Lecture 8

Question 1

hormones : concentration, how are the actions terminated ?

Answer 1

Very low concentrations !
If in the bloodstream : degraded in the liver and kidneys.
If bound to receptor : enzymes in plasma or in lysosome

Question 2

3 classification schemes

Answer 2

• released controlled by brain or not
• GPCR, TK or intracellular receptors
• Peptide / steroid / amine (thyroid and catecholamines)

Question 3

for the 4 classes of hormones : release from cell, transport in blood, receptor, response

Answer 3

Peptide : exocytosis, free, membrane receptor, 2nd messenger -> change existing proteins

Steroid : simple diffusion, carrier protein, cytoplasm /nucleus, activation of genes -> new proteins

Catecholamines : exocytosis, free, membrane, second messenger system

Thyroid : transport protein, carrier proteins, nucleus -> activation of genes

Question 4

2 major classes of membrane receptors

Answer 4

1) GPCR : G turns on adenylyl cyclase, it converts ATP to cAMP, which activates kinase A -> phosphroylation of proteins -> cellular response

2) Tyrosin-kinase : receptor autophosphorylation -> signal for other molecules that bind to TK

Question 5

peptide hormone synthesis process

Answer 5

mRNA -> preprohormone. Signal sequence is cut -> prohormone. It goes to the Golgi -> peptide fragments are cut = creates active hormone. Secretory vesicle releases content into EC space.

Question 6

where are the adrenal glands ?

Answer 6

on top of kidneys

Question 7

layers of adrenal cortex and hormone they secrete, what kind of hormones are they and what is the parent compound ?

Answer 7

1) zona glomerulosa : aldosterone (salt and water balance)

2) zona fasciculata : cortisol (level of carbohydrate)

3) zona reticularis : sex hormones

They are steroid hormones -> derived from cholesterol

Question 8

adrenal medulla : what hormones it secretes, type of hormone ?

Answer 8

Norepinephrine and epinephrine

Question 9

thyroid hormones : chain of secretion, two forms, more of which ?

Answer 9

Hypothalamus secretes TRH -> pituitary secretes TSH -> thyroid secrets T3 and T4.
T3 is the active form, but produced less because T4 is easier to transport. T4 is then locally converted into T3.

Question 10

Glands in the brain ?

Answer 10

Hypothalamus, pineal gland (melatonin), pituitary gland

Question 11

Which hormone release does hypothalamus control ?

Answer 11

Catecholamine, vasopressin, oxytocin, pituitary gland hormones

Question 12

pituitary gland : two parts, which kind of tissue ?

Answer 12

posterior = neural tissue
anterior = epithelial tissue

Question 13

hypothalamic - anterior pituitary pathway

Answer 13

Trophic hormones released from hypothalamus go through portal system (isolated blood circulation).
Anterior pituitary releases 6 peptide hormones : prolactin, GH, ACTH, LH, FSH, TSH

Question 14

posterior pituitary : what does it do ?

Answer 14

it secretes hormones that were made IN THE BRAIN : oxytocin and vasopressin

Question 15

What is another wya of controlling the release of the trophic hormones ?

Answer 15

negative feedback from the hormones themselves (feedback to the thalamus and pituitary gland)