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AP Biology
Chapter 36 notes
Endocrine System
-Endocrine System
I. Function
A. Body’s source of hormones
B. Hormonally controls body function
II. Structure
A. Glands or gland cells
1. secretory cell or structure derived from epithelium, sources of hormones
2. 2 types
a. endocrine – ductless, secrete into bloodstream
b. exocrine – have ducts or tubes that secrete into epithelial tissue
3. 9 main
a. hypothalamus – brain, controls pituitary
b. pituitary – brain, “master gland”
-posterior (stores and secretes hormones made in hypothalamus)
-anterior (makes and secretes its own hormones)
c. adrenals – on kidneys
-medulla – inner portion
-cortex –outer portion
d. thyroid - throat
e. parathyroids - throat
f. gonads – lower abdomen, primary reproductive organs, secretes gametes and
sex hormones
-testes (male)
-ovaries (female)
g. pancreatic islets – endocrine clusters in the pancreas, abdomen
-alpha cells
-beta cells
-delta cells
h. thymus - chest
i. pineal - brain
4. others
a. stomach and small intestine
b. liver
c. kidneys
d. heart
B. Hormones
1. secretory products of endocrine glands, endocrine cells and some neurons that the
delivers to nonadjacent target cells
a. one type of signaling molecule (molecules that help integrate activities within
and between cells)
-some other signaling molecules are:
-neurotransmitters – that we talked about in nervous system
-local signaling molecules – released by many cells in localized
tissue
-phermones – secretions of exocrine glands that diffuse outside of
the body and act on other individuals
2. over 50 known hormones
3. we will study mainly vertebrate (human hormones), but invertebrates have hormones
as well
4. each “gland” or endocrine organ secretes specific hormones (see chart below)
5. target cells – any cell with receptors for a signaling molecule that may chamge its
activities in response to it
6. antagonistic
a. many hormones work in pairs to “counteract” each other
b. classic examples
-glucagon and insulin
-calcitonin and parathyroid hormone
-epinephrine and norepinephrine
7. 2 main types
a. steroid hormones
-lipid soluble so they can diffuse through the membranes
-can enter the cell and even the nucleus
-can affect gene expression by initiating or inhibiting transcription
-ex. estrogens, androgens, progesterone, cortisol, aldosterone
b. peptide hormones
-water soluble, cannot diffuse through membrane
-bind to membrane receptor, don’t get inside cell
-second messenger is activated inside the cell, the second messenger
affects gene expression
-cAMP is common second messenger
-ex. glucagon, ADH, OCT, TRH, insulin, STH, PRL, FSH, LH, TSH
C. Mechanisms
1. feedback
a. positive feedback – rising levels stimulates further secretion
b. negative feedback – rising levels inhibits further secretion
2. environmental factors can affect hormone secretion
a. ex. pineal gland secretes melatonin in the absence of light and is therefore
affected by time of day and seasons
3. direct responses to internal environment
a. the pancreatic islets respond to blood sugar levels
- if blood sugar drops the pancreas secretes glucagon to raise blood sugar
- if blood sugar is high the pancreas secretes insulin to lower blood sugar
4. therefore, some endocrine glands react to chemical changes and are not controlled by
hypothalamus and pituitary
5. hormones interact with protein receptors on target cells
a. different hormones act on different mechanisms in target cell
b. not all types of cells respond to a given signal
III. Chart
“Gland”/Source
Hypothalamus
-to control pituitary
-to store in pituitary
Pituitary
Posterior (stores
from hypothalamus)
Anterior
Intermediate
(not in humans)
Adrenal
Medulla (inner)
Hormone/Secretion
Thyroid
Parathyroids
Action/Function/Effect
-releasers
-GnRH
-TRH
-CRH
-inhibitors
-pituitary
-ADH
-OXT
-stored and
released from
pituitary
-ADH
-OXT
-kidneys
-mammary
-uterus
-water conservation
-induces milk release
-induces contractions
-ACTH
-FSH
-adrenal cortex
-ovaries, testes
-TSH
-LH
-thyroid
-ovaries, testes
-STH (GH)
-most cells
-PRL
-mammary
-stimulates release of cortisol
-In females, stimulates estrogen secretion
and egg maturation. In males, stimulates
sperm formation.
-stimulates release of thyroid hormones
-In females, stimulates progesterone
secretion, ovulation and corpus luteum
formation. In males, stimulates testerone
secretion and sperm release.
-promotes growth in young, induces
protein synthesis and cell division, has a
role in glucose/protein metabolism in
adults.
-stimulates and sustain milk production
-MSH
-pigment cells
-induces color change in response to
external stimuli
-epinephrine
-liver, muscle,
adipose
-smooth muscle
of blood vessels
-increase heart rate and force of
contraction, increase blood sugar, etc.
-promotes constriction or dilation of blood
vessels, controls blood flow
-most cells
-promote breakdown of glycogen, fats and
proteins, help raise blood sugar
-promote sodium reabsorption, help
control salt-water balance
-regulate metabolism, roles in growth and
development
-lowers Ca level in blood
-elevates Ca level in blood
-norepinephrine
Cortex (outer)
Target
-glucocorticoids
(cortisol)
-mineralocorticoids
(incl. aldosterone)
-triiodothyronine &
thyroxine
-calcitonin
-PTH
-kidney
-most cells
-bone
-bone, kidney
-stimulates release of hormone from target
-gonadotropin release (ex. FSH, LH)
-thyrotropin releasing
-cortisol releasing
-inhibit release from target
Gonads
Testes
-androgens
-testosterone
-general
-required in sperm formation,
development of genitals, sex traits, growth
and development
-estrogens
-general
-progesterone
-uterus, breasts
-required for egg maturation and release,
preparation of uterine lining, genital
development, sex traits, growth and
development
-prepares/maintains uterine lining,
stimulates development of breasts
-glucagon
-liver
-promotes glycogen breakdown, increases
blood sugar
Beta
-insulin
-liver, muscle,
adipose
-promotes cell uptake of glucose, lowers
blood sugar
Delta
-somatostatin
-inhibits digestion of nutrients, and their
absorption
-immunity
-influences daily biorythms and seasonal
sexual activity
-stimulates activities required for food
digestion and absorbtion
-calcitriol
-insulin
secreting cells
-T lymphocytes
-gonads
(indirectly)
-stomach,
pancreas,
gallbladder
-most cells
-bone marrow
-adrenal cortex
and arterioles
-bone, gut
-atrial natriuretic
hormone
-kidney, blood
vessels
Ovaries
Pancreatic Islets
Alpha
Thymus
Pineal
-Thymopoietin
-Melatonin
Stomach and Small
Intestine
-gastrin
-secretin
Liver
Kidneys
-somatomedins
-erythropoietin
-angiotensin
Heart
-stimulates cell growth and development
-Stimulates red blood cell production
-helps control secretion of aldosterone and
therefore Na reabsorption and blood press.
-enhances Ca reabsorption from bone and
Ca absorption from gut
-increases Na excretion; lowers blood
pressure