nerve impulses

Question 1

diff between nervous system and endocrine system

Answer 1

• chemical vs electrical
• slowe vs faster
• widepread resp vs not
• last longer vs doesnt

Question 2

difference between a nerve and a neurone

Answer 2

nerve made up of lots of neurones neurone = single cell

Question 3

basic function of dendrites

Answer 3

carry impulse towrds cell body
inc sa so synapses can be made with multiple neurons

Question 4

basic function of cell body

Answer 4

controls function of cell - where proteins and neurotransmitters will be produced

Question 5

basic function of the axon

Answer 5

carry impulses away from cell body

conduct impules quicker over long dists

Question 6

function of mit in motor neurone

Answer 6

produce atp for na/k pump for maintaing resting potential

Question 7

function of myelin sheath in motor neurone

Answer 7

made of membs of schwann cells

acts as an electrical insulator to speed up conduction as impulse jumps from node to node

Question 8

function of node of ranvier in motor neurones

Answer 8

gaps with no myelination - saltatory conduction

Question 9

function of schwann cells in a motor neurome

Answer 9

surround axon to protect it and provide electrical insulation

Question 10

differences between motor, relay, sensory neirones

Answer 10

• short dends long axon, short dends both s + l axon, long dends short axon
• cell body + dends iin cns, cell bodies in cns, cell body snd dends outside cns
• synapse with other neirones in cns x2, synapse with sensory receptor cells
• axons synapse with effector cells, synapse with other nuerones, with other neorones in cns

Question 11

function of m,r,s neurones

Answer 11

m - conduct impulse to an effector
r - connect sens neors with approp mot neurons
s - conduct impulse to cns

Question 12

what is resting potential

Answer 12

• axon memb is polarised (inside is more neg charged than outside)
• is a potential diff (of around -70mv)
• brought about by na/k pump which splits atp to pump ions - three na out 2 k in – more pos ions leave than enter cell
• also na and k ions cahnnels in memb usualy shut but leak - more k than na so diff down conc grad out cell

Question 13

steps of depolarisation

Answer 13

• stimulation - energy of a stim causes some sodium voltage gated channels in axon memb to open
• na+ ions diff through open channels along electrochem grad which triggers a reversal in potential diff across memb (becomes more pos on inside - depolaristaion)
• if stim strong enough fro thresh val to be met then more na cahnnels open and is greater influx of na ions by diff for full depolariation
• voltage changes from -70mv to +40 mv

Question 14

what is the all or nothing principle

Answer 14

id thresh not reached depolarisation deosnt occur and no signal can travel along the axon

Question 15

describe repolarisation

Answer 15

• inside of axon pos charged
• na gated channels close and k channels open
• k+ ions diff out of axon along grad which reploraises memb and returns to orig resting potent of -70mv
• action potential moves along memb

Question 16

describe hypopolarisation/refactory period

Answer 16

• short period after repolarisation when both the gated channels for na and k remain shut
• means memb cant be depolarised and no impukse can pass
• allwos for each action potential to be kept discrete no overlapping and ensures action potential pass in one direction only

Question 17

what does conduction velocity depend on

Answer 17

• axon diameter - larger the faster as less leakage of ions
• myleination of nuerone - acts as electrical conduction and impulse travels from one node of ranv to the next by saltatury conduction
• no synapses involved - more = slower
• temp - higher = faster due to enz controlling na/k pump

Question 18

what is saltatory conduction

Answer 18

when action potential jumps from node to node

when action potential is pres at one node influx of na ions causes displacement of k ions down axons as like charges repel which makes next node more pos (depolarises it) until threshold reached