Action potential L8

Question 1

action potential=

Answer 1

rapid change in electrical potential across the plasma membrane of a cell.

Question 2

Cells that generate action potentials (3)

Answer 2

neurons (nerve cells)
Muscle fibres (muscle cells)
Endocrine cells

Question 3

Action potential in neurons

Answer 3

initiates cell to cell communication

Question 4

action potential in muscle

Answer 4

initiates steps leading to muscle contraction

Question 5

Action potential in endocrine

Answer 5

initiates hormone release

Question 6

Graded response=

Answer 6

the response is proportional to the amount of excitation it receives.

Question 7

What is the space between cell body and axon called

Answer 7

axon hillock

Question 8

Where does an action potential first arrive

Answer 8

dendrites

Question 9

How do action potentials pass from the dendrites to soma

Answer 9

passively (graded response)

Question 10

What happens to negative and positive electronic potentials in the soma

Answer 10

they are integrated (summed)

Question 11

Sum of action potentials reaches the _____

Answer 11

axon hillock

Question 12

What response ensues at the axon hillock

Answer 12

all or nothing action potential

Question 13

What need to happen for an action potential at the hillock;

Answer 13

net electric potential> threshold

Question 14

What is a non-decremental spread

Answer 14

all or non response

Question 15

membrane potential=

Answer 15

the difference in electrical potential between inferior and exterior of a cell.

Question 16

What is a membrane potential measured in

Answer 16

volts or millivolts

Question 17

Stages of an action potential

Answer 17

stimulus 
depolarisation 
action potential 
repolarisation 
refractory period
resting state

Question 18

What is the normal resting membrane potential

Answer 18

-70 mv

Question 19

The charge of the inside of a neuron is

Answer 19

negative

Question 20

The charge of the outside of a neuron=

Answer 20

positive

Question 21

main ions involved in neurons action potential

Answer 21

sodium (Na+)

potassium (K+)

Question 22

The extracellular fluid contains lots (2)

Answer 22

sodium ions and chloride

Question 23

The inside of the cell contains (3)

Answer 23

negative proteins
phosphate ions
potassium ions

Question 24

leak ion channels are

Answer 24

always open, continually leak specific ions across membrane

Question 25

voltage-gated ion channels=

Answer 25

open or close in response to voltage change

Question 26

ligand gated ion channels=

Answer 26

open or close in response to chemical or drug

Question 27

Na+/ K+ pump is powered by

Answer 27

active transport (needs ATP)

Question 28

Na+/K+ ratio

Answer 28

pumps 3 Na+ out for every 2 K+ in

Question 29

Three main factors that set up the resting membrane potential

Answer 29

1. low protein permeability ( negative proteins can't leave) 2. Na+/K+ pump 3. High K+ permeability (moves freely through leak channels)

Question 30

More Na+ is

Answer 30

extracellular

Question 31

Equilibrium potential=

Answer 31

voltage at which ion's net flow across membrane is 0

Question 32

Equation that can predict a single ions equilibrium potential

Answer 32

nernst equation

Question 33

equilibrium potential for K+

Answer 33

-80mV

Question 34

Equilibrium potential for Na+

Answer 34

+61mV

Question 35

2 main things nernst equation considers

Answer 35

valence (charge) | Concentration gradient

Question 36

What equation can measure the resting membrane potential

Answer 36

goldmans equation

Question 37

Why is the resting membrane potential close to equilibrium potential of K

Answer 37

Because neurons are highly permeable to K+

Question 38

explain resting state of AP

Answer 38

-70mV all voltage-gated Na+ and K+ channels closed Only leak channels open

Question 39

Explain depolarisation (AP)

Answer 39

``` -55mV voltage sensitive (fast activation) gates of Na+ channels open----> sodium rushes into cells making it more positive ```

Question 40

What is threshold potential

Answer 40

-55mV

Question 41

explain repolarisation (AP)

Answer 41

+40mV | Voltage sensitive K+ channels open---> potassium rushes out of cell making the inside of the cell more negative again

Question 42

Explain after hyperpolarisation

Answer 42

-80mV | voltage sensitive K+ channels stay open and Na+ fast activation gates close

Question 43

below threshold what determines the action potential

Answer 43

magnitude of graded response

Question 44

Above threshold what determines the response

Answer 44

Frequency of action potentials (strong stimulus--> rapidly fire)

Question 45

What ensues one-way propagation of the action potential

Answer 45

refractory period (previous Na+ channels are inactivated)

Question 46

What happens on a myelinated axon

Answer 46

saltatory conduction

Question 47

2 things axon conduction velocity depends on

Answer 47

axon diameter | myelination

Question 48

unmyelinated axons are better for

Answer 48

smaller axons

Question 49

Myelinated axons are needed for

Answer 49

larger diameter axons

Question 50

In myelinated axons velocity ;

Answer 50

linear with diameter

Question 51

(3) myelinated axons

Answer 51

A alpha A beta A delta

Question 52

unmyelinated axon=

Answer 52

C fibres

Question 53

What does Tetrodotoxin do

Answer 53

Na+ channels blocker

Question 54

What is multiple sclerosis

Answer 54

T-cells attack myelin sheaths causing inflammation

Question 55

What does local anaesthetic do

Answer 55

reversibly block voltage-gated sodium channels