skeletal muscle Formative + made up exam questions:

Question 1

outline 3 steps for what happens when you fast for longer than 24 hours? [5 marks]

Answer 1

1. Decreased insulin and increased glucagon
2. increased proteolysis and amino release from muscle for fuel
3. activation of hormone sensitive lipase to increase lipolysis. Also increase in gluconeogenesis

Question 2

what are the 4 types of gluconeogenesis

Answer 2

• cori cycle
• cahill cycle
• glutamine cycle

Question 3

Describe the differences between skeletal and smooth muscle [6 marks]

Answer 3

1. Arrangement of contractile proteins - Skeletal muscle has a regular arrangement of contractile proteins (1/2 mark for just striated), Smooth muscle has proteins that criss-cross the cell
2. Control of contraction - Skeletal muscle is under somatic control, Smooth muscle is under autonomic control - 1/2 marks for voluntary and involuntary
3. Energy requirements - Skeletal muscle requires more ATP (more mitochondria), Smooth muscle has little ATP usage
4. Nuclei - Skeletal muscle cells are multi-nucleate AND have peripheral nuclei - need both for 1 mark
5. Control of contraction - Skeletal muscle contraction controlled by sarcoplasmic reticulum, Smooth muscle uses endocytotic vesicles

Question 4

Name and briefly describe the structure and function of the various protein that compose the thin filaments in striated muscle

Answer 4

1. The proteins are: actin, tropomyosin, troponin T, troponin I and troponin C [½ mark each].
2. Actin is the major structural component of the thin filament [½ mark] and arranged like a twisted double string of beads [½ mark].
3. Tropomyosin is a filamentous protein that sits in the spiral groove along the actin filament [½ mark] obscuring the myosin binding sites on actin [½ mark].
4. The troponins form a complex [½ mark] that moves the tropomyosin out of the way of the myosin binding site on actin [½ mark] when calcium ions bind to troponin C [½ mark]

Question 5

explain the basic principles of dual energy x-ray absorptiometry and outline three strengths and three limitations of this method for body composition analysis

Answer 5

1. DXA is a low dose radiation scan (1 mark)
2. Tissue composition is determined from the differences in energy attenuation of two different energy peaks (1 mark)
3. Strengths: accurate, reliable, no discomfort for patients, 4-compartment model (including mineral/bone), can be used to look at regional composition (3 marks)

Limitations: expensive specialist equipment, radiation exposure, radiation trained staff required to operate, no reference values for certain groups (3 marks)