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Biology A-Level > Nervous Coordination > Flashcards

Nervous Coordination Flashcards

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1
Q

Describe the cell membrane of a neurone at resting state

A
  • Outside: +ve charged compared to inside
  • bc more +ve ions outside
  • Membrane = polarised (diff. charge)
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2
Q

Define potential diff/voltage

A

Diff in charge

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3
Q

What is the v called when at rest?

A
  • Resting potential
  • -70v
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4
Q

The sodium-potassium uses ____ so ___ is required

A
  • AT
  • ATP
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5
Q

How is the resting potential created + maintained?

A
  • Sodium potassium pump
  • 3 Na+ moves out neurone, membrane not permeable so can’t diffuse back in
  • Creates Na+ electrochemical gradient
  • Pump also moves 2 K+ in neurone but membrane permeable so (facilitated) diffuse out through potassium ion channel
  • Makes outside +ve charged compared to inside
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6
Q

When does an action potential occur?

A
  • Stimulus big enough, Na+ channels open
  • Triggers rapid change in potential diff
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7
Q

What happens in the refractory period?

A
  • Neurone cell membrane can’t be excited straight away
  • bc ion channels are recovering
  • Na<strong>+</strong> channels closed during repolaristion + K+ channels closed during hyperpolarisation
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8
Q

Explain how the action potential moves along the neurone as a wave of depolarisation

A
  • During AP, some Na+ that enter neurone diffuse sideways
  • Causes Na+ channels in next region to open + Na+ diffuse into that part
  • Causes wave of depolarisation to travel along neurone
  • Wave moves away from parts of membrane in refractory period bc can’t fire AP
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9
Q

The refractory period acts as a time delay, what does the mean?

A
  • AP don’t overlap but pass along as descrete impulses
  • Limit to freq to which impulses can be transmitted
  • AP are unidirectional (1 direction)
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10
Q

Action potentials have an all or nothing nature, what does this mean?

A
  • Once threshold is reached, AP will always fire w/ same charge in v
  • If threshold not reached, AP won’t fire
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11
Q

What does a bigger stimulus result in?

A

More frequent AP

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12
Q

What factors affect the speed of conduction of action potential?

A
  • Myelination
  • Axon diameter
  • Temp
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13
Q

What is myelination?

A

When neurones have myelin sheath - electrical insulator

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14
Q

In the peripheral NS, what is the sheath made from?

A

Schwann cell

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15
Q

What are the sections btw the schwann cells?

A

Bare membrane - nodes of Ranvier

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16
Q

What are conc at the nodes?

A

Na+ channels

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17
Q

How does the action potential go across through a myelinated neurone?

A

Saltatory conduction

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18
Q

How does saltatory conduction take place?

A
  • Depolarisation only occurs at nodes of ranvier
  • Cytoplasm conducts enough electrical charge to depolarise next node, so impulse jumps node to node
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19
Q

How does an impulse travel along a non-myelinated neurone?

A

Travels as wave along whole length of axon membrane

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20
Q

Does an impulse travel faster along a myelinated or a non-myelinated neurone? Why?

A
  • Myelinated
  • Saltatory conduction allows impulses to travel quickly
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21
Q

How does the axon diameter affect speed of conduction?

A
  • Bigger diameter = less resistance to flow of ions
  • Depolarisation reaches other parts of neurone membrane faster
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22
Q

How does the temperature affect speed of conduction?

A
  • Temp inc = ions diffuse faster
  • Only upto 40ºc bc proteins denature + speed dec
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23
Q

Define synapse

A

Junction btw neurone + another neurone, neurone + effector cell

24
Q

How does synapses ensure that nerve impulses are unidirectional?

A

Reeceptors only on post synaptic membrane

25
Q

Why and how are the NT removed from the cleft?

A
  • So response doesn’t keep happening
  • Taken back into presynaptic neurone
  • Broken down by enzymes
26
Q

Define excitatory NT

A

Depolarise post synaptic membrane, making it fire an action potential if the threshold is reached

27
Q

Define inhibitory NT

A

Hyperpolarise post synaptic membrane, preventing it from firing an AP

28
Q

Define summation

A

Effect of NT released from many neurones is added together

29
Q

Spatial summation

A
  • Many neurones connect to 1 neurone
  • Small amounts of NT released from each neurone can be enough altogether to reach threshold in postsynaptic neurone + trigger AP
  • If inhibitory NT released = no AP
30
Q

Temporal summation

A
  • 2/more nerve impulses arrive in quick sucession from same presynaptic neurone
  • Makes AP more likely bc more NT released into synaptic cleft
31
Q

What does summation mean for synapses?

A

Synapses can accurately process info, finely tuning response

32
Q

Define neuromuscular junction

A

Synapses btw motor neurone + muscle cell

33
Q

What does acetylcholine bind to in neuromuscular junctions?

A

Cholinergic receptors called nicotine cholinergic receptors

34
Q

What are the diff btw cholinergic synapses + neuronmuscular junctions?

A
  • Post synaptic mebrane has lots of folds that form clefts - stores enzyme that break down ACh (acetyl cholinesterase)
  • More receptors
  • ACh always excitatory at neuromuscular junction- motor fires AP = tiggers response in muscle cell
35
Q

What are agonist drugs + what do they do?

A
  • Same/similar shape as NT so mimic their action at receptors
  • Means more receptors are activated
36
Q

What are antagonist drugs + what do they do?

A
  • Same/similar shape as NT so block receptors so can’t be activated
  • Fewer receptors can be activated
37
Q

What happens when drugs inhibit enzymes that break down NT?

A

More NT in synaptic cleft to bind to receptors + they’re there for longer

38
Q

What do some drugs stimulate the release of?

A

NT from presynaptic neurone so more receptors are activated

39
Q

What do some drugs inhibit the release of?

A

NT from presynaptic neurone so fewer receptors are activated

40
Q

Describe how a nerve impulse is transmitted across a cholinergic synapse (8)

A
  • Impulse causes Ca<strong>2+</strong> to enter axon
  • Vesicles move to presynaptic membrane
  • Acetylcholine released
  • Diffuse across synaptic cleft/synapse
  • Binds w/ receptor on post synaptic membrane
  • Na+ enter post synaptic neurone
  • Depolarisation of post synaptic membrane
  • If above threshold, AP produced
41
Q

Skeletal muscles

A

Muscles you use to move

42
Q

Tendons

A

Attach skeletal muscles to bones

43
Q

Ligaments

A

Attach bones to bones

44
Q

Why are muscles described as antagonistic pairs?

A
  • Contracting muscle: agonist
  • Relaxing muscle: antagonist
  • Bones of skeleton are incompressible so act as lever, giving muscles something to pull against
45
Q

Outline the structure of a skeletal muscle

A
  • Large bundles of long cells - muscle fibres
  • Cell membrane of muscle fibre - sarcolemma
  • Sarcolemma fold inwards + stick into sarcoplasm, folds = transverse tubule, help spread electrical impulse throughout sarcoplasm
  • Network of internal membrane (sarcoplasmic reticulum) runs through sarcoplasm, stores + releases Ca<span>2+</span> needed for contraction
  • Lots of mitochondria provide ATP
  • Multinucleate
  • Made up of myofibrils, specialised for contraction
46
Q

Myosin

A
  • Thick myofilament
  • Dark
  • A band
47
Q

Actin

A
  • Thin myofilament
  • Light
  • I band
48
Q

Contracted sarcomere

A
  • A band stays same
  • I band, H zone + sarcomere gets shorter
49
Q

Outline the structure of myofibrils when a muscle is at rest

A
  • Actin-myosin binding site is blocked by tropomyosin
  • Myofilaments unable to slide past bc myosin head can’t bind
50
Q

Outline the process when muscles contract

A
  • AP depolarises sarcolemm, spreads to t tubules + down SR, releases Ca2+ to sarcoplasm
  • Ca2+ binds to protein on tropomyosin, changes shape pulling tropomyosin out AM binding site on actin
  • Exposes binding site allowing myosin head to bind, forming AM cross bridges
  • CA2+ activates ATP hydralase, hydrolysing ATP
  • Energy causes myosin head to bend, pulling actin filament along
  • Another ATP provides energy to break AM cross bridge so myosin head detaches
  • Myosin head reattaches to another binding site
51
Q

What happens when muscles relax?

A
  • Ca2+ leave binding site + AT into SR
  • Causing tropomyosin to block AM binding site
  • Actin filament slides back to relaxed position, lengthens sarcomere
52
Q

Aerobic respiration

A
  • ATP generated via OP in mitochondria
  • Oxygen available
  • Long periods of low intenisity exercise
53
Q

Anaerobic respiration

A
  • ATP generated rapidly by glylosis
  • Pyruvate → lactate - causing muscle fatigue
  • Short periods of hard exercise
54
Q

ATP phosphocreatine system

A
  • ATP made by phosphorylating ADP - adding phosphate group from PCr
  • PCr stored inside cells but runs out quickly, short bursts of vigorous exercise
  • Generates ATP quickly
  • Anaerobic
  • Alactic
55
Q

Slow twitch muscle fibres

A
  • Contract slowly
  • Endurance activity
  • Work for long time w/o getting tired
  • Energy released slowly via aerobic respiration, lots of mitochondria + blood vessels
  • Red bc rich in myoglobin
56
Q

Fast twitch muscle fibre

A
  • Contracts quickly
  • Short bursts of speed + power
  • Get tired quickly
  • Energy released quickly via anaerobic respiration using glycogen. Few mitochondria + blood vessels
  • White bc lacks myoglobin

Biology A-Level (10 decks)

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