ENDOCRINE SYSTEM
I.
I.
A.
B.
C.
II.
II.
A.
B.
III.
III.
A.
B.
C.
INTRODUCTION
A.
the purpose of the endocrine system is to maintain homeostasis; like the nervous
system it provides control to maintain body function despite changing internal/external
conditions
B.
compared top the nervous system which responds in a rapid manner but whose effects
are short lived, the endocrine sys. response is slow but lasts longer and is widespread
C.
control is exerted by the secretion of hormones into the blood stream that target certain
processes such as metabolism, reproduction, altering the internal and external chemical
balances of cells and fluids, growth and development, and response to stress
COMPOSITION OF THE ENDOCRINE SYSTEM
A.
Endocrine vs. exocrine glands
1.
1.
exocrine glands secrete chemicals into a duct which carries the chem. to the
target tissue or organ. example the gall bladder, sweat glands, etc.
2.
2.
endocrine glands secrete chemicals (hormones) into extracellular space which
then diffuse into the bloodstream--ductless glands
B.
Primary endocrine glands
1.
1.
pituitary gland, thyroid gland, parathyroid glds., adrenal glds., pancreas, gonads
HORMONES
A.
Definition: chemicals produced by endocrine glands that provide control of body
activities to maintain homeostasis
B.
Target cell: cell that is effected by a hormone; all cells are targets of one or more
hormones; hormones only act on their target cells because of receptors on the surface of the
cell
C.
Hormonal action: water soluble vs. lipid soluble
1.
1.
water soluble--made of amino acids and their derivatives and proteins; cannot
diffuse through plasma membrane
2.
2.
binds to receptor on cell surface (adenylate cyclase) º converts ATP into
cAMP º cAMP diffuses throughout cells initiating reactions that lead to activation of
protein kinasesº activates other proteins in cell which act on molecules to change cell
a.
a.
changes may include stimulating or inhibiting metabolic pathways,
synthesis of proteins, altering membranes, secretion of cellular products
including hormones
3.
3.
lipid soluble--steroid hormones that diffuse easily through plasma mem.
4.
4.
binds to receptors in the cytoplasmº steroid/receptor move into nucleus and
bind to DNAº turns on the synthesis of specific genes to make proteins
(transcription/translation)
a.
a.
new proteins do specific jobs such as stimulating or inhibiting
metabolic pathways, altering rates of reactions or become structural components
of the cell
5.
5.
prostaglandins--steroids that are secreted by different parts of the body, act on
cells close to them (local hormones)
a.
a.
act by modifying effects of other hormones by inhibiting or stimulating
formation of cAMP, not true hormones
b.
b.
increase or decrease smooth muscle contraction, secretion of HCL in
stomach, contraction of uterus, cause inflammation, regulate metabolism, induce
sleep, antineoplastic
D.
IV.
IV.
A.
D.
1.
Hormonal control
1.
feedback control--hormones are very potent chemicals, uncontrolled release
would not be good ;
2.
2.
negative feedback system--provides response on opposite direction of stimulus,
the feedback is given by the hormone or its products which inhibit further hormone
secretion; most feedback systems in the body are this type
a.
a.
example: parathyroid gland and blood calcium levels
3.
3.
positive feedback--provides response in same direction as stimulus, chemical
feedback causes endocrine gland to secrete more hormone; move body further from
homeostasis
a.
a.
example: oxytocin produced by post. pituitary and uterine contractions
4.
4.
nervous control--only controls a few glands which secrete their hormones when
they receive nerve impulses
THE ENDOCRINE GLANDS
A.
Pituitary gland
1.
1.
located at base of brain, the size of pea weighing .5g, attached to hypothalamus
by infundibulum and lies within bony cavity called sella turcica
2.
2.
anterior lobe--composed of glandular epithelium enclosed by connective tissue,
release of 7 hormones controlled by releasing factors (R) from the hypothalamus
a.
a.
Growth hormone (GH) --stimulates body cells to grow and divide,
increases bone deposition, causes cells to increase uptake of A.A.s and increase
catabolism, helps maintain blood sugar by increasing conversion of glycogen to
glucose
b.
b.
Melanocyte-stimulating hormone (MSH)--increases melanin
production in skin
c.
c.
Prolactin (PRL) --stimulates and maintains milk secretion by
mammary glands, secretion plus ejection of milk is called lactation, levels of
PRL are also influenced by other hormonal changes..
d.
d.
Thyroid-stimulating hormone (TSH)--stimulates thyroid gland which
influences metabolism
e.
e.
Adrenocorticotropic hormone (ACTH)--stimulated to release by RF
in hypothalamus and by stress, causes cortex of adrenal gland to produce and
release hormones
f.
f.
Follicle stimulating hormone (FSH) -- in females stimulates
development of eggs each month and simulates ovaries to produce estrogen; in
males FSH stimulates production of sperm, FSH production controlled by
hypoth. in response to estrogen and testosterone levels (neg. feedback)
g.
3.
g.
Luteinizing hormone (LH)--in females works w/ estrogen to stimulate
ovaries to release ovum and prepare the uterus for implantation of egg, in males
stimulates testes to produce testosterone
3.
Posterior lobe -- composed of neuroglial cells that support terminal axons from
hypoth., does not produce hormones but stores two hormones produced by nerve cells
of hypothalamus
a.
a.
Oxytocin (OH) --stimulates contraction of smooth muscle of uterine
walls, stimulates cells around mammary ducts to contract leading to ejection of
milk; OT levels rise by positive feedback from uterine contraction (until baby is
delivered) and nursing (milk ejection plus rapid recovery of uterine muscles)
b.
B.
b.
Antidiuretic hormone (ADH) --regulates fluid balance in body by
increasing water reabsorption by kidneys, thus producing less urine; release
controlled by hypoth. which contains osmoreceptors stimulated by increasing
blood concentrationººADH production by hypoth. ºº transported to post.
pituitary and released ººkidneys reabsorb water and dilute blood concentration;
inhibited by excess water; also helps maintain blood pressure by stimulating
smooth muscle in walls of arterioles to contract in process called
vasoconstriction
B.
1.
THYROID GLAND
1.
located below larynx in front of trachea, consists of two lobes, composed of
glandular epithelium w/ outer C.T. capsule, divided into smaller regions called follicles
where hormones are actually produced and secreted
2.
2.
thyroxine and triiodothyronine (T4 and T3) --stimulate to release by TSH due
to low levels of T3 and T4 in blood, affect metabolism by
a.
a.
8 protein synthesis
b.
b.
8 fat metabolism
c.
c.
8 carbohydrate metabolism
d.
d.
8 heart rate and ventilation rate
e.
e.
8 actions of nervous system
3.
iodine is essential in diet for these hormones to be produced
4.
calcitonin --reduces calcium and phosphate levels in blood by decreasing
osteoclast activity and reabsorption by kidney
PARATHYROID GLAND
1.
located posterior to the thyroid gland
2.
produces parathyroid hormone (PTH) --increase blood calcium by
a.
a.
8 osteoblast activity
b.
b.
8 calcium and phosphate reabsorption in kidneys
3.
4.
C.
C.
1.
2.
D.
D.
1.
2.
3.
ADRENAL GLANDS
1.
located anterior to kidneys, divided into two distinct glands, the adrenal
medulla and adrenal cortex
2.
Adrenal medulla--outer region of adrenal gland, composed of modified nervous
tissue, releases hormones that cause changes like the sympathetic nervous system (fight
or flight or frolic)
a.
a.
epinephrine and norepinephrine--stimulated to release by sympathetic
system
(1).
(1).
8 lipid metabolism
(2).
(2).
8glycogenolysis--conversion of glycogen to glucose
(3).
(3).
vasoconstriction or vasodilation
(4).
(4).
8 heartrate and enlargement of airways
3.
Adrenal cortex--glandular epithelium forming inner layers of adrenal glands,
produces steroid hormones from cholesterol
a.
a.
glucocorticoids-- stimulated to release by ACTH; include cortisol and
cortisone; function to increase blood glucose by:
(1).
(1).
converting AA to glucose
(2).
(2).
stimulating gluconeogenesis in liver
(3).
(3).
also inhibits immune response and inflammation by stabilizing
lysosomes
b.
b.
mineralcorticoids--functions to maintain fluid balance by affecting
c.
E.
E.
1.
2.
dissolved ions, most important one is aldosterone which acts on the kidneys to
(1).
(1).
retaining Na+ and excreting K+ (the body is intolerant of wide
fluctuations in these two minerals
(2).
(2).
this helps the body conserve water and maintain blood pressure,
stimulus for release is low blood volume or high K+
c.
androgens and estrogens--sex hormones produced in both sexes but in
different amounts
PANCREAS
1.
gland located in abdominal cavity behind stomach, has both endocrine and
exocrine functions, Islets of Langerhans are groups of cells within pan. that produce and
release 2 hormones w/ opposite effects
2.
glucagon--stimulated to release by 9 in blood glucose of 8 in AA, functions 8
glucose by:
a.
a.
converting glycogen to glucose in liver
b.
b.
8 breakdown of triglycerides to free fatty acids in an effort to spare
glucose
c.
high blood glucose feeds back to % cells inhibiting
further release of glucagon
3.
insulin--stimulated to release by 8 blood glucose, has a
half life of 40 minutes, reduces glucose levels by:
a.
a.
stimulating glucose uptake by most cells except
nervous, renal, and blood cells
b.
b.
inhibiting fat breakdown
c.
c.
stimulating protein synthesis
4.
diabetes mellitus--" sweet siphon", diabetics produce
copious amounts of urine containing glucose, normal urine
contains none, this leads to pathogenic conditions
a.
a.
excess water loss as glucose in urine draws water
out of body
b.
b.
loss of electrolytes in urine, small changes are
dangerous
c.
c.
8 protein catabolism, most proteins are structural
or functional
d.
d.
8 lipolysisºº8 fatty acids and an acid condition in
body, acetone breath from ketone bodies, fatty acid
deposition on walls of arteries
c.
3.
4.
F.
F.
1.
2.
3.
4.
PINEAL GLAND
1.
located superior to the thalamus in cranial cavity
2.
melatonin -- functions are being studied but is available
in health food stores as a diet supplement
3.
thought to inhibit FSH and LH secretion by ant. pituitary
4