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Ch16 Endocrine – part 1
control systems
endocrine
nervous system
hormones as chemicals
steroids
made from cholesterol
estrogen, progesterone, testosterone
cortisol , aldosterone
amines
made from tyrosine
epinephrine, norepinephrine
thyroid hormone
polypeptides
longer chains than amines
insulin, growth hormone
glycoproteins
FSH , LH , TSH
cheap !
mechanisms of hormone action
affect nucleus - gene activation
acts as transcription factor
steroid family
non-steroid family
thyroid hormone Vitamin D
second-messenger systems
requires transduction
turns on/off specific enzymes
amines
steroid hormone mechanism
hormone enters cell
binds to and activates receptor – chaperonin
hormone-receptor moves to nucleus
binds to nuclear receptor (on DNA)
turns on/off specific gene - acts as transcription factor
protein synthesis of:
enzymes
structural protein
secretory protein
non-steroid family
Thyroxine:
T4 transported by TBG (thyroxine binding globulin)
T4 changed to T3 in cytoplasm
T3 binds to receptor on DNA
activation of genes
also:
Vitamin D
Vitamin A
problem?
1st messenger
2nd messenger
transduction
( 9-cis retinoic acid )
2 messenger systems - general
hormone can’t get through cell membrane
hormone
chemical in cytoplasm
1st messenger activates 2nd messenger
2nd messenger activates enzymes in cytoplasm
enzymes produce cell’s response
note: hormone effect based on enzymes present in cell
cAMP as 2nd messenger
hormone binds to receptor
receptor activates G-protein
=
G protein activates Adenylate cyclase
adenylate cyclase converts ATP  cAMP
cAMP activates protein kinase
protein kinase turns on/off enzymes in cell
transducer
inactivation
cAMP inactivated by phosphodiesterase
drugs that inhibit phosphodiesterase :
theophylline
bronchodilation
caffeine
viagra
other 2nd messengers
st
1 messenger
hormone
membrane enzyme
Phospholipase C
2nd messenger
IP3
(inositol triphosphate)
Calcium - w/ calmodulin
DAG (diacylglycerol)
effects of Ca as 2nd messenger
activates protein kinase
exocytosis / secretions
muscle contraction
steroid vs 2 messenger
speed
long term
2 messenger is faster
enzymes already present
steroid hormones effects last longer
amplification
2 messenger 1 hormone stim 1000’s of enzymes
steroid
1 hormone stim 1 gene transcription
multiple outcomes of 2 messenger system
can affect several diff enzymes in cell
>1 cell function may be turned on by one hormone
hormone affects on target cell
change plasma membrane permeability
activate / deactivate genes
activate / deactivate enzymes
control protein synthesis
stimulate secretion
mitosis
level of response depends on blood levels of hormone
long term effects of hormone
up-regulation
down-regulation
hormone increases effect
 # receptors
hormone decreases effect
 # receptors
stimulus of hormones
humoral changes
chemical levels in blood
Glucose , Ca++ , NaCl , O2
hormonal changes
other hormones
produced by other endocrine glands
neural changes
neurotransmitters
neuron stimulates endocrine gland
eg. adrenal medulla ; pancreas ; hypothalamus
another look at genetics
A cell’s gene is controlling the functions in a distant cell
cytoplasm of a distant cell
distant cell’s genes and protein synthesis
its cell membrane