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Physiology > Muscle Physiology > Flashcards

Muscle Physiology Flashcards

1
Q

What is the end of a neuron called?

A

Bouton.

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2
Q

What type of muscle is the motor and plate?

A

Skeletal

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3
Q

What are the two other names for a smoatic motor neuron?

A

Lower motor neuron or Alpha motor neuron.

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4
Q

How wide is the synaptic cleft?

A

20um no physical contact between the nerve and the muscle.

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5
Q

What are there lots of in the pre-synaptic nerve terminal and post synaptic terminal?

A

Lots of mitochondria.

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6
Q

If no physical contact how does the message transfer across the synaptic cleft?

A

Via the release of neurotransmitter acetylcholine (ACh) into the synaptic cleft.

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7
Q

Where is acetylcholine produced and stored?

A

It is produced in the nerve terminal and stored there is the synaptic cleft.

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8
Q

What happens after the release of the neurotransmitter acetylcholine into the synaptic cleft.

A

ACh binds to receptors on the muscle and this triggers the EPP (end plate potential) in muscle cell.

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9
Q

What type of muscle is used during an action potential?

A

Skeletal Muscle.

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10
Q

What happens to ACh after the chemical synapse

A

Acetylcholinesterase is broken down by AChE and the components are recylced.

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11
Q

What is an EPP?

A

EPP happens before muscle action potential.

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12
Q

What ions are needed for the sequence of an action potential?

A

Calcium ions.

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13
Q

What are the two types of skeletal muscle fibers?

A

Type I slow twitch, red muscle fibers ex: postural muscles and Type II fast twitch, white muscle fibers ex: extraocular muscles.

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14
Q

Which type of muscle fibers has more myoglobin? Type I or Type II?

A

Type I

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15
Q

Which type of muscle fiber has more mitochondria and a more used oxidative metabolism?

A

Type I, the other type has less mitochondria and more glycolytic metabolism.

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16
Q

What hydrolyzes ATP quickly?

A

Myosin ATPase isoform

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17
Q

Is the sarcoplasmic reticulum developed in the Type I more or the other type?

A

SR is more developed in the Type II fast twitch white fibers.

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18
Q

What is the gross structure of muscle?

A

Muscle fibers > myofibrils > myofilaments of actin and myosin giving the muscle its striated appearance.

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19
Q

What are the two proteins which make up the myofibril?

A

Actin (thin) and Myosin (thick)

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20
Q

Where is the calcium stored used in the muscle ?

A

In the sarcoplasmic reticulium

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21
Q

Do the muscle fibers have a lot of mitochondria?

A

Yes.

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22
Q

How is the spread of muscle action potentials spread?

A

Through the network of the T-tubules

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23
Q

What are myofibrils made up of?

A

Structures called sarcomeres.

24
Q

What is the sarcomere in relation to the muslce?

A

It is the contractile unit. The sarcomere extends from one Z disc to the next. IT gives muscle its striated appearance.

25
Q

What proteins are sarcomeres composed of?

A

Titin - anchoring, coiled disc connecting the sarcomere to the z-disc. Actin = thin filament. Myosin = thick filament.. Also Troponin and Tropomyosin which are additional p components of the ACTIN filaments.

26
Q

What is the order of the bands/zones of the sarcomere?

A

Z-disc, titin filament, A band, H zone/M line, A band, thick filament, Z-disc. Z-discs are not a part of the sarcomere.

27
Q

When is the green myosin head in contact with cross bridge?

A

When Pi has been released causing a conformational change in myosin. the cross bridge binds to actin.
Binds to troponin C element in the thin chain, the actin filament.

28
Q

What triggers the cross bridge to bind to actin?

A

Muscle action potential which triggers the release of calcium from the SR.

29
Q

What is the function of calcium in relation to the cross bridge cycle?

A

Calcium binds to troponin C of actin allowing the myosin crossbridge to interact with actin.

30
Q

When does the myosin head detach?

A

By the binding of ATP to the myosin head. Allowing it to release from actin.

31
Q

What allows for the power stroke i.e the sliding of the 2 filaments actin and myosin in the cross bridge cycle?

A

The detachment of the inorganic phosphate from the myosin head.

32
Q

After new ATP binds to the myosin causing it to detach from the actin what happens to the muscle?

A

The muscle relaxes and calcium in facilitated/pumped back into the SR, ATP is hydrolysed.

33
Q

What are the three stages of the muscle contraction- relaxing? How long dies it take?

A

Latent period (0), contraction period (5-25), relaxation period (25-55) msec. Tension/force

34
Q

What is a muscle twitch?

A

Contraction caused by relaxation period.

35
Q

What is tetanus/tetany?

A

This is a sustained muscle contraction. Flat line/plateau followed by fatigue. More force exhibited, more ap than a normal muscle twitch.

36
Q

How is tetanus in skeletal muscle manufactured?

A

At high levels of stimulation, temporal summation (more AP) there is a sustained rise in the intracellular calcium which allows for a greater force than during a single twitch.

37
Q

What is a motor unit?

A

This is an alpha motor neurone and all the muscle fibers innervated by that neurone.

38
Q

What determines the force of contraction of the motor units?

A

Depends on how precise the control is on that muscle.

39
Q

How would one increase the force of contraction on a smaller muscle unit ?

A

Muscle units are recruited first, as more and more force is needed more MU come into play. Increase in force/strength is graded proportional.

40
Q

What happens during prolonged contraction of a muscle ?

A

The muscle units rotate, some are contracting while some are not this prolongs the onset of fatigue.

41
Q

As muscle length increases there is an increase in tension developed… is there a limit to this?

A

Yes there is C - overstretched sarcomere with no overlap between actin and myosin.

42
Q

How is the maximum strength of contraction B achieved? 2.0um and 2.25um

A

As there is an optimal resting length for the sarcomere in order to achieve this.

43
Q

What happens if the sarcomere is too short ?

A

The actin filaments collide into each other and tension is also reduced.

44
Q

What varies with the load of the muscle?

A

The velocity of the muscle.

45
Q

What is isotonic, type of muscle contraction?

A

This is where there is constant tension, muscle length changes ex: moving an object through a distance.

46
Q

What is isometric, type of muscle contraction?

A

This is where there is a constant length, tension doesn’t exceed the load, object doesn’t tend to move.

47
Q

Where is smooth muscle found?

A

In the GI tract, in the autonomic functional areas of the body.

48
Q

Where is cardiac muscle striated?

A

Across the atria on top and ventricles on the bottom.

49
Q

What is the name of the cardiac muscle pacemaker and what is it able to do?

A

SN, sinoatrial node and it is capable of spontaneous depolarization aka action potentials.

50
Q

Which action potential takes longer, cardiac or skeletal?

A

The cardiac muscle is much longer, this stops the heart from going into a state of tetany. Heart is pump.

51
Q

What is said of the action potentials which when coupled with the gap junctions in the cardiac muscle?

A

All or nothing, no motor units or all. The entire muscle behaves like an electrical syntium where all muscle cells behave like one cell. No motor units in cardiac muscle.

52
Q

Does smooth muscle (autonomic) have sarcomeres or troponin as its components?

A

No, contractions occur in response to other stimuli ex: hormones and stretch.
Also poorly developed SR therefore extracellular calcium is very important together with the SR calcium.

53
Q

What is the name of the binding protein involved in smooth muscle contraction?

A

Calmodulin which is a calcium binding protein that activates the enzyme myosin light chain kinase (MLCK)

54
Q

What are the distinguishing factors between single unit muscle and multi-unit muscle?

A

Single unit muscle has many fibers contracting as a single unit hence the importance of gap junctions (peristalsis). Multi-unit muscle is controlled be nerve signals and individual muscle fibers may be stimulated by individual nerve fibers (muscles of eye).

55
Q

Describe the mechanism of smooth muscle contraction?

A

This is a basic mechanism of actin/myosin interaction with cross-bridge formation, this is the same as for the other 2 muscles but * thick * filaments are regulated with MLCK activation of myosin.

56
Q

What do all three muscle types need to function?

A

ATP.

Physiology (5 decks)

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