Kaplan Ch 5: Endocrine

Question 1

peptide hormones

Answer 1

• hydrophilic (can not pass through the plasma membrane and must bind to surface receptors)
• first messenger
• all peptide hormones are derived from larger precursor polypeptides that are cleaved during post-translational modification, sent to golgi for more modification, and released by exocytosis
• rapid, short lived effects
• are water soluble allowing them to travel freely in the bloodstream without a carrier

Question 2

Mechanism of activation of a G-protein coupled receptor

Answer 2

1. An extracellular signal binds to the GPCR 2. The receptor undergoes a conformational change, allowing it to bind to a G-protein 3. Receptor acts like a GEF, inducing the α subunit to release GDP. GTP will quickly take its place 4. Conformational change in α subunit causing it to dissociate from the receptor and the ß/γ complex

Question 3

How is cAMP made?

Answer 3

1. Signal activates GPCR 2. GPCR activates stimulatory G-proteins which activate adenylate (adenylyl) cyclase 3. Activated adenylyl cyclase converts ATP to cAMP

Question 4

How is cAMP destroyed?

Answer 4

cAMP phosphodiesterase

Question 5

Main use of cAMP?

Answer 5

cAMP is a second messanger used mainly on protein kinase A. PKA is used to modify enzymes and transcription factors by phosphorylation allowing it to act quickly or slowly on the cell.

Question 6

Steroid Hormones

Answer 6

• derived from cholesterol
• nonpolar (hydrophobic) and can thus easilly cross the cell membrane (intracellular or intranuclear receptors)
• binding of a steroid hormone to its receptor causes complex conformational changes and allows this complex to bind directly to DNA, increasing or decreasing transcription
• slower, long lived effects
• not water soluble and thus require carrier proteins to travel in bloodstream

Question 7

are hormones active when bound to carrier proteins?

How do concentrations of carriers affect hormone function?

Answer 7

no, they must dissociate in order to become active

increased levels of protein carriers cause less free hormone to be available and the body perceives lower levels of the hormone

Question 8

Amino Acid derived hormones (examples)

Answer 8

epi

norepi

triiodothyronine

thyroxine

Question 9

catecholamines

Answer 9

epi and norepi

bind to GPCR

Question 10

general endings of peptide and amin acid derived hormones

Answer 10

-in or -ine

Question 11

general endings of steroid hormones

Answer 11

-one, -ol, -oid

Question 12

direct hormones

Answer 12

act directly upon the body to cause physiological changes

Question 13

tropic hormones

Answer 13

hormones that stimulate the production of other hormones by other endocrine glands that will act on taget tissues

Question 14

hypophyseal portal system

Answer 14

conect the hypothalamus to the anterior pituitary. Allows for direct communication via tropic hormones and prevents noticable concentrations of these hormones from being present in the systemic circuit

Question 15

GnRH from the hypothalamus causes what hormone to be released from the anterior pituitary?

Answer 15

FSH and LH

Question 16

GHRH from the hypothalamus causes what hormone to be released from the anterior pituitary?

Answer 16

GH

Question 17

thyroid releasing hormone (TRH) from the hypothalamus causes what hormone to be released from the anterior pituitary?

Answer 17

thyroid stimulating hormone (TSH)

Question 18

Corticotropin releasing factor (CRF) from the hypothalamus causes what hormone to be released from the anterior pituitary?

Answer 18

adrenocorticotropic hormone (ACTH)

Question 19

Dopamine from the hypothalamus causes what hormone to be released from the anterior pituitary?

Answer 19

dopamine or prolactin inhibiting factor causes a DECREASE in prolactin secretion

Question 20

what hormones are released from the posterior pituitary and how is their release controlled?

Answer 20

Oxytocin and ADH or vasopressin are released from the posterior pituitary when neurons in the hypothalamus that extend into the posterior pituitary fire

Question 21

oxytocin

Answer 21

stimulates uterine contractions during labor (+ feedback loop), milk letdown during lactation, bonding behavior

Question 22

Antidiuretic Hormone (ADH or Vasopressin)

Answer 22

increases reabsorption of water in the collecting ducts of the kidneys in response to increased plasma osmolarity

Question 23

Products of the anterior pituitary

Answer 23

FLAT PEG (FLAT are tropic, PEG are direct)

FSH

LH

ACTH

TSH

Prolactin

Endorphins

GH

Question 24

Effect of FSH and LH on the body

Answer 24

stim by GnRH from the hypothalamus

act on the testes and the ovaries to release testosterone and estrogen/progesterone respectively

negative feedback to FSH/LH and GnRH

Question 25

Effect of ACTH

Answer 25

stimulated by CRF from the hypothalamus

acts on the adrenal cortex

stim. cortisol secretion

Negative feedback on CRH

Question 26

Effect of Thyroid stimulating hormone (TSH)

Answer 26

stimulated by TRH from the hypothalamus

acts of the thyroid to release thyroxine (T4)

thyroxine (T4) has only a slight effect on metabolism

T4 is converted to triiodothyronine (T3), which is the active hormone that stimulates metabolism

T3 exhibits negative feedback on TRH and TSH

Question 27

hormones that cause the development of milk ducts

Answer 27

high estrogen and progesterone levels, as seen in pregnancy

Question 28

where does bone growth originate?

Answer 28

the epiphysial plates

Question 29

function of the thyroid

Answer 29

setting basal metabolic rate (T3/T4)

calcium homeostasis (calcitonin)

Question 30

how are triiodothyronine (t3) and thyroxine (t4) produced?

Answer 30

the iodination of tyrosine (amino acid) in the follicular cells of the thyroid. The numbers 3 and 4 refer to the number of iodine atons attached to the tyrosine

Question 31

Increased T3 and T4 will lead to what?

Answer 31

• increased cellular respiration
• increased protein and fatty acid turnover
• increased metabolism
• negative feedback to TRH and TSH

Question 32

Three ways calcitonin works do decrease blood Ca

Answer 32

1. increase Ca excretion in the kidneys
2. decreased Ca absorption in the gut
3. increased storage of Ca in the bone

Question 33

PTH is antagonistic to what hormone?

Answer 33

calcitonin

Question 34

what are the corticoids and where are they secreted from?

Answer 34

corticoids are secreted from the adrenal cortex and they are steroid hormones that can be divided into three functional classes: glucocorticoids, mineralocorticoids, and cortical sex hormones

Question 35

glucocorticoids (two most common, their function, and the pathway for their secretion)

Answer 35

cortisol and cortisone

raise blood glucose by increasing gluconeogenesis and decreasing protein synthesis, decrease inflammation and immunologic responses

hypothalamus –> CRF –> anterior pituitary –> ACTH –> Adrenal cortex –> glucocorticoids

Question 36

Mineralocorticoids (most common, their function, and the pathway for their secretion)

Answer 36

• aldosterone
• salt and water homeostasis: increases Na reabsorption in the distal convoluted tubule and collecting duct of the nephron. Water will follow Na allowing for increase in BP and BV withouth ∆ in the osmolality (like with ADH). Also stimulates K and H ion excretion
• synthesized through the renin-angiotensin system (deceased BP = juxtaglomerular cells secrete renin in kidneys and ace is secreted in lungs)