Exercise Phys 4: Endocrine response

Question 1

Characteristics of steroid hormones and their receptors

examples?

Answer 1

Structurally related to cholesterol -> lipid soluble
- receptors usually intracellular -> effect protein synthesis/expression

e.g. cortisol, aldosterone (adrenal cortex)
testosterone, oestrogen

Question 2

Characteristics of non-steroidal hormones and their receptors - 2 types

examples?

Answer 2

Large, not lipid soluble -> receptors usually on surface
- transduce extracellular to intracellular response

Peptide or protein hormones e.g. insulin + glucagon

AA derived e.g. Thyroxine, (nor)adrenaline

Question 3

Characteristics of prostaglandins and receptors

example?

Answer 3

(pseudo)hormones -> derived from arachidonic acid

act as local hormones -> inflammatory response, swelling, vasodilation etc

e.g. thromboxane from platelets -> vasoconstriction

Question 4

Processes and hormones which increase blood glucose during exercise?

Answer 4

Glycogenolysis -> (glycogen -> glucose)
Gluconeogenesis -> (FFAs, protein -> glucose)

Hormones 
Glucagon
Adrenaline
Noradrenaline
Cortisol

Question 5

How does insulin affect glucose mobilisation by cells during exercise?

Answer 5

Insulin enables glucose uptake in muscle BUT

• during exercise, insulin conc. decreases
• cell sensitivity for insulin increases
• > results in increased glucose uptake using less insulin

Question 6

Describe pancreatic Beta cell release of insulin

Answer 6

Responds to changes (increase) in blood glucose
-> increases ATP synthesis in the cell

ATP blocks Katp (ATP sensitive potassium) ion channels

Depolarisation

• > activates Ca2+ channels
• > insulin release

Question 7

Insulin promotes what on the cell surface?

Answer 7

Expression of GLUT4 transporters

-> increases glucose influx into cell

Question 8

Describe glucagon release from pancreatic alpha cells

Answer 8

Responds to low blood glucose

• fire action potentials
• > provides steady release of glucagon
• Ca2+ and Na2+ channels contribute to depolarisation

Question 9

How does high glucose in the blood inhibit glucagon release?

Answer 9

Pancreatic alpha cells detect high glucose
- Katp blocked by increased ATP

Depolarisation
- > Na channels CANNOT RECOVER from inactivation

• reduces Ca2+ entry
• > reduced glucagon release

Question 10

What pathway stimulates glycogenolysis?

Answer 10

Glucagon stimulates glycogenolysis via Gs/cAMP/PKA mediated pathway

Question 11

How does adrenaline cause vasoconstriction in some areas but vasodilation in others?

Answer 11

binding to alpha-adrenoceptors in mesentery couples to Gq proteins
-> calcium channel activation + release and contraction -> vasoconstriction

binding to beta-adrenoceptors in skeletal muscle vessels coupled to Gs

• > K channel activation, Ca2+ channel inactivation
• > muscle relaxes, vasodilation