Guyton Review- Introduction To Endocrinology

Front 1

Types of coordination of body functions by chemical messengers:

Back 1

1. Neural
2. Endocrine
3. Neuroendocrine
4. Paracrine
5. Autocrine

Front 2

Endocrine:

Back 2

Hormones reach circulating blood and influence the function of cells some distance away

Front 3

Neuroendocrine:

Back 3

Neuroendocrine cells in hypothalamus with axons terminating in post. pituitary and median eminence. Secrete: ADH, oxytocin and hypophysiotropic hormones (which control hormone secretion from ant. pituitary)

Front 4

Classification of hormones:

Back 4

1. Proteins and peptides
2. Steroids
3. Derivatives of the amino acid tyrosine (thyroxine, triidothyronine, epi, norepi)

Front 5

Synthesis, storage and secretion of peptide hormones:

Back 5

On RER like normal proteins---> large prehormone---> cleaved at ER---> Packed by Golgi as prohormone in secretory granules (may contain enzymes for further modification of the prohormone)---> released by exocytosis after stimulation

Front 6

Synthesis, storage and secretion of steroid hormones:

Back 6

Synthesized from cholesterol esters located in cytoplasmic vacuoles. Synthesized on SER. No storage---> diffuse through plasma membrane

Front 7

Synthesis of hormones from tyrosine:

Back 7

No storage of thyroid hormones, diffuse through cell membrane once they appear in cytoplasm. But large stores of thyroglobulin.
Epi and norepi are stored in vesicles until released from adrenal medullary cells through exocytosis.

Front 8

Control of hormonal secretion:

Back 8

Negatve feedback:
Endocrine glands oversecrete hormones, which in turn drives target cells function. When there is too much function from the cell, a factor of the function feeds back to the endocrine gland and suppress its secretion.

Front 9

Hormonal receptors and their activation:

Back 9

1. On cell membrane (peptide and catecholamine hormones)
2. Within the cell in either cytoplasm of nucleus (steroid and thyroid hormones)

- Specific receptors for each hormone
- Signal generating mechanism--> change in intracellular processes by altering activity or concentrations of enzymes, carrier proteins and so on.

Front 10

Cell response to peptide and catecholamine hormones:

Back 10

Interaction with cell membrane receptors which often generates a second messenger. This often involves coupling G- protein in the cell membrane with second messenger

Front 11

Second messenger mechanism include following:

Back 11

1. Adenylyl cyclase- cAMP
2. Phospholipase C- protein kinase C
3. Calcium- calmodulin

Front 12

Adenylyl cyclase- cAMP:

Back 12

Stimulation inhibition of adenylyl cyclase---> synthesis of second messenger cAMP---> activates protein kinase A---> phosphorylation===> activates or inhibits target enzymes

Front 13

Plasma membrane phospholipids:

Back 13

Hormone- receptor interaction---> activates membrane bound phospholipase C---> cleave phosphatidylinisitol to diacylglycerol and inisitol triphosphate--> inisitol triphosphate release Ca2+ from ER--> Ca2+ activates protein kinase C---> protein kinase C phosphorylates enzymes (activates/inhibits)