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Flashcards in Neural Electrophysiology Deck (53)
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1

What are the 2 types of electrical signals from the neuron?

- propagated action potential that can travel long distances
- local grated potential that do not spread from their site of formation

2

Define propagated action potential.

can travel long distances

3

Define local grated potential.

do not spread from their site of formation

4

What is the potential difference?

- separation of charge ( negative from positive)
- measured in volts

5

In living things charges come from what?

ions separated by membranes; they can move through channels in membranes

6

Potential difference in living things is measured in____.

millivolts (mV)

7

What are the 2 types of ion channels?

- Passive (aka leakage) channels that ions move freely through
- Active (aka gated) channels that require energy

8

What are some characteristics of leakage channels?

- open randomly
- cells generally contain more K channels than Na channels

9

What are some characteristics of gated channels?

- can be open or closed (we can control them)
- there are 3 types
a. voltage-gated channels
b. ligand-gated channel
c. mechanically-gated channel

10

What are voltage gated channels?

- a gated channel that opens or closes due to voltage change

11

What are ligand-gated channels?

- gated channels that open or close based on chemical stimuli

12

What are mechanically-gated channels?

- gated channels that open by mechanical stimulation

13

What is resting membrane potential?

- potential differnce measured acroos the cell membrane of an unstimulated (resting) nerve cell
- normally -60 to -70 mV

14

What is resting membrane potential?

- result of different composition of ICF (k and protiens) compared to ECF (Na and Cl)

15

What is determined by the relative permeability of membrane to Na and P?

Membrane potential

16

What are graded potentials?

small local deviations from resting membrane potential

17

What are 2 types of graded potential?

hyperpolarized (when membrane potential becomes more negative)
depolarized ( when membrane potential becomes more positive

18

When something is hyper polarized is is more ______.

negative

19

When something is depolarized it is more_______.

positive

20

What is an action potential?

(aka nerve impulse)
- brief, transient, local period of membrane depolarization
- membrane potential changes from -70mV to +30 mV and back again

21

What are the phases of an action potential?

- depolarization
- repolarization
- hyperpolarization

22

Depolarization is when....

resting membrane potential become more positive

23

Repolarization is when....

return of depolarization membrane potential to ward resting membrane potential

24

After- Hyperpolerization is when ....

there is a movement of resting membrane potential away from 0
- eg. -70 > -85 mV
- extra potassium leaks out of the cell causing the voltage to drop to -85mV

25

What is the threshold potential?

- -55mV
- the point at which a local potential becomes a self-propagating action potential

26

What is the all or nothing phenomenon?

- if the threshold potential is exceeded, an action potential is generated
- if the threshold potential is NOT exceeded, NO action potential is generated
- all action potentials are identical

27

What is the refractory period?

time following the onset of an action potential when it is impossible or difficult to produce a second one
(NO action potential during the ABSOLUTE REFRACTORY period; at the top of the curve on the graph)

28

What are some charactersitics of sodium gates?

- voltage-gated channels have 2 gates (activation gate, and inactivation gate (when closed it will not respond to stimuli)
- In a resting neuron the inactivation gate i open and the activation gate is closed
- depolarizaton opens activation gates, then closes in activation gates

29

When the cell is resting the inside is more ____ and the outside is more_____.

- inside is more negative
- outside is more positive

30

What are the 4 stages of changes in ion flow through voltage gated channels during the depolarization, and repolarization of an action potential

1. Resting state- voltage gated Na and K channels are closed
2. Depolarization- the depolarization to threshold -55mV, opens sodium channels and sodium rushes into the cell
3. Repolarization- K channels finally open so K leaves the cell, and Na inactivation gated channels close
4. Repolarization phase continues- outflow of K restores resting membrane potential, Na channel inactivation gates reopen and K channels close(p.469)