Unit 1. Lec 3- Skeletal and Smooth Muscle Physiology

Question 1

What are the 3 types of muscles

Answer 1

• Skeletal
• Smooth
• Cardiac

Question 2

Which muscle makes up most of the muscles in the body?

Answer 2

Skeletal muscle

Question 3

Describe the physical apperance of skeletal muscle

Answer 3

• Is straited, appears to have stripes
• NOT uniform

Question 4

Large muscle bundles are composed of what?

Answer 4

Myocytes or fibers (individual muscle cells)

Question 5

What does each myocyte contain?

Answer 5

Many myofibrils

Question 6

What does each myofibrils contain?

Answer 6

Many sacromeres (smallest functioning unit of muscle)

Question 7

How are sacromes arranged?

Answer 7

end-to-end in series

Question 8

What is each sacromere composed of?

Answer 8

• Actin
• Myosin
• Other moleculary machinery

Question 9

List the cellular units of skeletal muscle from largest to smallest

Answer 9

Myocyte–>Myofibrils–>sacromeres (actin/myosin)

Question 10

What is the function of individual sacromeres?

Answer 10

To generate contractile forces

Question 11

What is one sacromere bounded by?

Answer 11

2 Z-lines

Question 12

What are the two types of filaments in skeletal muscle?

Answer 12

• Thin Filaments (Actin)
• Thick Filaments (Myosin)

Question 13

What are the thin filaments of Skeletal Muscle?

Answer 13

Actin helix w/ tropomyosin & troponin complex attached

Question 14

What are thick filaments of Skeletal Muscle?

Answer 14

• Myosin II (ATPase b/c breakdown ATP for energy)
• Head and tail and it’s a alpha helix except the head

Question 15

Thin and thick filaments interact to produce _________.

Answer 15

force

Question 16

What is the organization of a sarcomere?

Answer 16

• I band: thin filaments only (actin only)
• H band: thick filaments only (myosin only)

Question 17

Explain the M line and A band of the sarcomere

Answer 17

• M line: thick filaments linked w/ accessory proteins
• A band: thick and thin filaments overlap

A>H zone

Question 18

What increases the overlap btw myosin and actin?

Answer 18

Decreasing I band & H zone

Question 19

Explain the neural control of skeletal muscle cells

Answer 19

Neuromuscular Junction:
1. Nerve axon innervating each muscle fiber
2. Release Acetylcholine (ACh) from vesicles
3. ACh binds to AChR (receptor) which is permeable to Na+, K+, and Ca2+

Question 20

What is the role of Acetylcholinesterase?

Answer 20

Breaks down ACh to decrease ACh in synpases to stop contraction

Question 21

How are muscle cells innervated?

Answer 21

Each muscle is innervated by one nerve

Question 22

What causes depolarization in skeletal muscle cells?

Answer 22

ACh receptors

Question 23

Explain the Initation of Skeletal Muscle Contraction

Answer 23

1. Ca2+ release from the Sacroplasmic reticulum
2. Ca2+ binds to Troponin complex and initiates a conformational change
3. Tropomyosin (which initially was blocking the binding site) slides into the groove btw the actin strands
4. Myosin can now bind actin

Troponin complex (accesory proteins bound too tropomyosin & actin)