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endocrine system

the sum of all the body's hormone-secreting cells and tissues; hormones are released into the bloodstream and are broadcast throughout the body

homeostasis

how animals maintain a relatively constant internal environment even when the external environment changes significantly

negative feedback system

responds to the change in a way that counteracts it (uses antagonistic hormones)

antagonistic hormones

inverse hormones

positive feedback system

a change in some variable that triggers mechanisms that amplify rather than reverse the change

thermoregulation

how animals maintain their internal temperature within a tolerable range

osmoregulation

the process by which animals control solute concentrations and balance water gain and loss

ADH

important hormone in the regulation of water balance; produced in the hypothalamus and stored in and released from the pituitary gland; makes collecting ducts more permeable to water, so more water leaves the filtrate, resulting in more concentrated urine and reduced loss of water from the body

renin

an enzyme, is released in the kidney; activates angiotensin II if blood pressure or blood volume drop

angiotensin II

acts as a hormone and causes arterioles to constrict, which will raise blood pressure

aldosterone

causes the kidney to reabsorb more Na+, which increases retention of water and blood volume and pressure

endocrine glands

ductless and secrete hormones directly into body fluids

hormones

chemical signals that cause a response in target cells

cell-surface receptors

bind the hormone, and a signal transduction pathway is triggered, which consists of a series of molecular events that initiate a response to the signal

intracellular receptors

bound by hormones that are lipid-soluble; then acts as a transcription factor, causing a change in gene expression

hypothalamus

receives information from nerves throughout the body and from other parts of the brain and then initiates endocrine signals in response

posterior pituitary

an extension of the hypothalamus that stores and secretes oxytocin and ADH

oxytocin

causes contraction of the uterine muscles in childbirth and ejection of milk in nursing

anterior pituitary

consists of endocrine cells that synthesize and secrete several hormones

FSH

stimulates development of the ovarian follicles in females and promotes spermatogenesis in males by acting on the cells in the seminiferous tubules

luteinizing hormone

triggers ovulation in females and stimulates the production of testosterone by the interstitial cells of the testes

2 kinds of chemical signaling mechanisms

Steroids & peptides/proteins (non-steroids)

Steroid Signaling

passes through cell & nuclear membrane, binds w/ receptor in nucleus, & activates transcription that results in protein synthesis

Non-steroid (proteins/peptides) Signaling

binds to cell membrane surface, activates signal transduction which activates existing cytoplasmic proteins (process is faster than steroid response)

Hormone Creation Path

ribosomes in rough ER -> golgi apparatus (modified to final structure) -> secretory vesicles -> blood stream

Target Cells

cells equipped w/ the right receptors to respond to a certain hormone

If blood glucose is high:

pancreas releases insulin which stimulates cells to take up glucose & the liver to convert glucose into glycogen

If blood glucose is low:

pancreas releases glucagon which stimulates the liver to break down glycogen and release glucose into the blood stream

lining of digestive tract

in the stomach/small intestine; produces gastrin (-> stomach), secretin (-> pancreas) and cholecystokinin (-> gallbladder)

gastrin

(lining of digestive tract -> stomach) stimulates production of gastric juice (a mixture of pepsin & HCl)

secretin

(lining of digestive tract -> pancreas) stimulates release of pancreatic juice into the small intestine

cholecystokinin

(lining of digestive tract -> gallbladder) stimulates gallbladder to send bile to the small intestine

adrenal glands

adjacent to the kidneys; produces epinephrine and norepinephrine (-> various)

epinephrine and norepinephrine

(adrenal glands -> various) increases metabolic rate, breathing rate, glycogen breakdown rate in liver, and blood pressure; stimulates fat cells to release fatty acids; causes "fight/flight" response

pancreas

in abdominal cavity below stomach on left; produces insulin (-> body cells & liver) and glycogen (-> liver)

insulin

(pancreas -> body cells & liver) causes body cells to take up glucose from blood and the liver to remove glucose from the blood and store it as glycogen (decreases blood sugar levels)

glucagen

(pancreas -> liver) causes liver to break down glycogen and release glucose to blood (increases blood sugar levels)

parathyroid

4 glands embedded in thyroid; produces parathyroid hormone (-> bones & kidneys)

parathyroid hormone

(PTH) parathyroid -> bones & kidneys; increases blood calcium levels

thyroid

in neck region around pharynx; produces thyroxine (-> various) and calcitonin (-> bones and kidneys)

thyroxine

thyroid -> various; stimulates/maintains metabolic processes/metabolic rate; needs iodine to be made

calcitonin

thyroid -> bones and kidneys; decreases blood calcium levels

anterior pituitary

hangs just below hypothalamus; ACTH (-> adrenal cortex), thyroid stimulating hormone (-> thyroid), growth hormone (-> bones), prolactin (-> mammary glands) and follicle stimulating hormone/luteinizing hormone (-> testes and ovaries)

ACTH

(anterior pituitary -> adrenal cortex; regulates secretions of stress hormones (corticosteroids) by the adrenal cortex

thyroid stimulating hormone

(anterior pituitary -> thyroid); TSH; regulates secretion of thyroxine

Growth hormone

(anterior pituitary -> bones); GH; regulates proper growth of bones and cartilage

gigaintism

caused by too much growth hormone as a child

pituitary dwarfism

caused by too little growth hormone as a child

acromegaly

caused by too much growth hormone as an adult

prolactin

(anterior pituitary -> mammary glands); PRL; stimulates mammary gland growth and milk synthesis in mammals

follicle stimulating hormone and luteinizing hormone

(anterior pituitary -> tests & ovaries); FSH and LH

posterior pituitary

hangs just below the hypothalamus; produces oxytocine (-> mammary glands & uterine muscles), Antidiuretic hormone (->kidneys)

Antidiuretic hormone

posterior pituitary -> kidneys; ADH; regulates osmolarity of blood by influencing kidney filtration and urine production

oxytocine

posterior pituitary -> mammary glands & uterine muscles; stimulates uterus contractions and causes milk ejection during nursing

hypothalamus

part of cerebrum in lower center of brain; primary intersection between nervous system and endocrine system; produces releasing and inhibitory hormones (-> anterior pituitary); connected by blood to pituitary which allows for immediate and accurate regulation

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