Physiological Response to Work Lecture 22

Question 1

What are the ten steps of initiation of muscle contraction

Answer 1

1. Activity in cerebral cortex, basal ganglia and cerebellum
2. Motor cortex firing
3. Impulses in descending motor pathways
4. Motor neuron excitation
5. Impulse propagation to axon terminals
6. Neuromuscular transmission
7. Impulse propagation along sarcolemma
8. Impulses into T-tubules
9. Calcium release from sarcoplasmic reticulum
10. Engagement of cross-bridges

Question 2

Describe the phosphagen system

Answer 2

Mammalian muscles involves the use of phosphocreatine. Reacts with ADP to regenerate ATP when the latter is depleted by muscular contraction
Rapid system it also fatigues rapidly exhausted in 8-10 seconds

Question 3

Describe the glycolytic system

Answer 3

Utilises glucose or glycogen to regenerate ATP at the expense of glucose - metabolised to pyruvate
This system is based in the cytosol of the muscle and also produces ATP very rapidly
Becomes quite fragile quickly in 30-90 seconds when working anaerobically

Question 4

Describe the aerobic system (respiration in mitochondria)

Answer 4

Uses pyruvate from glycolysis or lipids from amino acids to produce ATP
Complex and slow process however doesnt become fatigued
This system uses two biochemical pathways: The Tricarboxylic Acid Cycle (TAC) and electron transfer chain
TAC metabolies carbon skeleton to carbon dioxide and transports this to the electron chain via NAPD and FADH2

Question 5

What are the three problems that occur when exercise is prolonged?

Answer 5

Muscle competes with the brain for blood glucose
Muscle glycogen stores are relatively small
The heat produced from the increase in the metabolism is high