Overall Review

Question 1

Movement of an ion across a plasma membrane is determined by…

Answer 1

Concentration Gradient of Ion
Voltage Difference
Conductance of the ion channels

Question 2

Define Input resistance of a cell

Answer 2

Relationship between current injected and change in membrane potential

(Change in V)/I

Question 3

Define Length Constant (w/out equations)

Answer 3

Physical length of axon it take for a voltage to drop by 37%

Question 4

Define Time Constant (w/out equations)

Answer 4

Length of time required for the voltage to drop to 37% of Vo

Question 5

List five characteristics of an AP

Answer 5

Triggered by Depolarization
All or Nothing
Propagates/Is Maintained
Undershoot and Overshoot
Has an absolute refractory

Question 6

Identify three experimental findings that indicate that Na is the inward flow.

Answer 6

Extracellular Na Removal
tetrodotoxin
Nearnst (voltage clamp at 55)

Question 7

Sodium channel – describe the 3 states

Answer 7

Open – Inactivation gate is open intracellularly, voltage gate open
Closed – Inactivation gate is open, but voltage gate blocks the opening of the channel
Inactivated – Voltage Gate Open, but Inactivation gate is closed

Question 8

Why is depolarization resulting in Na influx considered regenerative?

Answer 8

Depolarization opens Na channels, increasing Na conductance. More Na into the cell further depolarizes it.

Question 9

Describe excitable membrane repolarization following depolrization.

Answer 9

Opened/Inactivated Na channels + Activated K channels
gK ends up greater than in resting state fr a brief hyperpolarization period
Na/K pump returns resting potential

Question 10

How does myelin speed axonal conduction?

Answer 10

• Prevents current leakage

- Say something about saltatory conduction

Question 11

Difference between spatial and temporal integration?

Answer 11

Spatial = summation of APs from different locations

Temporal - summation of APs that occur in the same location at different times

Question 12

What is the driving force for movement of an ion across the membrane?

Answer 12

Emem-Eion

Question 13

Describe the fate of acetylcholine in the synapse.

Answer 13

Broken down by acetylcholinesterase
Choline taken back into cell by Na/Choline transport system
Regeneration by acetyltransferase

Question 14

Describe the fate of synaptic glutamate

Answer 14

Taken in by glial cells
Converted to glutamine
Released and taken up by neuron
reconverted

Question 15

Describe the cross bridge cycle

Answer 15

Normal – Myosin unbound, ATP binds
ATP hydrolysis causes myosin head to bend, binds to actin
Release of ADP+P caused the myosin head to revent back to normal position
ATP binding causes release from binding site

Question 16

How does Ca allow myosin to bind to actin?

Answer 16

Ca binds to troponin
Tropomyosin is moved
Myosin can bind actin at myosin binding sites

In smooth muscle, Ca binds calmodulin, activated MLCK, and activates myoin

Question 17

How does the sarcoplasmic reticulum and transverse tubule system function in regulation of contraction in striated muscle?

Answer 17

Dep. of T Tubule opens its Ca channel through a conformational change.

Voltage gated, then calcium gated calcium channel
Moves troponin out of the way

Question 18

What is the size principle and how does it work?

Answer 18

The body will progress from slow, to fatigue resistant, to fast fatigue fibers.
It allows the cell to focus on the amount of current it needs to put out?
Less current is needed to activate S, so increasing levels of current will continuously add in larger fibers.