Lecture 3 (axon potential + channels)

Question 1

action potential (mv)

Answer 1

+30/+40mv

Question 2

resting potential (mv)

Answer 2

-70mv

Question 3

graded potential

Answer 3

proportional to the stimulation

Question 4

action potential

Answer 4

all or nothing

Question 5

temporal summation

Answer 5

stimulations across time (stimulation 2 adds to stimulation 1)
greater affect, ripple effect

Question 6

spatial summation

Answer 6

stimulation across space (multiple stimulations at the same time)
creates larger ISPS or EPSP

Question 7

types of summation

Answer 7

spatial (across space) and temporal (across time)

Question 8

where to graded potentials integrate?

Answer 8

at the axon hillock

Question 9

process of voltage gated Na+ channel (action potential)

Answer 9

1.) voltage gated ion channel opens (Na+ floods in)
2.) Strong depolarization (+40mv = EPSP)
3.) Gated ion channel closes
4.) Sodium potassium pump (3Na+ out, 2K+in) restore equilibrium
5.) absolute refractory (no firing)
6.) relative refractory (firing, but greater than usual stimulation -90mv)
7.) restore equilibrium (-70mv)

Question 10

EPSP

Answer 10

Excitatory post-synaptic potential

Question 11

IPSP

Answer 11

Inhibitory post-synaptic potential

Question 12

factors that affect axon potentials

Answer 12

1.) threshold differences

2.) action potentials differ in shape

3.) rate of action potential discharge for the same amount of depolarization

4.) hebbian synapses

5.) temperature, time of day ect.

Question 13

resting potential (balanced by:)

Answer 13

concentration gradient and the electrostatic gradient

Question 14

concentration gradient

Answer 14

molecules diffuse from high to low pressure

osmotic pressure

K+ ions diffuse out of cell (can get back in through pump)
Other ions cannot get in as easily (selective permeability)

Question 15

electrostatic gradient

Answer 15

different concentrations of electrical charges

K+ attracted to negative intracellular charge. CL- ions repelled by intracellular charge

Question 16

nernst equation

Answer 16

equation for cell equilibrium
(only perfect but not quite)
leakage of K+ out, and Na+ comes into the cell

Question 17

resting potential (how and at what mv?)

Answer 17

when the flow of K+ ions leaving the cell = flow of K+ ions coming in

through sodium potassium pump (3Na+ out, 2K+ in). Build up K+ in the cell. so K+ diffuse out. leads to negative charge, so K+ come back in.

-70mv

Question 18

Excitatory synapse (what gated ion channels open?)

Answer 18

Na+ opens
K+ closes

Question 19

Inhibitory synapses (what gated channels open?)

Answer 19

K+
Cl-

Question 20

ways of opening gated ion channels (4 ways:)

Answer 20

1.) Chemical change in shape (ligand binds to a receptor) causing channel to open

2.) Gene-couple protein receptors (GPCR)
Second messenger action

3.) voltage change

4.) mechanical deformation (such as by touching things with your hands)

Question 21

how do axons get over the “distance problem”?

Answer 21

Saltatory conduction (speeds up action potential!)
Regenerative potential

Question 22

Saltatory conduction (steps)

Answer 22

Beads of myelin on the axon

Na+ channel opens on the nodes of Ranvier (depolarization)

action potential jumps from node to node

Question 23

disease that affects saltatory conduction

Answer 23

multiple sclerosis
(Immune system generates antibodies that attack myelin)

** affects coordination and interpretation of sensory input

Question 24

steps of action potential moving through pre-synaptic neuron:

Answer 24

1.) axon potential arrives at axon terminal
2.) depolarization causes Ca2+ gated ion channel to open
3.) Ca2+ vesicles fuse to the pre-synaptic membrane and rupture –releasing neurotransmitter into the cleft
4.) Crosses the cleft and binds to the post-synaptic membrane (specialized ligands)
5.) changes the excitatory level of the post-synaptic cell (may causes ISPS or EPSP)

Question 25

mechanisms built into synapse that allow neurons to fire again: (2)

Answer 25

1.) Degration = enzymes that split and breakdown neurotransmitter

2.) Reuptake = neurotransmitter is reabsorb back into the axon terminal via transporters on the pre-synaptic neuron

Question 26

Reuptake

Answer 26

neurotransmitter is reabsorb back into the axon terminal via transporters on the pre-synaptic neuron

Question 27

Degradation

Answer 27

enzymes that split and breakdown neurotransmitter

Question 28

Types of receptors: (two)

Answer 28

1.) Ligand Gated Ion Channel (Ionotropic)
*ligand bind to a receptor which causes the neuron shape to change (open gate/close gate)

2.) Metabotropic
G-CPR

*bind to a G protein out side of the cell, actives a second messenger inside the cell

Question 29

Ligand Gated Ion Channel (Ionotropic)

Answer 29

ligand binds to a receptor

pore opens, ions flow through

causes change in membrane potential

Question 30

metabotropic receptors

Answer 30

gene-couple protein receptors

ligand binds to gene-protein which actives second messenger inside the neuron

bigger changes:
*change in membrane charge
*alter energy use
* alter gene transcription
*slower, more amplified reactions (can open multiple pores at once)

Question 31

Gap junction

Answer 31

Electrical synapse

*no modulation
* fast
*connexons
*restricted to local processing

• thought to be involved with epilepsy