Download Endocrine

Integration and Control:
THE ENDOCRINE SYSTEM
Campbell & Reece Chapter 45
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Endocrine
• Hormones: substances produced by particular tissues
of the body carried by the bloodstream to "target
cells," upon which they exert special effects
• *Hormones are secreted by glands, made mostly of
epithelial tissue
• Exocrine glands: secrete into ducts (sweat glands,
digestive glands)
• Endocrine glands: secrete hormones (into
bloodstream) "ductless glands"
• Endocrine Gland--->hormone--> Bloodstream------>
target organ/tissue
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• Hormones may be:
– Steroids
– Peptides/proteins;
– Amino acids
• Active in very small quantities
• Controlled by:
– Negative Feedback
• Rapid degradation by the body
Hormonal communication http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter20/animation__hormonal_communic
ation.html
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• Positive & Negative feedback
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/ch
apter20/animation__positive_and_negative_f
eedback__quiz_1_.html
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Mechanisms of Action of Hormones:
2 Main ways that Hormones Effect Target Cells:
Intracellular receptor molecules- steroids, thyroid hormones
Membrane receptor molecules- amino, peptide, protein
hormones
A. Intracellular Receptors
• Steroid hormones and thyroid hormones are soluble in lipids and pass freely
through cell membranes; must contact receptor site with in a cell
• This changes a cell’s actions (protein synthesis, etc.)
B. Membrane Receptors
• Combine with receptors on or in the membrane target cells
• Once combined, send a second messenger inside ? to the nucleus (cyclic AMP)
• May simply increase/decrease a cell’s permeability to substances
Action of Steroid Hormones http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/007243731
6/120109/bio46.swf::Mechanism%20of%20Steroid%20Hormone%20Action
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The Hypothalamus-Pituitary Axis:
• Pituitary was once
considered the "master
gland" until it was learned
that it was under control
of the hypothalamus
(brain region)
• The hypothalamus makes
several hormones which
travel to and are released
by the pituitary lobes.
• Target tissues are
stimulated by (or
inhibited by) release of
these hormones into the
bloodstream.
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Hormone
Anterior
Pituitary
Posterior
Pituitary
Major Target Organ(s) Effects
Growth hormone (GH) Liver, adipose tissue
Promotes growth
(indirectly), control of
protein, lipid and
carbohydrate
metabolism
Thyroid-stimulating
hormone (TSH)
Thyroid gland
Stimulates secretion of
thyroid hormones
Adrenocorticotropic
hormone (ACTH)
Adrenal gland (cortex)
Stimulates secretion of
glucocorticoids
Prolactin (PRL)
Mammary gland
Milk production
Luteinizing hormone
(LH)
Ovary and testis
Control of reproductive
function
Follicle-stimulating
hormone (FSH)
Ovary and testis
Control of reproductive
function
Antidiuretic hormone
(ADH)
Kidney
Conservation of body
water
Ovary and testis
Stimulates milk ejection
and uterine
contractions
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Oxytocin
The Hypothalamus-Pituitary Axis:
PITUITARY:
•About the size of a
kidney bean
•Divided into three
lobes: Anterior,
posterior,
intermediate
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Anterior Pituitary
Somatotropin = growth hormone (GH), stimulates protein
synthesis, growth of muscle and bone
• Deficit: midget
• Excess: giantism (acromegaly)
• Affects glucose metabolism; inhibits uptake and oxidation of
glucose by cells, stimulates breakdown of fatty acid for energy
(conserves glucose)
Prolaction (PRL) –stimulates the secretion of milk in mammals
• controlled by inhibiting hormone in hypothalamus
• continued by nerve impulses from suckling; hypothalamus
(supply upon demand)
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Intermediate Pituitary Lobe
• Melanocyte- stimulating Hormone (MSH)
• (Wikipedia) ...stimulate the production and
release of melanin (melanogenesis) by
melanocytes in skin and hair.
• MSH is also produced by a subpopulation of
neurons in the hypothalamus.
• MSH released into the brain by these neurons has
effects on appetite and sexual arousal.
• More important for color change in reptiles, etc.
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Posterior Pituitary Lobe
• Hypothalamus releases Oxytocin and antidiuretic
hormone (ADH) and stores it here, released by
posterior pituitary
• Oxytocin- "milk let down" hormone, stimulates
uterine contractions, smooth muscle contraction
(BP regulation)
• Antidiuretic Hormone (ADH)- a.k.a. vasopression
(increase BP) decreases excretion of water by
kidneys. Increases permeability of water in
nephrons
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Regulation of The Other Glands:
•
Regulation: negative feedback system involving a gonadotropic (gonadstimulating) hormone
LH (luteinizing hormone): produced by ant. pituitary
• In males:
– LH is carried by blood to stimulate testes
– as blood level of testosterone increases, LH production decreases
• In females:
– rise in LH stimulates ovulation
FSH (follicle-stimulating hormone):
• In males: acts upon the sertoli cells of the testes, important for
spermatogenesis
• In females: stimulates maturation of germ cells, sets mentrual cycle
• High concentrations of LH cause germ cells to produce an inhibitor,
"inhibin", which will then lower LH levels
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The Endocrine Glands
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Testes
• Androgens- the "male sex hormones"
• Testosterone (steroid) is one type. Produced
in the testes necessary for sperm production
and secondary sex characteristics:
•
•
•
•
•
genitals
larnyx (voice change)
skeletal enlargement
muscle tissue
acne
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The Ovaries
• Estrogens- the "female sex hormones"
• Different kinds of estrogen hormones: estriol, estrone,
and estradiol (most important)
• Produced by ovaries by stimulation of FSH from pituitary
• Stimulate development of secondary sex characteristics
(breast development, genital development, distribution of
body fat)
• Progesterone- maintenance of pregnancy, uterus
• (estrogen, progesterone interaction= menstrual cycle)
• estrus cycle diagram, showing hormone fluctuations in the
mare http://www.equinereproduction.com/articles/estrous.htm
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Prostaglandins
• Hormone-like chemicals differ from other hormones:
• Fatty acids (formed by oxygenation of Arachidonic Acid)
• Produced by cell membranes of most organs (as opposed to
specific glands)
• Often exert effects on the tissues that produce them
• The target tissue may be that of another person (e.g. in
semen, for fertilization)
• More patent than hormones (needed in smaller amounts)
• Effects- stimulation of smooth muscle (uterusmenstruation labor); blood vessel dilation/constriction (BP
down, up); inflammatory response by T-cells
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Adrenal Glands
• Adrenal Cortex- outer layer of adrenal glands;
major source of steroid hormones
• Adrenal glands lie on top of kidneys ("adrenal")
• Humans: two major groups of adrenocortical
steroids
• Glucocorticoids
• Mineralocorticoids
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Adrenal Cortex: Glucocorticoids
• Glucocorticoids- used to suppress inflammation
(medical)
• Cortisol- (most important) mainly the formation
of glucose from fats and proteins. Inhibit up take
of glucose by most cells (except brain and heart).
Release increases during excitement etc.; work
with sympathetic nervous system.
• Secreted in response to Adrenocorticotropic
Hormone (ACTH), secreted by Ant. Pituitary
("master gland") which is stimulated by hormone
released from Hypothalamus
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Adrenal Cortex: Mineralocorticoids
• Affect the ion concentration in the blood; water
loss/retention.
Aldosterone- (example) regulation of ions (K+, Na+)
• Affect the transport of ions across membranes of
the NEPHRONS
• Deficiency leads to Na+ ion loss (via urine) = loss
of water = lowers blood pressure
• Since adrenal cortex is source of androgens (male
and female) sex hormones, a tumor can increases
male secondary sex characteristics (e.g. bearded
ladies)
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Adrenal Medulla
• Central portion of adrenal made up of
neurosecretory cells (rather than epithelial)
• Adrenaline and Noradrenalin- increase rate
and strength of heartbeat; raise BP; dilate
resp. passages (act as enforcer of sympathetic
N.S.)
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Pancreatic Hormones:
"Islets of Langerhans"
• Insulin: secreted in response to rise in blood sugar or
AA concentration. It lowers blood sugar by stimulating
up take of glucose (conversion of glucose to glycogen
by liver)
• Glucagon: increases blood sugar by breakdown of
glycogen glucose in liver and breakdown of
fats/proteins
• Somatostatin: synthesis of insulin
• Five different sugar-regulating hormones (growth
hormone, cortisol, insulin, adrenalin, glucagon)
http://highered.mcgraw• Diabetes- insulin too low
hill.com/sites/0072495855/student_view0/chapter
20/animation__blood_sugar_regulation_in_diabetic
• Hypoglycemia- insulin too high s.html
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Thyroid Gland:
• Located on top of Larynx
• Controlled by "hypothalamus- pituitary axis" - TSH (thyroidstimulating hormones a.k.a. "thyrotropin"
• A. Thyroxine
• Accelerates rate of cellular respiration (metabolism)
• differs from androgens, estrogens, corticosteroids because it is an
amino acid with 4 iodine atoms (T4), also T3
• B. Calcitonin: inhibits release of calcium ions [Ca2+ ions] from
bones. Secretion is controlled by Ca ion conc. in fluid around thyroid
cells.
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Thyroid diseases
• Goiter is a swelling of the thyroid gland, results from
low iodine in diet
• Hyperthyroidism: (overproduction) weight loss,
nervousness, fatigue. Most common cause in Grave's
Disease.
• Hypothyroidism: (underproduction) dwarfism in infants
(Cretinism) low energy, low brain cell development, can
be caused by insufficient iodine in diet
• autoimmune disease of thyroid : Hashimoto's
thyroiditis
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Parathyroid Glands:
• Located below thyroid, pea- size, smallest
endocrine gland
• Parathormone: essential in mineral
metabolism, regulation of Calcium and
Phosphate ions in blood
• stimulates release of Ca?? ions from bones;
secreted in response to low blood [Ca2+]
• (Calcium = blood coagulation, muscle
contraction, nerve function)
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The Pineal Gland
• Small lobe in forebrain, near center
• Involved in "photoperiodism"- seasonal
enlargement of ovaries etc.
• Secretes hormone: Melatonin (up/down,
day/night)
• Melatonin: causes pigment cells to open/close
"biological clock"
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