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
Hormones
Nervous System Endocrine System
rapid response neurotransimitters short distances regulate neurons,
muscle, glands, endocrine cells (area of overlap)
slower response hormones short or long distances regulate functions of
most organ systems
signaling processes in animals: classified by 2 criteria:1. type of secreting cell2. route signal takes to reach target
Intercellular Communication
hormones ECF bloodstream target cells
functions:1. maintain homeostasis2. mediate responses to environmental
stimuli3. regulates growth & development
Endocrine Signaling
molecules that act over short distances reach target solely by diffusion
◦ ex: cytokines released by T helper cells 2 types:1. paracrine2. autocrine
Local Regulators
http://sites.sinauer.com/cooper5e/animation1501.html
animation
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 territory3. attract mates: female giant silk moth
releases pheromone that can attracgt a male up to 4.5 km away
Pheromones, an Exception
Cellular Response Pathways
Water-Soluble Lipid-Soluble
secreted by exocytosis
travel thru blood bind to cell-surface
signal receptors induces changes in cytoplasmic molecules might alter gene transcription (signal transduction)
diffuse out of endocrine cell bind to transport molecules in blood diffuse into target cells bind to intracellular receptors trigger gene transcription
effects hormone has can vary if target cells differ in molecules that receive or produce the response to the hormone
Multiple Effects of Hormones
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
Signaling by Local Regulators
Feedback Loop Regulations
Negative Feedback Positive Feedback
stimulus initiates a response that will reduce the effect of the stimulus
stimulus initiates a response that reinforces the stimulus
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
Target Tissues of Insulin
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 hydrolysis2. convert a.a. & glycerol glucose
Target Tissues of Glucagon
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
Diabetes Mellitus
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
Type II Diabetes: Insulin Resistance
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
Coordination of Endocrine & Nervous Systems in Vertebrates
1. ADH: antidiuretic hormone (vasopressin)
◦ 1 of several hormones that act on kidneys◦ increases water retention in kidneys
(decreases urine vol/ increases blood plasma vol : maintains blood osmolarity wnl
2. Oxytocin◦ increases strength on uterine contractions
in labor◦ regulates milk secretion by mammary
glands
Posterior Pituitary Hormones
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
Evolution of Thyroid Function
Animal Function Mammals develops mammary ` glands & milk synthesis Birds regulates fat
metabolism Amphibians delays metamorphosis Fish regulates salt & water ` balance
Prolactin Functions