(2) Central Endocrine Glands

endocrine system is…

slow, indirect, longer acting (longer half-life) + has to release chemical messengers/hormones INTO the blood stream

hydrophillic hormones

aka lipophobic, includes peptide, catecholamines, indoleamines

lipophillic hormones

aka hydrophobic, includes steroids, thyroid hormones (amino acids)

tropic hormones

regulate hormone secretion by another endocrine gland

non-tropic hormones

act directly on target cells and tissues to produce physiological effects

exocrine glands

secrete products into ducts which empty into body cavities or body surface

sweat, oil, mucous, & digestive glands

endocrine glands

secrete products (hormones) into intersitial space diffuse to bloodstream

primary endocrine glands

pituitary, thyroid, parathyroid, adrenal, pineal

secondary endocrine glands

hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small intestine, skin, heart, & placenta

endocrine hormones

hormones that have a biological effect far away

paracrine hormones

hormones that have a biological effect nearby

autocrine

hormones that act on the secreting cell (itself)

circulating hormones

endocrine

local hromones

paracrine, autocrine

endocrine glands - hormone delivery

Ductless glands

Secrete to extracellular space

• Diffuse to capillary endothelium

• Transported by interstitial fluid and bloodstream

nerve cells - hormone delivery

extend to target cells, release hormone specifically + locally

nerve cells - paracrine

at the level of synapse → neurotransmitters

nerve cells - endocrine

signals diffuse directly into interstitial space → neurohormones

proteins

thyroid stimulating hormone, insulin, parathyroid hormone

most abundant

proteins - size

> 100 aa

peptides - size

< 100 aa

proteins - location

pituatitary gland (anterior: FSH, LH, ACTH, GH, TSH, Prolactin | posterior: ADH, Oxytocin)

pancreas (insulin, glucagon)

amino acid derived

thyroid hormone, epinephrine/adrenaline

amino acid derived - location

adrenal medulla (catecholamines, noradrenaline, dopamine)

thyroid gland (thyroid hormones T3/T4)

steroid

made of cholesterol, but NOT solely cholesterol based

cortisol, aldosterone, testosterone

steroid - location

adrenal cortex

gonads (oestrogen, progesterone, testosterone)

lipid soluble hormones

steroids, thyroid hormones, nitric acid

need to be bound to plasma proteins -> most produced in the liver

the active form is…

the free form

water-soluble hormones

amines, peptdes, proteins, glycoproteins, eicosanoids

mostly negative so likes water

free travel thru bloodstream, longer half life

permissiveness

when one hormone must be present for the full effect of another hormone to be expressed

syngergism

the combined effect of two or more hormones is greater than the sum of their individual effects (often summarized as 1 + 1 = 3)

antagonism

the effects of one hormone oppose or counteract the effects of another hormone

at skeletal muscle, insulin stimulates…

glucose uptake

at liver cells, insuling stimulates

glycogen synthesis

at adipocytes, insuling stimulates…

triglyceride synthesis

steroids go into what part of the cell

cytoplasmic

thyroid hormones go into what part of the cell

membrane transporters → nuclear receptors

5 ways which target cells can become desensitized

1. receptor sequestration

2. receptor down-regulation

3. receptor inactivation

4. inactivation of signaling protein

5. production of inhibitory protein