Module 5.3

Question 1

what are sensory receptors

Answer 1

specialised cells that can detect changes in our surroundings
most are energy transducers

Question 2

what is a transducer

Answer 2

converts one form of energy into another

Question 3

what is a pacinian corpuscle

Answer 3

pressure sensor that detects changes in pressure on the skin

Question 4

structure of a pacinian corpuscle

Answer 4

series on concentric rings of connective tissue wrapped around the end of a nerve

Question 5

How does a pacinian corpuscle work

Answer 5

when pressure on the skin changes the connective tissue rings deform which pushes against the nerve ending

Question 6

function of a sensory neurone

Answer 6

carry the action potential from a sensory receptor to the CNS

Question 7

function of a motor neurone

Answer 7

carry an action potential from the CNS to an effector such as a muscle or gland

Question 8

structure of a relay neurone

Answer 8

dendrites
cell body
axon
synaptic endings

Question 8

function of a relay neurone

Answer 8

connect sensory and motor neurones

Question 8

structure of a motor neurone

Answer 8

dendrites
cell body
axon
axon terminals

Question 9

structure of a sensory neurone

Answer 9

sensory receptor
dendron
cell body
axon
synaptic ending (in the CNS)

Question 10

difference between types of neurone

Answer 10

motor neurones have their cell body in the CNS and have a long axon
sensory neurones have a long dendron which goes to the cell body just outside the CNS then a short axon going into the CNS
relay neurones have many short dendrites and a short axon

Question 11

what makes neurones myelinated

Answer 11

schwann cells wrap around the neurone forming a fatty sheath

Question 12

function of myelinated neurones

Answer 12

most sensory and motor neurones associated with schwann cells
prevent the movement of ions across the membrane so it can only occur at the nodes of ranvier
impulse jumps from one node to the next which is faster

Question 13

function of non-myelinated neurones

Answer 13

also associated with schwann cells but one schwann cell wrap around several neurones
impulse moves along the neurone in a wave which is slower

Question 14

advantages of myelination

Answer 14

quicker transmission
100-120 m/s vs 2-20 m/s
carry action potentials over longer distances
carry impulse from receptor to CNS and from CN to effector
non-myelinated often used in coordinating body functions where speed is not needed

Question 15

what is the resting potential voltage

Answer 15

60-70 mv

Question 16

what do sodium potassium pumps do at rest

Answer 16

pump 3 sodium ions out for every 2 potassium ions that are pumped in

Question 17

what do voltage-gated sodium channels do at rest

Answer 17

they are closed

Question 18

what do potassium channels do at rest

Answer 18

some are open so membrane is more permeable to potassium than sodium

Question 19

What is a node of ranvier

Answer 19

areas of the neurone between schwann cells where ions can diffuse across the membrane

Question 20

how is an action potential started

Answer 20

generator potential from synapse or stimulus in the generator region of a neurone

Question 21

what happens to the voltage gated-sodium channels when generating an action potential

Answer 21

a few open allowing sodium ions into the cell
produces a small depolarisation
sodium ions diffuse causing other voltage gated channels to open

Question 22

What voltage is an action potential

Answer 22

+40mV

Question 23

what voltage is the threshold potential

Answer 23

-50 mv

Question 24

what happens after an action potential

Answer 24

sodium channels close potassium channels open

Question 25

What is repolarisation

Answer 25

potassium ions diffuse out of the cell making the cell negative again

Question 26

What is hyperpolarisation

Answer 26

potential difference overshoots slightly to over the resting potential ensure the action potential does not flow backwards

Question 27

What is the refractory period

Answer 27

after an action potential the sodium and potassium ions are in the wrong place it is impossible to stimulate the neurone into another action potential for a short time until cell is restored by odium potassium pumps also stops action potential travelling wrong way

Question 28

what are local currents

Answer 28

when sodium ions are allowed to flood into the neurone causing depolarisation sodium ions move down concentration gradient to other regions

Question 29

propagation of action potential in unmyelinated neurones

Answer 29

local currents movement of sodium ions away from point in membrane causing other sodium channels to open allowing for more sodium ions to enter which depolarising the surrounding membrane causing more opening of sodium channels etc

Question 30

propagation of action potential in myelinated neurones

Answer 30

saltatory conduction ionic movement only occurs at the nodes of ranvier sodium ions diffuse from one node to another the action potential jumps

Question 31

advantages of saltatory conduction

Answer 31

speed of transmission is increased

Question 32

what is the intensity of all action potentials

Answer 32

+40mv

Question 33

how is intensity of a stimulus conveyed

Answer 33

higher frequency of action potentials

Question 34

what is the pre-synaptic bulb

Answer 34

the end of a presynaptic neurone before the synapse

Question 35

What are the specialised features of the pre-synaptic bulb

Answer 35

many mitochondria for ATP large amount of smooth ER for packaging NTs in vesicles Large number of vesicles Large number of voltage gated calcium channels on the plasma membrane

Question 36

specialisations of the post-synaptic membrane

Answer 36

specialised sodium ion channels that can respond to acetylcholine channels have specific receptor site for NT

Question 37

What happens in the presynaptic bulb to transmit a signal

Answer 37

action potential opens voltage gated calcium channels calcium ions diffuse into synaptic bulb calcium ions cause vesicles to move to and fuse with the presynaptic membrane Acetylcholine is release through exocytosis

Question 38

What happens on the post synaptic membrane to transmit a signal

Answer 38

acetylcholine binds with receptor sites on sodium ion channels sodium ion channels open sodium ion channels diffuse into post synaptic neurone generator potential/excitatory post-synaptic potential is created if threshold potential is reached new action potential is created

Question 39

what does acetylcholinesterase do

Answer 39

hydrolyses acetylcholine into ethanoic acid and choline so acetylcholine left in the cleft is not constantly opening sodium channels on post synaptic membrane products are recycled

Question 40

What is an excitatory post synaptic potential

Answer 40

makes the neurone more likely to continue the action potential depolarises membrane alone is not sufficient to produce an action potential in a post synaptic neurone

Question 41

what is summation

Answer 41

when several excitatory post synaptic potentials combine together to increase the membrane depolarisation to reach the threshold

Question 42

What is temporal summation

Answer 42

when summation results from several action potentials in the same presynaptic neurone

Question 43

what is spatial summation

Answer 43

when summation results from actions potentials arriving from several different presynaptic neurones

Question 44

What is an inhibitory post synaptic potential

Answer 44

reduce the chance of an action potential in the post synaptic neurone reduce the effect of summation