Homeostasis
- receptor
- control center (brain)
- effectors (correct)
stable maintained by feedback loop
negative feedback
causes corrective mechanisms to stop.
temperature regulation/sweating
positive feedback
causes corrective mechanisms to continue
child birth/oxytocin during labor
major cut
what are amplitude modulated signals;
endocrine
what are frequency-modulated signals;
nervous system
intercellular chemical signals;
cell to communicate other cells
- neurotransmitters
- neuromodulators
- hormones
neurohormones =
norepinephrine, ADH, oxytocin
hormones =
a substance/chemical messengers secreted by an endocrine tissue “into the blood” circulation that act on a target tissue to produce a specific response.
autocrine =
local, same cell type
prostaglandin (lipid compounds from fatty acids
paracrine =
para=around, two close to each other
paracrine=cell affect other cell type locally without transported in blood
- somatostatin (=GHIH)
tropic =
tropic hormones regulate activity of various other endocrine glands
- pheromone
chemical structure
membrane bound receptor:
- amino acid derivative (small)=epinephrine, norepinephrine, TH, melatonin
- peptide (group of amino acid/larger)=TRH, ADH, oxytocin, glucagon, calcitonin
- protein (very big)=GH, prolactin, insulin
chemical structure
inside cell;
- steroid=estrogen, progesterone, testosterone, cortisol, aldosterone
- eicosanoids (lipids derived from cell membranes) =prostaglandin, thromboxane
hormone secretion rate
most hormone are not at constant rate
- pulsatile secretion
- circadian (daily cycle) rhythm of secretion
patterns of hormone regulation:
- humoral (liquid)
plasma glucose changes insulin release
plasma Ca changes PTH release - neural (faster)
epinephrine/norepinephrine from adrenal medulla - hormonal (stimuli of one endocrine gland secreted by another)=anterior pituitary is regulated by Releasing (RH) and Inhibiting (IH) from the hypothalamus
long half-life
fat/cholesterol soluble molecule
short half-life
water soluble
outside cell work through G-protein
rapid onset and short duration
Hormones are eliminated by:
- liver = enzymatic degradation(can’t hold anymore)
- kidney =filter everything & hormone, return necessary
Down-regulation
ignore message
- decreased number of receptors by fatigue or after long stimulation
Up-regulation
respond quickly
- stimulus increases the rate of receptor synthesis
- number of receptors increases
Hormone receptors
Membrane-bound receptors bind to:
water soluble (protein) or large-molecular-weight hormones
Hormone receptors
intracellular receptors bind to:
lipid-soluble (hydrophobic) hormones, receptor is inside cell, do not go to G-protein
Hormone receptors
activate G-proteins that activate Second-messenger system:
water soluble (outside) hormones
- glucagon bind to glucagon receptor
- epinephrine
Steroid hormone & TH direct gene activation:
direct (steroid-inside) synthesis/make of proteins
- aldosterone
