Unit 11: Exercise Physiology LO's

Question 1

Identify sources of ATP used by exercising muscle.

Answer 1

1. Free ATP in cells
2. Phosphocreatine
3. Aerobic pathway
4. Anaerobic pathway

Question 2

Compare and contrast aerobic and anaerobic metabolism in exercising muscle.

Answer 2

Aerobic pathway: production of ATP from glucose or fatty acids via glycolysis, citric acid cycle and oxidative phosphorylation (electron transport chain). Requires oxygen.

Anaerobic pathway: production of ATP via glycolysis only (referred to as glycolytic metabolism). No oxygen required.

Question 3

Describe an exercising muscle’s use of energy substrates to create glucose for ATP production.

Answer 3

Aerobic pathway:
Sources of glucose:
a. Plasma glucose (from absorbed nutrients or
from metabolic processes in the liver)
b. Glycogen stores in muscle cells
c. Glycogen stores in liver cells (glycogenolysis helps to maintain plasma glucose levels)
d. Gluconeogenesis – production of glucose from fats (via glycerol) and protein (via amino acids.). Gluconeogenesis will begin once glycogen stores in the liver start to run low and will help to maintain plasma glucose levels.

Sources of fatty acids:
a. Plasma fatty acids (from absorbed nutrients
and lipolysis of adipose tissue)
b. Triglycerides stored in muscle cells.

Anaerobic pathway:

• In the absence of oxygen pyruvate is converted to lactic acid (lactate).
• • Lactate can be converted to glucose in the liver
• Produces ATP very quickly, but does not produce a lot of ATP (only 2 per glucose, compared to the 32/glucose for the aerobic pathway).

Question 4

Describe the changes in plasma glucose and plasma hormone levels during periods of exercise. Identify the homeostatic challenges and the homeostatic goals.

Answer 4

Hormonal regulation of metabolism during exercise:
- The hormones that control metabolism (see Unit 10) play important roles in the
mobilization and conversion of substrates for muscle metabolism.

?

Question 5

Explain how physiologists quantify the intensity of periods of exercise.

Answer 5

All exercise activities use a combination of carbohydrates and fats to supply the ATP needed for muscle contraction However, exercise intensity and duration influences which substrates are used more:

• LOW and MODERATE intensity exercise (less than 60% of maximum intensity) use a higher proportion of fat metabolism for ATP production.
• HIGH INTENSITY exercise (more than 70% of maximum( uses a higher proportion of carbohydrate (glucose) metabolism for ATP production.
• In LONG DURATION ENDURANCE EXERCISES, after ~ 60 min, the body will begin to deplete its carbohydrate stores and will begin to transition more to the use of fats (which can contribute up to 80% of the energy needs during an endurance exercise such as running a marathon).

Question 6

Describe how oxygen consumption changes during and after exercise and describe VO2max.

Answer 6

From chapter summary:

The intensity of exercise is indicated by OXYGEN CONSUMPTION (VO2)

A person’s MAXIMAL rate of oxygen consumption (VO2MAX) is an indicator of that person’s ability to perform endurance exercise

Oxygen consumption increases rapidly at the onset of exercise. EXCESS POSTEXERCISE OXYGEN CONSUMPTION (EPOC) is due to ongoing metabolism, increased body temp, & circulating catecholamines

Question 7

Identify the factors that can limit exercise.

Answer 7

Limiting factors include:

1. The ability of muscle fibres to obtain and use oxygen (more important during sub maximal exercise activity). This can relate to the number of mitochondria a muscle has, which increases with training.
2. The ability of the cardiovascular system to deliver oxygen and nutrients to the working muscles, i.e. cardiovascular fitness. Improving cardiovascular fitness will improve the ability of this system to deliver oxygen and nutrients which will improve exercise endurance.

Question 8

Describe or diagram the mechanisms and the outcomes of ventilatory responses to exercise. Identify the homeostatic challenges and the homeostatic goals.

Answer 8

Exercise increases the rate and depth of breathing, which provides the oxygen needed to meet the increase in oxygen consumption.

Effects of Exercise on blood gases:
- Arterial PO2, PCO2 and pH do not change significantly during mild to moderate exercise. Pulmonary and alveolar ventilation increase to meet demands.

?

Question 9

Describe or diagram the mechanisms and the outcomes of cardiovascular responses to exercise. Identify the homeostatic challenges and the homeostatic goals.

Answer 9

At start of exercise, the increase in movement is detected by proprioceptors and stretch receptors in joints and muscle tissue. These signals are relayed to the cardiovascular control centers (CVCC) of the medulla. In response the CVCC decreases parasympathetic activity and increases sympathetic activity, resulting in an increase in heart rate and contractility as well as other responses that increase mean arterial pressure (MAP) to ensure adequate blood flow and perfusion to working muscle tissue.

(CO increases with exercise b/c of increases VR & symp. stimulation of HR & contractility)

?

Question 10

Describe the feedforward reflexes that anticipate homeostatic challenges of exercise.

Answer 10

From chapter summary:

When exercise begins, feedforward responses prevent significant disruption of homeostasis

Question 11

Describe or diagram the homeostatic thermoregulatory responses and mechanisms that take place during periods of exercise.

Answer 11

In response to high temperature, the hypothalamic thermoregulatory centre will activate sympathetic cholinergic neurons to stimulate sweat glands and cause vasodilation in the skin to promote heat loss

Mechanisms of heat loss cause other challenges for homeostasis:
- SWEATING – causes dehydration and decreased blood volume (hypovolemia) both of which will increase blood
osmolarity.
- CUTANEOUS VASODILATION – decreases peripheral resistance and diverts blood flow away from muscles.

If the amount of vasodilation and reduced blood volume cause blood pressure in the vena cava to drop substantially (i.e. decreased central venous pressure and decreased venous return),the body will stop thermoregulating to preserve blood flow to the brain.

Question 12

Describe what has been proven and what has been suggested about the influence of exercise on health.

Answer 12

1. Exercise lowers the risk of cardiovascular disease
2. Exercise can improve Type 2 diabetes mellitus
3. Exercise may improve immune function
4. Exercise may reduce stress and improve mental health and cognitive function

From chapter summary:
Studies suggest that SEROTONIN release during exercise may help alleviate depression