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Biology A2 Unit 5 > 10 Coordination > Flashcards

10 Coordination Flashcards

1
Q

The nervous system uses…

A

nerve cells to pass electrical impulses along their length

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2
Q

The nervous system stimulates

A

target cells by secreting neurotransmitters onto them

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3
Q

Nervous communication is…

A
  • rapid
  • short-lived
  • localised
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4
Q

Hormonal system produces…

A

chemicals that are transported in blood plasma

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5
Q

Hormonal communication is…

A
  • slower
  • long lasting
  • widespread
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6
Q

Chemical mediators are…

A

chemicals released from cells that have an effect on cells in the immediate vicinity

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7
Q

two examples of chemical mediators

A

histamine

prostaglandins

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8
Q

Histamine is released…

A

following injury or in response to an allergen

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9
Q

Histamine causes…

A

dilation of small arteries/arterioles
increased capillary permeability
localised swelling, redness and itching

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10
Q

prostaglandins are found…

A

in cell membranes

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11
Q

prostaglandins cause

A

dilation of small arteries/arterioles

changes in blood pressure and neutrotransmitters

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12
Q

prostaglandins affect

A

pain sensation

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13
Q

Plants do not have…

A

a nervous system

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14
Q

Plants must respond to…

A

light
gravity
water

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15
Q

Plants respond to external stimuli by

A

plant growth factors

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16
Q

Plant growth factors… (3)

A
  • exert influence by affecting growth
  • made by cells throughout the plant rather than organs
  • some affect the tissues that release them
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17
Q

Example of a plant growth factor and its effect…

A

IAA -indoleacetic acid

causes plant cells to elongate

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18
Q

Response to light directed at a shoot from one side (6)

A
  • tip cells produce IAA which is transported down the shoot
  • initially transported to all sides as it moves down
  • light then causes IAA to move towards the shaded side
  • IAA builds up on the shaded side
  • IAA elongates cells so cells on shaded side grow more
  • they grow faster so the shoot bends towards the light
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19
Q

IAA … growth in root cells

A

decreases

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20
Q

Neurones…

A

are specialised cells adapted to rapidly carrying nerve impulses from one part of the body to another

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21
Q

Six key parts of neurones

A
  • cell body
  • dendrons
  • axon
  • Schwann cells
  • myelin sheath
  • nodes of Ranvier
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22
Q

Neurone cell body contains…

A

nucleus and large amounts of rough ER (for neurotransmitter production)

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23
Q

Dendrons are…

A

extensions of the cell body that subdivide into smaller branched fibres

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24
Q

Dendrons carry…

A

nerve impulses towards the cell body

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25
Q

Axon is..

A

a single long fibre

that carries nerve impulses away from the cell body

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26
Q

Schwann cells…

A

surround the axon

protecting and insulating it

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27
Q

A myelin sheath

A

forms a lipid rich covering to the axon

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28
Q

Nodes of ranvier are…

A

gaps between adjacent Schwann cells where there is no myelin sheath

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29
Q

Sensory neurones (3)

A
  • transmit impulses from a receptor to an intermediate/motor neurone
  • one dendron carries impulse towards cell body
  • one axon carries impulse away from cell body
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30
Q

Motor neurones (2)

A
  • transmit impulses from an intermediate/sensory to an effector
  • long axon and many short dendrties
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31
Q

Intermediate neurones (2)

A
  • impulses between neurones (sensory to motor etc)

- numerous short processes

32
Q

Define nerve impulse

A

a self-propagating wave of electrical activity along the surface of the axon membrane

33
Q

Three ways movement of Na+ and K+ across the membrane is controlled

A
  • phospholipid bilayer prevents diffusion across
  • ion channels, gated/non gated control ion movement
  • Sodium-potassium pump controls active transport of Na+ out and K+ in
34
Q

Sodium-potassium pump

A

actively transports potassium into the axon and sodium out of the axon

35
Q

The resting potential is usually

A

-65mV

36
Q

The resting potential is caused by…

A
  • 3Na+ actively transported out with 2K+ actively transported in to the axon. So more Na+ out than in.
  • Na+ diffuse back into axon, K+ diffuse back out.
  • But more K+ gates open, so they diffuse out faster.
  • So even more positive ions out than in
37
Q

At resting potential, chemical and electrical gradients are balanced when…

A
  • Positively charged outside makes movement of Na+/K+ out difficult
38
Q

When a stimulus is received, an action potential

A

causes a temporary reversal of axon membrane charges (depolarisation)

39
Q

Depolarisation occurs because…

A

Channels in axon membrane open/close, causing ion movement.

40
Q

7 steps of action potential

A
  • Resting potential, some K+ channels are open but K+ closed.
  • Stimulus, causes Na+ channels to open and Na+ diffuses in, trigger reversal
  • More Na+ channels open, more diffusion into axon
  • +40mV; Na+ channels close and K+ channels open.
  • More K+ channels open, diffusing out and repolarising membrane
  • Hyperpolarisation, then
  • K+ channels close and Na+/K+ pump operates again (repolarisation)
41
Q

The resting potential is maintained by…

A

active transport of Na+/K+ ions

42
Q

The size of an action potential…

A

remains the same from one end of axon to another

43
Q

One region of depolarisation acts as…

A

a stimulus for depolarisation of the next region

44
Q

At resting potential…

A

the Na+ concentration outside axon is high relative to inside
the K+ concentration outside axon is low relative to inside
therefore the axon membrane is overall negative compared to the outside

45
Q

A stimulus causes…

A
  • a sudden influx of Na+ ions therefore a reversal of charge on the axon
  • the membrane is therefore depolarised
46
Q

The influx of sodium ions into the axon causes…

A

the opening of Na+ channels further along the axon, depolarising it

47
Q

Behind the region of depolarisation, the Na+ voltage-gated channels…

A

close and K+ channels open

K+ leaves the axon along an electrochemical gradient

48
Q

The region behind the action potential returns to its charged state when…

A

the K+ ion movement has continued to the extent that the axon membrane is now negative with respect to the inside

49
Q

Repolarisation of the neurone allows…

A

Na+ ions to be actively transported out, returning the neurone to its resting potential.

50
Q

In myelinated axons, the myelin sheath acts as…

A

an electrical insulator, preventing action potentials forming

51
Q

In a myelinated neurone, action potentials occur only at…

A

the Nodes of Ranvier

52
Q

The process of an action potential jumping from node to node is…

A

saltatory conduction

53
Q

The speed of an action potential along a myelinated neurone is…

A

faster than an unmyelinated neurone

54
Q

Factors affecting the speed of a nerve impulse

A
  • myelination
  • diameter of the axon
  • temperature
55
Q

The greater the diameter of an axon…

A

the faster speed of conductance as fewer ions leak from the axon

56
Q

A higher temperature affects the speed of a nerve impulse how?

A

ions diffuse faster at higher temperatures

enzymes of respiration function faster to produce ATP for active transport

57
Q

The refractory period occurs when…

A

Na+ voltage-gated channels are closed so a new action potential cannot be generated

58
Q

Purposes of the refractory period: (3)

A
  • ensures propagation in one direction only
  • ensures discrete impulses as they are separated
  • limits number of action potentials
59
Q

The all-or-nothing principle means…

A

below the threshold value, no action potential is generated

above the threshold value, an action potential is generated

60
Q

How is strength of stimulus detected?

A

Larger stimulus may create more impulses

Different neurones with different threshold values

61
Q

A synapse is…

A

the point where the axon of one neurone connects with the dendrite of another, or with an effector.

62
Q

Synapses transmit impulses by releasing…

A

neurotransmitters

63
Q

The synaptic knob…

A

contains many mitochondria and endoplasmic reticulum to manufacture neurotransmitter

64
Q

Neurotransmitter is stored in…

A

the synaptic vesicles

65
Q

Once neurotransmitter is released…

A

it diffuses across the synaptic cleft to receptor molecules on the postsynaptic neurone

66
Q

Synapses act as junctions, allowing

A
  • a single impulse to be transmitted to different neurones to produce different responses simultaneously
  • impulses to be combined to produce a single response
67
Q

neurotransmitter is made only…

A

in the presynaptic neurone

68
Q

Unidirectionality means…

A

synapses can only pass impulses in one direction

69
Q

Spatial summation is…

A

-a number of presynaptic neurones simultaneously release neurotransmitter to exceed the threshold value, triggering an action potential

70
Q

temporal summation means…

A

a single presynaptic neurone releases neurotransmitter many times to exceed the threshold value and trigger an action potential

71
Q

Inhibition causes…

A

Cl- channels to open and hyperpolarise the membrane, making it less likely an action potential will be created

72
Q

Cholinergic synapses have neurotransmitter,

A

acetylcholine

73
Q

Cholinergic synapses occur…

A

in the central nervous system and at neuromuscular junctions

74
Q

6 steps of cholinergic synapse transmission

A

1) action potential causes Ca2+ to enter presynaptic knob
2) Ca2+ causes vesicles to move and fuse with presynaptic membrane, releasing Ach into the cleft
3) Ach fuses with receptor sites on the Na+ ion channels, causing them to open and Na+ to diffuse in rapidly
4) Na+ influx depolarises membrane, causing an action potential
5) Acetylcholinesterase acts on Ach, breaking it up and causing it to diffuse back into presynaptic neurone.
6) ATP recombines the choline and ethanoic acid back to Ach, which is stored in vesicles. Na+ channels close when no Ach.

75
Q

Two main forms of communication in mammals

A

Nervous system

Hormonal

Biology A2 Unit 5 (7 decks)

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