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A2 Biology > 5.1.3 Neuronal Communication > Flashcards

5.1.3 Neuronal Communication Flashcards

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1
Q

What do neurones transmit

A

Nerve impulses rapidly around the body

These impulses are in a electric nature

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2
Q

What is the function of a dendrite

A

Small extensions that carry impulses towards the cell body

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3
Q

What’s the function of the cell body

A

Produced protein neurotransmitters and ATP, has nucleus cytoplasm rough ER and mitochondria

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4
Q

What is the function of the myelin sheath

A

Lipid covering that insulated the axon speeding up nerve impulses by allowing Saltatory conduction

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5
Q

What is the function of Schwann cells

A

Produce myelin sheath

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6
Q

What is the function of node of ranvier

A

Gap between Schwann cells

No myelin sheath here

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7
Q

What is the function of the axon

A

Carries nerve impulses away from cell body, thing long cytoplasm with plasma membrane

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8
Q

What is the function of terminal end branches

A

Connect neurons to muscle

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9
Q

What is the job of the sensory neurones

What is the structure like

A

Carries action potentials from sensory receptor cells to intermediate neurones/ brain

Cell body in middle of neurone
Shorter axon
Dendrons present
Dendrites do not connect directly to cell body

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10
Q

What is the job of the motor neurones

What is the structure like

A

Carries action potentials from relay neurones to effector ( muscles or glands )

Cell body at end of neurone
Dendrites connect directly to cell body
Longer axon
No dendron

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11
Q

What is the function of relay neurones

What is the structure

A

Transmit impulses between neurones like sensory to motor

Cell body central to neurone
Dendrites connect to directly to cell body
Many short axons
Dendron present

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12
Q

Describe Schwann cells

A

Wraps around the axon except at the nodes of ranvier

Produces myelin sheath which insulates, this sheath is fatty and does not allow Na+ or K+ ions into or out of the axon

So depolarisation can only occur at the nodes

Hence action potential jumps from one node to the next

This is saltatory conduction

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13
Q

What’s the benefit of myelin

A

Speeds up conduction of action potentials due to faster depolarisation

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14
Q

What does polarised mean

A

Unequal distribution of

Charge

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15
Q

What is the name for a concentration gradient when we are dealing with ions

A

Electrochemical gradient

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16
Q

Describe the distribution of charge when at resting potential

A

Negative charge inside

Positive charge outside

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17
Q

Describe the sodium potassium pump

A

Actively transports 2k+ in and 3Na+ out of the axon

Using ATP

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18
Q

How is resting potential maintained

A

Sodium potassium pump used ATP to actively transport 3Na+ out and 2K+ in to the axon

Many K+ ion channels are open so K+ ions diffuse back out of the axon

Voltage gated Na+ ion channels are closed

Fewer Na+ ion channels are open, so fewer Na+ ions can diffuse back in

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19
Q

What two things do all sensory receptors have in common

A

They are all specific to a single type of stimulus

They are all transducers- converts one form of energy into a different form of energy

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20
Q

What are the 4 types of sensory receptors

A

Mechanoreceptor (stimulus is pressure and movement- eg pacinian corpuscle)

Chemoreceptor (stimulus is chemicals eg olfactory receptors in nose)

Thermoreceptors (stimulus is heat eg end-bulbs of Krause)

Photoreceptors (stimulus is light eg cone cell)

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21
Q

What is pacinian corpuscle

A

A transducer- converts mechanical energy into electrical energy

A pressure receptor

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22
Q

Describe how an action potential is generated in a pacinian corpuscle

A

Pressure ca sides the corpuscle to deform

Stretch mediated Na+ ion channels in the neurone membrane open

Na+ ions diffuse in

depolarising the membrane

if the threshold is reached an action potential is generated

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23
Q

the greater the pressure, the greater…

A

the frequency of nerve impulses along the neurone

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24
Q

what is the all or nothing law

A

if the stimulus is not strong enough, the generator potential does not reach the threshold value, depolarisation of membrane is inefficient, there is no action potential

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25
Q

describe the distribution of charge when at action potential

A

negative outside

positive inside

26
Q

explain what happens sat resting potential -70mv

A
  • sodium potassium ion pump uses ATP to actively transport 3 Na+ ions out and 2K+ ions into the axon
  • voltage gated sodium ion channels are closed
  • fewer Na+ diffuses in
  • K+ ion channels are open so K+ ions diffuse out of the axon
27
Q

what happens at depolarisation

A
  • pressure applied to pacinian corpuscle
  • stretch mediated sodium ion channels open
  • sodium ions idffuse into the axon creating a generator potential
  • causes voltage gated sodium ion channels to open, Na+ move in
  • if it goes above -50mv threshold dit causes all sodium ion channels to open and more sodium infuses in (POSITIVE FEEDBACK)
  • until +40mv action potential is reached
28
Q

what happens during repolarisation

A

voltage gated sodium ion channels close

  • voltsage gated K+ ion channels open
  • K+ ions diffuse out of the axon
29
Q

what happens during hyperpolarisation

A
  • very high rate of K+ ion diffusion out of the axon\
  • voltage falls below resting potential
  • voltage gated K+ ion channels close
  • sodium potassium pump restores resting potential
30
Q

what is there function of a Schwann cell

A

wraps around the axon and produces myelin
myelin provides electrical insulation
prevents movement of ions into/out of neurone
prevents depolarisation

31
Q

what does myelin prevent from entering the axon

what does this mean

A

does not allow Na+ or K+ ions to pass through it

depolarisation can only occur at the nodes of ranvier

32
Q

what is saltatory conduction

what’s the advantage of this

A

where the action potential jumps from one node to the next

-advantage= conserves energy as sodium potassium pump (which uses ATP) can only operate at the nodes

33
Q

what do unmyelinated neurones have instead

A

voltage gated sodium ion channels along the whole length of the axon, all channels have to open as the impulse is transmitted down which takes time

causes localised currents

means the whole axon has to be depolarised

34
Q

describe multiple sclerosis

A

an autoimmune disease where the body own immune system recognises antigens on myelin sheath as non self

this myelin is attacked by t killer cells and antibodies are produced

prevents saltatory conduction so slows down conduction of action potentials

35
Q

what is the effect of increased temperature

A

higher temp= mol have more KE

  • faster diffusion rate of Na+ ions across axon
  • faster movement of vesicles and faster diffusion of neurotransmitter
36
Q

what happens if temperature gets too high

A

the sodium potassium pump is denatured ( as they are proteins)
fluidity of the phospholipid bilayer is disrupted
synaptic enzymes are denatured (acetylcholinesterase)

37
Q

what is the effect of as larger axon diameter

A

the wider the axon diameter, the faster the speed of conduction, less reistance to flow of ions in cytoplasm

38
Q

what does the refractory period prevent

A

the propagation of the action potential backwards - can only go forwards
UNIDIRECTIONAL

also means action potentials cannot overlap

limits the frequency at which action potentials are generated

39
Q

where does the refractory period start

A

after depolarisation

40
Q

what is the effect of the puffer fish toxin

A

have a toxin called tetradotoxin
this blocks the voltage gated sodium ion channels in human nerve cells
preventing action potentials

41
Q

give an example of an excitatory neurotransmitter

A

acetylcholine

42
Q

give an example of an inhibitory neurotransmitter

A

GABA

43
Q

what do excitatory neurotransmitters cause

A

the depolarisation of the post synaptic membrane which if goes above threshold an action potential will be generated

44
Q

what do inhibitory neurotransmitters cuase

A

the hyperpolaraisation in the post synaptic membrane and prevention of action potentials

45
Q

how do synapses allow transmission in one direction

A
  • only the presynaptic neurone releases neurotransmitter
  • only pre synaptic membrane has calcium ion channels
  • only post synaptic membrane has specific receptors
46
Q

why is there lots of mitochondria in neurones

A

produce ATP by aerobic respiration used to: recombine choline and ethnic acid into acetylcholine
and to allow the movement of secretory vesicles along the cytoskeleton

47
Q

describe the process of synaptic transmission

A

1) Na+ moves along the axon and into the pre synaptic bulb causing action potential and depolarisation
2) voltage gated Ca2+ ion channels open
3) calcium ion diffuse into the neurone
4) vesicles containing neurotransmitter move along the cytoskeleton using ATP towards the presynaptic membrane
5) vesicles fuse with the membrane in a process named exocytosis and neurotransmitter is released into the synaptic cleft
6) neurotransmitter diffuses across the synaptic cleft and attaches to receptors on post-synaptic membrane
7) receptors on the sodium ion channels, causes these channels to open and Na+ moves in
8) acetylcholine is then broken down in the cleft by the enzyme acetylcholinesterase forming choline and ethnic acid which diffuses back into the presynaptic bulb
9) choline and ethnic acid recombine with ATP to form acetylcholine which is stored in vesicles in the presyntpic cell

48
Q

what is the name of the protein attached to vesicles

A

snare proteins that bind to snare protein receptors on the membrane

49
Q

what effect does toxins have on the vesicle proteins sometimes

A

change the structure or digest them so no exocytosis can take place

50
Q

define spatial summation

A

when a number of presynaptic neurones connect to one post-synaptic neurone

this amplifies low level signals

51
Q

define temporal summation

A

when a single presynaptic neurone releases neurotransmitter as a result of an action potential several times over a short period

52
Q

why are synapses important (4)

A
  • allows neurones to communicate- cell signalling
  • ensure transmission of action potentials in one way
  • allows integration:
    1) convergence- one neurone can receive impulses from many
    2) divergence- one neurone can transmit impulse to many neurones
53
Q

what is the effect of amphetamines

A

trigger the presynaptic neurone to release more neurotransmitter

means the user has to replenish it after using the drug

54
Q

what is the effect of nerve gas

A

inhibit the enzyme acetylcholineesterase which means continuous action potentials

55
Q

what is the effect of alcohol

A

ethanol binds to GABA receptors changing their shape so they can better transport GABA and so increase the effect of GABA in the post synaptic neurone

56
Q

what is the effect of the atropine toxin from nightshade

A

has similar shape to acetylcholine
binds to receptors on post synaptic membrane
blocking them so ACh cannot bind
Na+ channels remain closed and cannot enter therefore no depolarisation

57
Q

could atropine be used as a antidote for nerve gas

A

yes atropine would compete for the ACh receptors so ACh cannot bind reducing depolarisation

58
Q

what is the purpose of reflex arcs

A

to protect the body from harmful stimuli and are innate

59
Q

why are reflex arcs so fast

A

because they are involuntary so do not use the brain
they are fast because the pathway is short and only use a few synapses
use myelinated neurones

60
Q

briefly describe a reflex arc

A
  1. receptor
  2. sensory neurone
  3. intermediate neurone in the spinal chord
  4. motor neurone
  5. effector
    - -> response
61
Q

describe the reflex arc of the knee jerk

A

1) stimulus= hitting the patellar tendon
2) sensory neurone transmits impulse to spinal chord
3) impulse travels down the motor neurone to the extensor muscles, they contract, at the same time relay neurone inhibits the motor neurone to flexor muscle and so relaxes
4) response= knee jerk

62
Q

describe the blinking reflex ( cranial reflex)

A

1) cornea is touched
2) impulse transmits down sensory neurones
3) passes through relay muscle in lower brain stem
4) down motor neurone which branches to both eyes and to eyelid muscles.

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