BIOL 1080 Chapter Notes - Chapter 3: Myxedema, Iodine, Autoimmune Disease

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22 Nov 2011
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Posterior Lobe
Does not produce any hormones of its own
Neurons on hypothalamus manufacture ADH and OT
Travel down the nerve cells into the posterior pituitary to
be stored and released
ADH – antidiuretic hormone
Main function to conserve body water by decreasing urine output
Prompts the kidneys to remove water from the fluid going
to the urine
Alcohol temporarily inhibits secretion of ADH
Increased urination causing dehydration and headache and
dry mouth
Also called vasopressin
Role in constricting blood vessels and raising blood
pressure, especially during times of severe blood loss
Deficiency may result from damage to either posterior pituitary
or area of hypothalamus responsible for its manufacturing
Resulting in diabetes insupidus
Excessive urine production and resultant dehydration
Treatment: administration of synthetic ADH in nasal
OT – oxytocin
Main functions:
Stimulate the uterine contractions of childbirth
stimulate milk ejection from the mammary glands
Control of OT is positive feedback mechanism
Pitocin is synthetic form of OT – can induce and speed up labour
Thyroid Gland
Shield-shaped, deep red structure in the front of the neck
In it are follicles
Cells line the walls of the follicles and produce
Thyroglobulin is the substance that T4 (thyroxine) and T3
(triiodothyronine) are made from
Very similar hormones
Diff number of iodine’s
T3 usually produced more, and then eventually converted
to T4
Will be considered TH combined
Nearly all body cells are target cells for TH
Broad effects
Regulates body metabolic rate and production of heat, maintains
blood pressure, and promotes normal development and
functioning of several organ systems
Affects cellular metabolism stimulating protein synthesis, the
breakdown of lipids, and the use of glucose for production of ATP
Pituitary gland and hypothalamus control release of TH
Falling levels of TH prompt hypothalamus to secrete
releasing hormone
This stimulates anterior pituitary to secrete TSH in
turn causing thyroid to release TH
Iodine is needed for production of TH
Simple goiter: enlarged thyroid gland caused by diet
deficient in iodine
Low intake of iodine:
level of TH is low
low level of TH triggers secretion of TSH
TSH stimulates increased production of thyroglobulin
Lack of iodine prevents formation of TH from accumulating T3
Still low level of TH, pituitary gland continues to release
increasing amounts of TSH
Causes the thyroid to enlarge
Undersecretion of TH during fetal development or infancy
Characterized by dwarfism and delayed mental and sexual
During adulthood
Fluid accumulates in facial tissues
Decreases in alertness, body temp, and heart rate
Oversecretion of TH causes Graves’ disease
Autoimmune disorder
Body produces y-shaped proteins called antibodies, mimic the
action of TSH
Stimulate the thyroid gland causing it to enlarge and
overproduce its hormones
Symptoms: increased metabolic rate and heart rate
Accompanied by sweating, nervousness and weight loss
Also have exophthalmos, protruding eyes caused by the
swelling of tissues in the eye orbits