Hormonal Response to Exercise

Question 1

What are the 4 processes that maintain plasma glucose when fasting or during exercise?

Answer 1

1. Mobilization of glucose from liver glycogen stores.
2. Mobilization of FFA from adipose tissue.
   - Spares blood glucose.
3. Gluconeogenesis from amino acids, lactic acid, and glycerol.
4. Blocking the entry of glucose into cells.
   - Forces use of FFA as a fuel.

Question 2

What are the 2 types of hormones?

Answer 2

• Permissive/slow-acting (thyroxine, cortisol, GH)
• Fast-acting (Epinephrine, norepinephrine, insulin and glucagon)

Question 3

How do permissive hormones act?

Answer 3

Act in a permissive manner to allow other hormones to exert their
full effect.

Question 4

How is GH essential for growth of al tissues?

Answer 4

Increases amino acid
uptake and protein
synthesis.

Question 5

How does GH spare plasma glucose?

Answer 5

1. Reduces the use of
   plasma glucose
2. Increases
   gluconeogenesis
3. Mobilizes fatty acids
   from adipose tissue

Question 6

How does GH preserve plasma
glucose concentrations?

Answer 6

• Increases gluconeogenesis in liver
• Blocks glucose entry to adipose cell to favour fat mobilization

Question 7

What happens to plasma GH with increased intensity?

Answer 7

Increase

Question 8

What is cortisol derived from and where is it secreted?

Answer 8

Cholesterol, secreted from adrenal cortex.

Question 9

What is cortisol stimulated by?

Answer 9

• Stress, via Adrenocorticotropic hormone
  (ACTH)
• Exercise

Question 10

When do cortisol levels peak?

Answer 10

First thing when you wake up.

Question 11

What are considerations with cortisol levels?

Answer 11

1. Diurnal variation:
   Concentrations peak in
   the am & drop
   throughout the day.
2. Events other than
   exercise, e.g.,
   emotional arousal

Question 12

How does cortisol change in response to exercise intensity?

Answer 12

↑ proportional to ↑ in exercise intensity.

Question 13

Where are catecholamines secreted from?

Answer 13

Adrenal medulla
- Epinephrine (E) (80%)
and norepinephrine(NE)

Question 14

How does Epinephrine and Norepinephrine increase during exercise?

Answer 14

In a linear fashion.

Question 15

What does endurance training cause in relation to catecholamines?

Answer 15

A very rapid decrease in catecholamine responses to a
fixed intensity exercise bout.

Question 16

Do trained individuals have higher or lower capacity to increase catecholamines?

Answer 16

Trained individuals have a greater capacity (~35% higher) to increase catecholamines compared to untrained individuals

Question 17

What effect does plasma epinephrine have on glycogenolysis?

Answer 17

Plasma epinephrine is a powerful simulator of glycogenolysis (via
beta1 receptor)
- High-intensity exercise results in greater increases in plasma epinephrine.

Question 18

Why does reduced effects of epinephrine not cause a major difference in glycogen depletion?

Answer 18

Breakdown of muscle glycogen is under dual
(redundant) control.
1. Intact sympathoadrenal
system not necessary to
initiate glycogenolysis
2. Does not mean that
epinephrine cannot, or
does not, cause
glycogenolysis

Question 19

How does plasma glucagon change during exercise?

Answer 19

Following an endurance training program, the glucagon response is diminished to the point that there is little to no increase during exercise.

Question 20

What is the primary stimulus for the secretion of insulin and glucagon?

Answer 20

Plasma glucose

Question 21

Despite glucagon (and other hormones favouring mobilization of FFA) being elevated with increasing exercise intensity, FFA oxidation decreases during heavy exercise. Why could this be?

Answer 21

May be due to:
1. High levels of lactic acid.
2. Elevated H+ concentration inhibits
HSL.
3. Inadequate blood flow to adipose
tissue.
4. Insufficient albumin to transport FFA
in plasma.

Question 22

Endurance training decreases lactate concentration at any fixed work rate causing..?

Answer 22

Reduced inhibition of FFA mobilization from adipose tissue.
- When this is combined with the training induced increase in mitochondria, the trained person can use more fat as a fuel, spare the limited CHO stores and improve performance.