Ch 8: Muscular Tissues

Question 1

What are the 3 types of muscle tissues?

Answer 1

Skeletal, cardiac, smooth.

Question 2

Describe each of the 3 muscles, location, control type, fibre shape, striated or not, number of nuclei per fibre, position of nuclei in cell, contraction speed, ability to remain contracted.

Answer 2

1. Skeletal striated muscle: bones, voluntary, elongated cylindrical with round ends, striated, many, peripheral, fastest, smallest.
2. Smooth: digestive tube, uterus, certain blood vessels, viscera (internal organs),involuntary, thin elongated with pointy ends, not striated, one, central, the slowest, the biggest.
3. Cardiac: heart, involuntary, elongated, cylindrical, branched, has gap junctions, striated, one, central, intermediate, intermediate.

Question 3

How long are sarcomeres?

Answer 3

They are 2 micrometers long.

Question 4

What are the thick and thin filaments?

Answer 4

Thick= myosin
Thin= actin

Question 5

What are the Z line, H zone, I band and A band in sarcomere.

Answer 5

1. Z line: the line that bisects the boundary between the sarcomeres.
2. H zone: only myosin.
3. I band: only actin
4. A band: both myosin and actin

Question 6

What are 3 connective tissue layers that cover the skeletal muscle tissue? Explain them.

Answer 6

1. Endomysium: covers each muscle fibre.
2. Perimysium: wraps a bundle of muscle fibre, the part of the muscle that has this fibre is called gaster/body.
3. Epimysium/fascia: envelope the muscle entirely.

Question 7

Describe cardiac vs skeletal muscles, 1. control types (by which nervous systems), 2. fibre arrangement (ramified or not), 3. microscopic appearance (striated or not),4. number of nuclei, 5. do they have intercalated discs, 6.how is their tube/sarcomere arranged, 7. action potential duration, 8. contraction time, 9. absolute refractory period.

Answer 7

Cardiac:
1. Vegetative nervous system
2. Ramified
3. Striated
4. One
5. Yes
6. 1 tube, In the z line
7. 150-300 m sec
8. 150-300 m sec
9. 150 - 300 m sec
Skeletal:
1. Somatic nervous system
2. Non Ramified
3. Striated
4. Many
5. No
6. 2 tubes arranged between A-I junctions
7. 1 - 2 m sec
8. 40 m sec
9. 1-2 m sec

Question 8

Describe initiation of muscle contraction.

Answer 8

1. Stimulus releases acth by motor neurons
2. ACTH crosses synaptic cleft
3. Mb of muscle fibre stimulated, = impulse transmitted through t tubules
4. Ca ions diffuse from sarcoplasmic reticulum to sarcoplasm + attach to troponin
5. Tropomyosin exposes actin binding spots
6. Bridges establish between myosin and actin
7. Actin filaments slide inwards along myosin filaments
8. Contraction, muscle fibres shorten

Question 9

Describe muscle fibre relaxation.

Answer 9

1. Muscle membrane do not receive stimuli cz acetylcholinesterase breaks down acth
2. By active transport calcium are brought inside t tubules + sarcoplasmic reticulum
3. Bridges between actin/myosin break
4. As muscle fibre relaxes = restores its length.
5. Interaction between actin + myosin is blocked by troponin + tropomyosin

Question 10

Do muscles in general follow the all or nothing law?

Answer 10

No they follow the gradual response law.

Question 11

Do smooth muscles havre gap junctions?

Answer 11

Sometimes.