L30 Muscle Tissue

Question 1

Sphincters are operated by what type of muscle?

Answer 1

Skeletal muscle

Question 2

What is being described:

Non-dividing cells surrounded by satellite cells and contained in a sarcolemma.

Answer 2

Muscle fibre

Question 3

What are muscular satellite cells?

Answer 3

Undifferentiated muscle stem cells with regenerative potential.

Function as a reserve that can be activated to replace or increase muscle, as necessary.

Question 4

When a satellite cell is activated by injury, what happens?

Answer 4

The satellite cell undergoes asymmetric division - forming one satellite cell and one myoblast. The myoblast matures and fuses to the muscle fibre.

Question 5

True or false: Skeletal muscle is striated

Answer 5

True

Question 6

True or false: Skeletal muscle is controlled by the autonomic nervous system

Answer 6

False, it requires somatic or voluntary input.

Question 7

Fused myocytes form a __1__, and are surrounded by endomysium.

Bundles of 1 form muscle fascicle, surrounded by __2__.

Bundles of 2 form muscle, surrounded by __3__.

Answer 7

1) muscle fibre
2) perimysium
3) epimysium

Question 8

What are the myofilaments inside a muscle fibre?

Answer 8

Thin: actin, tropomyosin, troponin

Thick: myosin

Question 9

What is a myofibril?

Answer 9

Any one of the contractile threads found in a muscle fibre.

Question 10

What are transverse tubules (T-tubules) and what do they do?

Answer 10

‘Tunnels’ throughout muscle fibres that conduct action potentials from the sarcolemma to initiate contraction.

Question 11

What is a sarcomere?

Answer 11

The smallest functional unit of muscle (not the smallest structural unit).

Contraction happens here.

Question 12

What forms the I band of the sarcomere?

Answer 12

Thin bands of actin

It looks lighter because actin is isotropic

Question 13

What forms the A bands of the sarcomere?

Answer 13

Thick bands of myosin

Anisotropic, therefore appears dark

Question 14

What is the Z line in the sarcomere?

Answer 14

Protein chain that supports the actin filaments (I bands).

Z = zig zag

Question 15

What is the M line in a sarcomere?

Answer 15

Consists of proteins supporting the thick myosin filaments

Question 16

Where is the H zone on a sarcomere?

Answer 16

The central region that contains only thick filaments

Question 17

How is contraction achieved in the sarcomere?

Answer 17

Sliding of thick and thin filaments in the zone of overlap.

Question 18

True or false: Striations can be found in cardiac muscle

Answer 18

True

Question 19

Is cardiac muscle mononucleated or multinucleated?

Answer 19

Mononucleated. Cells are not fused.

Question 20

Is skeletal muscle mononucleated or multinucleated?

Answer 20

Multinucleated.

Myoblasts fuse together to form multinucleated fibres

Question 21

Cardiac muscle contains intercalated discs at the ends of the cardiocytes. What structures are found here and why?

Answer 21

Gap junctions and desmosomes allow exchange of ions and molecules - allows spread of action potentials.

Question 22

True or false: A sarcomere Z line appears zig zag shaped, and the M line appears straight

Answer 22

True

z line = zig zag

Question 23

True or false: cardiac muscle contraction is not reliant on the nervous system for stimulation.

Answer 23

True

Pacemaker cells stimulate contractions; the nervous system can only alter the rate of activity.

Question 24

True or false: Smooth muscle is incapable of regeneration

Answer 24

False.

Smooth muscle cells can divide, therefore the tissue is capable of regeneration.

Question 25

True or false: Cardiac muscle is incapable of regeneration

Answer 25

True

Question 26

In which type of muscle will you NOT find sarcomeres?

Answer 26

Smooth muscle