Lecture 10 - Hormonal Control During Exercise

Question 1

How does the proportion of plasma energy change in relation to intensity increasing (VO2 max increasing)?

Answer 1

• the portion of plasma stays relatively stable
• the proportion is reduced because muscle energy increases significantly

Question 2

what is blood glucose homeostasis?

Answer 2

• maintenance of blood glucose levels during exercise

Question 3

what are the two reasons in which maintaining blood glucose homeostasis is important?

Answer 3

• glucose is a major substrate for metabolism
• glucose is the only fuel acceptable to the brain and other CNS tissues

Question 4

what is normal resting blood glucose concentration?

Answer 4

• 4.0-5.5 mmol/L
• 90-100 mg/dL

Question 5

what is the term for someone who cannot regulate blood glucose levels well?

Answer 5

• diabetic

Question 6

how does exercise affect blood glucose?

Answer 6

• causes a massive increase in glucose uptake from the blood

Question 7

why is it necessary for glucose uptake from the blood to increase?

Answer 7

• maintain energy for muscle contraction during exercise

Question 8

what are glut-4 transporters?

Answer 8

• transporters on the plasma membrane
• must be present to allow glucose to enter into the cell
• the amount of glut-4 is affected by exercise –> this affects the amount of glucose able to enter the cytosol

Question 9

why must glucose be restored in the blood immediately?

Answer 9

• if we only used the glucose stored in the blood, we would only have 25 calories worth of energy
• must be replenished or it would fall rapidly

Question 10

what organ is responsible for blood glucose?

Answer 10

• the liver
• also the gut and kidneys

Question 11

what are the two systems in the liver that release glucose into the blood?

Answer 11

• gluconeogenesis
• glycogenolysis

Question 12

what is hepatic glucose production?

Answer 12

• “the release of glucose from the liver”

Question 13

what are the steps for how gluconeogenesis produces glucose?

Answer 13

• start with pyruvic acid (aka lactic acid)
• creates glucose-6-phosphate (also can be produced by amino acids or glycerol)
• makes glucose
• *this is an anabolic system

Question 14

what are the steps for how glycogenolysis produces glucose?

Answer 14

• start with glycogen
• breaks down to produce glucose-1-phosphate
• breaks down again to produce glucose-6-phosphate
• this makes glucose
• *this is a catabolic system

Question 15

what is lipid mobilization?

Answer 15

• a strategy to reduce glucose from falling during exercise (supports the metabolism at the muscle level)

Question 16

How does lipid mobilization work?

Answer 16

• use free fatty acids to provide acetyl-CoA to the Krebs cycle
• increase in fat metabolism (means we can use less glucose in the muscles)

Question 17

what are adipocytes?

Answer 17

• subcutaneous fat (adipose tissue)

Question 18

what is the role of adipocytes in lipid mobilization?

Answer 18

• release fatty acid chains (from the triglycerides) through lipolysis
• into the blood
• transported with albumin
• taken up at the muscle
• form fatty acetyl CoA
• produce energy through the Krebs cycle and electron transport

Question 19

how is glucose regulated during exercise?

Answer 19

• homeostasis
• through the endocrine system (chemical communication) aka hormones
• through the nervous system (electrical communication) aka sympathetic nervous system

Question 20

what is the role of the endocrine system?

Answer 20

• controls all physiological processes that support exercise and maintain homeostasis
• does this by releasing hormones

Question 21

what are hormones?

Answer 21

• signalling molecules to trigger physiological processes within the body

Question 22

where are hormones produced and released?

Answer 22

• by glands transported by the circulatory system to target organs for regulating physiology
• specifically the endocrine glands (for exercise metabolism)

Question 23

how are hormones secreted?

Answer 23

• in pulsatile bursts (plasma concentration fluctuates)
• triggered by negative feedback - correcting an “error signal”

Question 24

what is the role of hormone receptors?

Answer 24

• hormones bind to specific receptors
• without receptors, hormones have no effect
• receptors are located at the target organ

Question 25

what is the action of hormones?

Answer 25

- exert effects after binding with receptor - do not directly affect cell activity (indirect causation) - initiate a predictable series of chemical reactions

Question 26

what are the 4 important endocrine glands for metabolism?

Answer 26

1. pancreas 2. adrenal gland 3. anterior pituitary gland 4. thyroid gland

Question 27

what is the role of endocrine glands?

Answer 27

- regulate the mobilization of fats and carbohydrates - influence the fuel utilization we use during exercise

Question 28

what is the role of the pancreas?

Answer 28

- endocrine regulation of metabolism - a gland important for regulating metabolism through the release of glucagon and insulin

Question 29

what is the importance of insulin?

Answer 29

- lowers blood glucose - counters hyperglycemia, opposes glucagon - facilitates glucose transport in cells - enhances synthesis of glycogen, protein and fat - inhibits gluconeogenesis - is not present in individuals with diabetes

Question 30

what is the importance of glucagon?

Answer 30

- raises blood glucose - counters hypoglycemia, opposes insulin - promotes glycogenolysis, gluconeogenesis

Question 31

What is type I diabetes?

Answer 31

- absolute insulin deficiency - no insulin is produced - exercise is important because of glut-4 and uptake (to help regulate glucose)

Question 32

what is type II diabetes?

Answer 32

- impaired glucose control - inadequate insulin production - reduced effect of insulin - negative feedback loops are disrupted

Question 33

how is blood glucose controlled?

Answer 33

- (understand diagram) - work in a negative feedback system - increase in glucose signals the release of insulin so glucose lowers and vice versa

Question 34

what is a sign of hypoglycemia?

Answer 34

- craving for candy/cereal etc.

Question 35

what is insulin-stimulated glucose uptake?

Answer 35

- insulin binds to the insulin receptors in the plasma membrane - initiates the same results as exercise does - glycogen synthesis = glucose uptake, stimulated by insulin

Question 36

how is glucose regulated by pancreatic hormones during exercise?

Answer 36

- blood glucose does not change even during moderate-to-heavy exercise for long periods of time - insulin falls during exercise (helps maintain glucose) - glucagon rises (more glucose is released)

Question 37

how does glucagon change during exercise?

Answer 37

- has a large percent increase at the beginning - remains high (to stop hypoglycemia) - insulin falls and glucose hardly changes

Question 38

what is the adrenal medulla?

Answer 38

- endocrine regulation of metabolism - a gland located above each kidney - releases catecholamines (epinephrine and norepinephrine) --> "fight or flight"

Question 39

what is the effect of epinephrine and norepinephrine release during exercise?

Answer 39

- increase sympathetic nervous system - stimulate glycogenolysis in muscle and liver - stimulate and maintain lipolysis (Epi) --> increase free fatty acids in the blood - suppress insulin secretion - supply blood to skeletal muscle - increase heart rate, increases blood pressure and increases contractile force - Norepinephrine also causes vasoconstriction to non-active areas to send more blood to the active muscles

Question 40

how does exercise influence norepinephrine and epinephrine?

Answer 40

- both are increased as exercise continues - this increases the fat metabolism so you can exercise for longer periods of time