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170 Cards in this Set
- Front
- Back
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What is physiology?
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how organisms function from subcellular level to an intact organism
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Cell
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Basic unit of life
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Cell contains
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sub-cellular structures and organelles composed of macromoelcules
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Macromolecules
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carbs
proteins fats nucleic acids |
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Cells are surrounded by
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plasma membrane
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unicellular organisms
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All vital processes occur at this level
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multicellular organisms
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cells specially adapted to form one or more functions
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Four Types of Tissues
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Epithelial
Connective Muscle Nerve |
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Compartmentalization
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functional divisions of tasks to specific areas
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Homeostasis
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maintenance of stable internal environment within healthy ranges regardless of changes in the external environment
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Name the mechanisms required to maintain homeostasis
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sensor
controller effectors |
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sensors
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monitors regulated variables and compares them to the set point
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controllor
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manipulates effectors
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effectors
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control elements
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two kinds of control systems
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negative and positive feedback
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negative feedback
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most commonly used mechanism
sensors first detect differences from set point controllers stimulate effectors to return to normal range |
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positive feedback
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sensors first detect a difference from set point
controllers move the system further from the set point |
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Levels of control and coordinator of control
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cellular level- DNA
Local level- cell factors, paracrine reactions sytematic level- central nervous system and endocrine system |
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Central Nervous System
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Sensors send signals via the nerves
The effectors would be muscles or glands It is a fast response and it is short term |
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Endocrine System
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sensors are specialized cells that send signals via hormones
effectors are glands,specialized cells and muscles slow response and long term |
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Body is predominately what percent of H2O?
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60 for men
50 in women This decreases with age |
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Importance of our bodies being in an aqueous solution
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-medium for short and long distance communication between cells
-helps maintain the cells shape because it is not compressible -helps with temp. control -most molecules present in the body and living systems are highly soluble in water |
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ICF (intracellular fluid)
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Fluid inside the cells (40% body weight)
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ECF (extracellular fluid)
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Fluid outside of cells (20% body weight)
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ECF is divided in 2 what 2 thing?
What are they? |
Interstitial Fluid
-between cells; 15% body weight Plasma and Lymph -fluid in body and fluid in lymphatic vessels -5%body weight Transcellular fluid -in specialized areas -cerebral fluid,aqueous humor |
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Composition of Body Fluid
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Uncharged organic substances,
electrolytes, |
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What are electrolytes?
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Chemicals which dissociate into water and are expressed in milliequivalents.
they conduct electricity Equivalent (no. of moles in an ion) x (valence of an ion) |
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Important ions in body fluid...
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Na+
K+ Ca++ Cl- HCO3- Proteins |
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Where is Na+ located?
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cation in ISF
very importat |
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Where is K+ located?
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Cation in ICF
Very important |
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What is Ca++ purpose?
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Important Cation for cell function
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Where is Cl- found?
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Most important anion in ISF
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What is HCO3- purpose?
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Important ECF buffer
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What are proteins purpose?
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Act a major anions in the ICF
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What is an osmotically active substance?
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Number of particles (regardless of size, mass or valence) in a liter of water expressed as milliosmoles
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What is osmolality?
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Sum total of all particles per liter of solution
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What is osmotic equillibrium?
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osmolalites of ICF and ECF are equal
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What if the osmolality of ISF differs from the osmolality of the ICF?
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Water can move across the mem.
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What is osmotic pressure?
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amt. of water pressure (aka hydrostatic pressure) it would take to prevent the water from moving according to the osmotic difference
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Body Sensors
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osmoreceptors in hypothalamus inthe brain
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Plasma Membrane functions
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-Seperates intra cellular fluid from extracellular fluid
-provides permeability barrier and highly selective filter -contains surface antigens: important for immune system recognition of self vs nonself -provides cell communication: receptors and signals transduction pathways for hormones and neurotransmitters -contain a variety of adhesion molecules: allows anchoring, tissue organization, intracellular communications, and cell shape |
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Plasma Mem. Structure
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-Fluid mosaic model
-composed primarily of lipids and proteins, minimally of carbs. |
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Lipids of the Plasma Mem.
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usually 50 % of mass of plasma mem.-% differs depending on cell type
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Def. of Phospholipids:
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-core structure of the plasma mem.
-arranged in a bilayer: inner and outer layers -have polar head and nonpolar tail -makes them amphipathic -The polar part is hydrophillic and faces fluid surface -have 2 long non-polar fatty acyl tail chains -hydrocarbon chains are hydrophobic -form permeability barrier to water soluble molecules |
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Cholesterol
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Hydrocarbon ring structure
-up to 20 percent total membrane lipid -stablizes membrane at room temp. which is 37 degrees C -increases membrane fluidity -resevior of precursor molecules for steroid hormones |
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Give info about the proteins in the plasma mem.
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-There are more than 100 diff protein make up the membrane mass
-integral and intrinsic proteins -there are also peripheral or extrinsic proteins |
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integral or intrinsic proteins
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make up 70 percent of mem. proteins
-embedded in the membrane by hydrophobic reactions -can be disrupted by detergents -some span the mem completely: transmembrane protein -they function as carriers and channels |
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peripheral or extrinsic proteins
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-stud either the outside of the protein or inside surface
-often are enzymes |
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Enzymes
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-catalyze reactions at surfaces of membranes
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Phosphatases
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enzymes built from an extrinsic protein that remove phosphate group from protein
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Kinases
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Enzyme built from an extrinsic proteion that adds a phosphate group to a protein
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Carbohydrates
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-make up 2- 10 percent of the membrane mass
-glycolipids and glycoproteins: these are involved in cell to cell recognition process and may act as a receptor components |
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What are the three different means for molecules to pass through the plasma mem.?
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Vesicular Transport
passive Transport Active Transport |
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Explain Vesicular Transport
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It is used for bulk trnasport: aka- transports large molecules
it requires alteration of plasma membrane it consumes energy fromt he break down of GTP or ATP Requires increased intracellular CA2++ |
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Two forms of Vesicular Transport
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Endocytosis, Exocytosis
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Endocytosis
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infolding of membrane to allow molecules to enter the cell
phagocytosis-cell eating pinocytosis-cell drinking receptor mediated endocytosis |
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Exocytosis
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fusion of vesicle with plasma membrane so that it may eject the molecule from the cell
constitutive= secretory product made and immediately released regulated=secretory products made and stored until signaled for release |
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Transcytosis
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endocytosis across one membrane and exocytosis across the other membrane
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Passive Transport
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Does not require energy input from the cell
includes: diffusion and osmosis |
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Diffusion
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Energy for diffusion is from Brownian motion, which is normal random thermal motion of atoms or molecules
driven by GRADIENTS until dynamic equillibrium is reached there are 3 gradients: electrochemical chemical electrical |
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chemical gradient
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difference in conc. causes net movement from higher to lower molecular concentration
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electrical gradient
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differences in charges causes net movement with like charges repelling each other and unlike charges attracting one another
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electrochemical gradient
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combination of chemical and electrical gradients
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types of diffusion accross membrane
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simple diffusion
facilitated diffusion |
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Simple Diffusion
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Carrier independent
Occurs through lipid bilayer |
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Membrane protein channels or pores
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nonlipid soluble substances travel though here
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How do lipid soluble substances travel though membrane?
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though intramolecular spaces of membrane lipids
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Channel Protein
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ransmembrane protein, with central water-filled passage or pore
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What is a name for a water channel?
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Aquaporins
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Ion Channels
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They can be gated, leak channels, voltage gated, ligand gated, mechanically gated, intracelluar messenger gated
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What is a gated channel?
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They have modifications that allow channel to be opened or closed
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What is a gated channel Classified by?
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selectivity: to one or more ions
conductance: measure of how readily an ion moves through the channel retrification: movement of ions into cell easier than movement out (inward rectifier) |
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What are leak channels?
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They are usually open
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What are voltage gated channels?
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They reposnd to alrerations in mem. pot. (in other words- charge changes)
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What are ligand (chemical) gated channels?
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They open by binding signaling molecule
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What are mechanically gated channels?
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respond to physical deformation
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What are intracellular messenger gated channels?
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Responds to change in intracellular signal
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Facilitated Diffusion
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It is carrier Dependent
Uses a carrier protein to pass though the membrane |
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What is a carrier protein?
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it is a transmembrane protein that undergoes transformational change to transport nonlipid soluble molecules
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What will a carrier protein possible be affected by?
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competitive inhibition
non-competitive inhibition saturation |
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What do the Letters in the equations:
J=- D A Change in C/Change in x mean? |
It is called Ficks Law
J= net movement D= diffusion coefficient P= permeability coefficient C=Concentration Diff A= Area x= membrane thickness membrane thickness is constant J is inversely proportional to mol. weight (size) J is directly proportional to temp. |
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what is diffusion trapping
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alteration of a solute after it is moved across the mem., preserves the gradient
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Describe Electrical Charge
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Ions usually diffuse through Ion Channels
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Nernst Equation
Eion= -61.5/Z log [ioni] [ion o] |
Determines the electrochemical equilibrium potential of any given ion
z= valence |
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Osmosis
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a type of simple diffusion
net movement of water though selectively permeable mem. |
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what is the normal osmolarity range of ECF and ICF
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285-295 osmoles, rounded to 300 however
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what is osmosis caused by>
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a conc diff of solures across mem. when permeability of solutes is low compared to the permeability of water
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how does osmosis occur?
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moves from high water to low water
or you can say low solute to high solute |
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What is osmotic pressure?
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the amount of hydrostatic pressure needed to stop net movement of water
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Tonicity
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osmolality
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isotonic and isoosmotic
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solution with the same osmolarity as the plasma
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hypotonic
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solutions with less osmolarity than plasma, the cell will commonly swell and even rupture or lyse
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hypertonic
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solutions with more osmolarity than plasma, the cell will commonly shrink or shrivel (crenulate)
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Active transport
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This is an energized transport AGAINST and electrochemical gradient
Requires a "pump" carrier protein |
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Primary active transport
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all transported molecules are moved against their energy gradient
energy for this transport come directly from the hydrolysis of ATP associated with the pump |
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Secondary active transport
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Energy for this transport is indirectly provided by ATP
The ATP hydrolysis is not associated with the carrier Generally the movement of Na+ into the cell down its conc or energy gradient is coiuple with the transport of another molecule against its conc. gradient |
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Types of transport Pumps and exchangers
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Pump a carrier that uses ATP
Transmembrane protein uniporter symporter antiporter |
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Uniporter
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binds and transports only one substance against its energy gradient
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Symporter
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binds two or more molecules on the same side of the mem.
usually one of the substances moves with its energy gradient and the other goes against which is sec. active transport |
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Aniporter
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binds two diff substances on opposite surfaces of mem, from each other
may be prim. or sec. active transport |
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Na+/K+ ATPase
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most common in cells
maintains normal cell volume, pressure and resting mem. pot. Uses ATP hydrolysis allows movement of 3 NA+ ions out of cell and 2 K+ into the cell Creating a net loss of one pos. charged ion in the cell so it will be classified as endergonic pump the cellular energy expenditure for this pimp is high- it accounts for 1/3 of the body's energy supply |
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membrane potential
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cellular proteins are trapped withing the cell tend to carry a net neg. charge
therefore this tends to inhibit the net movement of K+ ions outside of the cell because + like neg. and it favors the movement of anions (Cl-) out of the cell |
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What does a mem. pot. result in
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in an assymetric distribution of ions across the mem.
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Electrical potential of a mem.
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causes by difference in a net charge inside and outside the cell
provides an electrical potential so that ions will flow |
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Explain a resting mem. pot.
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all cells have a resting mem. pot.
Intra cellular fluid of all cells have a negatively charged mem. resting mem. potential when compared to the extracellular fluid |
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What RMP do most cell have?
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Average of -70 mV
But it can range from -9 to -90 mV |
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Explain RMP and excitable cells?
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These cells are cells like nerve cells and muscle cells
and they have a lower RMP than other cells that are non-excitable. |
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Name some factors contribution to resting mem. pot.
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differences in permeability of ions
proteins that are trapped inside of the cell contribute to the neg charge inside of the cell- they influence ion distribution electrogenic pump (such as NA/K ATPase equilibrium potential of all of the permeable ions Chord conductance Equation (Goldman's equation) |
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What is an electrogenic pump?
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pumps na out and k in. this produces an net neg. charge inside of the cell
this contribution of the pump with vary in different kinds of cells some disturbances in potential can be adjusted by changing the pump activity |
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What is meant by equilibrium potential of all permentant ions?
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The Nernst equation predicts the equilibrium potention of ONE single ion
ASSUMES FREE PERMEABILITY, however, this is not always the way the ion works and therefore the ion may not be freely permeable does NOT take in to consideration the pump activity |
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When using Goldman's equation, what is it used for? what are some necessary facts about it?
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It is the weighted average of equilibrium taking all the ions into consideration
this weighting factor accounts that all the ions are permeable if ones ion weighting factor increases others must decrease K conductance is ten times greater than Na under resting conditions due to K leak channels K has the biggest influence on RMP Changes of K in the ECF will alter the RMP in all cells |
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Action potential is what kind of response?
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All or none
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What is an AP?
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it is a rapid or large change in membrane potential followed by a return to rmp
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Describe a depolarizing stimulus...
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if the cell is less negative or less polar, it moves the potential closer to zero
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Describe hyperpolarizing stimulus
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cell more negative/more polar, moves the membrane potential more negative, further away from zero
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What is a sub-threshold response?
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The stimulus is a local reponse
the stimulus produces a non-propagated potential where the size of potential decreases exponetially with distance from initiation site |
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What is a threshold point?
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if the stimulus is large enough it will reach this. This means that an action potential will be initiated
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Explain what happens when action potential is initiated?
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positive feedback occurs
polarity of a cell reverses |
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what is self-propagating electrical impulse?
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it depolarizes and adjacent membrane
the action potential is carried along the cell with out decrement (meaning loss in quantity) |
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What is the duration of action pot. for neurons and muscle cells?
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~4 ms
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How do size and shape of cell relate to AP?
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There is a constant cell shape, size and amplitude for a given kind of cell.
this means that size and shape differ from one excitable tissue to the next |
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What is the structure of a neuron?
What is a neuron? |
there is soma (cell body) dendrites, axon and axon terminals, and an axon hillock
a neuron is a nerve cell and it is a fuctional unit of a nervous system the shape of a neuron varies but contains the same4 basic components |
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What are the purpose of dendrites?
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Dendrites receive info from other nerve cells
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What is the purpose of an axon?
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carries the nerve impulse to other nerve cells or effectors
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what is an axon hillock?
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an axon hillock is the initial section of an axon where and axon leaves the soma aka cell body
this is usually the site where action potential is generated it has a high concentration of voltage gated NA channels This means that it has the lowest threshold for activation |
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describe the purpose for an axon terminal?
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they contain neurotransmitter vesicles (which can be thought of as chemical packages)
tranmit information to the next nerve cell at a junction called a synapse |
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Name the diff phases of a neuron action potential
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RMP
Sub Threshold Threshold depolarization phase repolarization phase hyperpolarization phase refractory periods |
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What happens at the rmp in relation to sodium channels?
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The sodium channels are gated and they are closed
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What happens to RMP in relation to K channels?
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They are mainly leak channels and this means that they are open
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Explain RMP
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the NA VG channels are closed
The K leak channels are open and K moves freely in reference to the eqilibrium |
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Explain a threshold point
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it is a point of no return
is low in nerve cells and muscle cells maybe slowly or rapidly reached when a depolarizatind stimlus added it can reach this point when a threshold point is reached an Action potential is initiated- this gives the all or nothing response |
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Name different ways in which a threshold point can be reached
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summation of smaller sub-threshold stimuli
a large intensity single threshold is applied |
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What is a summation of smaller sub-threshold stimuli...explain...
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this means multiple stimuli that are smaller are added close together in time to continue to increase the reponse
in other words the next small stimuli is added before the previous one has decayed |
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what is a supra-threshold stimulus?
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It is a stimulus (a polarizing stimulus) that is larger than one required to reach threshold, however, it will not increase its "size"
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Describe what is meant when a positive feedback mechanism is reached or initiated in relation to a threshold, etc.
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It will trigger an opening of fast acting NA VG channels
The conductance with go from 500 to 5000 fold! |
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describe the polarization phase...
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Entry of sodium pulls the mem. pot toward Na Equilibrium potential
the membrane will overshoot the isoelectric point and inside of the cell will become potential slower acting voltage gated K channels will begin to open when K leaves slowly this will slowly depolarize, counteracting the impact of Na entry |
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Describe the refractory stage
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starts at +30 mV
the fast acting VG Na channels with begin to close this will make a rapid decrease in Na conductance More slow activating voltage-gated K channel will open This will increase K conductance and will help return the RMP to normal in 1 ms |
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what is the hyperpolarization period?
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Slower phase of AP
Fast acting Na channels are closed Slow acting VG K channels slow to close the mem. pot. is pulled toward K equilibrium pot the mem pot is more neg than resting levels slow actiong VG K channels close and cellular pumps restore RMP |
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What is a refractory period
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minimum time after an cation potential had been generated before the membrane can respond again
axons with short refractory periods can conduct APs at a higher rate than those with long refractory periods |
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What is an absolute refractory period
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it is approx. 1 ms
it goes from the beginning o the action potential until 2/3 of the repolarization is complete if all Na channels are open, you cant get anymore open than open, therefore, you cant open anymore also once these channels are closed you cant open them right away NO STIMULUS REGARDLESS OF STRENGTH CAN INITIATE ANOTHER ACTION POTENTIAL DURING THIS PERIOD |
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How would you get another AP during relative refract. period?
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You would have to have a stimulus that would open more fast acting VG Na channels to open to counter act the hyperpolarizing effect of the still open voltage -gated K channels
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What is a relatively refractory period?
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this follows the absolute refractory period and lasts up until RMP is established
requires a stronger stimulus than normal to rereach threshold |
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What is a nerve impulse?
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this is like the wave.
It is a wave of movement of action potentials down the axon |
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An action potential is ____________ response occurring at _________________ on the membrane.
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local; one specific area
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When AP is initiated at one point of the membrane, what happens next?
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it triggers AP in neighboring areas
this happens by adjacent areas being affected by influx of pos. ions during repolarization |
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What does self-propagating mean?
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Domino-like effect
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can ap travel back to previously activated areas?
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No
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Velocity of action potentials...explain it
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In a neuron if the diameter of an axon is larger in diameter, it will have a faster conduction rate, meaning that it will travel faster do to lower resistance to conduction
(think of a hose, the larger, the more water can go through) |
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What is Myelin?
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Myelin is a lipid material that covers axon
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What is myelin's purpose?
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acts as a insulator, it prevents loss of current and flow of ions between ICF and ECF
it creates Nodes of Ranvier causes the AP to jump from node to node increases velocity of AP up to 50 x faster than unmyelinated neurons conserves energy (meaning it uses less ATP) |
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What is saltatory conduction?
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when appears to jump from node to node
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what is nodes of ranvier?
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gaps that occur btwn myelin producingcells and only place where ion exchange can occur
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Name some myelinated cells and their function
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Schwann Cells, they produce myelin and surround nerves in peripheral nervous system (outside brain and nervous system)
Oligodendrycytes, produce myelin and surround nerves in central nervous system ( within brain and spinal cord) |
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What is a synapse?
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It is a place where info is transferred from one cell to another
this process is called synaptic transmission |
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What is an electrical synapse?
Where are they found? |
allows direct passage of ions from one cell to another through GAP JUNCTIONS
Electrical synapses are found in cardiac and smooth muscle |
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Chemical synapse
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involves two kinds of cells, pre- and post- synaptic and a space between them
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What is a presynaptic neuron?
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converts an electrical signal to a chemical one
this chemical signal is called a neurotransmitter |
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Where is a neurotransmitter released from?
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An axon terminal
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What is a synaptic cleft?
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a physical gap that a neurotransmitter diffuses across
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what sis a postsynaptic membrane?
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it is an active region
contains a receptor specific for a neurotransmitter that is released when a neurotransmitter binds to this receptor is activates a coupling mechanism this changes cellular response (signal transduction pathway) has catabolic enzymes= located on the outside of the mem., they break down the Neurotransmitters to prevent continual stimulation |
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what is used to stop the continual stimulation of postsynaptic cell?
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catabolic enzymes
they are located on the outside of the mem. |
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what are the types of chemical synapses, their locations?
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axodentritic =axon terminal to dendrite
axosomatic= axon terminal to soma axoaxonal= axon terminal to axon neuromuscular junction= axon terminal to muscle synapse en passant= axon terminal and smooth muscle |
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What are some types of synapses based on speed of transmission?
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ionotropic= involves fast chemical transmission; binding of neurotransmitter to receptor directly gates ion channel which is a ligand gated channel
metabotropic= this is slow chemical transmission; the receptor coupled G protein, involves mult. steps involving 2nd msgers and formation of kinases and phosphatases that amplify the signaling events, this activated milt. pathways and regulates mult cell fcts., it also indirectly alters mem. conductance though ion channels |
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What us a presynaptic neuron
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the axon ends contain neurotransmitter packaged in vesicles
each vesicle contains a fixed number of neurotransmitters an arriving AP causes a depolarization of axon terminal this will activate the Ca2+ voltage gated channels on the plasma mem.- this will Ca++ influx will allow neurotransmitter vesicles to fuse with pre-synaptic membrane The number of vesicles are directly proportional to the ICF Ca++ concentration |
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What is exocytosis?
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quantal release of neurotranmitter in synaptic cleft
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How do you restore the mem. potential ?
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use Na+/K+ ATPase
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What is a re-uptake pump used for?
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removal of unused neurotransmitter in cleft
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What is the time required for diffusion of NT across cleft?
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~0.5 ms
this is called the synaptic delay |
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Give the sequence of event at chemical synapse
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exocytosis of NT
Removal of free ICF Ca++ Na-Ca++ antiporter is activated the mem pot is restored using NA/K pumps Re-uptake pumps remove unused NT |
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What is the Na+/Ca++ ATPase for?
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it is an antiporter using sec. active transporter
it is activated by the increase of intracellular Ca++ need to get Ca++ outside of cell, so it wiil leave the cell and Na++ will come in and then the NA/K pump will get the Na out of the cell. |
