Lecture 26: Skeletal Muscle Energy, Types & Function

Question 1

How long can the ATP in a muscle cell sustain contraction?

Answer 1

2-4s

Question 2

How do muscle cells sustain longer contractions?

Answer 2

The breakdown of CP (creatine-phosphate) can resynthesise ATP and provide 20s contractions.

Question 3

What are the 2 types of metabolism and how do they differ?

Answer 3

Anaerobic Metabolism does not require O2, is fast, inefficient and good for short term responses. ATP, CP, glycolysis.

Aerobic Metabolism requires O2, is slower, more efficient and steady for longer term responses. Oxidative phosphorylation.

Question 4

How is energy required for muscle relation?

Answer 4

Pumping of Ca2+ back into the SR and uncoupling the crossbridge both require ATP.

Question 5

What occurs if muscle cells are depleted of energy (ATP)?

Answer 5

Rigor Mortis.

Question 6

What is the difference between white and red muscle cells?

Answer 6

Red have high myoglobin conc., high aerobic enzymes, req. lots of O2.

White have low myoglobin conc. and low aerobic enzymes.

Question 7

What is myoglobin?

Answer 7

Oxygen binds to myoglobin like it does to haemoglobin in blood. Red muscle cells appear red due to oxygen-iron (Fe) binding.

Question 8

Which type of myosin do red and white and intermediate muscle cells have, and what is their response speed like?

Answer 8

Red: slow, Myosin type 1.

White: fast, Myosin type IIx

Intermediate: Myosin type IIa

Question 9

What is a twitch?

Answer 9

A single potential in a single motor unit, the smallest tension a muscle can produce.

Question 10

What is treppe, and why does it occur?

Answer 10

Repeating stimuli cause increasing levels of tension. Occurs because of sustained Ca2+ levels, heat and more sensitive actin-myosin interactions.

Question 11

What is tetanus, and why does it occur?

Answer 11

A series of very closely spaced twitches which sum to produce a long, smooth contraction.

Question 12

What is incomplete tetanus?

Answer 12

Fluctuations from individual twitches still visible.

Question 13

What does strength training do to muscles?

Answer 13

Increase # of contractile filaments (hypertrophy), more power, imporved anaerobic metabolism.

Question 14

What does endureance training do to muscles?

Answer 14

Increase blood supply to muscles, increase in # blood vessels, # mitochondria, # aerobic enzymes. Improved aerobic metabolism.

Question 15

What does disuse do to muscles?

Answer 15

Loss # contractile filaments. (atrophy). Less power

Question 16

What are the two factors of exhaustion?

Answer 16

Physiological: ATP depletion, glucose depletion, glycogen and O2. Build up of metabolic products.

Psychological: Feedback from muscles produces sensation of fatigue, regardless of contractile capability.