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A Level Biology > 6B Nervous Coordination > Flashcards

6B Nervous Coordination Flashcards

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1
Q

What are the three types of muscles?

A

Smooth muscles, cardiac muscle, skeletal muscles

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2
Q

What are smooth muscles?

A

They contract without conscious control- found in the walls of internal organs (except the heart, stomach and intestine)

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3
Q

What are cardiac muscles?

A

They contract without conscious control but is only found in the heart

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4
Q

What are skeletal muscles?

A

The type of muscles that you can use to move

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5
Q

How are skeletal muscles attached to the bone?

A

By tendons

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6
Q

Agonist

A

Contracting muscle

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7
Q

Antagonist

A

Relaxing muscle

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8
Q

Muscle fibres

A

Large bundles of long cells

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9
Q

Sarcolemma

A

Muscle cell’s cell membranes

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10
Q

Sarcoplasm

A

Muscle Cell’s cytoplasm

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11
Q

T-Tubules

A

Parts of the sarcolemma that fold into the sarcoplasm that help to spread electrical impulses through the entire of the sarcoplasm so they reach all parts of the muscle fibre

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12
Q

Sarcoplasmic Reticulum

A

A network of internal membranes that store and release calcium ions

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13
Q

Adaptations of muscle fibres

A

Lots of mitochondria for ATP, multinucleate (contain many nuclei) and lots of myofibrils

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14
Q

Myofibrils

A

bundles of thick and thin myofilaments that move past each other to allow for muscle contraction

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15
Q

Myosin

A

Thick myofilaments

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16
Q

Actin

A

Thin myofilaments

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17
Q

Dark bands

A

Myosin and overlapping actin

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18
Q

Light bands

A

Only contain actin

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19
Q

Sarcomeres

A

A short unit of myofibril

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20
Q

Z-Line

A

The end of the sarcomere

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21
Q

M-Line

A

The middle of the sarcomere

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22
Q

H-zone

A

Only contains myosin filaments

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23
Q

A-band

A

Dark band

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24
Q

I-band

A

Light band

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25
Q

Describe the sliding filament theory

A

myosin and actin filaments slide over each to make the sarcomeres contract- during contraction, the z-lines get closer together (sarcomeres get smaller)

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26
Q

Describe the myosin filament

A

Globular head that is hinged so can move back and forth

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27
Q

Describe the actin filament

A

Have binding sites for the myosin heads

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28
Q

Tropomyosin

A

Blocks the actin myosin binding site

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29
Q

What happens when an action potential reaches the muscle cell?

A

It depolarises the sarcolemma. Depolarisation spreads through the t-tubules to the sarcoplasmic reticulum. The sarcoplasmic reticulum then releases calcium ions into the sarcoplasm

30
Q

How do calcium ions trigger a muscle contraction?

A

They bind to troponin which is attached to the tropomyosin. Troponin changes shape which causes tropomyosin to leave the actin myosin binding site. Calcium ions also activate the enzyme ATP hydrolase

31
Q

Actin myosin cross bridge

A

The bond that is formed when the actin and myosin head bind, after the tropomyosin has been removed

32
Q

How does ATP aid in muscle contraction?

A

ATP hydrolase is triggered which breaks down ATP into ADP and Pi. The energy released causes the myosin head to bend, pulling the actin filament along in a rowing action. ATP is the hydrolysed again to break the actin myosin cross bridge. The myosin head then moves to the next binding site

33
Q

How do muscles return to their resting state?

A

Calcium ions leave their binding site and move back via active transport into the sarcoplasmic reticulum (this requires ATP again). This causes the tropomyosin molecules to move back into the actin myosin binding site

34
Q

How do muscles get energy for contraction?

A

Aerobic respiration, anaerobic respiration, ATP-phosphocreatine (PCr) system

35
Q

What is APT-phosphocreatine system?

A

A phosphate group is taken from Pcr and added to ADP. PCr runs out after a few seconds so is used for short bursts of energy
ADP + PCr = ATP + Cr

36
Q

Why are there higher levels of creatinine in people who exercise more?

A

Some of the creatine (Cr) is broken down into creatinine and pass from the body via the kidneys. A high muscle mass= higher creatinine levels. High creatinine levels can also indicate kidney damage

37
Q

What are the two types of skeletal muscles?

A

Slow twitch and fast twitch

38
Q

Slow twitch muscles

A

Contract slowly and can work for a long time without getting tired. Energy is released via aerobic respiration

39
Q

Fast twitch muscles

A

Contract very quickly but also get tired quickly. Energy is released through anaerobic respiration and also PCr

40
Q

What is myoglobin and why so slow twitch muscles have more?

A

A red coloured protein that stores oxygen for aerobic respiration

41
Q

Describe a neurone at its resting potential

A

Outside of membrane is positively charged compared to the inside- more positive-. Potential difference is -70mV. The resting potential is maintained by a sodium potassium pump and potassium channels in the membrane of the neurone

42
Q

Describe the sodium potassium pump of a neurone at resting potential

A

The active transport of 3Na+ out for every 2K+ in. This creates a sodium electrochemical gradient. Potassium ions can move back out via facilitated diffusion through the potassium channels

43
Q

Describe the changes in potential difference during an action potential

A

A stimulus excites the neurone, causing the opening of the sodium ion channels. This makes the neurone less negative. Once a threshold is reached (-55mV) voltage gated sodium ion channels open. (depolarisation). At a P.D of +30mV the Na+ channels close and the K+ channels open (repolarisation). K+ ions overshoot as they are too slow to close- hyperpolarisation. The ion channels reset and the sodium potassium pump returns the membrane to its resting potential

44
Q

Describe how an action potential moves down the neurone

A

As a wave of depolarisation- Na+ ions diffuse sideways, causing Na+ channels of the next region of the neurone to open

45
Q

Describe the refractory period and why it is important

A

Ion channels can’t be opened- acts as a time delay. This means action potentials won’t overlap, there’s a limit to the frequency that action potentials can be transmitted, and so action potentials are unidirectional

46
Q

What are the three factors that affect the speed of conductions of the action potentials?

A

Myelination, axon diameter, temperature

47
Q

How does myelination affect the speed of conduction of an action potential?

A

They have a myelin sheath which acts as an electrical insulator. Depolarisation only happens at the nodes of Ravnier, where Na+ channels are concentrated, this means the cytoplasm of the neurone can help the action potential jump to the nodes (salatory conduction)

48
Q

What is the myelin sheath made from?

A

Schwann cells

49
Q

Salatory Conduction

A

The cytoplasm of the neurone can conduct enough electrical charge to depolarise the next node, so the impulse “jumps” from node to node

50
Q

How does axon diameter affect the speed of conduction of action potentials?

A

Quicker with bigger diameters because there’s less resistance to the flow of ions, so depolarisation reaches other parts of the cell membrane quicker

51
Q

How does temperature affect the speed of conduction of action potentials?

A

Ions diffuse faster at higher temperatures do to having more kinetic energy

52
Q

Synapse

A

The junction between two neurones

53
Q

The synaptic clef

A

The tiny gap between the cells at the synapse

54
Q

Where is the synaptic knob

A

On the presynaptic neurone

55
Q

What does the synaptic knob contain?

A

Synaptic vesicles filled with chemicals called neurotransmitters

56
Q

What happens when an action potential reaches the presynaptic neurone?

A

The action potential triggers the release of the neurotransmitter into the synaptic clef

57
Q

What does the neurotransmitter do?

A

It diffuses across the synaptic clef and binds to the specific receptors on the postsynaptic neurone, which triggers an action potential

58
Q

Why are impulses across the synapse unidirectional?

A

The specific receptors for the neurotransmitter are only on the postsynaptic neurone

59
Q

How and why is the neurotransmitter removed from the synaptic clef?

A

The are taken back into the presynaptic neurone or broken down by enzymes to stop the response- prevent constant stimulation.

60
Q

What are synapses called that use acetylcholine?

A

Cholinergic synapses

61
Q

Describe the second messenger model that is used to transport ACh across the synaptic clef

A

An action potential arrives at the synaptic knob of the presynaptic neurone. The action potential stimulates the opening of voltage-gated calcium ion channels. Calcium ions diffuse into the synaptic knob. The Ca2+ ions cause the vesicles to move to and then fuse with the presynaptic membrane. The vesicles then release ACh into the synaptic clef

62
Q

Exocytosis

A

The vesicles releasing the neurotransmitter into the synaptic clef

63
Q

Describe how the neurotransmitter binds to the receptors and creates an action potential

A

The neurotransmitter binds to the specific receptors on the post synaptic membrane. Na+ ions open in the postsynaptic membrane. The influx of Na+ ions causes depolarisation, and an action potential is triggered if the threshold is reached

64
Q

What enzyme is used to break down ACh in the synaptic clef? and describe the process

A

Acetylcholinesterase then the products are reabsorbed into the presynaptic neurone and is used to make more ACh

65
Q

What are excitatory neurotransmitters

A

Depolarise the postsynaptic membrane, making it fire an action potential (if the threshold is reached)

66
Q

What are inhibitory neurotransmitters?

A

Hyperpolarise the postsynaptic membrane, preventing it from firing an action potential

67
Q

Summation

A

The effect of neurotransmitter released from many neurones is added together

68
Q

Spatial Summation

A

Many neurones connect to one neurone

69
Q

Temporal summation

A

Two or more nerve impulses arrive in quick succession from the same presynaptic neurone- more neurotransmitter is released into the synaptic clef

70
Q

Neuromuscular junction

A

a synapse between a motor neurone and a muscle cell

71
Q

How can drugs affect the action of neurotransmitters?

A

Some have the same shape, so are complementary to the receptors- so more receptors are activated
Some block receptors so they can’t be activated by neurotransmitters
Inhibit the enzyme that breaks down the neurotransmitter- more neurotransmitters to bind to the receptors
Stimulate the release of the neurotransmitter from the presynaptic neurone
Some inhibit the release of neurotransmitters

A Level Biology (10 decks)

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