Possible Effects of Hormones
- Change membrane permeability
- Change protein synthesis
- Change enzyme activity
- Induce or stop secretory activity
- Change genetics
- Stimulate mitosis
The effect on the body can vary over time.
The same hormone can have different effects on different tissues depending on what processes the receptor is linked to.
Growth hormone control
- stimulus - exercise, sleep, stress
- hypothalamus- increase in GHRH secretion and a decrease in somatostatin (SS) secretion
- anterior pituitary - increase of GH secretion
- increase in plasma GH levels
- Liver and other cells- increase in insulin like growth factor 1 (IGF1) secretion
- increase in plasma IGF1 levels
- effects a variety of tissues
Follicular phase before ovulation
- day 1 - start of uterine bleeding, lasts about 5 days.
- oocyte is developed
- day 5-14 - endothelial layer increases in thickness
Ovulation occurs on day 14
Luteal phase after ovulation
- ends on day 28
- secretory phase
Control of thyroid hormone concentrations
- low blood level of thyroid hormones or low metabolic rate stimulates the release of TRH.
- TRH is carried to the anterior pituitary which stimulates the release of TSH
- TSH is released into the blood and stimulates thyroid follicular cells
- thyroid hormones are releasedd into the blood
- elevated level of thyroid hormones inhibits the release of TRH and TSH -> negative feedback
Effects of thyroid hormone on the body
- increase mitochondria size and number
- increased cellular leakage of Na+. Increases Na pump activity so uses more ATP and generating heat.
- increased cardiac, respiratory, catabolism, use of glucose and lipids
- increased beta-adrenergic receptor activity in the heart, increasing the response to noradrenaline/adrenaline. Can change heart rate.
necessary for normal childhood growth and to maintain adult body functiom
Control of Aldostrone
- Renin/angiotensin - low blood pressure and low blood volume causes renin to be released from the kidney. Na+ levels in blood increase and as a result more water is retained by the kidney and blood volume and pressure returns to equilibrium.
- low Na+ levels and high K+ levels cause aldostone to be released and the kidney to release renin.
- Atrial natriuretic peptide released from the cardiac atrial cells in response to high blood volume inhibits renin and aldostrone release
- ACTH does not control aldostrone but its presence is necessary for release. During serious stress, very high levels os ACTH can raise aldosterone release.
Response to stress
- Immediate- fight or flight. Hypothalamus and Adrenal medulla activated. release of adrenaline and nor-adrenaline. reduces gut and urinary activity. increased renin, aldosterone, water and sodium retention, blood pressure.
- delayed- hypothalamus releases hormones.
- CRH-ACTH-cortisol: increased glucose production by protein production
- GHGH-GH : lipoysis amd glycogen breakdown.
- TRH -TSH-thyroxine : increases metabolic rate
- insulin - increases transpor of glucose into cells
- Exhaustion- is periods of stress go on for too long then resources are used up, activity is impaired, depressed immunity, wasting muscles.
Regulation of Blood Sugar Levels
Important as glucose is the only energy source for the brain. too little sugar and the body goes into shock- potential death. too much sugar causes cellular dehydration and tissue damage.
- liver stores glycogen.
- Insulin and glycagon are regulated by direct feedback of glucose levels.
- low blood sugar levels stimulates the hypothalamus, adrenaline is released from the adrenal medulla causing the liver to release glucose.
- long term low blood sugar - HGH and cortisol increase glucose production and switch the body to fat metabolism.