endocrinology

Question 1

purpose of coordination of physiological processes

Answer 1

• in living organisms, there is coordination between different systems like - movement, respiration, circulation, digestion, excretion, and metabolism
• need communication

Question 2

two major ways that the body coordinates itself

Answer 2

endocrine system and central nervous system

Question 3

how do cells communicate without touching (long-distance communication)?

Answer 3

• cells that don’t touch can communicate thru chemical substances that are secreted by releasing cells and interact with specific receptors on different target cells
• signaling thru receptors leads to specific physiological changes

Question 4

what are main two things needed in endocrine signaling?

Answer 4

hormone + receptor

Question 5

endocrine signaling involves

Answer 5

• a hormone secreted into the blood by the endocrine gland
• hormone is transported by blood to a distant target site

Question 6

what is endocrine signalling pathway? anterior pituitary gland –>

Answer 6

anterior pituitary gland –> blood vessels (LH + FSH) –> gonads (target site) –> to cells of ovary and testis or steroid hormone (estrogens-female + androgens-male)

Question 7

neuroendocrine signalling

Answer 7

starts with a stimulus –> hypothalamus, hormone A is secreted –> hypothalamo-pituitary portal vessels causes an increases in plasma hormone A –> anterior pituitary, hormone B is secreted –> increase in plasma b hormone –> third endocrine gland, hormone C is secreted so increase in plasma hormone C –> target cells of hormone C respond to hormone C
- chain reaction

Question 8

what is calcium good for? is it a hormone?

Answer 8

calcium is good for your bones but it also is a hormone because there is a receptor that recognizes ionic calcium in the blood

Question 9

paracrine signalling

Answer 9

very local - one cell releases a signaling susbtsance and a distant target cell has a receptor for this substance

Question 10

autocrine signalling

Answer 10

cell that talks to itself - it releases a substance such as a growth hormone and it has the receptor to also recognize this substance

Question 11

communication by hormones (or neurohormones) - what are the 6 steps?

Answer 11

1) SYNTHESIS of the hormone by endocrine cells (or neurons in neurohormone)
2) RELEASE of hormone by endocrine cells (or neurohormones by neurons)
3) TRANSPORT of hormone or neurohormone to target site by blood stream
4) DETECTION of hormone/neurohormone by specific receptor protein on/in target cells
5) CHANGE IN CELLULAR METABOLISM triggered by hormone-receptor interactions
6) REMOVAL OF HORMONE which often terminated cellular response
** each stage = potential source of regulation

Question 12

communication by hormones (or neurohormones) - what are the 6 steps?

Answer 12

1) SYNTHESIS of the hormone by endocrine cells (or neurons in neurohormone)
2) RELEASE of hormone by endocrine cells (or neurohormones by neurons)
3) TRANSPORT of hormone or neurohormone to target site by blood stream
4) DETECTION of hormone/neurohormone by specific receptor protein on/in target cells
5) CHANGE IN CELLULAR METABOLISM triggered by hormone-receptor interactions
6) REMOVAL OF HORMONE which often terminated cellular response
** each stage = potential source of regulation

Question 13

“classical” endocrine organs

Answer 13

hypothalamus, anterior + posterior pituitary, thyroid + parathyroid glands (4), heart + atrial natriuretic peptides (ANP), adrenal glands, cortex and medulla, pancreas (islets of Langerhans), ovaries (female) + testis (male)

Question 14

hypothalamic-pituitary signalling

Answer 14

• via blood vessels of the pituitary stalk
• hypothalamic-hypophyseal portal system: from hypothalamus to adenohypophysis (anterior pituitary)
• hypothalamic neurohormones either activate to inhibit activity of 1/6 hormone-producing cells to anterior pituitary
  either releasing hormones (releasing factors) or inhibiting hormones (inhibiting factors)

Question 15

what does hypothalamus produce? what do they depend on?

Answer 15

produces releasing + inhibiting hormones
- depends on effects of pituitary
- releasing = hypothalamus to pituitary –> stimulates release of corresponding pituitary hormone
- inhibiting = opp effects

Question 16

classes of hormones based on structures

Answer 16

• peptides and proteins –> glycoproteins and peptides (all encoded by genes)
• steroids + amines (small molecules)
• ionic calcium (Ca signalling in cells = crucial, no genes are need to make ionic Ca)

Question 17

synthesis of protein hormones

Answer 17

• to be secreted, you need to go thru the secretory pathway
• produce a primary translated version of protein that contains internal extension = PREPROSEQUENCE –> this directs new polypep to secretory
• in journey, it is cleaved off so hormone is released into circulation
• therefore mature form lacks a pre-pro sequence (acts as barcode to direct)

Question 18

structures of steroid hormones - what are the 4?

Answer 18

cortisol - major glucocorticol
aldosterone - controls blood pressure
testosterone - precursor of estradiol
estradiol - estrogen
** steroid can get into cell because they are able to pass the membrane

Question 19

structural difference of testosterone and estradiol

Answer 19

ring in testost. cant aromatize because this would put 10 electrons around one carbon
- therefore you get enzyme aromatase that burns ff methyl group and converts into alcohol
- testos can spontaneously become estradiol

Question 20

properties of hormone receptors

Answer 20

1) SPECIFIC: recognition of single hormone or hormone family
2) AFFINITY: binding hormone at its physiological concentration
(receptor interactions depend on range of conc of hormone, ex. low conc = low interactions, vise versa)
3) SHOULD SHOW SATURABILITY: ex. a finite number of receptors are available
4) MEASURABLE BIOLOGICAL EFFECT: measure response due to interaction of hormone with its receptor, otherwise there is no point of hormone receptor binding

Question 21

receptor regulation

Answer 21

1) receptors can be upregulated by increasing their active in response to hormone or their synthesis
2) receptors can be downregulated either by decreasing their activity or their synthesis

Question 22

3 mechanisms by which a hormone can exert effects on target cells:
1) direct effects on function at cell membrane

Answer 22

• least common
  -insulin = polypeptide, does not enter cells, so has receptors on cell surface
  -receptor is stuck where is is
• has to be able to send signals

Question 23

3 mechanisms by which a hormone can exert effects on target cells:
2) intracellular effects mediated by second messenger systems

Answer 23

-cyclic AMP binds to kinase
- wakes it up - foes and phosphorylates other proteins
- turns them on or off

Question 24

3 mechanisms by which a hormone can exert effects on target cells:
3) intracellular effects mediated by genomic or nuclear action

Answer 24

-receptors recognized by steroid hormones
- signaling by nuclear receptors which include receptors for steroid hormones

• functions in nucleus thru receptors to regulated gene transcription
• = change in protein content leads to change in function of cell
• depending on receptor, either absence of hormone, its either in cytoplasm or already in nucleus
  -T3 + T4 bind to a nuclear receptor –> thyroid hormone receptor (TR) - its already in nucleus in the absence of thyroid hormone
• its switched on by binding thyroid hormone