Exercise Phys 4: Endocrine response Flashcards
Characteristics of steroid hormones and their receptors
examples?
Structurally related to cholesterol -> lipid soluble
- receptors usually intracellular -> effect protein synthesis/expression
e.g. cortisol, aldosterone (adrenal cortex)
testosterone, oestrogen
Characteristics of non-steroidal hormones and their receptors - 2 types
examples?
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
Characteristics of prostaglandins and receptors
example?
(pseudo)hormones -> derived from arachidonic acid
act as local hormones -> inflammatory response, swelling, vasodilation etc
e.g. thromboxane from platelets -> vasoconstriction
Processes and hormones which increase blood glucose during exercise?
Glycogenolysis -> (glycogen -> glucose)
Gluconeogenesis -> (FFAs, protein -> glucose)
Hormones Glucagon Adrenaline Noradrenaline Cortisol
How does insulin affect glucose mobilisation by cells during exercise?
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
Describe pancreatic Beta cell release of insulin
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
Insulin promotes what on the cell surface?
Expression of GLUT4 transporters
-> increases glucose influx into cell
Describe glucagon release from pancreatic alpha cells
Responds to low blood glucose
- fire action potentials
- > provides steady release of glucagon
- Ca2+ and Na2+ channels contribute to depolarisation
How does high glucose in the blood inhibit glucagon release?
Pancreatic alpha cells detect high glucose
- Katp blocked by increased ATP
Depolarisation
- > Na channels CANNOT RECOVER from inactivation
- reduces Ca2+ entry
- > reduced glucagon release
What pathway stimulates glycogenolysis?
Glucagon stimulates glycogenolysis via Gs/cAMP/PKA mediated pathway
How does adrenaline cause vasoconstriction in some areas but vasodilation in others?
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