Endocrine system part 2 Flashcards
What is the role of the posterior pituitary gland (PPG)?
It’s basically a neural extension of the hypothalamus. Hormones are synthesized in the hypothalamus; axons pass down infundibulum, terminate in the PPG and release hormones.
What is the role of the anterior pituitary gland (APG)?
Secretes many different hormones (e.g., growth hormone)
What is the relationship between the APG and the hypothalamus?
Hypothalamus controls secretion of APG hormones via portal vessels connecting the two.
Typical sequence - Hypophysiotropic hormone controls secretion of an APG hormone, which in turn controls secretion of a hormone by a 3rd endocrine gland.
Give 2 examples of the effect of thyroid hormones throughout the body.
Protein synthesis in follicular epithelial cells
Increase in DNA replication and cell division
What controls the production of thyroid-stimulating hormones?
Controlled by negative feedback action of T3 and T4 on the ADG (and hypothalamus)
Actions of thyroid hormones - what does an increase in T3 and T4 levels associate with?
Increase T3 and T4 levels associate with increased oxidative substrate metabolism & increased mitochondrial enzyme activity
Therefore T3 & T4 = high metabolic rate
What are 3 physiological functions of cortisol during ‘non-stressful situations’?
1) Cortisol affects responsiveness of smooth muscle cells to epinephrine and norepinephrine (thus helps maintain normal blood pressure)
2) Cortisol required to maintain certain enzyme concentration and is involved in metabolic homeostasis (prevents plasma glucose dropping too far below normal)
3) Has anti-inflammatory + anti-immune functions
What are 5 physiological functions of cortisol during ‘stressful situations’?
1) Effects metabolism
2) Enhanced vascular reactivity, improving CV performance
3) Protective effects against damaging influences of stress
4) Inhibition of inflammation and specific immune responses
5) Inhibition of nonessential functions (reproduction)
What 4 effects does cortisol have on metabolism during stressful situations?
o Stimulation of protein catabolism in bone, lymph muscle and elsewhere
o Stimulation of liver uptake of amino acids and their conversion to glucose (gluconeogenesis)
o Maintenance of plasma glucose concentration
o Stimulation of triglyceride catabolism in adipose tissue, with release of glycerol and fatty acids into the blood
What is the relationship between cortisol and exercise?
Plasma cortisol concentrations always higher post-exercise than pre-exercise
What are the 5 most important hormones to human growth?
- Growth hormone (GH)
- Insulin-like growth factors 1 and 2
- T3 (essential for growth during childhood and adolescents)
- Insulin (mainly during foetal life)
- Testosterone and estradiol
What hormones secretes growth hormone and what hormone inhibits it?
Secretes - Growth hormone-releasing hormone
Inhibits - Somatostatin
What does testosterone promote?
Muscle growth and development of male sex characteristics
What does oestrogen promote?
Development of female sex characteristics, regulates menstrual cycle and adipose tissue growth
What is the response of sex hormone (testosterone) to exercise?
Sex hormone level increases dramatically immediately post exercise.
This increase in sex hormone levels helps build muscle and reduce body fat.
What produces DHEAs (precursors for sex hormones)?
The Adrenal Cortex
What ages do DHEA and DHEAS production peak at?
20-30 (declines progressively after this)
What is the relationship with DHEA/S levels following low/moderate intensity exercise in young AND old adults?
DHEA increases following low/moderate intensity exercise in young people, however not in older adults.
