Endocrine System

Question 1

how are the endocrine system and nervous system similar?

Answer 1

both rely on chemical messengers that bind to receptors on target cells
they share many chemical messengers (epinephrine can be neurotransmitter and a hormone)
both regulated mostly through negative feedback
both preserve homeostasis

endocrine is slower since chemical messengers are delivered through bloodstream. slower onset, but longer lasting than nervous system chemical communication

Question 2

what are the primary endocrine glands?

Answer 2

hypothalamus
pituitary
thyroid
parathyroid
pineal
thymus
adrenal glands

Question 3

describe endocrine cells

Answer 3

glandular secretory cells that release secretions int the blood.
Hormones are released into the blood in low amounts and circulate in the blood flow, acting on cells through interactions with specific receptors

Question 4

describe endocrine tissues

Answer 4

their job is to secrete hormones into extracellular fluid.
the endocrine system interacts with the nervous system: endocrine glands are often under nervous control, and some hormones are released from neurons (neurohormones)
the hypothalamus-pituitary complex is the neuroendocrine interface

Question 5

what is different about invertebrate endocrine systems?

Answer 5

they have few endocrine glands, they rely on neurohormones more than hormones

Question 6

what are the 3 hormone classes

Answer 6

amino acid derivatives
peptide hormones
lipid derivatives

Question 7

what are amino acid hormones

Answer 7

structurally related to amino acids.
commonly derived from tyrosine (thyroid hormones, nor/epinephrine) or tryptophan (melatonin).

Question 8

what are peptide hormones

Answer 8

chains of amino acids.
glycoproteins (pituitary gland= TSH, LH, FSH)
small proteins (hypothalamus= ADH, oxytocin. pituitary = GH, MSH, prolactin. pancreas= insulin, glucagon. Parathyroid hormone from parathyroid gland)

Question 9

what are lipid derivatives

Answer 9

built from fatty acids or cholesterol.
eicosanoids (ex. prostaglandins) = coordinate cellular activities and enzymatic processes like blood clotting
steroid hormones (ex. estrogens and progesterone) = bound to transport proteins so they stay in blood longer

Question 10

describe the mechanism of action for hormones

Answer 10

a hormone can remain in the blood for a short or long time (minutes to days). its effects follow similar trends.

hormones can be inactivated by
- diffusion out of bloodstream
-absorbed or broken down by liver or kidneys
- broken down by enzymes in the plasma or interstitial fluid

hormones that are not lipid soluble are unable to cross cell membrane and therefore interact with receptors on cell membrane, using 2nd messengers.

Question 11

mechanism of action for lipid soluble hormones

Answer 11

can cross cell membrane and interact with receptors inside the cell

steroid: diffuse through membrane, bind to internal receptors, then the hormone-receptor complex binds to DNA, which activates genes and influences protein synthesis. leads to alteration of cellular structure, and target cell response.

thyroid: transport across membrane, binds to receptors on mitochondria, hormone-receptor complex binds to DNA, leading to gene activation, protein synthesis and target cell response (+ ATP production)

Question 12

explain endocrine reflexes

Answer 12

controlled via negative feedback. can be triggered by changes in extracellular fluid composition, neurotransmitter at neuroglandular junctions, or arrival/removal of a hormone.

humoural stim in parathyroid: low Ca2+, stimulates PTH, which increases Ca2+ levels of
neural stim in spinal cord: preganglionic sympathetic fibres stim adrenal medulla cells, secretes epinephrine and norepinephrine (catecholamines)
hormonal stim in pituitary: hypothalamus secretes hormones that stim other endocrine glands to secrete. (ex. thyroid, gonad, adrenal)

Question 13

describe the pituitary gland

Answer 13

pituitary secretes many important hormones that regulate growth, reproduction and metabolism. secretes 9 hormones.

anterior (adenohypophysis) and posterior (neurohypophysis). both parts controlled by neurosecretory cells of closely associated hypothalamus

Question 14

how does the hypothalamus integrate the nervous and endocrine system?

Answer 14

regulatory hormones from hypothalamus are secreted to specialized hypothalamic-pituitary portal capillary system, which carries neurohormones to anterior pituitary where they stim or inhibit release of pituitary hormones at anterior lobe. axons from hypothalamus terminate in posterior pituitary, they release neurohormones directly into the blood

1. secretion of regulatory hormones to control activity of adenohypophysis (anterior)
2. production of ADH and oxytocin from posterior of pituitary on command
3. control of sympathetic output to adrenal medullas (secretes nor/epinephrine)

Question 15

explain the hypothalamic-pituitary portal capillary system

Answer 15

connects the brain (hypothalamus) to anterior pituitary
blood flows from median eminence to anterior pituitary.
hypothalamic hormones go directly to secretory cells to control anterior pituitary. hypothalamus hormones are released as neurohormones.

tropic hormones- hormones that stim the release of other hormones

there are capillary beds between hypothalamus and pituitary gland

Question 16

pituitary gland feedback loops

Answer 16

anterior
ACTH to adrenal, makes nor/epinephrine and glucocorticoids
TSH to thyroid, makes T3/T4
GH to liver, males somatomedins for bone/muscle
PRL to mammary glands
FSH to testes or ovaries, which makes testosterone and estrogen/progesterone

posterior
MSH to melanocytes
OXT to uterus, or prostate gland
ADH to kidneys

Question 17

hypothalamus and pituitary hormones

Answer 17

hypothalamus: PRH, dopamine, TRH, CRH, GHRH,GHIH, GnRH

anterior pituitary: PRL, TSH (T3+T4), ACTH (cortisol), GH (liver, IGF), FSH (androgens/estrogens), LH (germ cells)

Question 18

what hormones are secreted by thyroid gland

Answer 18

TH (thyroxine) and T4 + T3 in response to TSH from anterior pituitary

regulates metabolism among other functions

Question 19

how are thyroid hormones made?

Answer 19

made from protein thyroglobulin inside follicles

thyroid follicles, have TG, within colloid, synthesis occurs
TSH released into blood from pituitary, receptors on follicular cells are slimmed and TH released.

TG binds to receptors which creates G coupled protein response, using 2nd messengers (cAMP). it is spliced, and T3 + T4 are cut off and secreted into blood vessel. Need TSH to get the ATP to finish this process.

Question 20

hormones of thyroid and parathyroid

Answer 20

make calcitonin and PTH (parathyroid hormone). these are antagonists to control Ca2+ levels.

low Ca levels, PTH released to absorb as much as possible.

Question 21

describe the control of extracellular calcium

Answer 21

thyroid gland makes calcitonin, leads to increased excretion and absorption of Ca inn bone. blood Ca declines, this triggers parathyroid to step in, secrets PTH which releases stored Ca into blood. blood Ca increases, and so on

Question 22

summarize the regulation of blood glucose

Answer 22

precisely controlled: if blood glucose is too high, brain can’t function. but too low, it throws off osmotic balance of blood

insulin lowers blood glucose
glucagon raises blood glucose

Question 23

describe the pancreas’ role in blood glucose regulation

Answer 23

pancreas secretes glucagon and insulin in response to blood glucose levels.

glucagon is secreted by alpha cells, stim glucose release into blood in response to low blood glucose levels.
insulin secreted by beta cells, promotes glucose uptake from blood in order to lower blood glucose.

Question 24

negative feedbacks for blood glucose

Answer 24

blood glucose too high > beta cells make insulin > glucose uptake in cells increases > plasma glucose decreases

blood glucose too low > alpha cells make glucagon > tissues begin to extract and pump out more glucose > blood glucose increases

hormone antagonism= opposite effects, facilitates fine-tuned control over homeostatically regulated variables.

Question 25

vertebrate stress response

Answer 25

involves hormonal coordination

in sympathetic nervous system, adrenal secretes epinephrine, pancreas decreases insulin, increases glucagon.
hypothalamus, increase in CRH, releases hormones for ACTH, which ends up increasing blood glucose levels adrenals make cortisol.

Question 26

adrenal cortex and stress response

Answer 26

adrenal gland secretes many hormones, its made of outer cortex and internal medulla. contains interrenal cells that secrete glucocorticoid (cortisol) that triggers energy mobilization (And increase blood glucose)

contains chromaffin cells that release catecholamines when sympathetic nervous system is activated. these stim the cardiovascular system and regulate pancreatic hormones

Question 27

hormone coordinations

Answer 27

additive effects: 2 hormones add together
synergistic effects: 2 hormones work together with greater effect than if you just added them
permissive effects: first hormone needed for 2nd to work
antagonistic effect: hormones have opposite effects