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Biology > p2: nervous coordination > Flashcards

p2: nervous coordination Flashcards

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1
Q

two divisions of nervous system

A
  • CNS: brain and spinal cord
  • Peripheral nervous system: nerves from and to the brain and spinal cord

and
- voluntary NS: voluntary conscious control
- autonomic NS: involuntary or subconscious

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2
Q

describe how the structure of dendrites enable it to serve its function

A
  • thin extensions on post synaptic membrane
  • receives chemical signals
  • carries impulses to nerve endings
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3
Q

describe how the structure of the myelin sheaths enable it to serve its function

A
  • electrical insulation
  • speeds up transmission
  • formed from schwann cells
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4
Q

describe how the structure of terminal end branches enable it to serve its function

A

forms a synapse
releases neurotransmitters

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5
Q

explain the advantages of simple reflex arcs

A
  • rapid
  • protect against damage to body tissues
  • dont have to be learnt
  • help escape predators
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6
Q

as a neurone transmits an impulse, its rate of oxygen consumption increases. explain why.

A
  • ATP required for active transport
  • Na+ moved out along the whole length of axon in non myelinated
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7
Q

describe how a resting potential is maintained in a neuron

A
  • active transport of sodium ions across membrane
  • membrane more permeable to K+ ions
  • differential permeability to K+ and Na+ ions
  • out of neurone, Na+ concentration higher and K+ conc higher inside neurone
  • 3Na+ out and 2K+ in
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8
Q

the potential across the membrane is reversed when an action potential is produced

A
  • sodium ion channels protein
  • Na+ ions diffuse in
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9
Q

how is an action potential generated?

A
  • membrane reaches threshold and becomes depolarised
  • reversal of resting potential
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10
Q

depolarisation

A
  • stimulus causes membrane to be more permeable to Na+ ions
  • if reaches threshold, Na+ ion channel proteins open and inside becomes more positive
  • K+ ion channel proteins mainly closed
  • high conc of positive ions inside cell = action potential
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11
Q

repolarisation

A
  • when reached 40 mV the Na+ channel proteins close
  • K+ CHANNEL PROTEINS OPEN
  • K+ ions diffuse out down a conc gradient = repolarisation
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12
Q

hyperpolarisation

A
  • K+ ion channel proteins remain open longer than needed, so cell more negative (-90mV)
  • sodium potassium pump restores back to (-70mV)
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13
Q

all or nothing response

A
  • action potential only occurs if all Na+ voltage-gated ion channel proteins opemn
  • threshold reached
  • subthreshold = no action potential
  • action potential size is always the same
  • full size action potential always given regardless of size of stimulus
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14
Q

define threshold

A

minimum intensity of stimulus

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15
Q

refractory period

A
  • time taken to restore the resting potential
  • period of inactivation following transmission of an impulse
  • limits number of impulses per second
  • maximum frequency of impulse transmission
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16
Q

impulse transmission

A

action potentials act as stimulus to adjacent polarised areas of membrane
- is passed along

17
Q

describe how the speed of conduction could vbe increased ina neurone

A
  • axon is myelinated which provides insulation
  • action potential jumps from node of ranvier to node of ranvier (saltatory conduction)
  • axon has a large diameter
  • so less resistance to flow of ions
18
Q

saltatory conduction

A

imoulses travel from node of ranvier to node
- depolarisation occurs only at nodes
- less axon needs to be depolarised so increases rate of transmission

19
Q

factor affecting rate of impulse conduction

A
  • myelin sheaths
  • temperature, higher KE so increased diffusion of ions
  • larger axon diameter greater speed of conuctance and increases number of channel proteins
20
Q

give two reasons why transmission across a cholinergic synapse is unidirectional?

A
  • impulses are unidirectional from pre to post SN
  • vesicles containing neurotransmiters only in presynaptic neurone a
  • receptor proteins only in post SN
21
Q

where is acetyl choline found?

A

parasympathetic branch of NS

22
Q

describe the sequence of events leading to the release of acetylcholine and its binding to the post synaptic membrane

A
  • depolarisation of presynaptic membrane
  • Ca 2+ ions open and calcium ions enter synaptic knob
  • vesicles fuse with presynaptic membrane and release acetyl choline
  • acetylcholine diffuses across synaptic cleft
  • acetylcholine binds to receptors on the post SN
  • sodium ions enter post SN leading to depolarisation
23
Q

when a nerve impulse arrives at a synapse, it causes the release of a neurotransmitter from vesicles in the presynaptic knob. describe how.

A
  • depolarisation causes calcium ion channel proteins to open
  • calcium ions enter by faciliated diffusion
  • vesicles fuse with preSN
24
Q

neuromuscular junction

A
  • synapse between motor neurone and muscle cell
  • uses acetylcholine which binds to nicotinic cholinergic receptors
25
Q

what are the major differences between the cholinergic synapse and the neuromuscular synapse

A
  • in neuro, postSN has lots of folds that form clefts, increase SA so more acetyl enzymes hydrolyse acetyl at a faster rate
  • postSN has more receptors
  • action potential always triggers a response in muscle cell
26
Q

the binding of GABA to receptors on postSN membranes causes negatively charged chlorine ions to enter postSN

explain how this will inhibit transmission of nerve impulses by postSN neurones

A
  • inside neurone is more negative
  • not enough Na+ ions to reach threshold
  • for action potential/depolarisartion
27
Q

myelination affects the rate of conduction of a nerve impulse. explain how.

A
  • myelination provides electrical insulation
  • action potential jumps between nodes of ranvier
  • fewer jumps to travel length of axon
28
Q

describe how the inhibition of acetylcholinesterases affects the action of synapses

A
  • acetyl choline not broke down
  • Na+ ions continue to depolarise/create action potentials
29
Q

summation

A

build up of neurotransmitters within the synapse

30
Q

spatial summation

A
  • causes release of enough neurotransmitters to reach threshold
  • causes an axtion potential in postSN
  • different neurones converge at a single synapse
31
Q

temporal summation

A
  • one presynaptic neuroe but impulses arrive at rapid succession
  • cumulative effect sufficient to depolarise postSN
32
Q

fatigue

A

if rate of transmission higher than rate reformed, then fatigued
- cant generate an action potential is postSN until transmitter is regenerated

33
Q

excitatory neurotransmitters

A
  • cause an action potential in postSN makes resting potential LESS negative, so less Na+ ions required to reach threshold
34
Q

inhibitory neurotransmitters

A
  • resting potential becomes hyperpolarised
  • less likely to reach threshold
  • less likely to generate an action potential
35
Q

effects of drugs on synapses:

A
  • stimulate NS by creating more action potentials
  • similar shapes to neurotransmitter so bind on postSN and mimic effect
  • or reduce action potentials so inhibitoty effect
  • ior ncrease release of neurotransmitters
  • inhibit enzymes hydrolysing neurotransmitters
36
Q

ao2 examples of drugs

A

cocaine: prevents hydrolysis of neurotransmitters
- codeine: binds to receptors for endorphins
- heroin: binds to receptors for endorphins in pain pathways
- valium: increases effect of GABA
caffeine: reduces threshold for excitation of neurones
- botox inhibits release of acetylcholine

Biology (29 decks)

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