Muscles 1

Question 1

What is Myalgia?

Answer 1

Muscle pain

Question 2

What is Myasthenia?

Answer 2

Weakness of the muscles

Question 3

What is myocardium?

Answer 3

A muscular component of the heart

Question 4

What is myopathy?

Answer 4

Disease of the heart muscle

Question 5

What is the name of the plasmalemma (cell membrane) of a muscle cell?

Answer 5

Sarcolemma

Question 6

What is the cytoplasm of a muscle cell called?

Answer 6

Sacroplasm

Question 7

What is the name of smooth endoplasmic reticulum (SER) of a muscle cell?

Answer 7

Sacroplasmic Reticulum

Question 8

What muscle types are ‘striated’? How is it different to non-striated?

Answer 8

Skeletal and cardiac
Made up of contractile fibrils which lie in parallel bundles (seen under the microscope). A series of bands forming sarcomeres.

Question 9

What are the properties of red skeletal fibres in skeletal muscle?

Answer 9

Small, highly vascularised, numerous in mitochrondria, cause slow, weak contractions e.g. Postural muscles in back.

Question 10

What are the properties of white skeletal fibres in skeletal muscle?

Answer 10

Larger, poorer vascularised, fewer mitochrondria, causes strong, fast contractions e.g. Muscles controlling fingers.

Question 11

What are intermediate fibres?

Answer 11

Have properties of both red and white fibres.

Similar in appearance to red fibres but similar endurance to white.

Question 12

What is myoglobin?

Answer 12

A protein containing haem (an oxygen storing molecule), takes oxygen to the muscle.
Similar in structure to hameoglobin, in acidic conditions where working muscles produce CO2, gives up oxygen to myoglobin to feed muscles.

Question 13

What is a group of muscle fibres called?

Answer 13

A fascicle

Question 14

What is the name of the outer sheath of a fascicle?

Answer 14

The perimysium

Question 15

What is the name of the area inbetween muscle fibres?

Answer 15

The endomysium

Question 16

Where is a sarcomere on a myofibril located?

Answer 16

Between two Z bands

Question 17

What is disuse atrophy?

Answer 17

Atrophy = reduction in number of cells

E.g. Bed rest - loss of protein, reduced fibre diameter, loss of power.

Question 18

What is muscle atrophy?

Answer 18

A general term for muscle reduction - ageing - 50% of muscle is lost by the age of 80.

Question 19

What is denervation atrophy?

Answer 19

Damage to the nerves causing muscle weakness

Question 20

What is hypertrophy?

Answer 20

Enlargement of organ/tissue due to increase in size of cells.
Increase in fibre diameter.

Question 21

Describe skeletal muscle sacromere bands in relation to actin and myosin and how these come together to make a contraction.

Answer 21

A sarcomere lies between two Z bands. Half way between the Z bands is H band. Myosin lies across the H band and actin lies across the Z band. In a contraction, myosin and actin cross over to shorten and contract, and separate to lengthen and relax.

Question 22

Starting with skeletal muscle, what are the 5 levels from large to small?

Answer 22

Skeletal muscle
Fascicle
Muscle fibre
Myofibril
Myofilaments

Question 23

Explain how ATP and the interaction between myosin and actin can cause a ‘power stroke’.

Answer 23

Actin and myosin lie parallel to one another.
ATPase (hydrolysis of ATP to ADP and P) causes myosin to extend and attach to a binding site on actin - this causes a ‘power stroke’.
Myosin remains attached to actin until a further ATP uncouples the myosin head and releases it.

Question 24

What is troponin and explain its role in a power stroke.

Answer 24

When a muscle is relaxed, troponin blocks the binding site for myosin.
When Ca2+ molecules are present, they bind to the troponin, exposing the binding sites and causing a conformational change.
This causes a ‘cross bridge’ and a contraction occurs.
Troponin is used as a marker for cardiac ischaemia (lack of blood oxygen to heart).

Question 25

What is creatine kinase and what is it a marker for in a blood test?

Answer 25

A metabolically active enzyme in tissues like muscle. Is released into blood by damaged skeletal muscle and brain and is used to diagnose heart attacks.