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Biology > Module 5.3 > Flashcards

Module 5.3 Flashcards

Neuronal communication

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1
Q

what are sensory receptors

A

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

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2
Q

what is a transducer

A

converts one form of energy into another

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3
Q

what is a pacinian corpuscle

A

pressure sensor that detects changes in pressure on the skin

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4
Q

structure of a pacinian corpuscle

A

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

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5
Q

How does a pacinian corpuscle work

A

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

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6
Q

function of a sensory neurone

A

carry the action potential from a sensory receptor to the CNS

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7
Q

function of a motor neurone

A

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

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8
Q

structure of a relay neurone

A

dendrites
cell body
axon
synaptic endings

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8
Q

function of a relay neurone

A

connect sensory and motor neurones

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8
Q

structure of a motor neurone

A

dendrites
cell body
axon
axon terminals

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9
Q

structure of a sensory neurone

A

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

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10
Q

difference between types of neurone

A

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

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11
Q

what makes neurones myelinated

A

schwann cells wrap around the neurone forming a fatty sheath

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12
Q

function of myelinated neurones

A

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

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13
Q

function of non-myelinated neurones

A

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

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14
Q

advantages of myelination

A

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

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15
Q

what is the resting potential voltage

A

60-70 mv

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16
Q

what do sodium potassium pumps do at rest

A

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

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17
Q

what do voltage-gated sodium channels do at rest

A

they are closed

18
Q

what do potassium channels do at rest

A

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

19
Q

What is a node of ranvier

A

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

20
Q

how is an action potential started

A

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

21
Q

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

A

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

22
Q

What voltage is an action potential

A

+40mV

23
Q

what voltage is the threshold potential

A

-50 mv

24
Q

what happens after an action potential

A

sodium channels close
potassium channels open

25
Q

What is repolarisation

A

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

26
Q

What is hyperpolarisation

A

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

27
Q

What is the refractory period

A

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

28
Q

what are local currents

A

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

29
Q

propagation of action potential in unmyelinated neurones

A

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

30
Q

propagation of action potential in myelinated neurones

A

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

31
Q

advantages of saltatory conduction

A

speed of transmission is increased

32
Q

what is the intensity of all action potentials

A

+40mv

33
Q

how is intensity of a stimulus conveyed

A

higher frequency of action potentials

34
Q

what is the pre-synaptic bulb

A

the end of a presynaptic neurone before the synapse

35
Q

What are the specialised features of the pre-synaptic bulb

A

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

36
Q

specialisations of the post-synaptic membrane

A

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

37
Q

What happens in the presynaptic bulb to transmit a signal

A

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

38
Q

What happens on the post synaptic membrane to transmit a signal

A

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

39
Q

what does acetylcholinesterase do

A

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

40
Q

What is an excitatory post synaptic potential

A

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

41
Q

what is summation

A

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

42
Q

What is temporal summation

A

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

43
Q

what is spatial summation

A

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

44
Q

What is an inhibitory post synaptic potential

A

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

Biology (18 decks)

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