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Chemical Signals in Animals Chapter 45 The Endocrine System Hormone is a chemical signal that is secreted into body fluids (blood) and communicates regulatory messages within the body Target cells respond to hormones Two systems of internal communication and regulation: nervous system and endocrine system Nervous: high speed signals along neurons
movement in response to env changes Endocrine: all of an animals hormone secreting cells
endocrine glands: hormone secreting organs (ductless glands directly into body fluids) Endo and nerv are structurally, chemically, and functionally related -endo organs contain nerve cells called NEUROSECRETORY CELLS
secrete hormones
many chemicals = signals in nervous system, hormones in endocrine sys
-each system affects the output of the other .. release of milk: suckling = sensory cells -> nervous signals -> hypothalamus -> oxytocin from pituitary -> secrete milk Invertebrates: hormones = reproduction and development
nerve and hormne interaction
-Arthropods: crustaceans: growth and repro, water balance, movement of pigments, reg of meta
aquire adult characteristics in single, terminal molt .. molting is triggered by ECDYSONE
also favors development of adult characteristics (cater -> butter)
ecdysone production is controlled by 2nd hormone: brain hormone (bh)
stimulates prothoracic glands to secrete ecdysone -balanced by juvenile hormone (JH) . secreted by corpora allata
propotes retention of larval characteristics
high JH = molting but just larger larva
low JH = pupa -> metamorphosis
local regulators act between cells on a localized scale
upon release: taken up by target cells, broken up by enzymes, or hend by extracellular matrix thus, can only affect local targets .. Pheromones carry messages between different individuals of a species
ie mate attraction
local regulators: neurotransmitters: one neuron to another, or one neuron to muscle, gland
Nitric oxide (NO) multiple functions
highly reactive/toxic
affects targets in few seconds and breaks down
secreted by neurons
. Funct as a neurotransmitter .. secreted by white blood cells kills cancer cells and bacteria in bf
sec by endothelial cells in blood vessels makes smooth muscle relax, dilating vessel walls -Growth Factors peptides and proteins that fuction as local reg
each can affect several types of cells and have variety of functions
Nerve growth factor NGF speeds rate of developing white blood cells -epidermal GF accelerates epid development
Insulinlike GF skeletal development (produced by liver)
transforming GF enhance the strength of synapses between neurons in brain of mature animal -Prostaglandins PGs*** - modified fatty acids derived from lipids of pm
in semen: promote contractions of uterus
-released by cells into interstital fluid func as local regulators
sec by placenta = changes in chem. Of uterus = induce labor (positive feedback)
-defense mech: induce fever and inflammation
intensify pain
^Aspirin: inhibits enzymes to synthesize prostagladins -PGE and PGF similar structures but different effects on smooth muscle cells of blood vessels serving lungs
PGE = relax (dilate blood vells, promote oxygenation)
PGF = contract (reduce blood flow)
thus: antagonistic
chem.
Approximate Word count = 1899
Approximate Pages = 7.6
(250 words per page double spaced)
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