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BIOLOGY > 6b nervous coordination > Flashcards

6b nervous coordination Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

describe neurones resting state

A

outside of membrane positicely charged
more positive ions on outside of membranes than inside
its polarised

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2
Q

what is the voltage across a memebrane at resting state

A

-70mv

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3
Q

what creates and maintains resting potentials

A

sodium potassium pumps

and potassium ion channels

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4
Q

describe how resting potential is made

A
  • sodium potassium pump pumps sodium ions out of neurone and as membrane isnt permeable to sodium ions they cannot diffuse back in
  • electrochemical gradient created
  • sodium potassium pump moves potassium ions into the neurone but membrane is permeable to potassium ions so they diffuse out of the neurone via potassium channels
  • creates positive charge outside of cell
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5
Q

how does sodium potassium pumps work

A

active transport to move 3 sodium ions out of neurone for every two potassium ions moved in
ATP required

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6
Q

describe stages of action potential

A

STIMULUS- excites nuerone membrane causing sodium channels to open
-membrane becomes more permeable to sodium so sodium ions diffuse into neurone down gradient making inside of neurone less negative

DEPOLARISATION- if the potential difference reaches threshold near -55mv more sodium ions open so more sodium ions diffuse into neurone

REPOLARISATION- at potnetial difference of +30 sodium ion channels close

  • potassium ion channels open
  • membrane more permeable to potassium so they diffuse out of neurone getting membrane back to resting potential

HYPERPOLARISATION-potassium ion channels slow to close so slight overshoot so potential difference becomes more negative than resting potential

RESTING POTENTIAL-ion channels reset -sodium potassium pump returns membrane to resting potential

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7
Q

what is the refractory period

A

after action potential neurone membrane cannot be excited again straight away as channels closed

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8
Q

explain wave of depolarisation

A

during action potential some sodium ions diffuse sideways causing sodium channels to open in next region of neurone causing wave of depolarisation

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9
Q

what happens due to refractory period

A
  • action potentials dont overlap they pass on discrete impulses
  • limit to frequency at which impulses can be transmitted
  • action potentials are unidirectional
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10
Q

describe all or nothing principle

A

bigger stimulus doesnt mean bigger action potential it means more frequent action potentials

if threshold isnt reached action potential will not fire

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11
Q

what three factors affect the speed of conduction of action potentials

A

myelination
axon diameter
temperature

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12
Q

what is a myelin sheath

A

electrical insulator

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13
Q

what cells make up myelinated sheath

A

schwann cells

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14
Q

what are between schwann cells

A

nodes of ranvier where sodium ions are concentrated

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15
Q

why does myelinated sheath increase speed of conduction to action potential

A

in myelinated neurone depolarisation only happens at the nodes of ranvier

cytoplasm conducts enough electrical charge to depolarise next node so impulse jumps from node to node

this is saltatory conduction

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16
Q

why is speed of conduction slower in non myelinated sheath

A

as impulses have to travel along the whole length of axon membrane

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17
Q

how does the diameter of axon effect speed of conduction

A

bigger axon means action potential conducted quicker as less resistance to flow of ions so depolarisation reaches other parts of neurone cell membrane quicker

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18
Q

how does temperature effect speed of conduction of action potential

A

speeds up diffuseion but after 40 degrees proteins begin to denature

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19
Q

what is a synapse

A

junction between two neurones 12

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20
Q

how does synapse work

A
  • presynaptic neurone has synaptic knob which contains synaptic vesicles filled with neurotransmittors
  • when action potential reaches end of neurone ig causes neurotransmitters to be releases to synaptic cleft and diffuse across tpo the postsynaptic membrane and bind to specific receptors
  • when they bind with receptors they can trigger action potential
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21
Q

explain how synapses are unidirection

A

as receptors are only on postsynaptic membrane

22
Q

how are neurotransmitters removed

A

removed from cleft to stop response from happening

taken back into presynaptic neurone and broken down by enzymes

23
Q

describe nerve impulse across a cholingeric synapse

A

1-action potential arrives at synaptic knob of presynaptic neurone

2-action potential causes stimulates calcium ion channels to open

3- calcium ions diffuse into the synaptic knob

4-influx of calcium causes synaptic vesicle to move to presynaptic membrane

5-vesicle releases acetylcholine into synaptic cleft |(exocytosis)

6-ACH diffuses across cleft and binds to spefic cholinergic receptor on post synaptic membrane

7-causes sodium ion channels to open in postsynaptic neurone

8-influx of sodium ions causes depolarisation

9- action potenital generated if threshold reached

10-acetylecholineesterase breaks down ACH and products go to presynaptic neurone

24
Q

what do excitatory neurotransmitters do

A

depolarise postsynaptic membrane making it fire action potential if threshold

25
Q

what do inhinbitory neurotransmitters do

A

hyperpolarise the postsynaptic membrane preventing from firing action potential

26
Q

what is summation

A

when effects of neurotransmitters from multiple neurones are added together - weak stimulius

27
Q

what are the two types of summation

A

spatial and temporal

28
Q

describe spatial summation

A

1- many neurones conected to one neurone
2-small amounts of neurotransmitters from each neurone are added together to reach threshoold in postsynaptic neurone
3- if some are inhibitory neurones then action potential may not be reached

29
Q

what is temporal summation

A

two or more nerve impulses arrive in quick succesion from same presynaptic neurone - action potential more likely as more neurotransmitters in synaptic cleft

30
Q

what is a neuromuscular junction

A

synapse between motor neurone and muscle cell

31
Q

in neuromuscular junctions what does acetylcholine bind to

A

receptrors called nicotinic cholinergic receptors

32
Q

what are the difference of neuromuscular junction and cholinergic synapse

A

post synaptic membrane has lots of folds forming clefts where enzyme acetylcholineesterase is stored

postsynaptic membrane has more receptors than pother synapses

acetylecholine is always excitatory

33
Q

describe agonist drugs effect on synapse

A

same shape as neurotransmitters
mimic there action at receptors
so more receptors activated

34
Q

describe antagonist drugs effect on synapse

A

block receptors

so cannot be activated by neurotransmitters

35
Q

how do drugs that inhibit enzymes effect synapse

A

more neurotransmitters

as less enzymes to break them down

36
Q

how do drugs work that effect presynaptic enurone

A

stimulate release of neurotransmitters or inhibit them

37
Q

what are skeletal muscles

A

use to move

38
Q

how is skeletal muscle attached to bones

A

tendons

39
Q

how are bones attached to other bones

A

ligaments

40
Q

how do muscles work together to move arm

A

work in antagonistic pairs
one contracts one relaxes
uses bone as lever as its incompressible- ridgid

41
Q

what are skeletal muscles made up of

A

large bundles of long cells called muscle fibres

42
Q

what is the cell membrane of muscle fibres called

A

sarcolemma

43
Q

describe structure of sarcolemma in muscle fibres in skeletal muscle

A

bits fold inwards and stick into sarcoplasm

these fold called transverse tubules which help spread electrical impulses evenly throughout muscle fibres

44
Q

what is the sarcoplasmic recticulum and how does it help muscle contraction

A

network of internal membranes which run through sarcoplasm

stores and releases calcium ions for muscle contraction

45
Q

why do muscle fibres have a lot of mitochondira

A

to provide atp for muscle contraction

46
Q

why are muscle fibres said to be multinucleate

A

contain multiple nuclei

47
Q

describe microfibrils in muscle fibres

A

long cylindrical

made of proteins highly specialised for contraction

48
Q

what does myofibrils contain which help muscles contract

A

thick myosin filaments and thin actic filaments

49
Q

what are thick myofilaments made from

A

protein myosin

50
Q

what are thin myofilaments made from

A

protein actin

51
Q

what are a bands

A
52
Q

what are a bands

A

BIOLOGY (20 decks)

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