BIO 202 Exam 3

List and decribe the mechanisms for cell communications

• gap functions (pores in cell for chemicals to pass into next cell)

• neutrotransmitters (released by neurons)

• paracrine (local hormones) - secreted into tissue fluids and affect neighbor cell

• hormones = chemical messengers that travel via bloodstream

hormone

a chemical messenger secreted into the bloodstream, stimulates response in another tissue or organ

What must target cells have for their hormone to be effective?

receptors

endocrine organs

• pineal gland

• pituitary gland

• hypothalamus

• thyroid gland

• thymus

• pancreas

• adrenal gland

• ovary

• testes

• parathyroid glands

endocrine vs. exocrine

• endocrine

  • no duct

  • releases hormones into tissue fluids

  • have dense capillary networks to distribute hormones

  • intracellular effects, alter target cell metabolism

• exocrine

  • carry secretion to body surface or other organ cavity

  • extracellular effects (food digestion)

Does this describe a nervous or endocrine system?

• electrical impulses and neurotransmitters, adapts quickly to continual stimulation

• reacts quickly (1-10 msec), stops quickly

• local effect, specific effects on target organs

Does this sound like a exocrine or endocrine system?

• hormones in blood, adapts slowly (days to weeks)

• reacts slowly (seconds to days), may continue long after simulus stops

• general effect, widespread effects on many organs

hypothalamus

• located in brain

• connected to the pituitary gland by a complex of blood vessels called the hypothalamo-hypophyseal portal

• regulates primitive functions (water balance, sex drive)

• produces hormones that stimulate or inhibit secretion of anterior pituitary hormones

• produces hormones stored in the posterior pituitary

tropic hormones

hormones that regulate other endocrine glands

pituitary gland

suspended from hypothalamus by stalk (infundibulum)

• made up of the adenohypophysis (anterior) and neurohypophysis (posterior)

• housed in sella turcica of sphenoid bone

hormones of posterior pituitary

Oxytocin (OT) and Antidiuretic Hormone (ADH)

• both produced in hypothalamus, transported to posterior lobe by hypothalamo-hypophyseal tract

• nerve signals trigger release

ADH (antidiuretic hormone)

• increases water retention, thus reducing urine volume and preventing dehydration

• also called vasopressin - can cause vasoconstriction

oxytocin

• released during sexual arousal and orgasm

• stimulates uterine contractions and propulsion of semen

• promotes feelings of sexual satisfaction and emotional bonding between partners

• stimulates labor contractions during childbirth

• stimulates flow of milk during lactation

• promotes emotional bonding

anterior pituitary hormones

• follicle stimulating hormone (FSH)

• Luteinizing hormone (LH)

• Thyroid stimulating hormone or Thyrotropin (TSH)

• Adrenocorticotropic hormone (ACTH)

• Prolactin (PRL)

• Growth hormone (GH) or Somatotropin

Anytime you seen the word “releasing or “inhibiting” that hormone is coming from the ____

hypothalamus

follicle-stimulating hormone (FSH)

• stimulates development of eggs and follicles in ovaries

• stimulates production of sperm in testes

luteinizing hormone

• stimulates ovulation → progesterone secretion in females

• stimulates testosterone secretion in males

adrenocorticotropic hormone (ACTH)

• regulates response to stress, effect on adrenal cortex of the adrenal glands and secretion of glucocorticoids

• regulates secretion of insulin from pancreas

prolactin (PRL)

• milk synthesis in mammary glands

• increased LH sensitivity and increased testosterone secretion in males

antidiuretic hormone (ADH)

• targets kidneys to increase water retention, reduce urine

• prevents dehydration

• also functions as neurotransmitter

growth hormone (somatotropin)

pituitary produces at least 1000x more GH than any other hormone

• targets lives to produce insulin-like growth factors

• involved with protein synthesis, lipid metabolism, carbohydrate metabolism, electrolyte balance

If a man was castrated, what happens to his GnRH levels?

• levels will increase

  • lack of negative feedback

  • removing the testes removes hypothalamic stimulation, so GnRH will continue to be released

hypopituitarism

• pituitary dwarfism

  • childhood low GH

• panhypopituitarism

  • complete cessation of pituitary secretion

  • causes broad range of disorders (infertility, metabolic)

  • diabetes insipidus - low ADH, 10x normal urine output

hyperpituitarism

• gigantism in childhood

• acromegaly in adulthood

  • thickening of bones, soft tissues of hands, feet and face

pineal gland

• peak secretion 1-5 yrs, starts shrinking age 7

• secretion has dropped to 25% by end of puberty

• may regulate timing of puberty in humans

• synchronize circadian rhythm

• synthesizes melatonin from serotonin

thymus

• involuntary after puberty

• secretes hormones that regulate development and later activation of T-lymphocyte

  • thymopoietin, thymosin, thymulin

What is the largest endocrine gland?

Thyroid gland

• anterior and lateral sides of trachea

• 2 lobes connected by isthmus

What hormones does the thyroid gland secrete?

• Thyroid hormones (2)

  • T3 (triiodothyronine) and T4 (thyroxine or tetraiodothyronine)

  • increases body’s metabolic rate and O2 consumption

  • increases heat production

  • increases heart rate and contraction strength

  • increases respiratory rate

• calcitonin

  • lowers blood Ca2+

  • promotes Ca2+ deposition and bone formation

congenital hypothyroidism (low TH)

infant suffers from abnormal bone development

• thickened facial features

• low temperature

• lethargy

• brain damage

myxedema (adult hypothyroidism, low TH)

• low metabolic rate, sluggishness

• sleepiness, weight gain, constipation, dry skin and hair, cold sensitivity, increased blood pressure and tissue swelling

endemic goiter vs. toxic goiter

• endemic goiter

  • dietary iodine deficiency

  • thyroid gland needs iodine to synthesize TH

  • no TH - no negative feedback and increased TRH and TSH

• toxic goiter (Graves disease)

  • autoimmune disease

  • antibodies mimic TSH - increased TH and increased metabolism

  • increased HR, nervousness, sleeplessness, heat sensitivity, and exophthalmos (bulging eyes)

parathyroid glands

4 small glands partially embedded in the posterior suface of thyroid gland

• secrete parathyroid hormone (PTH) when calcium is low

  • PTH increases blood Ca2+ by inhibiting urinary Ca2+ excretion, promoting urinary phosphate excretion, bone resorption

hypoparathyroidism

• causes dramatic decrease in blood calcium levels

• leads to tetany → muscles don’t relax → muscle spasms → contraction of larynx muscles → suffocation

hyperparathyroidism

excess PTH secretion

• can be caused by a tumor

• leads to bone resorption → bones become soft and deformed

• increases blood Ca2+ (hypercalcemia)

• muscles are weak

• sluggish reflexes

• cardiac arrest

what does the adrenal medulla secrete?

catecholamines (function as hormones & neurotransmitters)

• 85% epinephrine (adrenalin)

• 15% nor-epinephrine (nor-adrenalin)

what does the adrenal cortex secrete?

corticosteroids

• mineralcorticoids

  • control electrolyte balance, aldosterone that retains Na+ and excretes K+

• glucocorticoids

  • cortisol

  • stimulates fat and protein catabolism and gluconeogenesis

  • can cause immune suppression with long-term presence

• sex steroids

  • androgens - important for sex characteristics

  • estrogen - important after menopause when ovaries stop producing

pheochromocytoma

tumor of adrenal medulla

• with hypersecretion of epinephrine/nor-epinephrine

• causes increased BP, increased metabolic rate, hyperglycemia, glycosuria, nervousness, indigestion, sweating

• leads to exhaustion and decreased immune function

Cushing syndrome

an example of glucocorticoid hypersecretion

• protein is catabolized = loss of muscle and bone mass

• causes hyperglycemia, hypertension, weakness, edema

• abnormal fat deposition beteen shoulders and face

androgen hypersecretion

• causes enlargement of penis or clitoris and premature onset of puberty

Addison disease

• hyposecretion of glucocorticoids and mineralcorticoids by adrenal cortex

• hypoglycemia, Na+, and K+ imbalances, dehydration, hypotension, weight loss, weakness

• increased ACTH secretion

• stimulates melanin synthesis → bronzing

• fatal dehydration

pancreas

• retroperitoneal, inferior and dorsal to stomach

• mostly exocrine digestive organ with pancreatic islets of endocrine cells that produce:

  • insulin from beta cells

  • secreted when blood glucose is high

  • binds to insulin receptors on cells to allow glucose to enter cells

  • stimulates glycogen, fat, and protein synthesis

  • antagonizes glucagon

glucagon

comes from alpha cells

• secreted when blood glucose is low (diet or fasting)

• stimulates glycogenolysis (hydrolysis of glycogen)

• fat catabolism

• absorption of aa for gluconeogenesis

somatostatin/growth hormone inhibiting hormone

comes from delta cells

• paracrine secretion (diffuses to cells within the same organ (pancreas))

• modulates secretion of alpha and beta cells

• inhibits nutrient digstion and absorption which prolongs absorption of nutrients

diabetes mellitus

• caused by hyposecretion or inaction of insulin

• signs & symptoms

  • polyuria (excess urine)

  • polydipsia (increased thirst)

  • polyphagia (increased hunger)

  • hyperglycemia - high blood sugar

  • glycosuria - glucose in urine

insulin-dependent diabetes mellitus (IDDM)

Type 1 or juvenile diabetes

• no known cause in some cases

• some have autoimmune destruction of beta cells

• treated with diet, exercise, monitoring of blood glucose, and injections of insulin

non-insulin-dependent diabetes mellitus (NIDDM)

Type II

• 90% of diabetes

• due to insulin resistance

• risk factors - heredity, age obesity

• treatment - weight loss, diet, exercise

endocrine functions of heart

Atrial natriuretic factor/peptide (ANF) or ANP

• when BP is too high, muscles in right atria secrete ANF to lower BP

• increases urine output and sodium excretion

endocrine functions of kidneys

Calcitriol

• increases Ca2+ and phsophate absorption, thus lowers loss for bone deposition

Erythropoietin

• stimulates bone marrow to produce red blood cells (RBCs)

endocrine functions of stomach and small intestines

enteric hormones

• coordinate digestive motility and secretion

endocrine functions of liver

• angiotensinogen (prohormone)

  • precursor of angiotensin II, a vasoconstrictor

• erythropoietin

• somatomedins - mediate action of GH

endocrine functions of placenta

• secretes estrogen, progesterone, and others

  • regulates pregnancy, stimulates development of fetus, and mammary glands

3 classification of hormones

• hormones

  • derived from cholesterole

  • hydrophobic - need transport protein to travel through the bloodstream

  • sex steroids, corticosteroids

• peptides and glycoproteins

  • 3-200 amino acids, hydrophilic

  • OT and ADH

  • all releasing/inhibiting hormones from hypothalamus

  • RER removes segment, forms prohormone, Golgi complex modifies into hormone

• monoamines

  • derived from tyrosine; most are hydrophilic

  • melatonin synthesized from tryptophan

  • catecholamines, TH

hormone transport

steroids and thyroid hormone (hydrophobic)

• require transport protein, but easily enter cell

monoamines and peptides (hydrophilic)

• transport easily in blood, but can’t enter cell

• bind to receptors

where are hormone receptors located?

found on plasma membrane, mitochondria, in nucleus

• usually thousands for a given hormone

• exhibit specificity - receptor is specific to one certain hormone

• exhibit saturation - if all receptors are filled, then there can be no more effect

up-regulation

• low receptor density - weak response

• increased receptor density - increased sensitivity

• stronger response

down-regulation

• high receptor density - strong response

• reduced receptor density

• reduced sensitivity

• diminished response

synergistic effects

more of an effect is exhibited when 2 hormones work together

permissive effects

one hormone enhances a cell/organ’s response to a second hormone that comes later

antagonistic effects

actions of one hormone opposes that of another hormone

• decreased effect

hormone clearance

• hormone signals must be turned off

• take up and degraded by liver and kidney

• excreted in bile or urine

• metabolic clearance rate (MCR) - how fast body gets rid of particular hormone

• half life - time required to clear 50% of hormone

stress

any situation that upsets homeostasis and threatens one’s physical or emotional well-being

• ex. injury, surgery, infection, intense exercise, pain, grief, depression, anger, etc

general adaption syndrome (GAS)

3 stages

1. alarm reaction

2. stage of resistance

3. stage of exhaustion

alarm reaction

• initial response - fight or flight

  • incresed epinephrine and norepinephrine levels

  • increased HR

  • increased BP

  • increased blood glucose levels

  • increased circulation to muscles

  • sodium and water retention (aldosterone)

stage of resistance

• glycogen reserves are gone

• hypothalamus secretes corticotropin-releasing hormone

• pituitary gland then secretes ACTH

• adrenal cortex secretes cortisol and