Lecture 9.2 - Control of metabolism - exercise and pregnancy

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Questions and Answers

What is the primary role of insulin during muscle glucose uptake?

Regulating glycogen synthesis

Increasing glucose uptake through GLUT4 (correct)

Stimulating glycogenolysis in liver

Stimulating lipolysis

During a marathon, which fuel source is depleted in a few minutes?

Liver glycogen

Muscle glycogen (correct)

Glucose

Fatty acids

What is the primary function of glucagon during exercise?

Stimulating glycogenolysis in muscle

Regulating glucose uptake

Stimulating glycogenolysis in liver (correct)

Stimulating lipolysis

What is the primary effect of adrenaline on muscle metabolism during exercise?

Stimulating glycogenolysis in muscle Signup and view all the answers

What is the primary effect of growth hormone on fuel metabolism during a marathon?

Mobilizing fatty acids Signup and view all the answers

What is the primary effect of cortisol on fuel metabolism during prolonged exercise?

Stimulating gluconeogenesis Signup and view all the answers

What is the primary benefit of regular exercise on glucose metabolism?

Improved glucose tolerance Signup and view all the answers

What is the primary characteristic of a marathon in terms of exercise intensity?

Low intensity, long duration Signup and view all the answers

During high-intensity exercise, what is the primary mechanism for ATP regeneration?

Anaerobic pathways Signup and view all the answers

Which of the following is NOT a function of the body's response to exercise?

Storing excess energy for future use Signup and view all the answers

What is the primary fuel source for the brain during exercise?

Blood glucose Signup and view all the answers

During a marathon, what is the approximate energy requirement per minute?

800 kJ/min-1 Signup and view all the answers

What is the primary function of glycogen storage in muscle cells?

To provide energy for high-intensity exercise Signup and view all the answers

During low-intensity exercise, what is the primary source of energy for the muscles?

Fatty acids Signup and view all the answers

What is the byproduct of anaerobic metabolism during high-intensity exercise?

Lactate Signup and view all the answers

During exercise, what is the primary function of the liver's glycogen storage?

To support circulating glucose levels Signup and view all the answers

What is the approximate duration of energy supply from stored glycogen in muscle cells during high-intensity exercise?

60 minutes Signup and view all the answers

During high-intensity exercise, why is the body unable to deliver extra oxygen to the muscles?

Inability to increase oxygen delivery in time Signup and view all the answers

What proportion of metabolism is anaerobic during the initial 30 seconds of exercise?

95% Signup and view all the answers

What is the primary reason for the limited capacity of fatty acids as a fuel source during exercise?

All of the above Signup and view all the answers

What is the primary source of energy during the finishing sprint phase of exercise?

Anaerobic metabolism of glucose from glycogen Signup and view all the answers

What is the primary advantage of muscle glycogen as a fuel source during exercise?

It can be mobilized rapidly Signup and view all the answers

What is the primary characteristic of exercise with a duration of 20 minutes or more?

95% aerobic metabolism Signup and view all the answers

What is the primary destination of lactate released into the circulation during high-intensity exercise?

Liver for gluconeogenesis via the Cori cycle Signup and view all the answers

Study Notes

Physiological Adaptations to Exercise

Humans are well adapted to exercise, with many physiological and biochemical processes specifically configured to meet the acute oxygen and metabolic fuel needs of muscles.
Exercise involves changes in multiple systems, including the musculo-skeletal, cardiovascular, respiratory, temperature, and urinary systems.

Metabolic Response to Exercise

The body needs to mobilize stored fuels at a rate to match increased activity, preserving blood glucose levels to protect the brain.
The magnitude and nature of the response depend on the type of exercise, intensity, duration, and physical condition and nutritional state of the individual.

Energy Requirements of Exercise

Resting metabolic rate is approximately 4 kJ/min-1.
Energy requirements increase with exercise intensity and duration, with examples including:
- 100m sprint: 200 kJ/min-1, 30 kJ total
- 1500m race: 140 kJ/min-1, 500 kJ total
- Marathon 42km: 800 kJ/min-1, 10,000 kJ total

Energy Sources

ATP is required for muscle contraction, with very short-term stores lasting about 5 seconds.
ATP must be rapidly recreated by oxidative phosphorylation (aerobic) and anaerobic pathways.
Energy sources include:
- ATP and creatine phosphate (short-term stores)
- Glucose (circulation and tissue stores)
- Fatty acids (circulation and tissue stores)
- Glycogen (muscle and liver stores)
- Triacylglycerols (tissue stores)

Fuel Utilization

During high-intensity exercise, ATP is created anaerobically, producing lactate and H+.
During low-intensity exercise, aerobic metabolism uses fatty acids and glucose.
The proportion of anaerobic to aerobic metabolism varies with exercise duration, with:
- 0-30 sec: 95% anaerobic
- 2-4 mins: 40-50% anaerobic
- > 20 min: 95% aerobic

Phases of Response

Initial sprint: muscle ATP and creatine phosphate
Long middle phase: aerobic metabolism of glucose from glycogen and fatty acids
Finishing sprint: anaerobic metabolism of glucose from glycogen

Mobilizing Reserves

Insulin and glucagon play key roles in mobilizing glucose and glycogen stores.
Adrenaline and growth hormone stimulate glycogenolysis and lipolysis.
Cortisol mobilizes fats and stimulates gluconeogenesis.

Benefits of Exercise

Regular exercise produces improved exercise capacity, adaptations, and multiple health benefits, including:
- Better balance of lean tissue and fat
- Lower blood lipids and blood pressure
- Improved glucose tolerance and insulin sensitivity
- Reduced risk of mortality, especially cardiovascular over 5 years

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Description

Explore the physiological and biochemical processes that enable humans to adapt to exercise. Learn how the body meets the oxygen and metabolic fuel needs of muscles during physical activity.