endocrine- basics

Question 1

endocrine vs exocrine

Answer 1

exocrine - secretes out a duct to lining outside of the body or inside the body (lining of organ)

endocrine-no ducts, secrete into EXTRACELLULAR FLUID and act on TARGET cells ->hormones (chemical messengers- to remote parts of body)

Question 2

what is the manner in which most endocrine cells secrete their hormones? why does this matter for checking hormone levels?

Answer 2

Usually pulsatile in manner- something messes up homeostasis and they are secreted to restore it
—> so ordering random hormone level is useless.

Question 3

which endocrine gland is the only one that does NOT secrete in a pulsatile manner?

Answer 3

thyroid

Question 4

what causes secretion of hormones? what causes inhibition of hormone secretion?

Answer 4

secretion: Disruption of homeostasis
inhibition: Restoration of homeostasis (reduction of stimulus) AKA “Negative feedback”

Question 5

what are the two ways in which hormones can circulate? how is the majority of it circulating?

Answer 5

free (biologically active)

or protein bound (majority)

Question 6

what does “trophic” mean?

Answer 6

the hormone stimulates a target cell and activates secretion of ANOTHER hormone from that gland
(AKA induces second messenger secretion)

Question 7

what are the three types of hormones?

Answer 7

proteins (peptides)
steroids
amines

Question 8

protein hormones: water or lipid soluble?

Answer 8

make up the majority of hormones

-are water soluble

Question 9

steroid hormones: what are they derived from? water or lipid soluble?

Answer 9

derived from parent molecule: cholesterol

- all lipids

Question 10

what is the significance of steroid hormones all being lipids?

Answer 10

CAN cross cell membrane, but don’t dissolve in plasma well- need carriers for plasma

Question 11

amine hormones: what are they derived from? water or lipid soluble?

Answer 11

Derived from amino acid- tyrosine

tyrosine has ring that makes it resemble lipid, so these are relatively lipid soluble.

Question 12

what two groups are included in the amine hormones?

Answer 12

thyroid hormone + catecholamines

Question 13

which hormones act on intracellular receptors?

Answer 13

Steroid (& thyroid) : b/c pass through membrane easily

Question 14

which hormones act on membrane receptors?

Answer 14

Protein & amine (except thyroid): b/c can’t pass through membrane
Require second messenger system- (change what goes on inside the cell = effect)

Question 15

how does the 2nd messenger system work?

Answer 15

1. Hormone (first messenger) does not enter cell - acts on membrane receptor
2. Hormone-receptor binding triggers increase in an intracellular molecule/ion (second messenger)
3. Second messenger orchestrates cellular effects, generally rapid

Question 16

2nd messenger system: 1st + 2nd messenger- Linked by _____ in cell membrane

Answer 16

G-proteins

Question 17

what are two 2nd messenger systems that we care about? and the other two?

Answer 17

cAMP (most common for h2o soluble hormones)
Phospholipase C
(also tyrosine kinase + cGMP)

Question 18

what is the most commonly used 2nd messenger?

Answer 18

cAMP

Question 19

what are the steps of the cAMP system? (7)

Answer 19

1. Hormone binds receptor
2. Receptor activates G protein
   * 3. Activated G protein activates adenylate cyclase
   * 4. Adenylate cyclase converts ATP to cAMP
   * 5. cAMP activates protein kinase A
3. Protein kinase A phosphorylates cellular proteins
4. Phosphorylated proteins alter metabolic activity of cell

Question 20

cAMP system: Increase in cAMP level is usually short or long? _______ converts cAMP to AMP?

Answer 20

• short-lived

- Phosphodiesterase (PDE)

Question 21

what does the word “kinase” indicate?

Answer 21

phosphorylation (adding a phosphate group)

Question 22

what are the steps of the phospholipase C system? (8)

Answer 22

1. Hormone binds receptor
2. Receptor activates G protein
   * 3. Activated G protein activates phospholipase C
   * 4. Phospholipase C cleaves PIP2 into DAG & IP3
   * 5. IP3 causes Ca+2 release from endo(sarco)plasmic reticulum
   * 6. DAG & Ca+2 activate protein kinase C
3. Protein kinase C phosphorylates cellular proteins
4. Phosphorylated proteins alter metabolic activity of cell

Question 23

steroid and thyroid hormones diffuse into target cell, then bind to what 3 possible receptors?

Answer 23

steroid: Bind to nuclear + cytoplasmic
thyroid: bind nuclear + mitochondrial

Question 24

what are the actions of steroid + thyroid hormones once bound to cytoplasmic, nuclear or mitochondrial receptors?

Answer 24

cytoplasmic + nuclear: binds DNA, alters transcriptions- mRNA translated into new proteins

mitochondrial: alters mitochondrial activity = increased ATP

Question 25

what is different from the effects of steroid and thyroid hormones compared to other hormones (that use 2nd messengers) ?

Answer 25

steroid + thyroid: Effects take longer to occur BUT the effects last longer as a result

Question 26

how does the tyrosine kinase system work?

Answer 26

same as cAMP and phospholipase C system... | 2nd messenger system- phosphorylation of intracellular proteins = effect on target cell.

Question 27

what are the two types of activity that hormones receptors may have with tyrosine kinase? (examples of each?)

Answer 27

Some hormone receptors have intrinsic tyrosine kinase activity (i.e. Insulin) Some hormone receptors are associated with tyrosine kinase enzymes (i.e. Growth hormone)

Question 28

mutated tyrosine kinase often result in what?

Answer 28

cancer. | think of growth hormone that is assoc. with tyrosine kinase enzyme

Question 29

negative feedback may be ____ or ____, may involve ____ or _____ mechanisms

Answer 29

Can be direct or indirect | May involve neural or humoral mechanisms

Question 30

define "up-regulation"

Answer 30

Up-regulation: increase in receptor number, usually in response to decreased hormone levels --> Increases sensitivity to hormone

Question 31

define "down-regulation"

Answer 31

Down-regulation: decrease in receptor number, usually in response to increased hormone levels -->Decreases sensitivity to hormone

Question 32

what are the 3 mechanisms of endocrine control that the hypothalamus initiates?

Answer 32

1. Produces & transports hormones to posterior pituitary gland for secretion 2. Secretes regulatory hormones that control activity of anterior pituitary gland 3. Contains cell bodies of sympathetic neurons that stimulate adrenal medulla

Question 33

what are the two anatomic relationships of the hypothal. to the pituitary ? both course through where?

Answer 33

neural and vascular | - both course through infundibulum

Question 34

what is the neural relationships of the hypothal. to the pituitary? which lobe?

Answer 34

Neuron cell bodies in supraoptic & paraventricular "nuclei" (groups of cell bodies) -Posterior lobe

Question 35

what is the vascular relationship of the hypothal. to the pituitary? which lobe?

Answer 35

Hypothalamic-hypophysial portal system of capillaries | -Anterior lobe

Question 36

Neuron cell bodies in supraoptic nucleus primarily produce what hormone? Neuron cell bodies in paraventricular nucleus primarily produce what hormone?

Answer 36

- supraoptic (produces ADH/vasopressin) | - paraventricular (produces oxytocin)

Question 37

a collection of cell bodies in the CNS is called what? (weeds)

Answer 37

"nucleus"

Question 38

post. vs anterior pituitary: which is an actual gland?

Answer 38

post pituitary not an actual gland- just contains the nerve endings from the hypothal -neuronal relationship ant pituitary - gland - hormonal relationship (hormones travel in portal system via veins)

Question 39

ADH/oxytocin transported via ___ for secretion into where?

Answer 39

via axons, secretion into hypophyseal veins in posterior pituitary.

Question 40

Hypothalamic neurosecretory neurons produce what two kinds or hormones? where are they released into?

Answer 40

``` releasing hormones (RH) and release-inhibiting hormones (RIH) BOTH into hypothalamic-hypophysial portal capillaries ```

Question 41

RH and RIH from hypothalamic neurosecretory neurons have what function?

Answer 41

Control secretory function of anterior pituitary endocrine cells