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ENDOCRINOLOGY
Reading: Chapter 11
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Neural vs. Endocrine Communication
Neural
-electrical/hardwired (phone)
-fast (msec)
-short-term changes
-electrical impulse + NT’s
-localized action (stim. 1 muscle or gland)
RESULT =
Endocrine
-chemical (mail)
-relatively slow
-long-term and/or
cyclical changes
-hormones (dilution, so you need
greater sensitivity)
-widespread action (many tissues)
RESULT = homeostasis
reproduction
growth
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Fig. 11.01
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Fig. 11.02
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“Neuroendocrine System”
The nervous & endocrine systems are very closely intertwined.
Hypothalamus (nervous tissue) controls endocrine secretions
What chemical is both a neurotransmitter and a hormone?
Norepinephrine
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GENERALIZED ENDOCRINE FUNCTIONS
1. Maintains Homeostasis:
Dehydration =
Nutrition =
Infection =
regulate water & electrolyte balance
transport across cell membranes,
metabolic rate, energy balance,
control smooth muscle activity, glands
immune system activity
2. Control Reproduction & Development:
-Gamete development, ovulation (timing), parturition, lactation
-Growth of various tissues
-Development (imbalances can impair brain dev.)
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Hormones: mechanism of action
Gland = cluster of epithelial cells that secrete
Exocrine Gland = -secretion via DUCT
-sweat, mucous, sebaceous, …….
Endocrine Gland = -secretion into BLOOD
-so these are highly vascular tissue
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What is a hormone?
A substance secreted by a cell (into the
blood), that has an effect on the function of
another “target” cell.
A “chemical messenger”
Two types/groups, divided based on chemical nature.
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Water Insoluble Hormones
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STEROIDS
Synthesized from cholesterol, on SER
4 ring structure (C & H)
Carried in plasma by carrier proteins
Example: sex hormones
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Water Soluble Hormones
• Dissolve in plasma (no carriers needed)
Amines: -derived from amino acids (a.a’s)
Peptides: -short chains (2 to 12) of a.a’s
Proteins: -100 to 200 a.a’s
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Target Tissues
• Target tissues have specific receptors
–
–
–
–
Receptors = proteins or glycoproteins
Each receptor recognizes one hormone
But, each cell can have 2000 to 100,000 receptors!
More receptors = greater sensitivity to that hormone
NOTE:
-only tissues w/ receptor are affected
-water soluble & insoluble hormones have
v. different actions at target tissues
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Action of Steroids (lipid soluble)
a.
b.
b.
c.
d.
e.
f.
Steriod hormones attach to carrier proteins in plasma which:
-increases solubility
-prevents their excretion
-creates a reserve
Dissociate from carrier to pass through cell membrane
Bind w/ new carrier inside cell, usually the nucleus
Hormone/carrier complex bind w/ DNA
Specific genes = activated
Specific proteins are made depending on which genes are activated
The newly synthesized protein may change __________ or produce some other
effect associated with a particular steriod hormone.
PROPORTIONAL RESPONSE
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Action of Water Soluble Hormones
1. Hormones = soluble in plasma (do you need a
carrier?)
2. Hormones can’t cross cell membrane
3. So, receptors found on surface of cell
4. H-R complex on cell surface triggers changes inside
the cell
5. H-R-receptor binding activates a cascade response
inside target cell
6. [Proteins are ________ so that they are capable of
activating and inactivating enzymes & produce the
effect associated w/ particular _____ hormone. 14
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Control of Hormonal Secretions
Negative Feedback Based On:
-amount of hormone produced (thyroxin)
-concentration of a product created in response to a
particular hormone (blood sugar level)
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Low Thyroxin
(+)
Anterior Pituitary
TSH
(-)
Thyroid
Thyroxin
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Control of Hormonal Secretions
Neural Control: -epinephrine released from adrenal medulla
-due to pre-ganglionic stimulation (what branch
of the nervous system?)
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Hormonal Interactions
Synergistic: 2+ hormones working together
Estrogen + progesterone + PL + oxytocin 
Antagonistic: Effect of 1 hormone opposed by another
Insulin opposes the action glucagon
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Removal of “yesterday’s” hormones
Water Soluble Hormones
• Do these enter the cell?
• Removed/broken down in minutes  short term changes
• Excreted by _____________
Water Insoluble Hormones
• Do these enter the cell?
• Why might these stay in the blood longer?
• Limited kidney clearance
• Mainly removed by ______________
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Pituitary Gland (hypophysis)
Embryogenesis: Nerve Tissue + Epithelial Tissue
1. Neural portion  -floor of diencephalon
-grows down to form neural stalk
2. Oral epithelium 
-making roof of mouth in embryo
-a little piece pinches off
-wraps around ant. part of neural stalk
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Pituitary Gland (hypophysis)
- located below hypothalamus
- has 2 portions: anterior pituitary (adenohypophysis)
posterior pituitary (neurohypophysis)
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Posterior Pituitary
-neurohypophysis  highly innervated
-no “gland cells”
-stores and releases ADH & oxytocin, hormones produced by
hypothalamus
-neurons run from hypothalamus, through infundibulum, to
posterior pituitary
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1) antidiuretic hormone (ADH)
-stimulates retention of H2O in the kidneys.
-absence of ADH causes diabetes insipidus.
2) oxytocin
- stimulates contractions during labor.
- stimulates uterus constriction post-partum.
- stimulates milk letdown.
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Anterior Pituitary
-adenohypophysis
-composed of glandular epithelial tissue
-no innervation
-no direct blood supply, blood receive via portal vein
-produces 6 major hormones
-hormones are only released in response to releasing factors from
hypothalamus
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Anterior Pituitary (con’t)
-produces 6 major tropic hormones.
-tropic hormone  act on other tissues to trigger growth,
increased activity, or hormone release
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The 6 Anterior Pituitary Hormones
1)
Thyrotropin (troph = to feed or nourish)
-also called Thyroid Stimulating Hormone (TSH)
-stimulates thyroid to increase in size and activity.
2)
Adrenocorticotrophic Hormone (ACTH)
- stimulates adrenal cortex to increase in size & activity
3)
Prolactin (PL)
-stimulates milk production in women
-possible electrolyte regulation in men
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4) Somatotropin = Growth Hormone (GH)
-stimulates growth of tissue (bone, muscle, organs)
-maintains tissues
-produced throughout life, but there is a surge in adolescence
-Until age 25 = long bone growth & soft tissue growth
-After age 25 = health and repair of soft tissues only
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Growth Hormone Abnormalities
a)
b)
c)
d)
Gigantism
Acromegaly
Dwarfism
Abuse in athletes
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Growth Hormone Abnormalities
a) Gigantism:
-too much GH before age 25
-tumor in pituitary gland
-very tall
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Growth Hormone Abnormalities
Acromegaly: -too much GH after age 25
-growth of soft tissues (nose, chin, hands…)
-pituitary gland tumor
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Growth Hormone Abnormalities
c) Pituitary Dwarfism: -insufficient GH
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Growth Hormone Abnormalities
d) Abuse in athletes…why? Effect of age?
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5 & 6) gonadotrophic hormones
a) follicle stimulating hormone (FSH)
-stimulates follicles to develop
-follicle = ova + surrounding cells (make estrogens & progesterone)
-stimulates the production of sperm
b) luteinizing hormone (LH)
-LH stimulates ovulation in females
-in males it stimulates the interstitial cells in testes to make
testosterone (in males LH is called ICSH)
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Hypothalamus
- Part of both the nervous & endocrine systems.
- Controls pituitary gland w/ releasing & inhibitory factors
GHIH decreases GH sec.
GHRH  increases GH sec.
PIH  decreases PL sec.
PRH  increases PL sec.
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ENDOCRINOLOGY
Reading: Chapter 11
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Non-Pituitary Endocrine Glands
1. Adrenal gland
- located just above the kidneys.
- each gland has 2 separate portions: inside = medulla
outside = cortex
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Adrenal Cortex:
Mineralocorticoids
-primarily aldosterone (steroid)
-stimulates the kidneys to retain sodium
-controlled by ACTH from ant. Pit.
-controlled by kidneys (neg. feedback)
aldosterone
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Adrenal Cortex:
Glucocorticoids -mainly cortisol
-released during stress (coping mechanism)
*increases blood glucose levels
*vasoconstriction  decreases inflammation
*stabilizes lysosomes  reduce cell destruction
Cortisol
(hydrocortisone)
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Adrenal Cortex:
Androgens: -male sex hormones
-little effect in males (high testosterone from testes)
-stimulate libido & muscle development in females
Androgens
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Adrenal Cortex:
Abnormalities:
-excess androgens = masculinization in females (adult vs. fetal)
-adrenal failure = Addison’s disease (unable to reg. Na & K)
-excess adrenal activity = Cushing’s syndrome
-too much cortisol = fat storage in
face & on back
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Adrenal Medulla
-stimulated by ANS
-E &small quantities of NE are released
Epinephrine
Norepinephrine
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2. Thyroid Gland
- located just below the larynx.
- Produces 2 major hormones = thyroxin & thyrocalcitonin.
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a) Thyroxin -a metabolic hormone
-made when iodine is available
-increases BMR & ATP production/use
-increases oxygen consumption
-increases rate of heat production
-stimulates protein synthesis
-works permissively w/ GH & insulin to accelerate
growth
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Low Thyroxin
(+)
Hypothalamus
(-)
TRH
Anterior Pituitary
(-)
TSH
Thyroid
Thyroxin
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b) calcitonin (thyrocalcitonin)
-stimulates osteoblast activity
-lowers blood calcium levels
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Abnormalities of the thyroid gland:
1)
hypothyroidism
-insufficient activity of thyroid
-decreased metabolic rate
-sluggish & tiered
-cretinism in infants (abnormal NS dev.)
-diagnose with low thyroxin & high TSH
-treat with thyroxin
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Abnormalities of the thyroid gland:
2)
hyperthyroidism -increased metabolic rate.
-weight loss, nervousness, insomnia
-exophtalmia
-treat with surgery or iodine blockers
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Abnormalities of the thyroid gland:
3) goiter
-enlarged thyroid
-many causes, including lack of iodine
-treat with iodine & cosmetic surgery
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3) parathyroid glands
usually 4 glands located on the dorsal surface of the thyroid.
produce parathyroid hormone (PTH, or parathormone)
PTH stimulates osteoclast (bone eaters) activity
Stimulate calcium retention by kidneys & intestines
raises blood Ca
-
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4) Pancreas
-
Located next to stomach & duodenum.
Has exocrine and endocrine functions.
Endocrine tissue = Islets of Langerhans.
2 major hormones: glucagon and insulin.
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Glucagon -produced by alpha cells in the islets
-released when blood glucose levels fall (hypoglycemia)
-causes breakdown of glycogen, glucose rel. from tissues
-blood glucose returns to normal levels
Glucagon
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Insulin
-produced by beta cells in the islets
-released when blood glucose levels rise (hyperglycemia)
-causes glucose to move into cells
-lowers blood glucose levels
-glucose is stored in the liver & muscle as glycogen (glycogenesis)
Insulin
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Diabetes Mellitus
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Type I
Juvenile onset (under age 25)
Insulin dependant
Usually sudden onset
Autoimmune destruction of beta-cells
~10% of all diabetics
Family history is rare
“Starvation” of cells
Body uses fat for energy
Leads to ketoacidosis & coma
Long-term: renal & retinal problems,
hypertension, arteriosclerosis, gangrene
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Type II
Adult onset ?????
NOT insulin dependant
Usually gradual onset
Lack insulin receptors at target cells
~90% of all diabetics
Strong links within family
Treated with drugs to stimulate
insulin secretion
Also with diet & exercise
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5) pineal gland
-
located near the midbrain
produces melatonin
important for seasonal breeding
in humans it is important for sleep-wake cycles
increased light  decreased melatonin
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6) Thymus
-located just below sternum
-large in children but atrophies in adults
-produces thymosin  stimulates the immune system
Thymosin
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7) Gonads
-ovaries in women (estrogens & progesterone)
-testes in men (testosterone)
Testosterone
Estrogens
Progesterone
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Do endocrine organs have other functions?
Most often, YES!
Give me some examples:
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8) Prostaglandins
-hormone like chemicals produced by most cells
-important in inflammation, clotting, BP, uterine
contractions and many other functions
-inhibited by ibuprofen
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END
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