimeric carrier protein inside portion has ATPase activity?
a. large alpha subunit b. large beta subunit c. small alpha subunit d. small beta subunit |
a. large alpha subunit
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in Na+ K+ pump which multimeric carrier protein function is unknown?
a. large alpha subunit b. large beta subunit c. small alpha subunit d. small beta subunit |
d. small beta subunit
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in Na+ K+ pump which multimeric carrier protein may anchor protein complex to cell membrane?
a. large alpha subunit b. large beta subunit c. small alpha subunit d. small beta subunit |
d. small beta subunit
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T or F the Na+ K+ pump may run in reverse under certain circumstances?
|
True
ADP+Pi--->ATP dependent on [ATP],[ADP]; Na+, K+ gradients |
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in the Na+ K+ pump what establishes and maintains gradients?
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the Na+ K+ pump does
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T or F the Na+ K+ pump is ionogenic.
|
False
the Na+ K+ pump is electrogenic (capable of producing electricity in living tissues) |
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what 3 things are important about the Na+ K+ pump being electrogenic?
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1. establishes electrical potential across membrane
2. critical for functioning of electrically excitable cells 3. neurons use up to 70% total energy to power Na+ K+ pumps |
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how do Na+ K+ pumps control cell volume?
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yields net efflux of ions, balancing osmosis into cell because the natural tendency for osmosis is to drive water into cell
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what are the 2 types of Ca2+ pumps with high specificity for Ca2+ binding?
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cell membrane pump
-drives Ca2+ into ECF -results in very low cytosolic [Ca2+] intracellular pump -located on membranes of organelles (mitochondria, sarcoplasmic reticulum) - concentrates internal stores of Ca2+ |
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what Ca2+ pump drives Ca2+ into ECF?
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cell membrane pump
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what Ca2+ pump results in very low cytosolic [Ca2+]
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cell membrane pump
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what Ca2+ pump is located on membranes of organelles?
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intracellular pump
e.g. mitochondria and sarcoplasmic reticulum |
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what Ca2+ pump concentrates internal stores of Ca2+?
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intracellular pump
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what 2 places that we learned have H+ Pumps?
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1. the gastric glands of stomach
-located on parietal cells 2. renal tubules and cortical collecting ducts of the kidney -located in intercalated cells |
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T or F the H+ pump is located on parietal cells in the kidney?
|
False
H+ pump is located on parietal cells in the GASTRIC GLANDS OF STOMACH H+ pump is located in INTERCALATED CELLS IN THE KIDNEY (renal tubules and cortical collecting ducts) |
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T or F the H+ pump is located in intercalated cells of the kidney
|
True
(renal tubules and cortical collecting ducts) |
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where are the H+ pumps which have a H+ concentrated 1 million-fold at apical surface?
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in the gastric glands of the stomach
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where are the H+ pumps which have H+ ions co-secreted with Cl- to produce HCL?
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in the gastric glands of the stomach
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T or F in the gastric glands of the stomach the H+ pump secrete H+ ions while Cl- is being secreted to produce HCL
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True
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HCl maintains what which optimizes enzyme activity?
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low pH
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where is the H+ pump located which secretes H+ into urine from blood?
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the renal tubules and cortical collecting ducts of kidney
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T or F the renal tubules and cortical collecting ducts of the kidneys secretes H+ which produces blood into the urine.
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False
it secretes H+ into the urine from blood |
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where is the H+ pump located which has up to 900-fold concentration gradient?
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the renal tubules and cortical collecting ducts of the kidney
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what are some co-transporters of secondary active transport?
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symporter
antiporter (counter-transport) |
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what type of transport is driven by potential energy of chemical gradients, not direct ATP hydrolysis?
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secondary active transport
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active transport of one molecule is coupled to transport of another molecules is called?
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co-transporter
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T or F in both symport and antiport binding induces conformational change
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True
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what do symports and antiports have in common?
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binding induces conformational change
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which co-transporter has 2 substances bind on the extracellular surface of the carrier protein?
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symporter
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which co-transporter is where both substance are transported in the same direction (both inside the cell)?
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symporter
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which co-transporter has 2 substances which bind to opposite surfaces of the carrier protein?
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antiporter
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which co-transporter is where substance are transported in opposite directions (one outside, one inside the cell)
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antiporter
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what are some examples of some symporters?
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glucose transporter
amino acid transporter other transporter which are not as important to this class are (chloride, iodine, iron, urate) |
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what are some examples of antiporters?
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Ca2+ transporter
H+ transporter |
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which symport is coupled with Na+ transport?
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both glucose and amino acid transport
the other transports might be as well (chloride, iodine, iron, urate) |
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which symport has high extracellular [Na+] which provides energy for transport?
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glucose transport
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which symporter has Na+ and glucose both transported into the cell?
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glucose transporter
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T or F the symporter amino acid transporter is a similar mechanism as glucose transporter.
|
True
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which symporter has different transporters which are specific to particular amino acids?
|
amino acid transporters
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other than glucose and amino acid transporters what other types of symporters are there?
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chloride
iron urate iodine |
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which type of antiporter is Na+ transported into the cell and its ion is transported outside the cell?
|
Ca2+ transporter
Na+ transported into the cell and Ca2+ is transported outside the cell |
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which type of antiporter is coupled by Na+ transport?
|
both
Ca2+ transporter H+ transporter |
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which type of antiporter is Na+ transported into the cell from the lumen and its ion is transported into the lumen of a tubule?
|
H+ transporter
Na+ transported into the cell from the lumen and H+ is transported into the lumen of a tubule |
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active transport and diffusion combined to transport substance across sheet or membrane is what type of active transport?
|
active transport through cellular sheets
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where does active transport through cellular sheets or membrane take place?
|
intestinal epithelium
renal tubule epithelium exocrine gland epithelium gallbladder epithelium choroid plexus and other membranes |
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what are some examples of Na+ transport in epithelium?
|
Na+ diffuses across luminal surface to cell interior
Na+ actively transported across basal and lateral surfaces outside of the cell leads to concurrent osmosis of water outside of the cell |
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when Na+ diffuses across luminal surface to cell interior is an example of what type of Na+ transport?
|
Na+ transport in epithelium
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when Na+ actively is transported across basal and lateral surfaces outside of the cell is an example of what type of Na+ transport?
|
Na+ transport in epithelium
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what leads to concurrent osmosis of water to the outside of the cell?
|
Na+ transport in epithelium
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T or F all cell have electrical potential across cell membrane
|
true
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T or F the body as a whole is chemically negative?
|
false
chemically neutral |
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what are some cell type which are electrically excitable?
|
neurons and muscles
|
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T or F neurons and muscles are electrically excitable
|
true
|
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what are some cells which passively utilize changes in membrane potential?
|
glandular cells
macrophages ciliated cells |
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T or F glandular cells, macrophages and ciliated cells passively utilize changes in membrane potential
|
True
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when cells are said to have unequal ion distributions what does that mean?
|
cell membranes have (-) charge on inside and a (+) charge on outside
e.g. they are polarized |
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T or F if the cell membranes have (-) charge on inside and (+) charge on the outside they are said to be polarized
|
True
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when you have unequal ion distribution, passive diffusion of ions through leak channels is also known as?
|
Donnan Equilibrium
|
|
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in the Donnan equilibrium membrane is _____ permeable to K+
a. more b. less c. both d. neither |
a. more
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in the Donnan equilibrium membrane is _____ permeable to Na+
a. more b. less c. both d. neither |
b. less
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when you have unequal ion distribution what accounts for 95% of resting membrane potential?
|
Donnan equilibrium
|
|
|
what are some properties of the Donnan equilibrium?
|
-membrane more permeable to K+
-membrane less permeable to Na+ -large anions cannot diffuse -accounts for 95% of resting membrane potential |
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T or F in the Donnan equilibrium large Cations cannot diffuse
|
False
large ANions cannot diffuse |
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when you have unequal ion distribution what accounts for 5% of resting membrane potential?
|
active pumping
|
|
|
T or F active pumping adds (+) charge to outside of the cell
|
True
|
|
|
when you have unequal ion distribution what are some properties of active pumping?
|
electrogenic Na+/K+ pump
adds (+) charge to outside accounts for 5% of resting membrane potential |
|
|
what is the equation for ohm's law?
|
V= IR
|
|
|
V= IR is the equation for what law?
|
Ohm's law
|
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difference in electrical potential (charge) between two points is called?
|
Voltage (volts)
|
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the difference in potential (voltage) across membrane (ECF/ICF) is called?
|
voltage for cells
measured in mV |
|
|
the difference in potential (voltage) across membrane (ECF/ICF) is measured in what?
|
mV
Voltage for cells |
|
|
what is considered the flow of charge?
|
current (amps)
|
|
|
what is considered the flow of ions across membrane?
|
current (amps) for cells
ion channels |
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|
T or F current for cells is normally low
|
true
|
|
|
resistance to current flow is called?
|
resistance (ohms)
|
|
|
resistance across the membrane is represented by what?
|
Rm
|
|
|
resistance along length of axon is represented by?
|
Ra
|
|
|
what is the reciprocal value of resistance (ohms)
|
the reciprocal value is conductance
|
|
|
T or F normally Ra is high which make it a good insulator.
|
False
normally "Rm" is high which makes it a good insulator. |
|
|
the storage or separation of charge is called?
|
capacitance
|
|
|
Cm= what?
|
membrane capacitance
|
|
|
T or F capacitive properties of phospholipid bilayer allows storage of charge.
|
True
|
|
|
what are some ways to do intracellular recording?
|
1. cell is penetrated with recording microelectrode (tip inserted in ICF)
2. whole cell patch clamping (alternative method) 3. reference electrode placed in ECF 4. signal amplifier and transducer allows recording 5. stimulator allows manipulation of voltage or current |
|
|
which type of intracellular recording contains silver chloride, electrolyte solution (similar to ICF)
|
when the cell is penetrated with recoding miroelectrodes (tip inserted in ICF)
|
|
|
which type of intracellular recording uses patch pipette in order to contact the cell and disrupt cell membrane?
|
whole cell patch clamping (alternative method)
|
|
|
which type of intracellular recording allows continuity of pipette solution and ICF?
|
whole cell patch clamping (alternative method)
|
|
|
which type of intracellular recording usually uses silver-silver chloride filament?
|
when the reference electrode is placed in ECF
|
|
|
what are the recording configurations of the current clamp?
|
electrophysiologist may inject current into cell
voltage is recorded used to record graded membrane potentials or action potentials |
|
|
what recording configuration is used to record graded membrane potentials or action potentials?
|
current clamp
|
|
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what recording configuration is used to record voltage?
|
current clamp
|
|
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what recording configuration may electrophysiologist inject current into cell?
|
current clamp
|
|
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what recording configuration is continuous application of current maintains, or "clamps" cell at desired holding potential?
|
voltage clamp
|
|
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what recording configuration can the membrane can be instantaneously stepped to new desired command potential?
|
voltage clamp
|
|
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what recording configuration does a electrophysiologist manipulates cell voltage so that continuous application of current maintains, or "clamps" cell at desired holding potential and then the membrane can be instantaneously stepped to new desired command potential?
|
voltage clamp
|
|
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what recording configuration records (+) or (-) current?
|
voltage clamp
current clamp measures voltage |
|
|
what recording configuration is used to record current flow from membrane ion channels?
|
voltage clamp
|
|
|
what is another name of equilibrium potential?
|
Nernst potential
|
|
|
T or F the equilibrium potential can be calculated for a specific ion but the Nerst potential cannot.
|
False
the equilibrium potential (AKA: Nerst potential) can be calculated for a specific ion |
|
|
what equals the membrane potential that exactly opposes net diffusion of that ion across the cell membrane?
|
energy ion (Eion)
also referred to as electomotive force (EMF) |
|
|
what equation do you use to calculate the Eion?
|
Nernst equation which is in mV
|
|
|
what is Nernst equation?
|
Eion=RT/ZF In([ion]0/[ion]i)
|
|
|
what is nernst equation?
|
Eion=(RT/ZF)ln([ion]outside[ion]inside)
|
|
|
in nernst equation what does:
R= T= Z= F= |
R=gas constant (R = 8.314 472(15) J K−1 mol−1)
T= absolute temperature in kelvins (310k at body temp) Z= ion valence F= Faraday constant (F = 9.648 533 99(24)×10^4 C mol−1) |
|
|
under normal conditions for a positive univalent ions what is Nernst equation
|
Eion=+61 log([ion]o/[ion]i)
the charge inside relevant to the charge outside |
|
|
under normal conditions for a negative univalent ions what is Nernst equation?
|
Eion=-61 log([ion]o/[ion]i)
the charge inside relevant to the charge outside |
|
|
if you do the Nernst equation and end up with a membrane potential of -70mV what does this mean about the inside of the cell to the outside of the cell?
|
it means the inside of the cell is 70mV more negative that the outside of the cell
|
|
|
when the physiological basis of the membrane potential at rest what can't you calculate using Nernst equation because ?
|
it only accounts for single type of ion
assumes ion is freely permeable |
|
|
when the physiological basis of the membrane potential at rest what equation only accounts for single type of ion?
|
Nernst equation
|
|
|
when the physiological basis of the membrane potential at rest what equation assumes ion is freely moving?
|
Nernst equation
|
|
|
when the physiological basis of the membrane potential at rest what equation accounts for multiple ions?
|
Goldman (or Goldman-Hodgkin-Katz) equation
used for real cell |
|
|
when the physiological basis of the membrane potential at rest what equation is used for real cells?
|
Goldman (or Goldman-Hodgkin-Katz) equation
|
|
|
when the physiological basis of the membrane potential at rest what equation accounts for ion permeability?
|
Goldman (or Goldman-Hodgkin-Katz) equation
|
|
|
when the physiological basis of the membrane potential at rest what equation has its value in mV?
|
Nernst and Goldman (or Goldman-Hodgkin-Katz) equation
|
|
|
what is the permeability constant for mammals:
PK+= PCl-= PNa+= |
PK+= 5.0 x 10^-7 cm/sec
PCl-= 1.0 x 10^-8 cm/sec PNa+=5.0 x 10^-9 cm/sec |
|
|
by convention, to account for differences in charge:
[cation]out --> [cation]in ---> [anion]out --> [anion]in ---> a. numerator b. denominator c. both d. neither |
[cation]out --> numerator (a)
[cation]in ---> denominator (b) [anion]out --> denominator (b) [anion]in ---> numerator (a) |
|
|
what is the reduced equation of Goldman (or Goldman-Hodgkin-Katz) equation?
|
Vm or Em=61 log((∑P+(∑[cation]out)(∑[anion]in))/(∑P+(∑[cation]in)(∑[anion]out))
|
|
|
with the given solve for Vm
Pk+= 5.0 x 10^-7 cm/sec Pcl-=1.0 x 10^-8 cm/sec PNa+=5.0 x 10^9 cm/sec [Na+]i=14mmol/L;[Na+]o=142 mmol/L [K+]i= 140mmol/L;[K+]o=4mmol/L [Cl-]i= 4mmol/L; [Cl-]o= 108mmol/L |
Vm=61log ((5.0x10^-7)(4) + (5.0x10^-9)(142) + (1.0x10^-8)(4))/((5.0x10^-7)(140) + (5.0x10^-9)(14) + (1.0x10^-8)(108)
Vm=61 log((2.75x10^-6)/(7.12x10^-5)) Vm= -86mV since Vm=-86mV which is close to Ek+=-94mV which means K+ current is the primary contributor to the resting membrane potential |
|
|
what 2 factors determine true cell Vm?
passive diffusion of ions across membrane ---> Vm= -86mV |
1. passive diffusion of ions across membrane ---> Vm= -86mV (calculated using goldman equation)
2. electrogenic Na+/K+ pump---> which generates additional -4mV so the actual Vm=-90mV |
|
|
what are some changes in membrane potential?
|
1. resting membrane potential: polarized state (-90mV)
2. may become depolarized (less negative) 3. may become hyperpolarized (more negative) |
|
|
T or F Vm can change in response to stimuli
|
True
|
|
|
what types of stimuli might produce a change in Vm?
|
1. electrical
2. chemical 3. mechanical |
|
|
what may produce 2 types of Vm changes?
|
1. passive responses (graded potentials)
2. active responses (action potentials) |
|
|
T or F passive and active responses may produce two types of Vm changes
|
True
passive (graded potentials) active (action potentials) |
|
|
magnitude of potential change directly proportional to amount of current is called?
|
graded potentials
|
|
|
T or F multiple graded potentials may summate.
|
True
|
|
|
graded potentials, magnitude of potential change directly proportional to amount of current may lead to _______and _______.
|
depolarization and hyperpolarization
|
|
|
in passive (graded) electrical responses to electrotonic conduction: potential changes confined to small region of plama membrane is called what?
|
local
|
|
|
in passive (graded) electrical responses to electrotonic conduction: magnitude inversely proportional to distance from stimulus is called?
|
decremental (not propagated)
-charges die out locally -charge is lost across the membrane bc of "leaky" channels |
|
|
T or F in passive (graded) electrical responses to electrotonic conduction the decremental changes die out locally
|
True
|
|
|
what are some characteristics of signaling which all graded potentials have?
|
1. only type of electrical communication by some neurons
2. play an important role in the initiation and integration of long distance signals by neurons and other cells |
|
|
what type of graded potentials signal by stimulation of sensory receptors?
|
receptors (generator) potentials
Ex: photoreceptors, mechanoreceptors, chemoreceptors, thermoreceptors, nociceptors |
|
|
what are some types of receptor (generator) potentials?
|
photoreceptors
mechanoreceptors chemoreceptors thermoreceptors nociceptors |
|
|
what type of graded potentials signal for the heart?
|
pacemaker potential
-special cell in the cardiac pace maker have "leaky" channels - leads to autonomously generated graded potentials - responsible for cardiac autorhythmicity |
|
|
what type of graded potentials are responsible for cardiac autorythmicity?
|
pacemaker potentials
|
|
|
what type of graded potentials leads to autonomously generated graded potentials?
|
pacemaker potentials
|
|
|
what type of graded potentials are special cells in the cardiac pacemaker have "leaky" channels
|
pacemaker potentials
|
|
|
what type of graded potentials are involved in synaptic transmission of nerve impulses?
|
postsynaptic membrane potentials
|
|
|
what type of graded potentials are synaptic transmission at neuromuscular junction?
|
EPP- end plate potential
|
|
|
what are some characteristics of Active electrical responses to action potential?
|
1. transient self-sustained change in membrane potential
2. action potential may result from threshold level of depolarization called threshold potential 3. magnitude of AP is much greater than magnitude of stimulus 4. once stimulated, all-or-none event 5. action potentials may not summate 6. regenerative |
|
|
T or F active electrical responses to action potentials are propagated over long distances without decrement.
|
True
|
|
|
T or F passive (graded) electrical responses to electrotonic conduction are propagated over long distances without decrement.
|
False
not propagated or decremental |
|
|
Active electrical responses to action potential: what results from rapid changes in ion conductance?
|
transient self-sustained change in membrane potential
|
|
|
Active electrical responses to action potential: what can last 1-5 ms (dependent on ion channel kinetics)?
|
transient self-sustained change in membrane potential
|
|
|
Active electrical responses to action potential: what occurs only on electrically excitable regions of cell membrane?
|
transient self-sustained change in membrane potential
|
|
|
Active electrical responses to action potential: action potential may result from threshold level of depolarization is called?
|
threshold potential
|
|
|
T or F Active electrical responses to action potential: the action potential may not summate
|
True
|
|
|
what are some importance of action potentials?
|
nerve signal transmission
muscle contraction |
|
|
what are action potentials important to nerve signal transmission for?
|
thought process
sensation motor pathways |
|
|
how do action potentials work for nerve signal transmission?
|
the electrical portion of nerve signal transmittal is carried in an action potential
|
|
|
how do action potentials work for muscle contraction?
|
the contraction of all muscles is initiated by a muscle action potential
|
|
|
T or F the contraction of all muscles is initiated by a muscle action potential
|
True
|
|
|
who were the 2 people in which were awarded the Nobel prize in 1963 for physiology or medicine for what they had discovered in 1949, that sodium is required for action potential not for resting Vm?
|
Hodgkin and Katz
discovered sodium dependence in 1949 awarded Nobel prize in 1963 for physiology or medicine |
|
|
what was the hypothesis of Hodgkin and Katz?
|
action potential due to Na+ influx through transiently permeable membrane
|
|
|
at rest K+ permeable, Vm is close to Ek+ (-91mV) but during action potential Na+ permeable, Vm does what?
|
moves towards ENa+(+65mV)
rest= K+ dependent action potential= Na+ dependent |
|
|
T or F from rest to action potential you need a mechanism for changing ions permeabilities called ion channels
|
True
|
|
|
what are the 3 stages of action potentials?
|
resting stage (polarized stage)
depolarization stage repolarization stage |
|
|
what primary stage of the action potential varies with cell and tissue type?
|
resting stage
-typical nerve cell--> -90mV -cardiac pacemaker cells--> -60mV -skeletal muscle--> -83mV |
|
|
what primary stage of the action potential does Na+ flow into the cell
|
depolarization stage
|
|
|
what primary stage of the action potential occurs when Vm exceeds threshold for voltage gated Na+ channels?
|
depolarization stage
|
|
|
what primary stage of the action potential K+ ions flow out of the cell?
|
repolarization stage
|
|
|
occurs when voltage gated K+ channels are open?
|
repolarization stage
|
|
|
what primary stage of the action potential when Vm moves back towards the resting membrane potential?
|
repolarization stage
|
|
|
T or F voltage-gated channels are protein channels with ion selectivity filter.
|
True
|
|
|
T or F voltage-gated channels have voltage changes which alter the secondary structure of the protein channel conformation: closed --> open
|
F
voltage-gated channels have voltage changes which alter the TERTIARY structure of the protein channel conformation: closed --> open |
|
|
how much longer does it take for voltage-gated channels to closed as compared to open?
|
10 times longer to close than open
|
|
|
T or F voltage-gated channels must be reset before they can open again
|
True
|
|
|
T or F voltage-gated channels: different channels have the same activation kinetics
|
False
voltage-gated channels: different channels have the DIFFERENT activation kinetics |
|
|
what are the 2 gates associated with voltage-gated Na+ channels?
|
fast gate (Activation gate)-on extracellular region
slow gate (inactivation gate)- on intracellular region |
|
|
what type of voltage-gated Na+ channels are closed at resting Vm?
|
activation gate (fast gate)
|
|
|
what type of voltage-gated Na+ channels rapidly open triggered at threshold (-70 to -50 mV)?
|
activation gate (fast gate)
|
|
|
what type of voltage-gated Na+ channels allows rapid Na+ influx (following electrochemical gradient for Na+), resulting in membrane depolarization?
|
activation gate (fast gate)
|
|
|
what type of voltage-gated Na+ channels results in membrane depolarization?
|
activation gate (fast gate)
|
|
|
what type of voltage-gated Na+ channels each channel allows 5-6 Na+ to move into the cell following sodium's electrochemical potential?
|
activation gate (fast gate)
|
|
|
what type of voltage-gated Na+ channels slow closing triggered at threshold (-70 to -50 mV)?
|
inactivation gate (slow gate)
|
|
|
what type of voltage-gated Na+ channels closes at peak of activation potential (+35 mV)?
|
inactivation gate (slow gate)
|
|
|
what type of voltage-gated Na+ channels Na+ can no longer enter the cell while inactivated?
|
inactivation gate (slow gate)
|
|
|
what type of voltage-gated Na+ channels cannot reopen until membrane repolarizes near resting Vm?
|
inactivation gate (slow gate)
|
|
|
what voltage-gated channel are closed at resting Vm?
|
voltage-gated K+ channels
|
|
|
what voltage-gated channel have a single activation gate?
|
voltage-gated K+ channels
|
|
|
what voltage-gated channel have slow activation kinetics?
|
voltage-gated Na+ inactivation gate
voltage-gated K+ channels voltage-gated Ca2+ |
|
|
what voltage-gated channel are located on intracellular region?
|
voltage-gated Na+ inactivation gate
voltage-gated K+ channels |
|
|
what voltage-gated channel results in membrane repolarization?
|
Voltage-gated K+ channels
|
|
|
T or F Voltage-gated Ca2+ channels are somewhat permeable to Na+ as well as Ca2+
|
True
|
|
|
T or F Voltage-gated Ca2+ channels are called "slow channels" due to slow kinetics.
|
True
|
|
|
where might you find Voltage-gated Ca2+?
|
they are prevalent in cardiac and smooth muscle
|
|
|
what voltage-gated channel are prevalent in cardiac and smooth muscle?
|
Voltage-gated Ca2+
|
|
|
point at which voltage gated channels are triggered to open is called?
|
threshold
|
|
|
what happens in the rising phase of Action potentials?
|
1. membrane depolarization as Na+ ions enter cell
2. sustained by Hodgkin cycle (positive feedback cycle) -depolarization opens more Na+ channels -more Na+ influx leads to greater depolarization -more depolarization opens further Na+ channels -cycle continues until all voltage-gate Na+ channels are activated 3. Vm approaches ENa+ |
|
|
what happens in the Hodgkin cycle?
|
(positive feedback cycle)
-depolarization opens more Na+ channels -more Na+ influx leads to greater depolarization -more depolarization opens further Na+ channels -cycle continues until all voltage-gate Na+ channels are |
|
|
point at which the Vm becomes positive?
|
overshoot
due to delayed Na+ channel inactivation, K+ channel activation is called |
|
|
point at which the cell reaches maximal positive Vm is called
|
peak
|
|
|
what 3 mechanisms determine timing and magnitude of action potential peak?
|
1. Na+ influx diminished as Vm approached ENa+
2. Na+ channels inactivate 3. K+ channels activate |
|
|
membrane repolarizaion as K+ ions leave cell through voltage-gated K+ channels is called?
|
falling phase
|
|
|
what is after hyperpolarization?
|
undershoot
|
|
|
what happens when some K+ channels remain open after Na+ channels close which leads to some excess K+ efflux?
|
undershoot
|
|
|
-Vm returns to resting level as both channel types reset is called?
|
recovery
|
|
|
what modulation of action potential waveforms is protein modification?
|
ion channel modulation
|
|
|
what modulation of action potential waveforms can change activation kinetics?
|
protein modifications
|
|
|
what modulation of action potential waveforms influence Na+ channel gating?
|
extracellular calcium levels
-deficit in [Ca2+]E --> lowers threshold for Na+ channels activation -may result in muscle tetany |
|
|
what modulation of action potentials can change cellular signaling?
|
action potential firing frequency
synaptic transmission |
|
|
membrane must recover for a period of time before another action potential can be generated at the same location what is this called?
|
refractory period
|
|
|
impossible for another action potential to be generated during this time is called?
|
absolute refractory period
|
|
|
T or F during absolute refractory period Na+ channels are inactive
|
True
|
|
|
New action potential generation is possible, but more difficult is called?
|
relative refractory period
|
|
|
what refractory period requires greater depolarizing stimulus?
|
relative refractory period
(must exceed normal threshold depol) Leaky K+ current will counteract depolarizing stimulus |
|
|
in what refractory period has "Leaky" K+ current will counteract depolarizing stimulus?
|
relative refractory period
|
|
|
what depolarizing stimulus has action potential's which persist throughout duration of stimulus?
|
"Tonic" firing pattern (non-accommodation)
|
|
|
what depolarizing stimulus initial burst of 1 or more action potential's at beginning of stimulus, then no response?
|
"Phasic" firing pattern (accommodation)
|
|
|
what depolarizing stimulus has different regulatory mechanisms?
|
"Phasic" firing pattern (accommodation)
e.g. calcium-activated K+ current |
|
|
what are 2 main types of accommodation?
|
slow depolarizing stimulus
-does not result in AP generation in some cell prolonged depolarizing stimulus -Tonic -phasic |
|
|
what type of accommodation does not result in action potential generation in some cells?
|
slow depolarizing stimulus
|
|
|
graded potential or action potential:
amplitude varies with strength of initiating stimulus? |
graded potential
|
|
|
graded potential or action potential:
can be summated |
graded potential
|
|
|
graded potential or action potential:
has no threshold? |
graded potential
|
|
|
graded potential or action potential:
no refractory period? |
graded potential
|
|
|
graded potential or action potential: non-regenerative
|
graded potential
is conducted decrementally (amplitude decreases with distance) |
|
|
graded potential or action potential:
duration varies with the initiating conditions |
graded potential
|
|
|
graded potential or action potential:
can be depolarizing or (hyper)polarizing |
graded potential
|
|
|
graded potential or action potential:
variable mechanisms? |
graded potential
(e.g. ligand-gated, mechanically-gated ion channels) |
|
|
graded potential or action potential:
all or none response |
action potential
|
|
|
graded potential or action potential:
once threshold is reached the amplitude is independent of initiating stimulus? |
action potential
all or none response |
|
|
graded potential or action potential:
cannot be summated? |
action potential
|
|
|
graded potential or action potential:
threshold must be reached prior to action potential generation? |
action potential
|
|
|
graded potential or action potential:
has a refractory period |
action potential
|
|
|
graded potential or action potential:
regenerative |
action potential
is conducted without decrement (amplitude is constant) |
|
|
graded potential or action potential:
duration is constant for a given cell type |
action potential
|
|
|
graded potential or action potential:
it is a depolarization (with overshoot in neurons) |
action potential
|
|
|
graded potential or action potential:
dependent on voltage-gated channels |
action potential
|
|
|
T or F a subthreshold stimulus produces a graded membrane potential
|
true
|
|
|
T or F graded potentials are a local response and have many functions
|
true
|
|
|
T or F threshold stimuli result in an action potential on excitable membranes
|
True
|
|
|
T or F an action potential is a change in the membrane polarity from depolarized----> polarized ---> repolarized
|
False
polarized ---> depolarized ---> repolarized |
|
|
T or F shape and firing frequency of action potentials are regulated uniquely in different cell types
|
true
|
|
|
energy stored as electrochemical gradient
a. batteries b. current generators c. resistors/conductors d. capacitors |
a. batteries
|
|
|
generate electrical potential
a. batteries b. current generators c. resistors/conductors d. capacitors |
a. batteries
|
|
|
Na+/K+ ATPase pump
a. batteries b. current generators c. resistors/conductors d. capacitors |
current generators
|
|
|
maintains electrochemical gradient
a. batteries b. current generators c. resistors/conductors d. capacitors |
b. current generators
|
|
|
lipid bilayer
a. batteries b. current generators c. resistors/conductors d. capacitors |
c. resistors/conductors
|
|
|
ion channels
a. batteries b. current generators c. resistors/conductors d. capacitors |
c. resistors/conductors
|
|
|
mediates current flow
a. batteries b. current generators c. resistors/conductors d. capacitors |
c. resistors/conductors
|
|
|
2 conducting materials separated by insulating material
a. batteries b. current generators c. resistors/conductors d. capacitors |
d. capacitors
insulator (membrane) conductors (ICF,ECF) |
|
|
allows storage of charge
a. batteries b. current generators c. resistors/conductors d. capacitors |
d. capacitors
|
|
|
T or F the lipid bilayer is a poor intrinsic conductor of ionic current
|
True
|
|
|
in the cell membrane almost all ion conductance is due to what?
|
ion channels
|
|
|
in the cell membrane what is inversely proportional to resistance (R)?
|
conductance (ɣ or g) is inversely proportional to resistance (R)
|
|
|
in the cell membrane Rm (membrane resistance) depends on what?
|
ion channel density
ion channel conductance |
|
|
at rest ɣm (conductance) is ____ and Rm (membrane resistance) is _____
|
ɣm is low; Rm is high
|
|
|
MACA: cell membranes are
a. batteries b. current generators c. resistors/conductors d. capacitors |
c. resistors/conductors
d. capacitors |
|
|
T or F cell membranes are resistant to ionic currents
|
True
therefore, membranes store charge (act as capacitors) |
|
|
in a cell membrane, membrane capacitance depends on what?
|
composition of insulating medium (phospholipid bilayer)
distance between conductive plates (ECF/ICF boundaries) -typically= 4nm |
|
|
T or F in a cell membrane, membrane capacitance affects time course for change in Vm
|
True
|
|
|
pure resistors produce what change in Vm
|
instantaneous change of Vm
|
|
|
pure capacitors produce what change in Vm?
|
linear rate of change in Vm
|
|
|
t=Rm x Cm is the equation for what?
|
time constant
which is important determinant of action potentials propagation rate and synaptic integration |
|
|
in the time constant if you have low t it produces what to Vm and AP?
|
change in Vm occurs more quickly
action potential regenerated at faster rate |
|
|
what equals the resistance to ionic current through cytoplasm along longitudinal axis?
|
Ra (axial or axoplasmic resistance)
aka: Rc (cytoplasmic resistance) |
|
|
Ra (axial resistance) is affected by longitudinal pathway of current flow and cross-sectional area of cell in two ways?
|
Ra increases with increase distance of longitudinal current flow
-due to ionic collisions Ra decreases with increasing cross-sectional area of cell -larger area allows more freedom of ionic movements |
|
|
T or F Larger diameter nerve fibers have lower Ra
|
true
|
|
|
what is the equation for the space constant?
|
λ =(Rm/Ra)^1/2
|
|
|
with high λ you have what in reference to Vm and AP
|
the change in Vm travels greater distance before decaying
action potentials are regenerated at a faster rate (low time constant) |
|
|
what are the 2 ways you can write the conduction velocity equation?
|
CV=Δd/Δt
or CV=λ/t (CV=((Rm/Ra)^1/2)/(Rm x Cm) |
|
|
what are 2 ways you can increase CV
|
increasing λ (common adaption)
-larger axon diameter--> lower Ra -axon myelination ---> higher Rm, lower Cm decreasing t (theoretically) -faster ion channel kinetics--> lower Rm -higher ion channel density--> lower Rm |
|
|
what could happen if the membrane has no inherent directionality?
|
action potential may propagate in either direction
backpropagation of the action potential's this occurs in some dendrites |
|
|
what could happen if the action potential is unidirectional?
|
once action potential is generated it never reverses course
local current flows bi-directionally, but cannot generate action potential in reverse direction refractory state of membrane prevents reverse propagation |
|
|
occurs in non-myelinated neuronal fibers?
a. continuous conduction b. saltatory conduction |
a. continuous conduction
|
|
|
action potential is regenerated at each adjacent section of cell membrane
a. continuous conduction b. saltatory conduction |
a. continuous conduction
|
|
|
depolarization wave is chased by repolarization wave down length of fiber
a. continuous conduction b. saltatory conduction |
a. continuous conduction
|
|
|
occurs in myelinated axons
a. continuous conduction b. saltatory conduction |
saltatory conduction
|
|
|
myelinated axons are wrapped in many layers of what?
|
myelin sheath
|
|
|
what is myelin sheath composed of?
|
concentric layers of plasma membranes which contain
-80% highly enriched lipids -20% less protein than most cells -lack channels and carrier proteins -very good insulator -protects axon |
|
|
myelin sheath membranes formed by glial cells in the CNS called?
|
oligodendrocytes
PNS- schwann cells |
|
|
myelin sheath membranes formed by glial cells in the PNS called?
|
schwann cells
CNS- oligodendrocytes |
|
|
nodes of Ranvier interrupt what?
|
the myelin sheath
|
|
|
T or F node of Ranvier are short (~2μm) of myelinated pateches of membrane between unmyelinated regions
|
False
node of Ranvier are short (~2μm) of UNmyelinated pateches of membrane between Myelinated regions occur at 1-3mm intervals along myelin sheath |
|
|
T or F most ion channels are concentrated at nodes
|
True
|
|
|
in the saltatory conduction where are action potentials regenerated?
|
only at the nodes of ranvier
AP leaps quickly from node to node AP conduction velocity is greatly increased |
|
|
in the saltatory conduction: in myelinated regions Rm is increase what is reduced?
|
Cm is reduced
electrotonic conduction speed is greatly increased between nodes |
|
|
which myelination deficiency has nuerodegenerative disease?
|
demyelination
|
|
|
which myelination deficiency loss (lesioning) of myelin sheathing?
|
demyelination
|
|
|
which myelination deficiency occurs in some autoimmune disorders?
|
demyelination
mutiple sclerosis-destruction of oligodendrocytes in CNS Guillain-Barre syndrome- PNS disease; may attack schwann cell myelination |
|
|
which myelination deficiency is associated with multiple sclerosis?
|
demyelination
destruction of oligodendrocytes in CNS |
|
|
which myelination deficiency Guillain-Barre syndrome?
|
demyelination
in PNS, may attack schwann cell myelination |
|
|
which myelination deficiency neurodegenerative or congenital defect?
|
dysmyelination
|
|
|
which myelination deficiency abnormal myelin formation?
|
dysmyelination
|
|
|
how are nerve fibers classified?
|
diameter
degree of myelination conduction speed |
|
|
largest diameter
a. Group A fibers b. Group B fibers c. Group C fibers d. all of the above |
a. Group A fibers
|
|
|
highly myelinated
a. Group A fibers b. Group B fibers c. Group C fibers d. all of the above |
a. Group A fibers
|
|
|
Max CV= 150m/s
a. Group A fibers b. Group B fibers c. Group C fibers d. all of the above |
a. Group A fibers
|
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somatic sensory and motor fibers
a. Group A fibers b. Group B fibers c. Group C fibers d. all of the above |
d. all of the above
group a is mostly somatic and motor but groups B&C are autonomic and somatic sensory fibers and motor fibers |
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does not have autonomic fibers?
a. Group A fibers b. Group B fibers c. Group C fibers d. all of the above |
a. Group A fibers
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intermediate myelination and diameter?
a. Group A fibers b. Group B fibers c. Group C fibers d. all of the above |
b. Group B fibers
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avg. CV= 15m/s
a. Group A fibers b. Group B fibers c. Group C fibers d. all of the above |
b. Group B fibers
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MACA: autonomic and somatic sensory fibers and motor fibers
a. Group A fibers b. Group B fibers c. Group C fibers d. none of the above |
b. Group B fibers
c. Group C fibers |
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smallest diameter
a. Group A fibers b. Group B fibers c. Group C fibers d. all of the above |
c. Group C fibers
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unmyelinated
a. Group A fibers b. Group B fibers c. Group C fibers d. all of the above |
c. Group C fibers
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avg. CV= 1m/s
a. Group A fibers b. Group B fibers c. Group C fibers d. all of the above |
c. Group C fibers
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many neurons input onto one?
a. convergence b. divergence |
convergence
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one neuron outputs onto many
a. convergence b. divergence |
b. divergence
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the connection between electrically excitable cells is called?
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synapse
presynaptic to postsynaptic |
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when a synapse goes from one neuron to another neuron it is called?
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internuncial synapse
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when a synapse goes from axon to dendrite it is called?
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axodendritic
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when a synapse goes from a axon to an axon it is called?
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axoaxonic
always an inhibitory |
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T or F axoaxonic synapses are always inhibitory.
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True
synapse from axon to axon |
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when a synapse goes from a neuron to a muscle cells it is called?
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neuromuscular junction
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when a synapse goes from a neuron to a gland cell it is called?
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neuroglandular junction
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synapses directly between muscle cells is called?
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and electrical synapses
cardiac muscle smooth muscle |
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where do electrical synapses occur through?
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gap junctions
permits both direct electrical coupling and exchange of other small cytoplasmic solutes |
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what are the two types of electrical transmissions which electrical synapses can be?
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bidirectional (non-rectifying synapse)
unidirectional (rectifying synapse) |
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where might you find electrical synapses?
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cardiac muscle
smooth muscle nervous system |
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T or F chemical synapses are faster than electrical synapses
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False
opposite electrical synapses have a short synaptic delay ~0.2ms |
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where might the speed of electrical synapses be useful?
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defensive reflexes
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what are some disadvantages of electrical synapses?
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less plasticity compared to chemical synapses
less capability for integrative/combinatorial signaling -no inhibitory signaling -lack variability of multiple chemical transmitters |
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T or F nerve impulses are transduced to chemical signals in the presynaptic cell and the transduced back to act on the postsynaptic cell
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True
action potential stimulates neurotransmitter ---> chemical(pre) --->neurotransmitter(post) |
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T or F chemical neurotransmission is always unidirectional
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True
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what are some advantages of chemical synapses?
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greater ability for long term modification
capable of complex integrative/combinatorial signaling -both excitatory and inhibitory signaling -complex regulation due to transmitter/receptors -modulation of signal gain |
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what branches to form many presynaptic connections (at terminals) with other cells?
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axon
AP's are propagated down axon toward presynaptic terminals |
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in a axon what separates pre- and postsynaptic membranes?
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synaptic cleft
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what receives 80-95% of presynaptic terminals?
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dendrites
electrical signals are conducted toward soma |
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what receives 5-20% presynaptic terminals?
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soma
also receives electrical signals from dendrites conducts electrical signals down axon |
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what connects soma with axon?
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axon hillock
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what is considered the SIZ (spike initiation zone)?
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axon hillock
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contains high density of voltage-gated Na+ channels
a. axon b. dendrite c. soma d. axon hillock |
d. axon hillock
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what is the mechanism of chemical neurotransmission? steps 1-7?
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1. depolarization of Vm at axon hillock generates AP
2. AP propagates down length of axon and depolarizes membranes at presynaptic terminal 3. depolarization results in transient localized influx of Ca2+ into PST's 4. influx of Ca2+ stims synaptic vesicle exocytosis 5. neurotransmitters diffuse across synaptic cleft and bind specific receptors on postsynaptic membrane 6. activated receptor mediates specific effect in postsynaptic cell 7. synaptic delay -0.3-5ms |
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in the mechanism of chemical neurotransmission a localized influx of Ca2+ into PST's stimulates synaptic vesicle exocytosis which is what?
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1. PST holds many vesicles containing specific neurotransmitters
2. Ca2+ stims signaling cascade -Ca2+ --> calmodulin -->protein kinase which phosphorylates membrane bound tethering proteins which release synaptic vesicles 3. vesicles migrate and fuse with presynaptic membrane 4. vesicular contents are released into synaptic cleft |
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the number of vesicles released per action potential is called?
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quantal number
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the postsynaptic response to contents of single vesicle is called?
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quantal size
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synaptic delay results from what?
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migration and fusion of vesicles
diffusion of neurotransmitters receptor binding and activation postsynaptic response (0.3-5ms) |
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post-synaptic receptor proteins: ionotropic or metabotropic:
fast acting? |
ionotropic
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post-synaptic receptor proteins: ionotropic or metabotropic:
receptor is also an ion channel? |
ionotropic
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post-synaptic receptor proteins: ionotropic or metabotropic:
ligand binding opens channel |
ionotropic
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post-synaptic receptor proteins: ionotropic or metabotropic:
few are also voltage gated |
ionotropic
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post-synaptic receptor proteins: ionotropic or metabotropic:
may produce excitatory or inhibitory |
both
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post-synaptic receptor proteins: ionotropic or metabotropic:
a receptor is coupled with second messenger system |
metabotropic
ACh or muscarinic receptors |
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post-synaptic receptor proteins: ionotropic or metabotropic:
slow acting |
metabotropic
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post-synaptic receptor proteins: ionotropic or metabotropic:
exchanges GDP for GTP upon ligand binding |
metabotropic
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what catalyzes ATP ---> cAMP + PPi?
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adenylate cyclase
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adenylate cyclase catalyzes ATP --> ?+?
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cAMP + PPi
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what cellular effects does cAMP possess?
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can change ion channel permeability
can activate other biochemical pathways can activate gene transcription |
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inhibitory or excitatory:
postsynaptic membrane is depolarized? |
excitatory
Vm approaches or exceeds threshold |
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inhibitory or excitatory:
activation of Na+ channels |
excitatory
inward Na+ current depolarizes membrane |
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inhibitory or excitatory:
postsynaptic membrane is hyperpolarized? |
inhibitory
Vm moves farther from threshold |
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inhibitory or excitatory:
outward K+ current? |
inihibitory
activation of K+ channels |
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inhibitory or excitatory:
inward Cl- |
inhibitory
activation of Cl- channels |
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what type of summation occurs when multiple PSP's are simultaneously generated from different synapses?
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spatial summation
may be from terminals arising from same neuron may arise from different neurons (more common) |
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what type of summation occurs when multiple PSP's are simultaneously generated from the same synapse in rapid succession?
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temporal summation
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where is presynaptic inhibition mediated at?
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axoaxonic synapses
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what are some modulations of postsynaptic responses?
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facilitation
synaptic fatigue synaptic protentiation |
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occurs when neurons are depolarized to subthreshold level
a. facilitation b. synaptic fatigue c. synaptic protentiation d. all of the above |
a. facilitation
facilitated neurons are more easily exited by successive exicitory postsynaptic potential |
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loss of neuron excitability resulting from excessive excitation due to rapid firing rate
a. facilitation b. synaptic fatigue c. synaptic protentiation d. all of the above |
b. synaptic fatigue
exhaustion of presynaptic neuron stores |
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exhaustion of presynaptic neuron stores
a. facilitation b. synaptic fatigue c. synaptic protentiation d. all of the above |
b. synaptic fatigue
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repeated presynaptic firing results in increase effect of presynaptic activity on postsynaptic cell.
a. facilitation b. synaptic fatigue c. synaptic protentiation d. all of the above |
c. synaptic protentiation
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T or F gases make use of the vesicular transport more than most neurotransmitters
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False
gases do not utilize vesicular transport they diffuse directly through cell membrane |
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what are some classifications of neurotransmitters?
|
cholinergic
biogenic amines amino acids purinergic gases |
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what is an example of a cholinergic neurotransmitter?
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acetylcholine (ACh) excitatory or inhibitory
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what are some examples of biogenic amines neurotransmitters?
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catecholamines- excitatory or inhibitory
-dopamine- -epi- -norepi- indoleamines -seotonin- inhibitory -histamine- excitatory |
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what are some examples of amino acids neurotransmitters?
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(GABA)- inhibitory
glycine-inhibitory glutamate-excitatory |
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what are some examples of purinergic neurotransmitters?
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ATP- excitatory or inhibitory
adenosine- inhibitory |
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what are some examples of gases which are neurotransmitters?
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all gases are excitatory
nitric oxide (NO) carbon monoxide (CO) |
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what are some neurotransmitters which produce an excitatory response only?
|
gases (NO, CO)
glutamate- amino acid histamine- indoleamines |
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what are some neurotransmitters which produce an excitatory response and a inhibitory response?
|
Cholinergic (Ach)
the Biogenic amines which are catecholamines -dopamine -epi -norepi ATP- purinergic |
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what are some neurotransmitters which produce only a inhibitory response?
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serotonin - biogenic amine, indoelamine
GABA- amino acid glycine- amino acid adenosine- purinergic |
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where are neuropeptides synthesized?
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in the soma
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what is the path of neuropeptides?
|
synthesized in soma ---> packed into vesicles via golgi apparatus ---> vesicles transport synaptic terminal via fast anterograde axonal transport --> partially recycled ---> back to soma via Retrograde axonal transport
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what are the inhibitory peptidergic's called?
|
endorphins
-dynorphin -enkephalin |
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what are the excitatory peptidergic's called?
|
tachykinins
-substance P -neurokinin A |
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where does acetylcholinesterase (AChE) cleave ACh?
|
in the synaptic clefts
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where does neurotransmitters are reabsorbed by what?
|
presynaptic cell or glia
e.g. Norepi |
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what exogenous substance mimic effect of endogenous neurotransmitters?
|
agonists
nicotine, muscarine--> active ACh receptors ethanol, valium--> activate GABA receptors |
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if you activate ACh receptors like nicotine does it is called a
a. stimulant b. depressant c. both d. neither |
a. stimulant
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if you activate GABA like ethanol or valium does it is called a
a. stimulant b. depressant c. both d. neither |
b. depressant
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what blocks neurotransmitter activation in reference to neuropharmacology?
|
antagonists
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what antagonists blocks ACh at mAChR?
|
curare, atropine
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what antaagonist blocks NE at beta adrenergic receptors?
|
propanolol
|
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what antagonist blocks adenosine?
|
caffeine
|
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in presynaptic modulation what inhibitory blocks ACh release?
|
botulinum toxin
|
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in presynaptic modulation what inhibitory blocks Ca2+ release?
|
some conotoxins
|
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in presynaptic modulation what stimulatory increases the release of NE?
|
amphetamines
|
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|
in presynaptic modulation what stimulatory increases the release of ACh
|
some spider venom
|
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in postsynaptic modulation what blocks NE destruction?
|
cocaine
|
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in postsynaptic modulation what blocks AChE?
|
nerve gas
|
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in postsynaptic modulation what blocks reuptake of serotonin?
|
SSRI's
commonly prescribed as antidepressant |
