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Biology Revision Year 2 > Nerves > Flashcards

Nerves Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

describe the neurone at resting potential.

A

the outside is + the inside - , the membrane is polarised, the voltage is approx - 70mV,

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2
Q

describe how the Na/K pumps maintain the resting potential

A

Na is moved out using active transport, Na cannot diffuce back in = electrochemical gradient, pottasium is pumped in but can move out via facilitated diffusion - making the outside + compared to the inside

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3
Q

when is a neurone depolarised?

A

when it is stimulated

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4
Q

describe what happens when the neurone is stimulated

A

the stimulus excites the cell membrane, causing Na ion channels to open. Na diffuses down the electrochemical gradient, making the inside less negative

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5
Q

describe depolarisation

A

if the threshhold is reached (-55mV) more channels open and Na diffuses rapidly into the membrane

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6
Q

describe repolarisation

A

when +3mV is reached the sodium channels close up. K diffuses out through the opened channels, returning the membrane to resting potential

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7
Q

describe the nervous system in comparison to the endocrine system

A

nervous system is short lived, fast and localised (endocrine opposite)

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8
Q

what is included in the CNS?

A

brain and spinal cord

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9
Q

what is the peripheral system?

A

all other neurones

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10
Q

what do we dived the peripheral into?

A

sematic and autonomic

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11
Q

what is the sematic nervous system?

A

concious decision eg) muscle movement

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12
Q

what is the autonomic nervous system?

A

unconcious eg) heart rate

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13
Q

what 2 sections can we divide the autonomic system into?

A

parasympathetic and sympathetic

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14
Q

describe the parasympathetic

A

decreases/ slows things down eg) heart rate

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15
Q

what neurotransmitter controls the parasympathetic?

A

acetylcholine

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16
Q

describe the sympathetic

A

increases/ speeds things up eg) heart rate

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17
Q

what neurotransmitter controls the sympathetic?

A

noradrenaline

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18
Q

describe the route from stimulus to response

A

stimulus - receptor - sensory - intermediate (cns) - motor - effector - response

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19
Q

describe the receptor

A

specific, cell or protein, transforms stimulus into nerve impulse

20
Q

describe the sensory neurone

A

Single long dendron, single short axon, (draw a diagram and check)

21
Q

decribe the intermediate neurone

A

within cns, many short dendrites/ axons (draw a diagram)

22
Q

describe the motor neurone

A

many short dendrites, single long axon, ends at neuromuscular junction

23
Q

describe the effector

A

muscle/gland

24
Q

describe the sodium pottassium pump

A

maintains the resting potential by active transport of Na+ out and K+ in. some K+ diffuse out by facilitated diffusion

25
Q

what happens at generator potential?

A

a weak stimulus causes some voltage gated Na+ channels to open, some Na+ diffuses in, threshold isnt reached so returns to resting potential.

26
Q

what happens at threshold?

A

many voltage gated Na+ channels open, Na+ diffuse into axon, positive feedback (rapid depolarisation)

27
Q

describe repolarisation

A

K+ channels open, K+ diffuses out, sodium ion channels close

28
Q

what is hyperpolarisation?

A

membrane potential is more negative than resting potential because K+ channels are slow to close

29
Q

what is the refractory period?

A

another action potential cannot be started, ensuring action potentials are discrete, unidirectional nervous impulse

30
Q

Describe how resting potential is established in an axon by the movement of ions across the membrane

A

Active transport of sodium out, diffusion of K in

making the inside more negative than the outside

31
Q

why can sodium and pottasium ions only pass through the membrane through proteins?

A

because they are polar, and not lipid soluble

32
Q

why doesn’t every stimulus produce an action potential?

A

because it has a refractory period
because it doesn’t reach threshold
not all the sodium channels open

33
Q

describe the role of calcium ions in synaptic transmission.

A

in the presynaptic neurone, calcium ions increase membrane fluidity allowing vesicles to fuse with it for exocytosis.

34
Q

describe the all or nothing principal

A

if a generator potential reaches threshold an action potential is triggered, all AP are the same size, stronger stimulus = higher frequency

35
Q

what is hyperpolarisation’s role?

A

creates a refractory period as so ions diffusing Bck don’t diffuse out. Ahead the AP is in resting potential ensuring undirectionality.

36
Q

what is the myelin sheath?

A

it is made up of schwann cells and acts as an electical insulator - so ions can not move in and out of the nuerone.

37
Q

describe the nodes of ranvier

A

they are gaps in the myelin sheath with high levels of Na/K channels, AP jump between nodes of ranvier.

38
Q

what is saltatory conduction?

A

AP jumps between the nodes of ranvier + speed and - distance

39
Q

How can we speed up transfer?

A

more Schwann cells increases saltatory conduction, increase temperature faster diffusion of action potential, diameter of the axon - increasing the diameter increases the speed, greater surface area for ion movement

40
Q

Describe the process of cholinergic synaptic transmission

A

AP at pre synaptic knob
voltage gated calcium ion channels open and calcium ions diffuse in
vesicles containing acetylcholine fuse with the presynaptic membrane (exocytosis)
acetylcholine diffuses across the synaptic cleft
acetylcholine binds with the receptor on the post synaptic membrane triggering an action potential
acetylcholineesterase breaks down acetylcholine to stop the response
acetylcholine is reabsorbed into the presynaptic knob

41
Q

How do synapses ensure that the nerve impulse is unidirectional

A

only receptors on the post synaptic membrane

neurotransmitters diffuse from high to a low conc

42
Q

What is synaptic divergence?

A

when one neurone joins many neurones –> spreads AP to other parts of the body

43
Q

What is synaptic convergence?

A

many neurones join a single neurone - amplifies a signal

44
Q

What is a neuromuscular junction?

A

a synapse between a motor neurone and a muscle fibre

45
Q

What is different about a neuromuscular junction compared to a cholinergic synapse?

A
  • more receptors on the post synaptic membrane so an AP is always triggered
  • acetylcholine-esterase is found in pits on the post synaptic membrane
46
Q

What is the name of the receptors on the post synaptic membrane?

A

nicotinic cholinergic recepters

47
Q

What does the sartcolema connect with that causes the release of calcium ions for muscle contraction?

A

the transverse tubules on the sarcolema connect with the sarcoplasmic reticulum

Biology Revision Year 2 (13 decks)

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