Lecture 9 - Hormonal Control During Exercise Flashcards
nervous system vs endocrine system communication
NS
- > electrical communication
ES
- > chemical communication
role of endocrine system
- > maintain homeostasis via hormones, that act on target cells
- > maintains homeostasis during exercise
*controls substrate metabolism, regulates fluid and electrolyte balance
how are glands stimulated to release hormones
Humeral Stimuli
- > control of hormone release in response to changes in extracellular fluid (i.e. iron blood conc.)
Hormonal stimuli
- > release of hormone in response to another hormone (2ns messenger)
Neural stimuli
- > the NS directly stimulates some glands (fight/flight)
what are Steroid hormones and which organs/structures secrete them
- > derived from choloesterol
- > lipid/fat soluble; can diffuse through the membrane
secreted by…
- > adrenal cortex
- > placenta
- > ovaries
- > testes
types of hormones
steroid and non-steroid hormones
non-steroid hormones
- > not fat soluble; cannot pass through the membrane
- > secreted in bursts
- > secretion is regulated by negative feedback
2 groups
- > protein/peptide hormones
- > amino acid hormones
is blood plasma conc. of hormones a good indicator or hormone action?
no
- > cells change sensitivity to hormones and the number of receptors on the cell
down/upregulation
Down-regulation
- > decease in the number of receptors during high plasma concentrations (desensitization)
Up-Regulation
- > increase in the number of receptors during high plasma concentrations (sensitization)
how are the effects of hormones limited
hormone-specific receptors limit the scope of their effects
- > no receptor on surface = no hormonal effect
where do hormones bind to receptors
hormone-receptor complex
where are the steroid hormone receptors found?
in the cytoplasm or nucleus of the cell, steroid hormones can cross the membrane
- > hormone-receptor complex will enter nucleus once activated
how do non-steroid hormones initiate a response in the cell if then cant cross the membrane
there’s a receptor on the cell membrane that, once activated, will activate a second messenger
- > the 2nd messenger will carryout hormonal effects and increase the hormones effect by activating other messenger
prostaglandins
- > 3rd class of (pseudo) hormones
- > derived from arachidonic acid
- > acts as a local hormone, immediate area
* inflammatory response
which systems/ glands contribute to the hormonal regulation of metabolism during exercise
endocrine glands are responsible for metabolic regulation during exercise
- > anterior pituitary gland
- > thyroid gland
- > adrenal gland
- > pancreas
*hormones release by these glands affect the metabolism of carbs and fats
anterior pituitary gland
- > attached to the inferior hypothalamus
- > 3 lobes (ant, intermediate, post)
- > releases growth hormone (GH)
*GH release is proportional to exercise intensity
Thyroid gland
- > secretes T3 and T4
*leads to increase in metabolic rate of al tissues, protein synthesis, # and size of mitochondria, glucose uptake in cell
- > ant. pituitary releases thyrotropin/thyroid stimulating hormone (TSH) which travels to thyroid to stimulate the secretion of T3 and T4
*exercise increases TSH release
Adrenal Medula
releases catecholamines (fight/flight)
- > nor/epinephrine (20%/80%)
- > catecholamines release influences BP, HR, BF, respiration, ect.
Adrenal Cortex
releases corticosteroids
- > glucocorticoids, mineralcorticoids, and gonadocorticoids
*major glucocorticoid is cortisol
- > which increases gluconeogenesis, FFA mobilization, protein catabolism
pancrease
releases insulin and glucagon
insulin
decreases blood glucose levels by…
- > increases glucose transport into cell
- > increasing the synthesis of glycogen
- > it counters hyperglycaemia and opposes glucagon
glucagon
raises blood glucose by…
- > increasing glyconeogenesis and glycogenolysis
- > counters hyperglycemia
adequate glucose during exercise requires…
- > glucose release by the liver and glucose uptake in muscles
hormones that increase circulating glucose
- > glucagon
- > epi/norepinephrine
- > cortisol
*also affected by GH and T3 and T4
as exercise intensity increases…
- > catecolamine release increases
- > glycogenolysis rate increase
- > muscle glycogen used up before liver glycogen
as exercise duration increases…
- > more liver glycogen is utilized
*increased muscle glucose uptake leads to increase liver glucose released
triglyceride
FFA + glycerol
lipolysis (fat breakdown) is caused by…
lipolysis is stimulated by lipase
- > decreased insulin
- > nor/epinephrine
- > cortisol
- > GH
regulation of fat metabolism during exercise
when glycogen is depleted, we need fat energy substrates
- > in response, hormones accelerate fat breakdown (lipolysis)
