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Rheumatology > Muscle physiology > Flashcards

Muscle physiology Flashcards

1
Q

What are the striations seen in muscle?

A

Actin (thin) and myosin (thick) filaments

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2
Q

What is a motor unit in muscle?

A

The motor neuron + the muscle fibre that it innervates

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3
Q

How is contraction stimulated in skeletal muscle?

A

Neurogenic stimulation

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4
Q

How is contraction of cardiac muscle stimulated?

A

Myogenic (pacemaker potential of the heart)

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5
Q

Is what type of muscle do you find gap junctions?

A

Cardiac

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6
Q

Is their gap junctions is skeletal muscle?

A

No

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7
Q

Is their neuromuscular junctions in skeletal muscle?

A

Yes

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8
Q

What ion is the link betweek exitation and contraction?

A

Contraction

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9
Q

Where does the calcium come from in skeletal muscle?

A

Sarcoplasmic reticulum

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10
Q

How is force of contraction increased in skeletal muscles?

A

Motor unit recruitment and summation of contractions

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11
Q

How is force of contraction controlled in cardiac muscle?

A

Frank starling mechanism

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12
Q

What is excitation contraction coupling?

A

The process by which the surface action potential results in activation of the contractile mechanism of the muscle fibre. An electrical stimulus is turned into a mechanical response.

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13
Q

What branch of the nervous system controls the movement of skeletal muscles?

A

Somatic

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14
Q

What is the functional unit of muscle called?

A

A sarcomere

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15
Q

In a muscle that requires fine precision and control will there be more or less fibres per motor unit?

A

Less

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16
Q

What is a z line is a muscle fibre?

A

The connection between the thin filaments of 2 adjoining sarcomeres.

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17
Q

How is muscle tension produced?

A

The sliding of actin over myosin filaments. This causes the muscle to shorten and a force to be produced which results in a movement.

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18
Q

How is the depolarization signal sent down to the sarcoplasmic reticulum?

A

Down the T tubules

19
Q

Opening of which channel causes the cell to depolarize?

A

Na+. This causes a sodium influx

20
Q

How does hyperpolarization occur?

A

Closure of Na+ channels and opening of K+ channels

21
Q

What needs to happen to the degree of depolarization before an action potential can be fired?

A

Must reach threshold

22
Q

What exactly is an action potential?

A

A transient depolarization of the cell membrane beyond the threshold potential followed by a hyperpolarization before returning to a normal resting membrane potential.

23
Q

How many nerves innervate each muscle fibre?

A

1

24
Q

Explain how calcium causes contraction in a skeletal muscle?

A

When muscles are resting the myosin binding sites on the actin molecule are covered. When calcium is release, it binds to troponin C which casuses a conformational change and exposes these sites. The myosin head then attaches to the actin molecule and releases a phosphate group. This then causes release of a molecule of ADP. A molecule of ATP then binds to the myosin head, causing detachment from the actin. The ATPase action of this cleaves ATP and produces energy.

25
Q

Explain the relaxation of muscle

A

Upon repolarizing calcium is actively pumped back out and into the sarcoplasmic reticulum. This causes a drop in intracellular calcium levels and causes tropomyosin to re - cover the myosin binding sites and causes relaxation.

26
Q

What two things control the degree of tension in a muscle?

A
  1. The number of fibres contracting within the muscle

2. The degree of tension developed by each contracting muscle fibre

27
Q

Is the duration of the action potential shorter or longer than the degree of the resulting twitch?

A

Much shorter

28
Q

With regard to action potentials, how is the force of contraction in muscles increased?

A

One AP = 1 twitch. If a second AP is fired before the muscle has fully relaxed then the second response in added to the first. As this keeps happening the degree of tension keeps increasing.

29
Q

Why can you not continue to fire APs simultaneously in cardiac muscle?

A

Due to the long refactory time

30
Q

What is meant by isotonic contraction?

A

Muscle tension remains constant but muscle length changes

31
Q

What is meant my isometric contraction?

A

Muscle tension increases at a constant muscle length

32
Q

When resting, is a skeletal muscle at its optimal length?

A

Yes

33
Q

What kind of movement requires isotonic contraction

A

Movement of objects and active body movement

34
Q

What kind of movement requires isometric contraction?

A

Maintaing body posture and supporting objects in fixed positions

35
Q

What is the stretch reflex?

A

A negative feedback that resists passive change in muscle length

36
Q

What tendon causes the knee jerk reaction?

A

Tendon of the quadriceps femoris

37
Q

What are the muscle spindle sensory fibres also known as?

A

Intrafusal fibres

38
Q

What are annulospiral fibres?

A

The sensory nerve endings of the intrafusal fibres

39
Q

Name the three different types of muscle fibres

A

Slow oxidative
Fast oxidative
Fast glycolytic

40
Q

Name three metabolic pathways that supply ATP to the muscle fibre

A
  1. Transfer of high energy phosphate from creatinine phosphate to ADP, creating an immediate source of ATP
  2. Oxidative phosphorylation (presence of oxygen)
  3. Glycolysis (absence of oxygen)
41
Q

What type of muscle fibres are used mainly for prolonged, relatively low work aerobic activity such an maintainence of posture?

A

Slow oxidative

42
Q

What type of muscle fibres are used in aerobic and anaerobic metabolism in prolonged, moderate activities such as jogging

A

Fast oxidation

43
Q

What type of muscle fibres use anaerobic metabolism and are mainly used for short term high intensity activities such as jumping.

A

Fast glycolytic

44
Q

What is the neurotransmitter at the neuromuscular junction?

A

Acetylcholine

Rheumatology (7 decks)

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