Hormonal Mechainsims

Question 0

Peptide hormones

Answer 0

Chains of amino acids

Hypothalamus, pituitary, pancreas, GIT

Question 1

Types of inter cellular messenger

Answer 1

Endocrine:
Hypothalamus->pituitary->target gland-> body
Carried in blood to target cell
Autocrine-> cell releases messenger that acts on the same cell->prostaglandins
Paracrine-> cell releases messenger that acts on another cell->somatostatin, insulin
Neuroendocrine->released by a nerve->carried in blood to target cell-> oxytocin, vasopressin (post. pit.)
Neurotransmitter

Question 2

Synthesis of peptide hormones

Answer 2

In endocrine cell
1. mRNA produced in nucleus attaches to ribosome-> preprohormone
2. mRNA processed by ribosome->protein-> modified by Golgi->prohormone
3. Packaged in to secretory granule by Golgi-> hormone
Stored in cell until release by exocytosis

Question 3

Transport of peptide hormones

Answer 3

Hydrophilic->cell walls
Not bound to plasma protein
Half life=minutes

Question 4

Action of peptide hormones

Answer 4

Eg insulin
Hormone-> receptor->tyrosine kinase(inside cell)->signal transduction-> physiological response
Eg glucagon
Hormone->receptor with G protien-> adenyl cyclase/cAMP-> signal transduction->physiological response

Question 5

Steroid hormones

Answer 5

Derived from cholesterol
cortisol, aldosterone (adrenal cortex)
Sex hormones (gonads)

Question 6

Synthesis of steroid hormones

Answer 6

Endocrine cells
Induced by a stimulus
1. Precursors molecule such as cholesterol->acted on by biosynthesic enzymes-> hormone
2.hormone released by simple diffusion immediately, not stored
3. Hormone binds to a plasma protein

Question 7

Transport of steroid hormones

Answer 7

Lipophillic
Bind to plasma proteins with weak reversible bonds
Half life=hours to days

Question 8

Action of steroid hormones

Answer 8

Same as thyroid hormones
1.hormone diffuses in and binds to a nuclear receptor
2.causes DNA to produce mRNA-> proteins and biological effects
Or hormone binds to a cytosolic receptor
Act to increase/decrease gene expression
Intra cellular receptors act as hormone regulated transcription factors

Question 9

Mechanisms by which endocrine disorders may develop

Answer 9

Hormone excess->hyper secretion->tumour or immunological factor
Lack of hormone-> hypo secretion->genetic, immunological attack, destruction by disease, surgical removal
Decreased target cell responsiveness

Question 10

Endocrine function tests

Answer 10

1. Signs and symptoms
2. Endocrine investigations
   A. Single point (base line)
   B. Dynamic or provocative test->check feedback control
   Stimulation test->suspected hypo secretion-> indicated by failure to stimulate
   Suppression test-> suspected hyper secretion->indicated by failure to suppress->autonomous secretion
   3.imaging