Campbell and Reece
Chapter 45



body‘s long-distance regulators
molecules secreted into ECF  circulate
thru body  communicate regulatory
messages thru out body
in animals that undergo metamorphosis
hormones stimulate growth of adult cells
& apoptosis of larval cells

with nervous system in charge of
communication & regulation thru out
body




rapid response
neurotransimitters
short distances
regulate neurons,
muscle, glands,
endocrine cells (area of
overlap)
Nervous System




slower response
hormones
short or long distances
regulate functions of
most organ systems
Endocrine System
signaling processes in animals:
 classified by 2 criteria:
1. type of secreting cell
2. route signal takes to reach target

hormones  ECF  bloodstream  target
cells
 functions:
1. maintain homeostasis
2. mediate responses to environmental
stimuli
3. regulates growth & development



molecules that act over short distances
reach target solely by diffusion
◦ ex: cytokines released by T helper cells
2 types:
1. paracrine
2. autocrine


http://sites.sinauer.com/cooper5e/anima
tion1501.html


not all secreted molecules act w/in body
method of communication between
members of some animal species
◦ ex:
1. foraging ant locates new food source  marks
its path back to nest with pheromones
2. define boundaries of territory
3. attract mates: female giant silk moth releases
pheromone that can attracgt a male up to 4.5
km away


ductless organs
secrete hormones directly into
surrounding fluid
1.
2.
3.
Polypeptide
Steroid
Amines



secreted by
exocytosis
travel thru blood
bind to cell-surface
signal receptors 
induces changes in
cytoplasmic
molecules  might
alter gene
transcription (signal
transduction)
Water-Soluble

diffuse out of
endocrine cell  bind
to transport
molecules in blood 
diffuse into target
cells  bind to
intracellular
receptors  trigger
gene transcription
Lipid-Soluble

effects hormone has can vary if target
cells differ in molecules that receive or
produce the response to the hormone


pathways by which local regulators trigger
responses same as those activated by
hormones
growth factors
◦ stimulate cell proliferation & differentiation

NO (nitric oxide)
◦ synthesized & released by endothelial cell when
O2 levels low  activates enzyme in smooth
muscle  vasodilation  increased blood flow

prostaglendins:
◦ aggregation of platelets  blood clotting
◦ promote fever & inflammation in immune
system
◦ smooth muscle contraction

occurs in all but simplest invertebrates

stimulus initiates a
response that will
reduce the effect of the
stimulus
Negative Feedback

stimulus initiates a
response that
reinforces the stimulus
Positive Feedback

Insulin lowers blood glucose levels by:
◦ stimulating nearly all cells *outside the brain
to take up glucose
◦ slowing glycogen breakdown in liver
◦ inhibiting glycerol (from fats) & a.a.  glucose
aka gluconeogenesis

*brain cells do not require insulin to take
up glucose


Glucagon influences blood glucose levels
mainly thru it effects on target cells in
liver
when serum glucose levels < normal (70 –
110 mg/100 mL) glucagon signals liver
cells to release glucose  blood by:
1. increase glycogen hydrolysis
2. convert a.a. & glycerol  glucose



deficiency of insulin in target tissues
hi blood glucose levels but cannot get into
cells so cells use fat as main substrate for
cellular respiration
acidic metabolites form during fat
breakdown  ketoacidosis
◦ low pH can be life threatening
◦ Na+ & K+ ions depleted



characterized by failure of target cells to
take up insulin from blood  elevated
blood glucose
7th most common cause of death in USA
contributing factors:
◦ genetics (defect in insulin receptor or insulin
response pathway)
◦ obesity
◦ age (though more children being diagnosed)
◦ sedentary lifestyle

Hypothalamus
◦ plays central role in integrating endocrine &
nervous systems
◦ receives info  initiates endocrine signaling
appropriate to environmental conditions
◦ sends releasing hormones to anterior pituitary
gland  sends tropic hormones to target glands
◦ sends hormones it makes to posterior pituitary
ADH: antidiuretic hormone (vasopressin)
1.
◦
◦
1 of several hormones that act on kidneys
increases water retention in kidneys (decreases
urine vol/ increases blood plasma vol :
maintains blood osmolarity wnl
Oxytocin
2.
◦
◦
increases strength on uterine contractions in
labor
regulates milk secretion by mammary glands



over time functions of a hormone have
diverged from species to species
ex: thyroxine (thyroid hormone) regulates
metabolism in most animal but in frogs it
function to resorb tadpole tail
Prolactin: in mammals develops mammary
glands & milk production but in birds:
regulates fat metabolism & reproduction;
in amphibians: delays metamorphosis; in
fish







Animal
Mammals
`
Birds
Amphibians
Fish
`

Function
develops mammary
glands & milk synthesis
regulates fat metabolism
delays metamorphosis
regulates salt & water
balance