3.6 Endocrine system

Question 1

hormone

Answer 1

signal secreted into the bloodstream by an ductless endocrine gland, targets distant cells with the appropriate receptor

DUCTLESS

Question 2

exocrine gland

Answer 2

secrete by way of ducts, leading to lumen or external world

Question 3

autocrine

Answer 3

signaling molecule modifies activity of the cell that secreted it

e.g. T cell secretes interleukin 2, which binds to T-cell

Question 4

classification of hormones

Answer 4

hydrophilic - peptides, amino-acid derivatives

hydrophobic - steroid hormones

Question 5

peptide hormones

Answer 5

a primary messenger

• synthesized in ER, modified in Golgi
• stored in vesicles, released by exocytosis
• communicate with cells by secondary-messengers, which amplify signals and alter the function of existing proteins/enzymes in the cytoplasm
• the effects are exerted rapidly (minutes-hours). brief duration
• modify the activity of existing enzymes

Question 6

2 subgroups of peptide hormones

Answer 6

1. polypeptides

2. amino acid derivatives

Question 7

insulin

Answer 7

a type of polypeptide hormone, with large tertiary structure with disulfide bridges

• excreted in beta cells of pancreatic islets of Langerhans in response to elevated blood sugar
• binds to a cell-surface receptor with a cytoplasmic domain possessing protein kinase
• anabolic

Question 8

amino-acid based hormones

Answer 8

contain NO peptide bonds

Tyrosine -> parent AA for catecholamines

Question 9

catecholamines

Answer 9

1. epinephrine
2. norepinephrine
3. dopamine

Above -> more like peptide hormones

4. T3/T4 -> more like steroid -> binds to DNA and activates transcription

Question 10

adrenaline

Answer 10

• adrenal medulla on activation of sympathetic NS
• bind to cell-surface receptors, triggers a cascade of events, that produces the second messenger cAMP, and activates protein kinases in cytoplasm

Question 11

steroid hormones

Answer 11

synthesized from cholesterol in smooth ER

• made only when needed
• cannot dissolve in plasma, instead they are stuck to proteins
• effect: diffusing through plasma membrane and binding with receptor in the cytoplasm
• once it has bound its ligand, steroid hormone-receptor complex is transported to the nucleus, where it acts as a sequence-specific regulator of transcription
• because they change the amount of protein, the effects are exerted slowly, over days and persist for days or weeks

Question 12

steroids regulating sexuality, reproduction, development

Answer 12

testes, ovaries, placenta

Question 13

steroids regulating water balance

Answer 13

adrenal cortex

Question 14

peptide versus steroid (DRAW TABLE)

Answer 14

p. 80

Question 15

regulation of endocrine system

Answer 15

dynamic, automatic - due to feedback regulation

Question 16

hormones that regulate hormones

Answer 16

tropic hormones

most hormones do negative feedback, or feedback inhibition

Question 17

ACTH

Answer 17

a tropic hormone that regulates another regulator (cortisol)

Question 18

hypothalamus

Answer 18

releases tropic hormones that regulate other tropic hormones

Question 19

hypophysis

Answer 19

another name for pituitary gland

Question 20

the two portal systems

Answer 20

hypothalamic-pituitary portal system

hepatic portal system

• two capillary beds in sequence, allows for direct communication between nearby structures

Question 21

anterior pituitary

Answer 21

adenohypophysis

controlled by hypothalamic releasing and inhibiting factors (tropic hormones)

Question 22

posterior pituitary

Answer 22

neurohypophysis

consist of axons which descend from the hypothalamus; neuroendocrine cells, neurons that secrete hormones into the bloodstream

ADH (antidiuretic hormone, or vasopressin), and oxytocin - produced in the paraventricular nucleus of the hypothalamus - these are peptides

Question 23

axon termini

Answer 23

not the site of protein synthesis; peptides are produced in nerve cell bodies in the hypothalamus and transported down the axons

Question 24

thyroid hormone

Answer 24

3 or 4 iodine per molecule

• increased by TSH from anterior pituitary, which is controlled by hypothalamus and CNS
• binds to receptor in cytoplasm of cells then regulates transcription in the nucleus
• changes metabolic rate and body temperature
• in children, will stimulate growth

Question 25

cortisol

Answer 25

adrenal cortex

• responds to ACTH
• mobilizes glycogen and fat stores to provide energy
• increases consumption of proteins for energy
• very important
• suppresses the immune system