Download Endocrine System Introduction

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Journal: What is the function of hormones?
***Hand in your journals when you are done.
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Made up of glands
that secrete
hormones into the
circulatory system
◦ Hormones are chemical
messengers that are
either proteins or lipids
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Controls rate of metabolism and tissue
maturation
Regulates ion concentrations in the blood
Water balance in the blood
Controls the production of immune cells
Controls blood glucose levels
Controls the development and functions of the
reproductive system
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Hormone is produced in small amounts by a
gland
Secreted into the interstitial fluid
Enters the circulatory system where it is
transported around the body
Acts on specific target cells by binding to
specific receptors either on the cell
membrane or inside cells
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The concentration of hormones determines the
strength of the signal and the magnitude of the
response
◦ Small concentration = weak signal = small response
◦ Large concentration = stronger signal = larger response
Neurotransmitters
Hormones
Chemical Messenger
Chemical Messenger
Released at chemical
synapse
Intended for close target
Released into bloodstream
Effect happens quickly
Effect takes time
Effect wears off quickly
Effect lasts longer
Affects single cell
Affects many cells
Travels to distant targets
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Regulated through negative feedback loops in
one of three ways
◦ Humeral Control
 Ex: Insulin secretion is controlled by blood glucose levels
◦ Neural Control
 Ex: Epinephrine is released from the adrenal gland because
of nervous system stimulation
◦ Hormonal Control
 Ex: Thyroid-stimulating hormone is released from the
pituitary gland and stimulates the release of thyroid
hormone
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When a hormone comes in contact with a target
cell, it binds to receptors at a binding site
◦ Specificity: Each hormone must have specific shape and
chemical make up to bind to each receptor
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Cells that do not have the specific receptors for a
hormone will not bind or respond to the
hormone
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The number of functional receptors affects the
amplitude of the cell’s response to a hormone
◦ More receptors produce a larger response
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Controlled through:
◦ Down-regulation : reducing the number of functional
receptors
◦ Up-regulation: increasing the number of functional
receptors
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Drugs with similar structures to specific
hormones may compete with those hormones
for their receptors
◦ Agonists: drug that binds to a hormone receptor
and activates it
◦ Antagonist: drug that binds to a hormone receptor
and inhibits it