Structure, Function, and Mechanisms

Question 1

endocrine function

Answer 1

circulate in body fluids and produce a specific effect on the activity of the cells, away from its point of origin

Question 2

neurocrine function

Answer 2

transmit molecular signal from neuron to its axon and then into blood stream to distant target cells

Question 3

paracrine function

Answer 3

secreted by endrocrine cells can also reach and act on target cells within the same locale simply by diffusing through the intersitial fluid separating the adjacent cells

Question 4

autocrine function

Answer 4

act back on the cells of their origin to modulate their own secretion or other intracellular processes

Question 5

preprohormone

Answer 5

peptide hormone right after translation before modification to final form

Question 6

prohormone

Answer 6

after the signal peptide is removed from the preprohormone within the ER

then transferred to the golgi for final processing and packaged into secretory granules

Question 7

peptide hormones characteristics

Answer 7

soluble in blood and thus circulates without being bound to anything

not soluble in the lipid environment therefore cannot enter the cells by simple diffusion

Question 8

catecholamine hormones

Answer 8

epinephrine, NE, DA

made from tyrosine

stored in the secretory granules and secreted in a manner similar to that of peptide hormones

Question 9

thyroid hormones

Answer 9

T3 and T4

made from tyrosine and iodide that occur with the amino acid already present in a large protein molecule

secretione of TH requires retrieval and enzymatic release form its protein storage form

Question 10

steroid hormone

Answer 10

cortisol, aldosterone, androgen, estrogen, and progestins, vit D

made from cholesterol by a series of reactions

not stored to any appreciable amount within the gland of origin

activation of biosynthetic sequence from cholesterol increases secretion of these hormones

Question 11

steps that lead to peptide hormone secretion

Answer 11

1. require increase of Ca2+ and cAMP
2. stimulates phosphorylation via cAMP and Ca+ dependent kinases
   - phosphorylate tubulin and promote microtubule and microfilament formation, which promote granule movement to the plasma membrane
3. Ca2+ also activates myosin light chain kinase leading to phosphorylation of myosin which is located on the surface of secretory granules

Question 12

initial determinant of the rate of hormone action

Answer 12

reaction between the hormone and receptor

Question 13

receptor kinetics

Answer 13

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Question 14

Scatchard Plot

Answer 14

represents ratio of bound hormone to free hormone

should be a straight line with a negative slope

slope = - Kd

intercept = Ro (receptor capacity)

**only small occupancy of receptors with hormone can yield max response

straight line = no cooperativity

exponential = negative cooperativity

Question 15

spare receptors

Answer 15

amount of unbound receptors when maximum response is achieved

with peptide hormones, relatively high due to greater signal amplification (secondary messengers)

Question 16

secondary messenger examples

Answer 16

cAMP
cGMP
Ca2+
IP3
DG

Question 17

hormone dose response curve

Answer 17

sigmoidal like an enzyme curve

shift down = decrease maximum responsiveness

shift right = decrease sensitivity

Question 18

how can amount of hormone secreted be determined from plasma and urine samples

Answer 18

radioimmuno assay (RIA)

ELISA

Question 19

problem with RIA

Answer 19

measures antigenic amounts of hormone, which may not be biologically active amount of hormone

and thus may not always be important for receptor binding

Question 20

ELISA

Answer 20

just as sensitive as RIA without the problem of radioactive waste

Question 21

binding of hormones by plasma proteins greatly influences the (?) of hormonal turnover

Answer 21

rates of

Question 22

metabolic clearance rate

Answer 22

expresses the sum of hormonal removal

equals the mass of hormone removed per unit of time divided by its plasma concentration

Question 23

Atrial and brain natriuretic peptide (ANP and BNP)

Answer 23

released by heart in response to an elevation of atrial pressure or blood pressure

(+) increase excretion of salt and water by the kidneys

(+) relaxation of vascular SmM and thus lower bp

(+) guanylyl cyclase/natriuretic peptide receptor –> (+) cGMP –> cGMP dependent kinases

Question 24

nitric oxide

Answer 24

paracrine mediator

made by NO synthase (Ca2+-calmodulin dependent enzyme that accelerates conversion of Arg –> citrulline and NO)

NO causes vasodilation in immediate viscinity

(+) cGMP