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Chapter 20: Endocrine System
Terms in this set (80)
are ductless organs that secrete hormones into the bloodstream
what other system besides the endocrine system functions to communicate signals throughout the body to bring about homeostasis?
endocrine glands produce chemical messenger molecules called?
true or false: a hormone can only affect target cells or organs (target organs) that have receptors for that specific hormone
what are the 3 chemical classes of hormones ?
chains of amino acids
-smaller chains are peptide hormones
small molecules made by altering the structure of an amino acid
type of lipid derived from cholesterol
hormone secretion is regulated by a self-adjusting mechanism called a
what are the two types of feedback loop?
negative feedback loop example
stimulus: eating food results in rising blood glucose level
-high blood glucose level is detected by insulin-secreting cells of pancreas.
-pancreas secretes the hormone insulin in response to high blood glucose levels
-insulin causes liver cells to take up glucose and store it as glycogen
-insulin stimulates other body cells to take up glucose
-as body cells take up blood glucose, glucose levels in the blood decline
-return to homeostatic blood glucose level and insulin release stops
positive feedback loop example
stimulus: Baby suckles at breast
-suckling sends impulses to hypothalamus
-hypothalamus signals posterior pituitary to release oxytocin
-oxytocin released into blood stimulates milk ejection from breast
-milk is released
-baby feeds and continues suckling, providing continued stimulus
what happens in a negative feedback?
a stimulus starts the process and a hormone causes the process to slow down or turn off
an example of negative feedback is blood glucose regulation
-eating a meal increases blood glucose
-in response, insulin is secreted
-insulin brings about a decrease in blood glucose
what happens in positive feedback ?
positive feedback accelerates the original process, ensuring it continues or speeding it up
an example of positive feedback is milk release from the mammary glands
-baby suckling stimulates oxytocin release
-oxytocin stimulates milk release
-continues suckling stimulates more oxytocin
what part of the brain is the control center of the endocrine system ?
describe the pituitary gland
located just inferior to the hypothalamus; connected by the infundibulum
housed by the sella turcica of sphenoid bone
divided into anterior and posterior pituitary
what hormones are secreted by the anterior pituitary ?
thyroid-stimulating hormone, follicle stimulating hormone, luteinizing hormone, adrenocorticotropin, growth hormone, prolactin, melanocyte-stimulating
thyroid-stimulating hormone function:
stimulates thyroid gland to release thyroid hormone
acts on mammary glands to stimulate milk production
follicle stimulating hormone and luteinizing function
act on gonads (testes and ovaries) to stimulate development of gametes(sperm and oocyte), release hormones
acts on melanocytes in the epidermis to stimulate melanin synthesis
growth hormone function
stimulates release of IGFs from the liver, which synergistically act on all body tissues ,especially cartilage, bone, muscle, and adipose connective tissue to stimulate growth hormone
adrenocorticotropic hormone function:
acts on adrenal cortex to cause release of corticosteroids
what hormones are released by the posterior pituitary ?
antidiuretic hormone and oxytocin
antidiuretic hormone function:
stimulates reabsorption of water from tubular fluid in kidneys; stimulates vasoconstriction in arterioles of body
on a female, it stimulates smooth muscle contraction in uterine wall; stimulates milk ejection from mammary glands. On a male, it stimulates contraction of smooth muscle of male reproductive tract
describe the thyroid gland
is the largest gland entirely devoted to endocrine activities
located inferior to thyroid cartilage and inferior to the trachea
what hormones are secreted from the thyroid gland?
increases metabolism, oxygen use, growth , and energy use; supports and increases rate of development
reduces calcium levels in body fluids; decreases bone resorption by osteoclasts and increases calcium loss through kidneys
describe the adrenal gland
paired adrenal glands sit on superior borders of the kidneys
each gland has an outer adrenal cortex and an inner adrenal medulla
what hormones are secreted from the adrenal cortex?
mineralocorticoids(aldosterone) from zona glomerulosa, glucocorticoids(cortisol, corticosterone) from zona fasciculata , gonadocorticoids (androgens) from zona reticularis
what hormones are secreted by the adrenal medulla?
norepinephrine and epinephrine
regulate electrolyte composition and concentration in fluids
stimulate lipid and protein metabolism; regulate blood glucose levels
protein synthesis in cells that respond to sex hormones
epinephrine and norepinephrine function
work with the sympathetic division of the ANS to stimulate fight--or-flight responses
describe the pancreas
sits between duodenum and spleen: posterior to stomach
composed mostly of pancreatic acini and contains pancreatic islets
what hormones are secreted by the pancreas?
the pancreatic islets secrete alpha cells, beta cells, delta cells, F cells
alpha cells function
secrete glucagon to raise blood glucose
beta cells function
secrete insulin to lower blood glucose
secrete somatostatin to slow release of insulin and glucagon to slow rate of nutrient absorption during digestion
F cells function
secrete pancreatic polypeptide to suppress somatostatin secretion from delta cells
what is the anterior pituitary gland also known as ?
what three areas is the anterior pituitary gland divided into?
pars distalis, pars intermedia, pars tuberalis
true/false: The anterior pituitary is controlled by regulatory hormones secreted from the hypothalamus
The hypothalamus secretes what?
hypothalamus secretes releasing hormones (RH) and inhibiting hormones (IH)
what two hormones are produced by the hypothalamus?
oxytocin and antidiuretic which are stored in and released from the posterior pituitary gland
How does the hypothalamus control the stimulation of the adrenal medulla?
By exciting the sympathetic nervous system, it stimulates adrenal gland to secrete hormones (epinephrine and norepinephrine)
where do the regulatory hormones travel through?
they travel through a blood vessel network called the hypothalamo-hypophyseal portal system
describe the hypophyseal portal system
-hypothalamus has primary plexus network drained by hypophyseal portal veins
-within anterior pituitary, the portal veins disperse into secondary plexus of capillaries (hypothalamic hormones exit blood and access anterior pituitary cells)
-blood from anterior pituitary enters systemic circulation via anterior hypophyseal veins
posterior pituitary description
is a neural part of pituitary gland
The posterior pituitary is comprised of :
pars nervosa and infundibular stalk
Neural connection between hypothalamus and posterior pituitary is the:
what cells in hypothalamus have unmyelinated axons in tract ?
when the neurosecretory cells fire impulses, what happens?
they release hormones from their terminals in posterior pituitary to bloodstream (antidiuretic hormone and oxytocin )
what is another name for antidiuretic hormone?
hypothalamic nuclei contain cell bodies of neurons that extend into posterior pituitary called?
supraoptic nucleus and paraventricular nucleus
what nucleus in hypothalamus produces oxytocin?
what nucleus in hypothalamus produces ADH?
what part of the posterior pituitary releases and stores oxytocin and ADH?
what is the thyroid composed of ?
the thyroid is composed of spherical structures called thyroid follicles containing colloid
cuboidal follicular cells produce and secrete a glycoprotein called ?
True/False: Iodine molecules are combined with TGB to make thyroid hormone precursors that are stored in colloid
when needed for secretion, follicular cells take up TGB and convert it into what hormone ?
describe the thyroid gland-pituitary gland negative feedback
-low body temperature signals hypothalamus to release thyrotropin-releasing hormone (TRH)
-THR causes anterior pituitary to release thyroid-stimulating hormone
-TSH stimulates thyroid follicular cells to release thyroid hormone
-TH stimulates many cells to increase metabolic rate, which raises body temperature
describes what happens when body temperature is increased.
-increased temperature inhibits TRH release
-TH inhibits release of TRH and TSH
what are parafollicular cells?
are large endocrine cells located between thyroid follicles
what is another name for parafollicular cells ?
what do parafollicular cells secrete?
secrete calcitonin in response to elevated blood calcium
describe parathyroid glands.
are small glands on posterior surface of thyroid gland
-usually 4 per person
Name the two types of cells in parathyroid gland
chief cells and oxyphil cells
what do chief cells secrete ?
secrete parathyroid hormone (PTH)
parathyroid hormone function
PTH raises blood calcium levels by stimulating osteoclasts (free calcium from bone); stimulating calcitriol synthesis (promotes calcium absorption from food); and preventing calcium loss through urine
What does pancreatic acini produce?
they produce alkaline secretions into ducts that lead to duodenum for digestion
describe pineal gland
is a small, cone-shaped body in posterior epithalamus
what do pinealocytes secrete?
melatonin, a hormone that makes us drowsy
what are the effects/function of melatonin?
-melatonin production increases at night to help set circadian rhythm
-melatonin also has effects on reproductive system hormones
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