Anatomy Exam 4-Final

in humans, the endocrine and nervous systems specialize in \___ and \___

communication and coordination

the endocrine system uses \___ to communicate

hormones

gap junctions

pores in the cell membrane allow signaling molecules, nutrients, and electrolytes to move from cell to cell

neurotransmitters

released from neurons to travel across synaptic cleft to second cell

paracrines

secreted into tissue fluids to affect nearby cells

hormones

chemical messengers that travel in the bloodstream and stimulate physiological responses in cells of another tissue or organ, often a considerable distance away

endocrine system

glands, tissues, and cells that secrete hormones

endocrine glands

organs that are traditional sources of hormones

exocrine glands

have ducts; carry secretion to an epithelial surface or the mucosa of the digestive tract; extracellular effects (food digestion)

endocrine glands

no ducts; contain dense, fenestrated capillary networks which allow easy uptake of hormones into the bloodstream; intracellular effects (altering target cell metabolism)

\___ cells defy rigid classification - release hormones, releases bile into ducts, release albumin and blood clotting factors into blood (not hormones)

liver

Nervous or Endocrine: which has a faster reaction time?

Nervous (ms timescale, compared to seconds to days for endocrine)

Nervous or Endocrine: which has persistent adaptation to long term stimuli?

Endocrine; it adapts slowly (compared to response decline with quick adaption for nervous)

Nervous or Endocrine: Area of effect is widespread and general

Endocrine; it affects many organs (nervous is targeted and specific to one organ)

norepinephrine, dopamine, and antidiuretic hormone function as \___

both hormones and neurotransmitters

example of both endocrine and nervous systems having similar effects on target cells

norepinephrine and glucagon both cause glycogen hydrolysis in liver

can the nervous system and endocrine system have an effect on each other?

yes, neurotransmitters can affect glands and hormones can affect neurons

\____ cells share characteristics with both the nervous and endocrine system

neuroendocrine (neuron-like cells that secrete oxytocin into blood)

hypothalamus

shaped like a flattened funnel; forms floor and walls of the third ventricle of the brain; regulates primitive functions from water balance and thermoregulation to sex drive and childbirth; many of its functions carried out by pituitary gland

pituitary gland

suspended from the hypothalamus by a stalk infundibulum; housed in the sella turcica, size and shape of a kidney bean; anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis)

adenohypophysis (anterior lobe)

anterior 3/4 of the pituitary; linked to the hypothalamus by hypophyseal portal system; primary capillaries in hypothalamus connected to secondary capillaries by portal venules

hypothalamic hormones regulate \___ cells

adenohypophysis; hypothalamic releasing and inhibiting hormones travel in hypophyseal portal system from hypothalamus to anterior pituitary; different hormones are secreted

neurohypophysis (posterior lobe)

constitutes posterior 1/4 of the gland; nerve tissue, not a true gland; nerve cell bodies in hypothalamus pass down the stalk as hypothalamo-hypophyseal tract and end in posterior lobe; hypothalamic neurons secrete hormones that are stored in neurohypophysis until released into blood

eight hormones produced in hypothalamus; six regulate the anterior pituitary, two are released into capillaries in the posterior pituitary

TRH, CRH, GnRH, and GHRH are releasing hormones that promote anterior secretion of TSH, PRL, ACTH, FSH, LH, and GH; PIH inhibits the secretion of prolactin, and somatostatin inhibits secretion growth hormone and thyroid-stimulating hormone by the anterior pituitary

posterior pituitary hormones

oxytocin (OT) and antidiuretic hormone (ADH); both stored and released by posterior pituitary; paraventricular nuclei of hypothalamus produce OT, supraoptic nuclei produce ADH; posterior pituitary does not synthesize them

FSH (follicle stimulating hormone)

gonadotropin hormone that stimulates the secretion of ovarian sex hormones, development of ovarian follicles, and sperm production

LH (luteinizing hormone)

gonadotropin hormone that stimulates ovulation, stimulates corpus luteum to secrete progesterone, stimulates testes to secrete testosterone

TSH (thyroid-stimulating hormone)

stimulates the secretion of thyroid hormone

ACTH (adrenocorticotropic hormone)

stimulates adrenal cortex to secrete glucocorticoids

PRL (prolactin)

after birth, stimulates mammary glands to synthesize milk

GH (growth hormone)

stimulates mitosis and cellular differentiation

ADH (antidiuretic hormone)

increases water retention, thus reducing urine volume, and preventing dehydration; also called vasopressin because it can cause vasoconstriction

OT (oxytocin)

surge of hormone released during sexual arousal and orgasm; promotes feelings of sexual satisfaction and emotional bonding between partners; stimulates labor contractions during childbirth; stimulates flow of milk during lactation; may promote emotional bonding between lactating mother and infant

is the rate of secretion of pituitary hormones constant?

no, it is regulate by hypothalamus, other brain areas, and feedback from target organs

hypothalamic and cerebral control

brain monitors conditions and influences anterior pituitary accordingly

in times of stress, the hypothalamus triggers the release of \___

ACTH

during pregnancy, the hypothalamus triggers \____ secretion

prolactin

posterior pituitary is controlled by \____

neuroendocrine reflexes; hypothalamic osmoreceptors trigger release of ADH when they detect a rise in blood osmolarity; infant suckling triggers hypothalamic response to release oxytocin

negative feedback in the pituitary gland

increased target hormone levels inhibit the release of hypothalamic and/or pituitary hormones; ex. thyroid hormone inhibits release of TRH by hypothalamus and of TSH by anterior pituitary

GH has widespread effects on body tissue, especially \____

cartilage, bone, muscle, and fat

GH induces \___ to produce growth stimulants

liver; insulin-like growth factors (IGF-I) or somatomedins (IGF-II); stimulate target cells in diverse tissues; IGF-I prolongs the action of GH

hormone half-life

the time required for 50% of the hormone to be cleared from the blood (GH \= 6-20 min, IGF-I \= about 20 hours)

GH: protein synthesis increases

boosts transcription and translation; increases amino acid uptake into cells; suppresses protein catabolism

GH: lipid metabolism increases

stimulates adipocytes to catabolize fats (protein sparring effect)

GH: carbohydrate metabolism

glucose-sparring effect, mobilizing fatty acids reduces dependence of most cells on glucose, freeing more for the brain; stimulates glucose secretion by liver

GH: electrolyte balance

promotes Na+, K+, and Cl− retention by kidneys, enhances Ca2+ absorption in intestine; makes electrolytes available to growing tissues

other functions/facts of GH

bone growth, thickening, and remodeling influenced, especially during childhood and adolescence; secretion high during the first 2 hours of sleep; can peak in response to vigorous exercise; also activated by ghrelin, which is released by the empty stomach; GH levels decline gradually with age

pineal gland

attached to the roof of third ventricle beneath the posterior end of the corpus callosum; after age 7, it shrinks down 75%; may synchronize with circadian rhythms; synthesizes melatonin from serotonin during the night

SAD (seasonal affective disorder)

depression that occurs in winter or in northern climates; symptoms include depression, irritability, and carbohydrate craving; 2-3 hours of exposure to bright light each day reduces the melatonin levels and the symptoms

thymus

plays a role in three systems: endocrine, lymphatic, and immune; bilobed gland in the mediastinum superior to the heart goes through involution after puberty; site of maturation of T cells important in immune defense; secretes hormones that stimulate development of other lymphatic organs and activity of T lymphocytes

thyroid gland

largest gland that is purely endocrine; composed of two lobes and an isthmus below the larynx; dark reddish brown color due to rich blood supply

thyroid follicles

sacs that make up most of the thyroid; contain protein-rich colloid

follicular cells

simple cuboidal epithelium that lines the thyroid follicles

the thyroid secretes \___ and \___ in response to TSH

thyroxine and triiodothyronine; increases metabolic rate, O2 consumption, heat production, appetite, growth hormone secretion, alertness, reflex speed

parafollicular (C or clear cells)

secrete calcitonin with rising blood calcium; stimulates osteoblast activity and bone formation in children

parathyroid glands

usually four glands partially embedded in posterior surface of thyroid gland; can be found from as high as hyoid bone to as low as aortic arch; secrete PTH which increases blood calcium levels and promotes synthesis of calcitriol; decreases urinary secretion

adrenal medulla

inner core, 10-20% of gland; has dual nature acting as an endocrine gland and a ganglion of the sympathetic postganglionic neurons called chromaffin cells; when stimulated, release catecholamines and a trace of dopamine directly into the blood stream

adrenal medulla (2)

as hormones, catecholamines have multiple effects; increase alertness and prepare the body for physical activity; mobilize high-energy fuels, lactate, fatty acids, and glucose; glycogenolysis and gluconeogenesis by liver boost glucose levels; epinephrine inhibits insulin secretion and so has a glucose-sparring effect (muscles use fatty acids, saving glucose for brain)

adrenal cortex

cortex surrounds medulla and secretes several corticosteroids from three layers of glandular tissue

zona glomerulosa (1)

thin, outer layer; cells are arranged in rounded clusters; secretes mineralocorticoids - regulate the body's electrolyte balance

zona fasciculata

thick, middle layer; cells arranged in fascicles separated by capillaries; secretes glucocorticoids and androgens

zona reticularis

narrow, inner layer of adrenal cortex; cells in branching network; secretes glucocorticoids, sex steroids

mineralocorticoids

from the zona glomerulosa; steroid hormones that regulate electrolyte balance; aldosterone stimulates Na retention and K excretion; water is retained with sodium by osmosis, so blood volume and blood pressure are maintained

glucocorticoids

secreted by zona fasciculata and zona reticulata in response to ACTH; regulate metabolism of glucose and other fuels; cortisol and corticosterone stimulate fat and protein catabolism, gluconeogenesis and release fatty acids of glucose into the blood; help body adapt to stress and repair tissues; anti-inflammatory effect becomes immune suppression with long-term use

sex steroids

secreted by zona fasciculata and zona reticularis

androgens

set libido throughout life, large role in prenatal male development

estradiol

small quantity from adrenals, but this becomes important after menopause for sustaining adult bone mass

medulla atrophies without the stimulation of \______

cortisol

some \____ cells of medullary origin extend into the cortex

chromaffin (they stimulate the cortex to secrete corticosteroids when stress activates the sympathetic nervous system)

glucagon

secreted by A or alpha cells; released between meals when blood glucose concentration is falling

in the liver, \___ stimulates gluconeogenesis, glycogenolysis, and the release of glucose into the circulation raising blood glucose level

glucagon

in adipose tissue, \___ stimulates fat catabolism and release of free fatty acids

glucagon

\______ is released to rising amino acid levels in blood, promotes amino acid reabsorption, and provides cells with raw material for gluconeogenesis

glucagon

insulin

secreted by b or beta cells; secreted during and after a meal when glucose and amino acid blood levels are rising

\___ stimulates cells to absorb nutrients and store or metabolize them, lowering blood glucose levels

insulin (promotes synthesis of glycogen, fat, and protein; supresses use of already-stored fuels; brain, liver, kidneys, and RBCs absorb glucose without insulin, but other tissues require insulin)

insufficiency or inaction of insulin is cause of \____

diabetes mellitus

\____ secreted by D or delta cells; partially suppresses secretion of glucagon and insulin

somatostatin (inhibits nutrient digestion and absorption which prolongs absorption of nutrients)

hyperglycemic hormones \______

raise blood glucose concentration (includes hormones from other glands; glucagon, growth hormone, epinephrine, norepinephrine, cortisol, and corticosterone)

hypoglycemic hormones \____

lower blood glucose

ovaries and testes are \___ glands

both exocrine and endocrine; exocrine \= whole cells (eggs and sperm), endocrine \= gonadal hormones (mostly steroids)

ovarian hormones

estradiol, progesterone, and inhibin

testicular hormones

testosterone, weaker androgens, estrogen, and inhibin

ovary

theca cells synthesize androstenedione; converted to mainly estradiol by granulosa cells

after ovulation, the remains of the follicle becomes the \____

corpus luteum; secretes progesterone for 12 days following secretion; follicle and corpus luteum secrete inhibin

functions of estradiol and progesterone

development of female reproductive system and physique including adolescent bone growth; regulate menstrual cycle, sustain pregnancy; prepare mammary glands for lactation

\___ suppresses FSH secretion from anterior pituitary

inhibin

testes

microscopic seminiferous tubules produce sperm; tubule walls contain sustentacular cells; interstitial cells lie in clusters between tubules

testosterone and other steroids from \______ nestled between the tubules; stimulates development of the male reproductive system in fetus and adolescent, and sex drive; sustains sperm production

interstitial cells

inhibin from \______ limits FSH secretion in order to regulate sperm production

nurse cells

endocrine function of the skin

keratinocytes convert a cholesterol-like steroid into cholecalciferol using UV from sun

endocrine function of liver

involved in the production of at least five hormones; converts cholecalciferol into calcidiol; secretes angiotensiogen (a prohormone), a precursor of angiotensin II; secretes 15% of erythropoietin; source of IGF-I that controls action of growth hormone

Hepcidin

promotes intestinal absorption of iron

endocrine function of kidneys

play a role in production of 3 hormones: convert calcidiol to calcitriol, the active form of vitamin D, increases Ca2+ absorption by intestine and inhibits loss in the urine; secrete renin that converts angiotensinogen to angiotensin I; produces 85% of erythropoietin

Angiotensin II is created by \____

converting enzyme in lungs; constricts blood vessels and raises blood pressure

erythropoietin function

stimulates bone marrow to produce RBCs

endocrine function of the heart

atrial muscle secretes two natriuretic peptides in response to an increase in blood pressure; these decrease blood volume and blood pressure by increasing Na+ and H2O output by kidneys and oppose action of angiotensin II

stomach and small intestine secrete at least 10 \____ hormones secreted by enteroendocrine cells

enteric; coordinate digestive motility and glandular secretion; cholecystokinin, gastrin, ghrelin, and peptide YY (PYY)

adipose tissue secretes \___

leptin (slows appetite)

osseous tissue

osteocalcin secreted by osteoblasts; increases number of pancreatic beta cells, pancreatic output of insulin, and insulin sensitivity of body tissues; inhibits weight gain and onset of type 2 diabetes

placenta

secretes estrogen, progesterone, and others; regulate pregnancy, stimulate development of fetus and mammary glands