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module 5 > 5.3 neural communication > Flashcards

5.3 neural communication Flashcards

1
Q

define sensory receptors

A

specialised cells that can detect changes/ of internal or external environments and can create an action potential

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2
Q

define transducer

A

a cell that converts one form of energy into another

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3
Q

what type of signal is created in the form of electrical energy

A

nerve impulse

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4
Q

define pacinian corpuscles

A

a pressure sensor that detects changes in pressure on the skin

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5
Q

what do photoreceptors(cones/rods) detect and where

A

changes to light intensity
retina

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6
Q

what do audio receptors detect and where

A

changes to sound/ vibrations
ear/cochlea

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7
Q

what does the pacinian corpuscle detect and where

A

changes to pressure
skin

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8
Q

what do oflactory cells detect and where

A

chemicals in the air
nose

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9
Q

what do chemoreceptors detect

A

changes to chemicals in food/air etc.

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10
Q

describe the structure of a pacinian corpuscle

A

oval shaped
series of concentric rings of connective tissue
around the end of a nerve cell

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11
Q

what happens when pressure on the skin changes

A

pacinian corpuscle rings of connective tissue deforms which pushes against nerve ending

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12
Q

how are nerve impulses generated

A

when pressure changes/ PC deforms = sodium channels are forced open
sodium cells diffuse into the cell
generator potential produced
Na+/K- pump in the membrane pumps 3 sodium out for every 2 potassium in
creates concentration gradient conc. of sodium outside increasing
conc. K inside increasing
membrane is more permeable to K- so some leak out
result of these ionic movements is a potential gradient across the cell membranes
cell is negatively charged

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13
Q

what is depolarisation

A

movement of ions across the membrane creates a change in the potential difference/ charge across the membrane
the inside of the cell becomes less negative compared to outside than usual

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14
Q

what causes an action potential to be initiated

A

larger stimulus so more gated channels will open
if enough are open then enough sodium ions enter the cell
potential difference changes significantly and will initiate an AP

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15
Q

what is a myelinated neurone

A

has an individual layer of myelin around it

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16
Q

what is the myelin sheath composed of

A

schwann cells

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17
Q

what are nodes of ranvier

A

gaps in the myelin sheath

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18
Q

what is a non-myelinated neurone

A

has no individual layer of myelin

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19
Q

what does a myelin sheath do

A

insulates myelinated neurones

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20
Q

function of sensory neurone

A

carries an impulse from receptor to CNS

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21
Q

structure of a sensory neurone

A

a long dendron
carry action potential from a sensory receptor to cell body
short axon carrying action potential into the CNS

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22
Q

function of a relay neurone

A

carries impulse from sensory neurone to motor neurone

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23
Q

structure of a relay neurone

A

connects sensory to motor neurone
many short dendrites and a short axon

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24
Q

function of a motor neurone

A

transmits impulse to the effector

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25
Q

structure of a motor neurones

A

cell body in the CNS
long axon that carries the action potential to effector

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26
Q

structure of a cell body

A

nucleus
many ER, mitochondria and ribosomes

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27
Q

structure and function of a dendron

A

extension from cell body
transmits impulses towards cell body

28
Q

structure and function of a dendrite

A

connects to other neurones
carries impulses towards the cell body

29
Q

structure and function of an axon

A

long nerve fibres
transmits impulses away from cell body

30
Q

what do neurones maintain a potential difference across

A

cell surface membrane/ plasma membrane

31
Q

advantage of neurone structure

A

long - transmit action potential over a long distance
many gated ion channels - control the entry of ions

32
Q

define resting potential

A

the potential difference across the membrane whilst the neurone is at rest

33
Q

how is resting potential established

A

Na+ ion gates fully closed
K+ ion gates are leaky/ more permeable = inside is more negative
sodium potassium pump
pumps out 3Na+ ions and pumps in 2K+ ions
using active transport
so inside becomes more negative

34
Q

what is resting potential at

A

-60mV

35
Q

where does the exchange of Na+K happen in myelinated neurones

A

nodes of ranvier

36
Q

how do you generate an action potential

A

higher conc. of Na+ outside the membrane
some Na+ open = Na+ diffuse down the conc. gradient
(membrane depolarises)
if large enough = passes threshold = action potential caused
voltage gated Na+ channels open
depolarisation reaches +40mV inside the cell

37
Q

stages of an action potential

A

membrane in resting state (polarised with -60mV inside)
higher Na+ inside, higher K+ outside
Na+ channels open = some Na+ diffuse into cell
membrane depolarises = becomes less negative (threshold -50mV)
positive feedback causes voltage gated Na+ ion channel to open
more Na+ = inside more positive (+40mV)
Na+ channels close and K+ open
K+ diffuse out
potential difference inside now negative (repolarisation)
potential difference overshoots = cell hyperpolarised (-70mV)
original resting potential restored (resting state)

38
Q

explain how positive feedback works when an action potential is generated

A

when there is sufficiant generator potentials to reach threshold = more Na+ gated channels open

39
Q

describe what the refractory period is

A

after an action potential = Na+ K+ are in the wrong places
concentration of them is restored by the sodium potassium ion pump
during this time another action potential cannot occur

40
Q

what does the refractory period stop from happening

A

the action potential going in the wrong direction
it keeps it going in one direction

41
Q

how is an action potential moved down a neurone

A

local currents caused by Na+ cause depolarisation

42
Q

describe how an action potential is moved down a neurone by local currents

A

when Na+ channels open and Na+ diffuse in
Na+ diffuse sideways along neurone (away from the area of higher concentraion)
this is the local current
causes slight depolarisation further down
causes Na+ voltage gated channels to open
the open channels allow rapid influx of Na+
causes a full depolarisation

43
Q

why doesn’t an action potential reverse its direction

A

concentration of Na+ behind the action potential is still high

44
Q

describe saltatory conduction

A

ionic movement only occurs at nodes of ranvier, cannot occur over myelin sheath
Na+ diffuse along from nodes of ranvier to the next
action potential jumps from one node to the next

45
Q

advantages of saltatory conduction

A

conducts action potential more quickly

46
Q

what is the all or nothing rule

A

an impulse/ action potential are all the same intensity and will all produce a depolarisation of -40mV

47
Q

what is the significance of the frequency of transmission in an action potential

A

stimulus at higher intensity = more sodium channels are open in the sensory receptor = more generator potentials produced
= more frequent action potentials produced

48
Q

what is a cholinergic synapse

A

a synapse that uses acetylcholine as a neurotransmitter

49
Q

what is a neurotransmitter

A

chemical used as a signalling molecule between two neurones in a synapse

50
Q

what is a synapse

A

the junction between two or more neurones where they can communicate with/signal to each other

51
Q

what is a synaptic cleft

A

gap between two neurones

52
Q

structure of a cholinergic synapse

A

acetylcholine as neurotransmitter
synaptic cleft between neurones

53
Q

what is the pre synaptic bulb

A

the end of a pre synaptic neurone

54
Q

features of a pre synaptic bulb

A

many mitochondria
large amount of smooth endoplasmic reticulum - packages neurotransmitter into vesicles
lots of vesicles
voltage gated calcium ion channels

55
Q

describe the post synaptic membrane

A

contains specialised sodium ion channels
receptor that is specific to acetylcholine
acetylcholine present in synaptic cleft = sodium ion gate opens

56
Q

transmission across the synapse

A

action potential arrives at bulb
voltage gated calcium ion channels open
calcium ions diffuse into synaptic bulb
calcium ions causes synaptic to move and fuse with pre synaptic membrane
acetylcholine is released (exocytosis) diffuses across cleft
binds to receptor sites on sodium ion channels in post synaptic membrane
sodium ion gates open
sodium ions diffuse into post synaptic membrane
generator potential created
new action potential created if above threshold

57
Q

what is the role of acetylcholinesterase

A

enzyme in synaptic cleft that stops the transmission of signals
by hydrolysing acetylcholine into ethanoic acid and choline (recycled into it) so no more action potentials continue to happen

58
Q

how is neural communication an example of cell signalling

A

transmitter released by pre synaptic membrane and post synaptic neurone responds to it

59
Q

what is summation

A

occurs when effects of several excitatory post synaptic potentials are added together

60
Q

excitatory post synaptic potential

A

one action potential only causes a few vesicles to move on and fuse with pre synaptic membrane = few acetylcholine molecules diffuse across = small depolarisation = not sufficient to cause action potential in post synaptic neurone

61
Q

inhibitory post synaptic potentials

A

an impulse which can reduce the effect of summation/ prevent an action potential in the post synaptic neurone

62
Q

temporal summation

A

several action potentials in the same pre synaptic neurone

63
Q

spatial summation

A

action potentials arriving from several different pre syanptic neurones

64
Q

how can an action potential be transmitted to several parts of the nervous system

A

one pre synaptic neurone might diverge to several post synaptic neurones

65
Q

explain what happens if we become habituated to stimulus

A

after repeated stimulation a synapse may run out of vesicles containing neurotransmitter = habituated to it

module 5 (7 decks)

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