Channels and Action Potentials

Question 1

Structure of cell membrane

Question 2

Role of proteins in cell membrane

Question 3

Types of gating

Question 4

Chemically gated channels

Question 5

Mechanically gated channels

Question 6

Voltage gated channels

Question 7

Function of semi-permeable membrane

Question 8

How do ions move across a semi-permeable membrane in response to a concentration gradient and an electric field?

Question 9

Nernst Equation (given)

Answer 9

How to use it:
When to use it:

Question 10

Na+ levels in intra/extra cellular regions of neurons

Answer 10

High:
Low:

Question 11

Cl- levels in intra/extra cellular regions of neurons

Question 12

K+ levels in intra/extra cellular regions of neurons

Question 13

Why aren’t all ions at Nernst equilibrium in a typical cell?

Question 14

Goldman’s Equation (given)

Answer 14

How to use, when to use instead

Question 15

Ions only affect the membrane potential if

Answer 15

the membrane in permeable to those ions

Question 16

If membrane is permeable only one ion

Answer 16

Membrane potential will be Nernst potential for that ion

Question 17

If membrane is highly permeable to one ion and not the others

Answer 17

Membrane potential will be near Nernst potential for that ion

Question 18

If a membrane is permeable to more than one ion

Answer 18

resting potential will be approximated as the average of the Nernst potentials for all permeable ions

Question 19

How many ions move to create a membrane potential?

Answer 19

A small number of ions move to create a membrane potential; intracellular and extracellular solutions remain effectively charge neutral and concentrations aren’t effectively changed by an action potential

Question 20

How to find refraction threshold

Question 21

How to find summation threshold

Question 22

how to find absolute refractory period

Question 23

how to find relative refractory period

Question 24

Depolarization

Question 25

Repolarization

Question 26

Hyperpolarization

Question 27

Is the threshold of a neuron always the transmembrane potential?

Answer 27

No, charge across membrane

Question 28

How does a neurotransmitter excite the cell?

Answer 28

quantal packs that result in membrane voltage change (exhibitory or inhibitory). Graded potentials can sum spatially or temporally. neurotransmitter excitation is unidirectional

Question 29

How does an electrical stimulus excite the cell

Question 30

Steps of the AP (overview)

Question 31

Membrane at rest

Question 32

Depolarizing stimulus

Answer 32

Usually a neurotransmitter, will create a graded potential that exceeds the threshold

Question 33

Na+ channels open, Na+ enters the cell

Answer 33

This causes Na+ permeability to increase and these are () gated channels

Question 34

Na+ entry causes cell to...

Answer 34

Depolarize

Question 35

Approaches Na+ Nernst potential

Question 36

K+ channels begin to open

Answer 36

This process is slow and increases K+ permeability

Question 37

Na+ channels close, K+ channels open

Answer 37

Na+ permeability decreases, K+ permeability increases, K+ channels are slower

Question 38

K+ moves out of cell, causes cell to...

Answer 38

Potentially hyperpolarize

Question 38

K+ channels close

Question 38

Cell returns to rest

Answer 38

Returns to resting ion permeability and resting membrane potential approaches K+ Nernst potential

Question 38

Activation gate in Na+ Channel

Answer 38

Role: What makes them open/close:

Question 39

How does gate behavior create refractoriness

Question 39

Inactivation gates in Na+ channel

Answer 39

Role: What makes them open/close:

Question 39

K+ activation gates

Answer 39

What makes them close:

Question 40

Why aren't K+ inactivation gates needed?

Question 41

Predicting behavior of a cell with ions concentrations and membrane permeabilities

Question 42

Differences between action potentials and graded potentials

Question 43

Action potential propagation down a neuron

Answer 43

* Na+ enters cell * Positive ions accumulate and repel from each other down the membrane * Positive ions inside membrane attract negative ions on opposite side and repel positive ions on opposite side through membrane capacitance --> causes depolarization * If depolarization is large enough, Na+ channels open * Cycle repeats

Question 44

How and why are excitation thresholds and propagation velocity related to axon diameter?

Question 45

Function of myelin

Question 46

Refractory behavior as related to activation and inactivation gates resetting

Question 47

Describe absolute and relative refractory behavior of cells

Question 48

Identify: cell body

Question 49

Identify: dendrites

Question 50

Identify: axon

Question 51

Identify: synapse

Question 52

Identify: myelin

Question 53

RC nature of membrane and summation of stimuli

Question 54

Difference between afferent and efferent neurons

Question 55

Reducing noise in a neural recording

Question 56

How do differential recordings of neural action potentials work

Question 57

Techniques and concepts from earthworm lab