a&p ch. 16: the endocrine system

the nervous and endocrine systems

coordinate body functions

nervous system releases

neurotransmitters

endocrine system releases

hormones

hormones

bind to target cell receptors

exocrine glands

secrete products into ducts, NOT hormones. sudoriferous glands, sebaceous glands, mucous glands, digestive glands

endocrine glands

secrete hormones; do not have ducts and secrete into interstitial fluid/ diffuse into blood. pituitary, thyroid, parathyroid, adrenal, pineal,

secreting cells

can be found in hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small intestine, skin, heart, adipose tissue, placenta *NOTE THAT NOT ALL OF THESE ARE PART OF THE ENDOCRINE SYSTEM, BUT THEY PERFORM SIMILAR FUNCTION

endocrine gland locations

hypothalamus, pineal, pituitary, parathyroid and thyroid, thymus, pancreas, adrenals, ovary and testes

hormone activity

enters blood capillary to circulate from a endocrine cell, is released to hormone receptors on distant target cells that contain specific receptors in order to produce action on target cells

lipid soluble hormones

bound to transport proteins; steroid, thyroid, nitric oxide

water soluble hormones

freely into plasma; amine hormones, peptide and protein hormones, eicosanoid hormones. we have more of these

chemical hormone classes

amino acid-based (amino acid derivatives, peptides, proteins), steroids/lipid based (from cholesterol - gonadal and adrenocortical hormones)

hormone response vary

depending on hormone and target cell

hormone responses

- synthesis of new molecules

- changing cell membrane permeability

- transport of substance

- altered rate of metabolic actions

- contraction of smooth or cardiac muscle

lipid soluble hormones bind to

receptors within target cells

steps to lipid soluble hormone action

lipid soluble hormone diffuses into the cell, activated receptor complex alters gene expression, newly formed mRNA directs synthesis of specific proteins on ribosomes, new proteins alter cell's activity

water soluble hormones bind to

receptors on the exterior surface of the target cell

steps to water soluble hormone action

binding of hormone to its receptor, activating G protein activating adenylyl cyclase, which converts ATP to cAMP, cAMP serves as second messenger to activate protein kinase, kinase phosphorylates cellular proteins, which cause reactions that produce physiological responses, phosphodiesterase inactivates cAMP (may occur after step 2 as well)

target cell response to hormone

based on hormone's concentration (hyper and hypo secretion), hormone receptors

synergistic effect

some hormones work well when another is in assistance

antagonistic effect

some hormones oppose the actions of others

up-regulation

target cells form more receptors in response to low hormone levels. can try to correct hypofunction and low regulation of hormone.

down-regulation

target cells lose receptors in response to high hormone levels

short burst hormone secretion regulation

signals from nervous system (adrenal medulla, sympathetic preganglionic neuron), chemical blood changes (blood glucose concentration and release of insulin or glucagon), others hormones (Thyroid stimulating hormone)

most hormone regulation achieved by

negative feedback

negative feedback loop controlling glucocorticoids

hormone of adrenal cortex, when level in the blood decreases, it stimulates the secretion of CRH from hypothalamus that reaches cells in anterior pituitary that secretes ACTH and targets zona fasciculata in adrenal cortex to secrete glucocorticoids.

hypothalamus and pituitary gland work together to

control endocrine glands

anterior lobe

75% of weight of pituitary, secretes 7 hormones; made of glandular epithelial tissue

posterior lobe

made of neural tissue, releases two hormones made by hypothalamus; made of neural tissue

hypophyseal portal system

system within the blood where releasing and inhibiting glands from the hypothalamus are secreted to pituitary gland; two capillaries connected by portal system

negative feedback loops

control secretions of thyrotrophs, gonadotrophs, corticotrophs

growth hormone

most plentiful anterior pituitary hormone, released in bursts by somatotrophs; controlled by growth hormone-releasing hormone + growth hormone-inhibiting hormone

anterior pituitary secretions

human growth hormone (hGH) *doesn't target other endocrine gland*, thyroid stimulating hormone (TSH), follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), adrenocorticotropic hormone (ACTH), melanocyte-stimulating hormone (MSH) *action not well known other than others have higher numbers in this hormone*

growth hormone (GH)

somatotropin; stimulates tissues to synthesize and secrete insulin-like growth factors that promote body tissue growth - acts on target cells

thyroid stimulating hormone (TSH)

thyrotropin; synthesis and secretion of thyroid hormones

follicle stimulating hormone (FSH)

gonadotrophs; females initiate development of oocytes and ovarian secretion of estrogens, men stimulate testes to produce sperm

luteinizing hormone (LH)

gonadotrophs; females stimulate secretion of estrogens and progesterone, ovulation and formation of corpus luteum; men stimulate testes to produce testosterone

prolactin (PRL)

lactotrophs; promotes milk production by mammary glands

adrenocorticotropic hormone

corticotropin; secretion of glucocortoids like cortisol

melanocyte-stimulating hormone

corticotrophs; causes darkening of skin when present in excess.

tropic hormones

hormones that stimulate other glands to release their hormones

hypothalamic releasing hormones

stimulating; secretion of hormone from anterior lobe

anterior lobe as master gland

because it can control the function of other endocrine glands

hypersecretion of GH

gigantism, results in adulthood of acromegaly

hyposecretion of GH

pituitary dwarfism

posterior pituitary gland

does not synthesize its own hormones but stores and releases them from axon terminals (oxytocin and anti-diuretic hormone (ADH)) produced by hypothalamus

axons and neurosecretory cells form the

hypothalamohypophyseal tract

ADH on targets

negative feedback; osmoreceptors; ADH targets kidneys and arterioles (small blood vessels) and causes vasal constriction, can work on special parts on the kidney to stimulate reabsorption of water and decreasing urine output. increase in blood volume (too much water in the blood) causes decrease in ADH, vice versa

oxytocin on targets

oxytocin targets uterus and mammary glands for positive feedback control during childbirth and stimulates ejection of milk *NOT LACTATION*, enhances contractions within the uterus

thyroid gland

butterfly shaped gland located anterior to trachea and inferior to larynx; have right and left lateral lobes connected by isthmus

follicular cells

stimulated by TSH to produce thyroxine (T4) (from anterior pituitary), triiodothyronine (T3) that contain iodide ions (amt according to number)

parafollicular cells

produce calcitonin to regulate calcium homeostasis

thyroid hormone actions (T4 thyroxine and T3 triiodothyronine) ***effects all body cells***

increases basal metabolic rate, maintains body temperature, stimulate protein synthesis, use of glucose and fatty acids for ATP, beta receptors attached to epinephrine upregulation, work with hGH and insulin to accelerate body growth

Hyperthyroidism

excessive activity of the thyroid gland; increased metabolic rate (high appetite, low weight)

hypothyroidism

decreased basal metabolic rate (slowed things), low body temperature, cold intolerance, low blood pressure

Thyrotropin-releasing hormone from hypothalamus and thyroid-stimulating hormone from anterior pituitary

stimulate synthesis and release of thyroid hormones: low levels in blood of T3 and T4 stimulates release of TRH, which carried to anterior pituitary releases TSH, released into blood and stimulates thyroid follicular cells, T3 and T4 released into blood by follicular cells, elevated levels inhibits release of TRH and TSH for negative feedback

myxedema

caused by extreme deficiency of thyroid secretion; also known as adult hypothyroidism; if lack of iodine then goiter can develop (enlargement on neck). happens as negative feedback when TSH is over secreted as a response to low TH levels. symptoms include low metabolic rate, thick and dry skin, puffy eyes and chills, constipation, edema, sluggishness, lethargy

Grave's disease

an autoimmune disorder that is caused by hyperthyroidism and is characterized by goiter and/or exophthalmos: bulging eyeballs; symptoms include elevated metabolic rate, sweating and irregular heartbeats, nervousness and weight loss. because antibodies mimic TSH, TH release is stimulated more than it needs to be

parathyroid glands

separate glands (4) on posterior surface of thyroid gland

chief cells

secretion of parathyroid hormone (PTH); activates osteoclasts and stimulates bone resorption for blood calcium concentration.

oxyphil cells

secrete excess PTH in cases of parathyroid cancer

adrenal glands

on top of each kidney; two regions: adrenal cortex and inner medulla (part of the sympathetic division of autonomic nervous system; receives stimulation from preganglionic sympathetic neurons and secretes epinephrine and norepinephrine)

adrenal gland cortex

zona glomerulosa (aldosterone/mineralocorticoids)glucose concentration , zona fasciculata (glucocorticoids and cortisol), zona reticularis (androgens); sympathetic nervous suystem

aldosterone

major mineralcorticoid that regulate sodium and potassium homeostasis "salt-retaining hormone" which promotes the retention of Na+ by the kidneys. na+ retention promotes water retention, which promotes a higher blood volume and pressure, detected when lower blood pressure

mineralcorticoids

secreted by zona glomerulosa that regulates mineral homeostasis

Renin-Angiotnensin-Aldosterone pathway (RAA)

controls secretion of aldosterone (reapsorption of sodium, removal potassium)

glucocorticoids

zona fasciculata, cortisol

secretion of glucocorticoids

regulated by negative feedback and ACTH to help control protein breakdown, glucose formation, lipolysis, resistance to stress, inflammation, immune responses

hypersecretion (cushing's syndrome)

depresses cartilage and bone formation and immune system, inhibits inflammation and disrupts neural, cardiovascular, gastrointestinal function caused by a tumor on pituitary, lungs, pancreas, kidney, or adrenal glands (can be characterized by lump on back of neck)

adrenal medulla

stimulated by sympathetic preganglionic neuron of autonomic nervous system

chromaffin cells

secrete adrenalin and noradrenalin involved in fight or flight

pancreas

both an endocrine and exocrine gland; also belongs to digestive system

pancreatic islits

form acini that are responsible for digestive enzyme secretion that are delivered to the gastrointestinal tract, pancreatic islits overall are responsible for secretion (contain alpha (glucagon), beta (insulin), delta (somatostatin), F (pancreatic polypeptide))

secretion of insulin and glucagon

controlled by negative feedback; insulin by beta cells and glucagon by alpha cells

diabetes mellitus (DM)

type 1 (hyposecretion of insulin) and type 2 (hypoactivity of insulin)

signs of DM

polyuria (large urine output), polydipsia (thirst), polyphagia (hunger and consumption)

type 1 treatment

insulin injections

gonads

ovaries and testes produce gametes

ovaries produce

estrogen and progesterone, relaxin, inhibin. estrogen promotes development of sex organs and reproductive system, progesterone maintains lining of uterus for pregnancy

testes produce

testosterone for secondary sex characteristics, and anabolic effects for protein synthesis and treatment of metabolic problems

pineal gland

secretion of melatonin

thymus

produces thymosin, thymic humoral factor, thymic factor, thymopoietin (maturation of the immune system's T cells)