Untitled Deck

Question 1

What are the 3 types of muscle in the body?

Answer 1

1. Cardiac
2. Smooth
3. Skeletal

Question 2

Where is cardiac muscle located?

Answer 2

Exclusively found in the heart.

Question 3

Where is smooth muscle located?

Answer 3

Walls of blood vessels and intestines.

Question 4

Where is skeletal muscle located?

Answer 4

Attached to incompressible skeleton by tendons.

Question 5

What does the phrase ‘antagonistic pair of muscles’ mean?

Answer 5

Pairs pull in opposite directions: agonist contracts while antagonist is relaxed.

Question 6

Describe the gross structure of skeletal muscle.

Answer 6

• Muscle cells are fused together to form bundles of parallel muscle fibres (myofibrils).
• Arrangement ensures there is no point of weakness between cells.
• Each bundle is surrounded by endomycium: loose connective tissue with many capillaries.

Question 7

Describe the microscopic structure of skeletal muscle.

Answer 7

• Myofibrils: site of contraction.
• Sarcoplasm: shared nuclei and cytoplasm with lots of mitochondria & endoplasmic reticulum.
• Sarcolemma: folds inwards towards sarcoplasm to form transerve tubules

Question 8

How does each band appear under an optical microscope?

Answer 8

I-band: light
A-band: dark

Question 9

How is muscle contraction stimulated?

Answer 9

1. Neuromuscular junction: action potential = voltage-gated Ca2+channels open.
2. Vesicles move towards & fuse with presynaptic membrane.
3. Exocytosis of acetylcholine (ACh), which diffuses across synaptic cleft.
4. ACh binds to receptors on Na+
   channel proteins on skeletal muscle cell membrane.
5. Influx of Na+ = depolarisation.

Question 10

Explain the role of Ca2+ ions in muscle contraction.

Answer 10

. Action potential moves through T-tubules in the sarcoplasm = Ca2+ channels in sarcoplasmic reticulum open.
2. Ca2+ binds to troponin, triggering conformational change in tropomyosin.
3. Exposes binding sites on actin filaments so actinomyosin bridges can form.