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Biology > Topic 6B: Nervous Coordination > Flashcards

Topic 6B: Nervous Coordination Flashcards

1
Q

What is a neurone like at rest?

A
  • Resting potential (around -70mv)
  • Polarised -> outside is positive - more +ve ions
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2
Q

How is the resting potential maintained?

A
  • Sodium-potassium pump
  • 3Na+ moved out - membrane not permeable to them - can’t diffuse back in - build up outside - sodium electrochemical gradient
  • 2K+ moved in - membrane more permeable to them so diffuse back out through K+ channels
  • Needs energy from ATP
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3
Q

How does depolarisation of a neurone occur?

A
  • Stimulus excites the neurone cell membrane opening voltage gated Na+ channels - Na+ move in (facilitated diffusion) - membrane becomes less negative - generator potential
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4
Q

How does an action potential form from a depolarised neurone?

A
  • If threshold reached - action potential formed
  • Membrane becomes more permeable to Na+ - more channels open - Na+ rush in by facilitated diffusion - further depolarisation
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5
Q

How does repolarisation occur?

A
  • Voltage gated Na+ channels close and K+ open
  • Na+ cannot enter but more K+ leave by facilitated diffusion - so axon becomes more negative
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6
Q

How does hyperpolarisation happen?

A
  • Voltage gated K+ channels slow to close - axon briefly too negative - more negative than the resting potential
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7
Q

How is the resting potential reset?

A
  • Ion channels reset
  • Sodium-potassium pump returns the membrane to the resting potential
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8
Q

What is the refractory period?

A
  • After an action potential - neurone cannot immediately be excited - ion channels are recovering - can’t be made to open
  • Na+ channels closed, K+ closed
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9
Q

Describe a wave of depolarisation

A
  • With an action potential - some Na+ move sideways (diffuse) - causes Na+ channels there to open and Na+ to enter
  • Wave moves away from the part of membrane in the refractory period - these cannot produce an action potential
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10
Q

How are impulses made discrete?

A
  • Refractory period - ion channels recovering - acts as a time delay between action potentials
  • Action potentials do not overlap
  • Limit frequency impulses can be transmitted
  • Action potentials unidirectional
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11
Q

How are action potentials all or nothing?

A
  • If the threshold reached - action potential always happens
  • Same change in voltage - always same size
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12
Q

How is a bigger stimulus expressed?

A
  • More frequent action potentials
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13
Q

What is myelin?

A
  • Electrical insulator
  • Schwann cells
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14
Q

What are patches of bare membrane on neurones called?

A
  • Nodes of Ranvier
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15
Q

How does myelination help impulses?

A
  • Depolarisation happens only at the nodes of Ranvier - impulse jumps - faster - only areas Na+ can move through
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16
Q

What is the movement of impulses in myelinated neurones called?

A
  • Saltatory conduction
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17
Q

What is an advantage of myelination?

A
  • Less ATP needed - resting potentials only re-established at the nodes - less work for sodium-potassium pump
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18
Q

How do impulses move in unmyelinated neurones?

A
  • Wave of depolarisation must pass through every section of the membrane
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19
Q

How does axon diameter affect the speed of impulses?

A
  • Wider = faster impulse transmission - less resistance to flow of ions in the cytoplasm
  • Smaller SA:V = fewer ions leak - action potentials propagate easier
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20
Q

How does temperature affect the speed of impulses?

A
  • Ions diffuse faster - have more kinetic energy
  • Enzymes in respiration work faster - more ATP for active transport in sodium-potassium pump
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21
Q

How is synaptic transmission unidirectional?

A
  • Receptors only on post synaptic membrane
  • Vesicles of neurotransmitter only in presynaptic neurone
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22
Q

What does an action potential do in the presynaptic membrane?

A
  • Action potential arrives at presynaptic knob
  • Voltage gated Ca2+ channels open
  • Ca2+ move in
    Make vesicles of neurotransmitter (ACh) move to the membrane, fuse and release into the synaptic cleft
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23
Q

What does neurotransmitter do once released?

A
  • ACh diffuses across the cleft, binds to complimentary receptors on postsynaptic membrane
  • Na+ channels open, N’a+ move in
  • Membrane depolarised
  • Action potential if threshold reached
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24
Q

What happens to ACh after the impulse has been transmitted?

A
  • Removed from cleft so the response stops
  • Acetylcholinesterase breaks it down - products reabsorbed into presynaptic neurone to reform ACh
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25
Q

What do excitatory neurotransmitters do?

A
  • Depolarise the postsynaptic membrane
  • Create action potential if threshold reached
  • e.g. Neuromuscular junction and Na+ channels open
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26
Q

What do inhibitory neurotransmitters do?

A
  • Hyperpolarise the postsynaptic membrane
  • Prevent an action potential by making it more negative
  • e.g. ACh in heart - K+ channels open and move out
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27
Q

What is temporal summation?

A
  • Multiple impulses from 1 presynaptic neurone in succession
  • Inc conc neurotransmitter in cleft
  • Inc likelihood of an action potential
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28
Q

What is spatial summation?

A
  • Multiple impulses from multiple presynaptic neurones all applied to one postsynaptic neurone
  • Add together for an action potential
29
Q

What is the sarcolemma?

A
  • Membrane of muscle cell
30
Q

What is the sarcoplasm?

A
  • Cytoplasm of muscle cells
31
Q

What is the sarcoplasmic reticulum?

A
  • Endoplasmic reticulum of muscle cells
32
Q

What is a neuromuscular junction?

A
  • Synapse between motor neurone and muscle cell
33
Q

What neurotransmitter is used and what does it bind to?

A
  • ACh
  • Nicotinic choligernic receptors
34
Q

What are the differences between a cholinergic synapse and a neuromuscular junction?

A
  • Postsynaptic membrane has folds - clefts that store acetylcholinesterase
  • Postsynaptic membrane has more receptors
  • ACh always excitatory - normally triggers a response
35
Q
A
36
Q

What are 5 ways a drug can impact synapses?

A
  • Same shape as neurotransmitter - mimic action - more receptors activated - agonist
  • Block receptors so they cannot be activated - fewer receptors activated - antagonist
  • Inhibit enzyme that breaks down neurotransmitter in cleft - more left in cleft
  • Stimulate release of neurotransmitter from presynaptic neurone - more receptors activated
  • Inhibit release of neurotransmitter from presynaptic neurone - fewer receptors activated
37
Q

What are antagonistic muscles?

A
  • Work in pairs to move a bone
  • One contracts, the other relaxes
38
Q

What is the general structure of a muscle?

A
  • Large bundles of long cells - muscle fibres
39
Q

What are t-tubules and what do they do?

A
  • Bits of sarcolemma fold inwards into the sarcoplasm
  • Helps spread electrical impulses throughout the sarcoplasm to all parts of the muscle fibre
40
Q

What does the sarcoplasmic reticulum do?

A
  • Stores and releases Ca2+
41
Q

What organelles do muscle cells have that make it specialised?

A
  • Lots of mitochondria - ATP for contraction
  • Multinucleated - DNA to code for proteins and enzymes
42
Q

What is myosin?

A
  • thick filament
43
Q

What is actin?

A
  • Thin filament
44
Q

What is the A band?

A
  • Dark bands
  • Myosin and overlapping actin
45
Q

What is the I band?

A
  • Light bands
  • Actin only
46
Q

What is the H zone?

A
  • Slightly dark
  • Only myosin
47
Q

What is the Z line?

A
  • Ends of sarcomeres
  • Centre of actin and I band
48
Q

What is the M line?

A
  • Middle of myosin and H zone
49
Q

What is a sarcomere?

A
  • 1 contracting unit of the myofibril
50
Q

What happens to the sarcomere length when it contracts?

A
  • Gets shorter
51
Q

What happens to the A band when it contracts?

A
  • Same length
52
Q

What happens to the I band when it contracts?

A
  • Gets shorter
53
Q

What happens to the H zone when it contracts?

A
  • Gets shorter
54
Q

What are myosin heads like?

A
  • Hinged globular heads - move back and forth
  • Has binding site for actin and ATP
55
Q

What are binding sites on actin like?

A
  • Has binding sites for myosin
  • Blocked by tropomyosin
56
Q

How does the muscle begin to contract?

Action potential to cross bridge formation

A
  • Nerve impulse arrives at neuromuscular junction - ACh released into cleft - binds to complimentary receptors on sarcolemma - Na+ channels open and Na+ move in
  • Action potential produced in sarcolemma and travels along t-tubules
  • Sarcoplasmic reticulum more permeable to Ca2+ - diffuse out into sarcoplasm - bind to tropomyosin
  • Binding sites on actin revealed, myosin binds and cross bridges are formed
57
Q

How do muscle filaments move past each other?

A
  • Myosin heads change angle - powerstroke
  • Actin pulled across myosin - ADP released
58
Q

How do myosin heads detach?

A
  • ATP binds to head, detaches, Ca2+ activates ATP-ase to hydrolyse ATP providing energy so myosin heads return to their original position - recovery stroke
59
Q

How does contraction continue?

After myosin detached

A
  • Myosin attaches to new site, continues
60
Q

What happens when muscle contraction is done?

A
  • Ca2+ pumped back into the sarcoplasmic reticulum
61
Q

What is the role of ATP in muscle contraction?

A
  • Allow myosin to attach
  • Cause head to move back to original position
  • ADP+Pi released from myosin head to cause it to ,move - powerstroke
62
Q

What are slow twitch muscles and what are they for?

A
  • Contract slowly
  • Endurance
63
Q

What are features of slow twitch muscles?

A
  • Fatigue slowly
  • Lots of mitochondria - aerobic respiration
  • Lots of blood vessels - O2 supply
  • Dark colour - myoglobin
64
Q

What are fast twitch muscles and what are they for?

A
  • Contract quickly
  • Fast movement
65
Q

What are features of fast twitch muscles?

A
  • Fatigue quickly
  • Fewer mitochondria and blood vessels
  • Anaerobic respiration - use glycogen stores
  • Light colour - less myoglobin
66
Q

How does aerobic respiration release energy?

A
  • Oxidative phosphorylation from electron transport chain
  • Needs O2
67
Q

How does anaerobic respiration release energy?

And features of this

A
  • Glycolysis
  • Produces lactate - muscle fatigue
  • Short periods only
68
Q

How does the ATP phosphocreatine system release energy?

A
  • Phosphorylate ADP using phosphate from PCr - stored in cells
  • Stored incells
  • Generates ATP quickly
  • Anaerobic and alactic

Biology (19 decks)

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