APHY 201 Module 15 Endocrine System
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endocrinology - ANS-Study of hormones and endocrine organs
functions of the endocrine system - ANS-1. control reproduction, development and
growth
2. prepare the body to combat stress
3. maintain electrolyte and water balance and blood pressure
4. maintain nutrient balance (glucose)
5. regulate cell metabolism
6. increase or decrease cellular activity by changing: plasma membrane permeability,
synthesis of proteins, enzyme functions, cellular secretions, rate of cell reproduction.
characteristics of the endocrine system - ANS-includes cells, tissues, and organs that
secrete hormones. These organs and tissues are scattered in different regions of the
body. Endocrine glands have no ducts so hormones are transported through blood and
lymphatic vessels.
hormones - ANS-chemical messengers produced by endocrine tissues and released
into the blood to alter the function of target cells
paracrines - ANS-chemical messenger for intercellular signalling produced by a
secretory cell and released into interstitial fluid to engage receptors on adjacent cells.
target cells - ANS-tissues with receptors for specific hormone
How are hormones specific? - ANS-act on specific target cells/target organs because
each hormone binds to protein receptors present on/in its target cell. Hormone binds to
proper receptor like a key in a lock.
exocrine glands - ANS--have ducts to transport their secretion
-action: extra cellular effect (enzyme on food)
endocrine glands - ANS--release secretion into blood or lymph vessels to travel to target
cells and induce an action: intracellular effect.
Steroid hormones - ANS--all steroid hormones are derived from cholesterol and are lipid
soluble. Ex. estrogen, progesterone, testosterone, cortisol, aldosterone
Amino acid-based hormones - ANS--contain amino acids, protein or glycoprotein. All
are water soluble except for thyroid hormone. Ex. insulin, glucagon, calcitonin, GH,
PRL.
Amino acid-based hormones use second messenger systems - ANS--hormone does not
enter the cell but binds to a plasma membrane receptor to initiate a second messenger
system that causes enzyme activation, secretory function, and/or permeability changes.
Steroid hormones and thyroid hormone (T3/T4) use direct activation of genes in the
nucleus - ANS--hormone enters the cell, gain access to the nucleus of the cell and bind
to intracellular receptors to alter the production of specific proteins
Hydrophilic hormones - ANS-All the amino acid-based hormones except thyroid
hormone (t3/T4). Use second-messenger systems to alter cell function.
Hydrophobic hormones - ANS-All the steroid hormones and thyroid hormone (T3/T4).
Alters gene expression to change target cell function.
Humoral stimuli - ANS-Changing blood levels of ions and nutrients directly stimulate
secretion of hormones. For example, low blood Ca2+ stimulates release of parathyroid
hormone and high blood Ca2+ stimulates the release of calcitonin.
Neural stimuli - ANS-Nerve fibers stimulate hormone release. For example, sympathetic
nervous system fibers stimulate adrenal medulla to secrete epinephrine.
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