action potentials

Question 1

depolarization

Answer 1

membrane potential becomes less negativw

Question 2

hyperpolarization

Answer 2

becomes more negative

Question 3

what does the direction of change in potential depend on

Answer 3

direction of movement of the ion - into = influx, out = efflux
charge carried by ion

Question 4

what does movement of ions across membranes requirw

Answer 4

ion channels

Question 5

what is passive movement of an ion through an ion channel dirven by

Answer 5

electrochemical gradient for that ion

Question 6

movement of na+ in response to the opening of sodium sleective channels

Answer 6

na+ flows inwardly generating an inward current

Question 7

why does the na+ produce an inward current

Answer 7

the concentration gradient is inward
electrical gradient is inward

Question 8

membrane potential of many neurones

Answer 8

-70mv

Question 9

equilibrium potential for na+

Answer 9

+60mv

Question 10

driving force for na influx

Answer 10

vm- ena

Question 11

movement of k+ in response to opening o k+ channels

Answer 11

k+ flows ourwardly generating an outward current

Question 12

why does k+ geenrate an outward current

Answer 12

conc gradient is outwards and has an energy which exceeds that of the electrical gradient which is inward

Question 13

equilibrium potential for k+

Answer 13

-90mv

Question 14

driving force for k+ efflux

Answer 14

vm - ek

Question 15

effect of opening na+/k+ channels upon membrane potential

Answer 15

membrane potential driven towards whichever channel is openign

Question 16

ion channel

Answer 16

protein complexes spanning lipid bilayer forming a central pathway that permits rapid flow of selected ions

Question 17

types of ion channels

Answer 17

voltage gated- membrane voltage
ligand gated- chemical substances
mechanical/ thermal- physical stimuli

Question 18

ion channel responsible for na+ channels

Answer 18

voltage activated na+ channels- depolarizing

Question 19

ion channel responsible for k+

Answer 19

voltage activated k+ channels - hyperpolarizing

Question 20

when are action potentials generated

Answer 20

when threshold is reached, all or none

Question 21

self reinforcing na+ channels meaning

Answer 21

the opening of a few channels causes further depolarisation; positibe feedback

Question 22

self limitting k+ channels

Answer 22

outward movement of k+ causes repolarization which turns off the stimulus for opening; negative feedback

Question 23

refractory period

Answer 23

na+ channels enter a non conducting, inactivated state during maintained depolarization

Question 24

what is repolarization required for

Answer 24

the channel to enter the closed state

Question 25

absolute refractory period

Answer 25

no stimulus, however strong, can elicit a second action potential ; all na+ channels inactivated

Question 26

relative refractory period

Answer 26

stronger than normal stimulus may eleicit a second action potential; mixed population of inactivated and closed channels, membrane is hyperpolarized

Question 27

role of dendrites

Answer 27

recieves incoming signals and passes to soma

Question 28

role of axon

Answer 28

conduct action potentials over long distances

Question 29

role of axon terminal

Answer 29

releases neurotransmitter to other cells

Question 30

strategies to increase passive current spread

Answer 30

increase axon diameter decraese leak of current across the axon; add myelin by schwann cells in PNS and ooligodendrocytes in CNS

Question 31

types of macroglia

Answer 31

schwann cells and oligodendrocytes

Question 32

saltatory conduction

Answer 32

jumping between nodes of ranvier

Question 33

what do preganglionic parasympathetic nerves agonise

Answer 33

nicotinic ach receptors of post ganglionic neuroneswha

Question 34

what do post ganglionic parasympatetic nerves agonise

Answer 34

muscarinic ach receptors

Question 35

which body fluid compartment contains largest volume of fluid

Answer 35

intracellular