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Flashcards in Neuronal Electrophysiology Deck (21)
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1

What is the difference between the action potentials of cardiac muscle compared to that of skeletal and smooth muscle?

Cardiac action potentials are much longer due to the delayed relaying of the AV node.

2

What does higher membrane resistance result in?

Higher membrane resistance will keep ions within the cell more and allow them to travel further down the neuron cell. It will increase the Space Constant.

3

What does higher internal resistance result in?

High internal resistance will prevent the spread of the action potential within the cell and it will reduce the Space Constant as a result.

4

What is the space constant?

Space constant is the distance where the signal decays to 37% of the original and it determines the speed of conduction.

5

What inactivates Na channels in the action potentials of neurons?

Na channels are deactivated by depolarization.

6

What Na channel gates are open at resting potential?

m activation gate is closed
h inactivation gate is open

7

What Na channel gates are open at activation?

m activation gate is open
h inactivation gate is open

8

What Na channel gates are open at inactivation?

m activation gate is open
h inactivation gate is closed

9

As the resting membrane potential increases what happens to Na channel availability?

Less Na channels are available as the RMP increases as it becomes more and more depolarized.

10

What is the absolute refractory period?

The time where stimulus is unable to generate another action potential

11

What is the relative refractory period?

The time where the neuron has not fully recovered but it can generate an action potential. The stimulus must be stronger than normal though.

12

How does myelination affect conduction? And the space constant?

Myelination rapidly increase the rate of conduction by increasing the membrane resistance, which in turn, increases the space constant.

13

How does extracellular hypercalcemia affect membrane excitability?

Decreases membrane excitability by raising the threshold for Na channel activation.

14

How does extracellular hypocalcemia affect membrane excitability?

Increases membrane excitability by lowering the threshold for Na channel activation.

15

How does hyperventilation affect membrane excitability?

Blows off CO2 which increases the pH and lowers the amount of Ca in the plasma -> increases membrane excitability

16

How does hypoventilation affect membrane excitability?

Retains excess COS which decreases the pH and increases the amount of Ca in the plasma -> decreases the membrane excitability

17

What is the effect of elevated K on membrane excitability?

Increased extracellular K will increase the resting membrane potential which will deactivate Na channels leading to slower conduction.

Increasing the RMP will make it easier to reach threshold for action potentials though.

18

What is the purpose of the long cardiac action potential?

It protects the heart from aberrant electrical activity.

19

How does Ca2+ modulate Na+ channel activity?

The proteins on the extracellular membrane are negative and calcium binds to them. This causes the h inactivation gate to close as it thinks the membrane is depolarized due to the +2 charge of Ca.

20

Where are the Na channels found on the axons?

Only on the nodes of Ranvier

21

How does myelination increase membrane resistance?

The myelin covers up the K+ channels to reduce leakage and thus the membrane resistance increases as a result.

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