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Biology A Level Unit 3 > Nervous System > Flashcards

Nervous System Flashcards

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1
Q

nervous system

A

detect stimuli, process information, initiate response

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2
Q

CNS

A

Central Nervous System = brain + spinal cord

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3
Q

PNS

A

Peripheral Nervous System = pairs of nerves from brain and spinal cord that contain sensory + motor neurones

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4
Q

basic nervous control mechanism

A 
stimulus
receptors 
(sensory neurones)
CNS
(motor neurones)
effector (muscle/gland)
response
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5
Q

reflex actions

A

rapid, involuntary, protective response to a stimulus

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6
Q

spinal cord

A

grey matter - mostly full of cell bodies/nuclei of neurones, stain darkly
white matter - mostly axons and myelin sheaths of neurones, axons dont stain darkly and myelin sheaths only stain lightly

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7
Q

hydra

A

no CNS
sense receptors respond to limited number of stimuli
small number of effectors
nerve net

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8
Q

human

A

CNS
sense receptors respond to wide range of stimuli
large number of efectors

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9
Q

neurones

A

nerve cells (motor, sensory, relay)

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10
Q

sensory neurones

A

bring impulses from receptors into CNS

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11
Q

relay neurones

A

receive impulses from receptors in CNS

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12
Q

motor neurones

A

carry impulses from CNS to effector organs

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13
Q

function of cell body

A

dendrites receive nerve impulses, transmit along axon, contain nucleus + ribosomes for protein synthesis, contain mitochondria for ATP synthesis

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14
Q

function of nucleus

A

DNA transcription

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15
Q

function of dendrites

A

receive impulse from other neurones, carry impulse to cell body

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16
Q

function of axon

A

transmits impulses away from cell body

17
Q

function of axon terminals

A

form synapses with other neurones

18
Q

function of myelin sheath

A

electrical insulator speeds up nerve impulse transmission, protects axon

19
Q

function of Schwann cells

A

wrap around axon to form myelin sheath

20
Q

function of nodes of ranvier

A

intervals between myelin sheath speed up nerve impulse transmission (impulses jump node to node = saltatory conduction)

21
Q

function of synaptic end bulb

A

swelling where neurotransmitter is synthesised

22
Q

resting potential definition

A

electrical potential difference found across membrane of resting neurone
membrane polarized -70mV, inside of membrane negative with respect to outside

23
Q

resting potential

A 
Na+/K+ pumps, energy from ATP - 3Na+ out, 2K+ in per ATP hydrolysed
differential permeability of membrane to Na+ + K+ ions - some K+ channels open for K+ to diffuse out but most Na+ channels shut to prevent Na+ diffusing in
negative ions (anions) of large proteins + organic phosphates remain in cytoplasm
24
Q

action potential description

A

change in electrical charge which occurs across axon membrane when stimulated
membrane depolarised +40mV

25
Q

action potential

A

energy of stimulus above ‘threshold’ level causes sudden opening of some Na+ channels, voltage change makes many voltage-gated Na+ channels open, rapid influx of Na+ into axon depolarised membrane
+40mV action potential established, Na+ channels close
voltage-gated K+ channels open, K+ diffuse out rapidly, membrane repolarises
potential difference overshoots below resting to -75mV (hyperpolarisation) - more K+ out than Na+ in
refractory period - K+/Na+ pump restores ionic balance to resting where voltage-gated Na+ channels open producing new action potential (ensures impulse is unidirectional)

26
Q

all or nothing principle

A

applies to threshold potential
nervous impulse either initiated or not (too small, no action potential)
will always reach +40mV
further increase in stimulus won’t increase size of action potential but give more frequent action potentials

27
Q

factors that affect speed of nerve impulse

A

myelination - myelin insulates axon preventing depolarisation, nodes of ranvier have voltage gated ion channels for depolarisation, node to node (saltatory conduction)
diameter - bigger diameter
temperature - higher temp (more kinetic energy Na+/K+ diffuse more quickly)

28
Q

synapse

A

gap between neurones

transmits nerve impulses between neurones in one direction only

29
Q

synapse between neurone + muscle

A

neuromuscular junction

30
Q

transmission across most synapses is

A

chemical rather than electrical

31
Q

synapse labels

A

axon, pre-synaptic membrane, synaptic knob, calcium ions, mitochondrion, synaptic vesicle, neurotransmitters, Na+ ,synaptic cleft, acetylcholine receptor with ion channel, post-synaptic membrane, dendrite, myelin sheath

32
Q

process of synaptic transmission

A

action potential arrives at axon terminal depolorising pre-synaptic membrane
Ca2+ channels open, Ca2+ ions rush into synaptic knob/axon terminal
synaptic vesicles containing neurotransmitter (acetylcholine) fuse with pre-synaptic membrane
acetylcholine released by exocytosis into synaptic cleft
acetylcholine diffuses across synaptic cleft and binds to receptors on post-synaptic membrane
Na+ channels in post-synaptic membrane open, Na+ ions enter + depolarise membrane
depolarisation above threshold generates action potential in post-synaptic, nerve impulse transmits along axon
acetylcholine broken down by acetyl cholinesterase in synaptic cleft, products (ethanoic acid + choline) diffuse back into axon terminal, ATP re-synthesises + packages acetylcholine into synaptic vesicles

33
Q

preventing merging of impulses

A

neurotransmitter reabsorbed so it can’t bind to receptor molecules on post-synaptic
acetyl cholinesterase catalyses hydrolysis of acetylcholine to form ethanoic acid + choline in synaptic cleft
Ca2+ actively transported out of synaptic knob so no more exocytosis of acetylcholine can occur

34
Q

psychoactive drugs

A

e.g. cannabis + cocaine affect synapses
THC in cannabis can increase/decrease release of neurotransmitters
cocaine blocks re-uptake of proteins
excitatory drugs (cocaine) increase post-synaptic transmission
inhibitory drugs (cannabis) decrease transmission

35
Q

excitatory drugs

A

stimulate nervous system by creating more action potentials in post-synaptic membranes
mimics neurotransmitters when binding to receptors on post-synaptic neurone
drug blocks uptake of neurotransmitter in synaptic knob
drug inhibits enzyme involved in breakdown of neurotransmitter

36
Q

inhibitory drugs

A

inhibit nervous system by creating fewer action potentials in post-synaptic membranes
prevents release of neurotransmitter from pre-synaptic knob
prevents entry of Ca2+ into pre-synaptic knob
binds with receptors on post-synaptic membrane blocking normal transmitter binding

37
Q

organophosphorous (OP) insecticides

A

act as acetyl cholinesterase inhibitors
in cholinergic synapse, insecticide combines with acetyl cholinesterase so it can’t breakdown acetylcholine
acetylcholine remains in synaptic cleft and on post-synaptic membrane causing repeated stimulation of post-synaptic neurone
if at neuromuscular junction, repeated stimulation causes repeated contractions of muscle to occur

Biology A Level Unit 3 (8 decks)

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