9 - Muscle Tissue

Question 1

What is myalgia?

Answer 1

Muscle pain

Question 2

What is myasthenia?

Answer 2

Muscle weakness

Question 3

What is myoclonus?

Answer 3

Muscle spasm

Question 4

What is a sarcosome?

Answer 4

A mitochondrion of a muscle cell

Question 5

What is myoglobin?

Answer 5

• Oxygen carrier protein similar to a single haemoglobin subunit
• Haemoglobin gives up oxygen to myoglobin in the muscle (especially at low pH - e.g. during exercise)

Question 6

Which forms of muscle are striated?

Answer 6

Skeletal muscle

Cardiac muscle

Question 7

Which forms of muscle contain myoglobin?

Answer 7

Skeletal muscle

Cardiac muscle

Question 8

Which forms of muscle are under involuntary control?

Answer 8

Cardiac muscle

Smooth muscle

Question 9

What is the cellular structural unit of striated muscle known as? Describe the ultrastructure of striated muscle.

Answer 9

Sarcomere

• Interlocking thin filaments (actin) and thick filaments (myosin)
• Actin filaments join at the Z disc
• Myosin filaments join at the M line

Question 10

What 3 bands are seen in a sarcomere?

Answer 10

I band - only actin (contains the Z disc)
H band - only myosin (contains the M line)
A band - where actin and myosin overlap

Question 11

Outline the mechanism of the sliding filament model of contraction.

Answer 11

1. Myosin binds to actin (ADP + Pi bound)
2. Power stroke (ADP + Pi released)
3. Cross-bridge detaches (ATP binds)
4. Myosin head prepares to reattach (ATP hydrolysed)

Question 12

Each muscle cell (fibre) contains numerous …………………, fibres are multinucleated and are surrounded by plasma membrane (……………..)

Answer 12

Myofibrils

Sarcolemma

Question 13

Muscle fibres are grouped into ………..

Answer 13

Fascicles

Question 14

What 3 connective tissues are found within a muscle? Where is each one found?

Answer 14

Endomysium - lies between muscle fibres
Perimysium - wrapped around fascicles
Epimysium - surrounds the whole muscle

Question 15

The point of origin of a muscle is where ………… is generated, the point of insertion of a muscle is where …………… is generated

Answer 15

Origin - tension

Insertion - movement

Question 16

What is hypertrophy?

Answer 16

Increase in tissue size by enlargement of the cells

Question 17

What is hyperplasia?

Answer 17

Increase in tissue size by multiplication of the cells (increase cell number)

Question 18

Describe the repair mechanisms possible in skeletal muscle.

Answer 18

• Cells are unable to divide
• Regenerate by mitosis of satellite cells (hyperplasia)
• These can also fuse with existing cells to increase mass (hypertrophy)

Question 19

Describe the repair mechanisms possible in cardiac muscle.

Answer 19

• Incapable of repair

- Fibroblasts invade, divide and lay down scar tissue

Question 20

Describe the repair mechanisms possible in smooth muscle.

Answer 20

• Retain mitotic activity and can form new cells

- Particularly in pregnant uterus - becomes thicker by both hypertrophy and hyperplasia

Question 21

What are the 3 different types of muscle fibre? How do their metabolic pathways for generating energy differ?

Answer 21

Type 1 (slow twitch) - oxidative
Type 2A (fast twitch) - oxidative/glycolytic
Type 2B (fast twitch) - glycolytic

Question 22

How do the 3 types of muscle fibre differ in terms of number of mitochondria?

Answer 22

Type 1 (slow twitch) - many mitochondria
Type 2A (fast twitch) - intermediate no.
Type 2B (fast twitch) - few mitochondria

Question 23

How do the 3 types of muscle fibre differ in colour?

Answer 23

Type 1 (slow twitch) - red
Type 2A (fast twitch) - red-pink
Type 2B (fast twitch) - white

Question 24

How do the 3 types of muscle fibre differ in time to fatigue?

Answer 24

Type 1 (slow twitch) - fatigue resistant
Type 2A (fast twitch) - moderate fatigue resistance
Type 2B (fast twitch) - rapidly fatigue

Question 25

How do the 3 types of muscle fibre differ in the type of activity they are used in?

Answer 25

Type 1 (slow twitch) - endurance/stamina
Type 2A (fast twitch) - assists both 1 and 2B
Type 2B (fast twitch) - strength/anaerobic

Question 26

How do the 3 types of muscle fibre differ in source of energy?

Answer 26

Type 1 (slow twitch) - fatty acids
Type 2A (fast twitch) - fatty acids and glycogen
Type 2B (fast twitch) - glycogen

Question 27

Cardiomyocytes communicate through …. ………… at their intercalated discs

Answer 27

Gap junctions

Question 28

Where are Purkinje fibres found? What is their role?

Answer 28

In the heart, starting at the atrioventricular node as the bundle of His and branching down the ventricular septum into the ventricular wall

Rapid conduction of action potentials to enable the ventricles to conduct synchronously

Question 29

Purkinje fibres are large cells containing lots of g…………., very few m………………. and many ……. junctions for electrical conduction

Answer 29

glycogen
myofibrils
gap

Question 30

Smooth muscle cell contraction is ………. and requires less energy from ……..

They can remain contracted for ….. to …….

Answer 30

slower, ATP

hours, days

Question 31

Smooth muscle membrane contains numerous …………. (cave-like invaginations).

What do these do?

Answer 31

Caveolae

Formed from caveolin proteins to sample the external environment so the cell can respond appropriately.

Question 32

What does smooth muscle do (i.e. where is it distributed)?

What is the clinical significance of this?

Answer 32

Forms the contractile walls of passageways and cavities to modify the volume (e.g. vasculature, gut, respiratory and urinary tracts)

Can be involved in disorders such as high blood pressure, asthma, IBS, incontinence etc.

Question 33

ANS fibres supplying smooth muscle release their neurotransmitters from …………… instead of having T tubules on the muscle membrane

Answer 33

Varicosities