The Excitable Cell

Question 1

How are APs coded

Answer 1

frequency

Question 2

Describe generation of an AP

Answer 2

all or nothing

Question 3

Describe an AP

Answer 3

unit of size - fixed

Question 4

What is the function of APs

Answer 4

travel along axons, in one direction

Question 5

How are graded potentials coded

Answer 5

size

Question 6

Describe graded potenitals

Answer 6

local signals that travel short distances, variable size

Question 7

Which direction do graded potentials pass

Answer 7

can travel both ways

Question 8

TRUE or FALSE - strength of stimulus affects strength of potential

Answer 8

True

Question 9

What is the resting potential

Answer 9

when no potentials are produced

Question 10

Describe the resting potential

Answer 10

negative - unequal distribution of charged molecules

Question 11

What is charge of the resting membrane potential

Answer 11

-70mv ish

Question 12

What physical forces control ion movements in solution

Answer 12

diffusion, electrical fields, ion movement

Question 13

What does the nernst equation calculate

Answer 13

equilibrium potential for an ion

Question 14

What channel is a key determinant of the resting potential

Answer 14

potassium channel

Question 15

Why is the resting potential so important

Answer 15

required for functioning nervous system

Question 16

What do ion pumps in membrane set up

Answer 16

ionic concentration gradient

Question 17

Describe the effect of high intracellular Ca in neurons

Answer 17

toxic

Question 18

Does calcium move in or out of neurons

Answer 18

out

Question 19

What does the Goldman equation calculate

Answer 19

resting potential

Question 20

What are the phases of an action potential

Answer 20

rising phase, overshoot, falling phase, undershoot

Question 21

What are the majority of action potentials mediated by

Answer 21

changes in permeability for sodium

Question 22

What are some action potentials mediated by

Answer 22

changes in permeability for calcium

Question 23

When are APs mediated by changes in permeability for calcium important

Answer 23

developing nervous system

Question 24

TRUE or FALSE - action potential propagation decreases along the axon

Answer 24

FALSE

Question 25

When are all sodium channels closed

Answer 25

resting state

Question 26

When do some of the sodium channels open

Answer 26

when membrane potential rises to -50mV

Question 27

Describe permeability changes of the membrane at -50mV

Answer 27

permeability for sodium increases, permeability for potassium decreases

Question 28

What does an influx of sodium cause

Answer 28

membrane depolarisation

Question 29

What happens when sodium channels close

Answer 29

repolarisation

Question 30

Describe permeability changes during repolarisation

Answer 30

permeability for potassium ions increase

Question 31

When are most of the potassium channels open

Answer 31

resting state

Question 32

describe the structure of voltage-gated sodium channels

Answer 32

complex proteins with 4 subunits

Question 33

Describe domain 4 of voltage gated sodium channels

Answer 33

special domain - positively charged AAs

Question 34

What is the function of domain 4 of voltage gated sodium channels

Answer 34

sense change in voltage

Question 35

Name some poisons affecting the excitable cell

Answer 35

Tetraethlyammonium, lidocaine, tetrodotoxin

Question 36

What is the effect of tetraethlyammonium on cells

Answer 36

blocks potassium channels

Question 37

What is the effect of lidocaine on cells

Answer 37

blocks Na+ channels - local anaesthietic

Question 38

What is the effect of tetrodotoxin on cells

Answer 38

blocks sodium channels

Question 39

Describe the rising phase of an action potential

Answer 39

rapid depolarisation

Question 40

What causes the rising phase of an action potential

Answer 40

influx of Na+ into neuron

Question 41

What happens during the falling phase of an action potential

Answer 41

voltage gated Na+ channels close, voltage gated K+ channels open

Question 42

What moves out of the neuron during the rising phase

Answer 42

K+

Question 43

How come an action potential only moves in one direction

Answer 43

sodium channels on one side are inactive

Question 44

What factors influence conduction velocity

Answer 44

myelination, diameter, permeability

Question 45

What does myelination act to increase

Answer 45

membrane resistance, space constant

Question 46

What is a disadvantage of myelination

Answer 46

high metabolic and volume cost

Question 47

What process do the nodes of ranvier induce

Answer 47

saltatory conduction

Question 48

When is myelination mainly used

Answer 48

long distances

Question 49

What does the space constant define

Answer 49

membrane potential decay

Question 50

Where are axon potentials generally generated?

Answer 50

axon hillock

Question 51

What type of potential do dendrites have?

Answer 51

graded potentials

Question 52

What does continuous stimulation of a neuron produce?

Answer 52

train of action potentials

Question 53

What is stimulus potential encoded by ?

Answer 53

action potential frequency

Question 54

What is a EPSP

Answer 54

excitatory post synaptic potential

Question 55

What is the effect of an EPSP

Answer 55

depolarises the membrane

Question 56

What is an IPSP

Answer 56

inhibitory post synaptic potential

Question 57

what is the effect of an IPSP

Answer 57

hyper polarises the membrane

Question 58

What is an IPSP a result of

Answer 58

activation of inhibitory receptors

Question 59

What are ionotropic receptors permeable for

Answer 59

chloride

Question 60

What are metabotropic receptors

Answer 60

GPCRs

Question 61

What are ionotropic receptors

Answer 61

ligand gated ion channels

Question 62

Which receptor is faster working - ionotropic or metabotropic

Answer 62

ionotropic

Question 63

TRUE or FALSE - Graded potentials can summate

Answer 63

TRUE