Muscle physiology

Question 1

What are the striations seen in muscle?

Answer 1

Actin (thin) and myosin (thick) filaments

Question 2

What is a motor unit in muscle?

Answer 2

The motor neuron + the muscle fibre that it innervates

Question 3

How is contraction stimulated in skeletal muscle?

Answer 3

Neurogenic stimulation

Question 4

How is contraction of cardiac muscle stimulated?

Answer 4

Myogenic (pacemaker potential of the heart)

Question 5

Is what type of muscle do you find gap junctions?

Answer 5

Cardiac

Question 6

Is their gap junctions is skeletal muscle?

Answer 6

No

Question 7

Is their neuromuscular junctions in skeletal muscle?

Answer 7

Yes

Question 8

What ion is the link betweek exitation and contraction?

Answer 8

Contraction

Question 9

Where does the calcium come from in skeletal muscle?

Answer 9

Sarcoplasmic reticulum

Question 10

How is force of contraction increased in skeletal muscles?

Answer 10

Motor unit recruitment and summation of contractions

Question 11

How is force of contraction controlled in cardiac muscle?

Answer 11

Frank starling mechanism

Question 12

What is excitation contraction coupling?

Answer 12

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.

Question 13

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

Answer 13

Somatic

Question 14

What is the functional unit of muscle called?

Answer 14

A sarcomere

Question 15

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

Answer 15

Less

Question 16

What is a z line is a muscle fibre?

Answer 16

The connection between the thin filaments of 2 adjoining sarcomeres.

Question 17

How is muscle tension produced?

Answer 17

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

Question 18

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

Answer 18

Down the T tubules

Question 19

Opening of which channel causes the cell to depolarize?

Answer 19

Na+. This causes a sodium influx

Question 20

How does hyperpolarization occur?

Answer 20

Closure of Na+ channels and opening of K+ channels

Question 21

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

Answer 21

Must reach threshold

Question 22

What exactly is an action potential?

Answer 22

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

Question 23

How many nerves innervate each muscle fibre?

Answer 23

1

Question 24

Explain how calcium causes contraction in a skeletal muscle?

Answer 24

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.

Question 25

Explain the relaxation of muscle

Answer 25

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.

Question 26

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

Answer 26

1. The number of fibres contracting within the muscle | 2. The degree of tension developed by each contracting muscle fibre

Question 27

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

Answer 27

Much shorter

Question 28

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

Answer 28

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.

Question 29

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

Answer 29

Due to the long refactory time

Question 30

What is meant by isotonic contraction?

Answer 30

Muscle tension remains constant but muscle length changes

Question 31

What is meant my isometric contraction?

Answer 31

Muscle tension increases at a constant muscle length

Question 32

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

Answer 32

Yes

Question 33

What kind of movement requires isotonic contraction

Answer 33

Movement of objects and active body movement

Question 34

What kind of movement requires isometric contraction?

Answer 34

Maintaing body posture and supporting objects in fixed positions

Question 35

What is the stretch reflex?

Answer 35

A negative feedback that resists passive change in muscle length

Question 36

What tendon causes the knee jerk reaction?

Answer 36

Tendon of the quadriceps femoris

Question 37

What are the muscle spindle sensory fibres also known as?

Answer 37

Intrafusal fibres

Question 38

What are annulospiral fibres?

Answer 38

The sensory nerve endings of the intrafusal fibres

Question 39

Name the three different types of muscle fibres

Answer 39

Slow oxidative Fast oxidative Fast glycolytic

Question 40

Name three metabolic pathways that supply ATP to the muscle fibre

Answer 40

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)

Question 41

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

Answer 41

Slow oxidative

Question 42

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

Answer 42

Fast oxidation

Question 43

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

Answer 43

Fast glycolytic

Question 44

What is the neurotransmitter at the neuromuscular junction?

Answer 44

Acetylcholine