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26 Cards in this Set

  • Front
  • Back
motor movement
Brain stem
homeostatic function

little bumps "spines": areas where synaptic signals are recieved

axon hillock- action potentials are generated here

axon terminals- at synapse, message is sent to the next cell
signal spreads from dendrites to cell body to axon hillock to axon terminals


Retinal Horizontal Cells
-sometimes have axons, sometimes not.
-even when present, axon does not conduct spikes but actually acts to keep two end of the cell isolated from one another
-both dendrites and axons receive and send signals

Retinal Amacrine Cells:
-never have axons
sometimes the dendrites conduct action potentials
-dendrites both receive and send signals at synapses
areas of signal spread from axon terminals to dentrites

they are specialized areas of contact bw cells that can be easily recognized in the electron microscope.
Cerebral Cortex
has pyramidal cells
3 examples of polarized neurons:
pyramidal cell from cerebral cortex

purkinje cell from cerebellum

stellate cell from cerebral cortex
Glial Cell
type of schwann cell that produces myelin, sheathing the axons of peripheral neurons (around axons going from spinal cord to muscle)

in pns, shwann cell makes sheath

in cns, oligodentrocyte makes sheath
-surround neurons, seem to produce protective enviroment
-they are tiny dendrites

astrocytes: look like starts.
-have endfeet that put cells into direct contact with capillaries of circulatory system and neurons.
-thought to serve a nutritive function
Molecules of the nervous system:
-Na/K ATPase
-Ca ATPase

(both use membrane proteins and energy of terminal phosphate of ATP to move ions across membrane)

-voltage-gated channels (Na)
-ligand-gated channels (glutamate receptors)
-second-messenger gated channels
(all channels create a change in voltage responsible for cell communication)

Metaboropic (heptahelicial) receptors
Na/K ATPase pump
integral protein: alpha subunit does most of the work. Beta subunit helps the protein to fold

the affinity of the binding sites for Na and K change as enzyme is phosphorylated.

ATP phosphorylates
-puts a phosphate directly onto an amino acid on the cytoplasmic side of the protein
-drives a conformational change and changes the affinity
-change in ion affinity and change in conformation moves the ions across the membrane

E1 protein conformation has Na affinity

E2 has no Na affinity so they are dropped and move across. it has high K affinity so they bind
Driving Force
pumping of ions across the membrane produces differences in concentrations for ions

Na higher outside cell, K higher inside cell

this creates a potential for a concentration gradient because there is too much Na outside and K inside. Difference produces a voltage called the RESTING POTENTIAL.
Typical Volatage Gated Channel
K+ channel
Typical Ligand Gated Channel
acetylcholine receptor
Second Messenger Gated Channels
similar in structure to voltage gated channels
Unstimulated Resting Potential
-70 mV

opening and closing of channels produces a flow of ions into or out of cell

flow of ions makes a change in membrane potential

changes in membrane potential are responsible for communicating information from one cell to antoehr
The inside of the cell is more _______ (negative or positive) than the outside.
negative by -60 mV
Resting Membrane Potential- membrane is selectively permeable to K+
K+ ions move selectively out of the cell

causes voltage across membrane to change, inside (cytoplasm) becomes more negative

As it gets more (-), K+ stops moving out of cell. Resting pot stabalizes

it's being pushed by diffusion but pulled back by charge of cell. this is what creates the resting potential
Nernst Equation
Ek=(RT)/(zF) x ln (K+)out/(K+)in

gives the membrane potential across a membrane that is effectively permeable to a single ion type such as K+ or Na+

answer produced is the number of ions that have to move. this number is very small (it doesn't take much to change the voltage).
If the membrane were permeable to K+, the resting potential of most neurons is______
-70 mV

this is less negative than the value from the Nernst eq. because nerve cells realistically also have some permeability to Na+

the resting potential is intermediate between the value it would have if the membrane were permeable only to K+ or only to Na+ but is much close tot the value predicted for K+
negative change in membrane potential
membrane potential becomes more postive
What happens when you open the ion channel?
produced a flow of Na+ ions into the cell

increases # of + ions inside cell, produces a positive going change in membrane potential (depolarization)

(meanwhile the K+ channels are always open because those are responsible for the resting membrane potential)
Conformational Change
when you change the voltage across a membrane, proteins can change the membrane by moving.
ex. charged amino acids want to move in response to the change in voltage

some open when something binds to them (which produces the conformational change)
Gated Ion Flow
ions present at different concentrations across the membrane want to flow from one side of the membrane to another by diffusion

difference also produces a force for the ion flow.
-if inside of cell is (-), (+) ions tend to flow inward and (-) outward.

when channels open in the membrane, they provide a pathway for ion flow from one side to the other

driving force then moves ions through the channels according to the sign of the diffusive electrical gradients

flow of ions across the membrane produces a current, flow of current produce a change in membrane potential
What are the two forces that combine to produce a driving force?
diffusive and electrical

diffusion is due to random molecular motion, not direct movement through the channel.