Endocrine System (Wk 8)

endocrine system

network of organs and glands responsible for producing hormones

hormones

chemical substances that travel via blood to reach target cell; must bind to receptor on target

humoral stimuli

response to changes in chemical levels in body

neural stimuli

nerves stimulate hormone release

hormonal stimuli

hormones can trigger release of other hormones

hypothalamus

secretes regulatory hormones; senses imbalances; connected w/ pituitary gland. Works together to regulate other glands and hormones

posterior pituitary gland

comprised of nervous tissue; connected directly to hypothalamus; releases oxytocin and ADH

Oxytocin

Stimulate uterine contractions

Antidiuretic hormone

Increase water retention/reabsorption in kidneys; released due to blood osmolarity; released by PPG

Anterior Pituitary Gland/adenohypophysis

Connected to hypothalamus indirectly; receives signals from hypothalamus thru blood vessels

Tropic hormones

Regulate release of other hormones; thyroid-stimulating hormone, adrenocorticotropic hormone, follicle stimulating hormone, luteinizing hormone, growth hormone made by APG

Non-tropic hormones

Do not regulate release of other hormones; prolactin, melanocyte-stimulating hormone

Adrenal gland

Located on top of kidneys

Adrenal cortex

Outer layer of adrenal gland

Adrenal medulla

Inner layer of adrenal gland; secretes epinephrine and norepinephrine

epinephrine/NE

targets various cell types; sympathetic response; triggered by neural stimulus

cortisol/glucocorticoids

targets glycogen —> glycogenolysis; targets fat —> lipolysis; target skeletal muscle —> turns proteins into amino acids; stimulated by ACTH

glycogenolysis

glycogen breaks down into glucose

aldosterone/mineralocorticoids

targets kidneys —> stimulate Na+ retention; triggered by low Na+ in blood/low blood pressure (humoral stimulus)

parathyroid/thyroid gland

regulate levels of Ca2+; impacts neural activity, muscle contraction, cell signaling, blood clotting

parathyroid gland (location)

located on posterior aspect of thyroid gland

thyroid gland (location)

located on trachea

parathyroid hormone

targets kidneys and enhances Ca2+ reabsorption in blood. targets osteoclasts to increase activity —> digests bone matrix —> release Ca2+ in blood; triggered by low blood Ca2+

calcitonin

antagonistic to PTH; decreases Ca2+ levels. targets kidneys —> Ca2+ excreted in urine. targets osteoclasts —> decreases activity (less bone is digested); triggered by too much Ca2+

T3/T4

targets various cells —> increase metabolic rate; stimulated by TSH

hypocalcemia

deficiency in Ca2+ levels; causes muscle tetany, low cardiac contractility, caused by low PTH secretion

hypercalcemia

high levels of Ca2+; causes low excitability of muscles and nervous tissue. Overworks kidneys —> kidney stones; result of tumors of PT gland (too much PTH)

pancreas

digestion, controls glucose levels. both exocrine and endocrine. located behind stomach, next to small intestine

acinar cells

enzymes for digestion

alpha cells

secretes glucagon hormone

beta cells

secretes insulin hormone

insulin

hormone that lowers blood glucose levels; dominant during absorptive state. can also target liver and skeletal muscles —> glycogenesis; stimulated by high glucose levels

glycogenesis

glucose into glycogen

glucagon

increase blood glucose levels. dominant during post-absorptive state. targets liver and skeletal muscles —> glycogenolysis; can also do gluconeogenesis —> converts substrates into glucose; released during low blood glucose

type 1 diabetes

insulin hormone deficiency; low insulin production

type 2 diabetes

decrease in insulin sensitivity; body (B cells) still produce insulin

hyperglycemia

elevated glucose levels

thymus gland

thymosin —> matures lymphocytes

pineal gland

melatonin —> induce sleepiness

adipocytes

leptin —> sense of being full

stomach

ghrelin —> sense of hunger

ovaries

estrogen and progesterone —> development of sexual characteristics and egg development; triggered by FSH and luteinizing hormone

testes

testosterone —> develops sexual characteristics and sperm development; triggered by luteinizing hormone