51 terms

ZOO 331 Endocrine System Chapter 16

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endocrine systems
acts with the nervous system to coordinate activity of body cells
influences metabolic activities by means of hormones transported in the blood
important endocrine glands
pituitary, thyroid, parathyroid, adrenal, pineal
endocrine tissue plus
pancreas, gonads
neuroendocrine organ
hypothalamus
hormones
chemical messengers released into the bloodstream and elicit a target cell effect
endocrine glands
no ducts, release hormones through diffusion
causes of hormonal release
humoral stimuli, neural stimuli, hormonal stimuli
humoral stimuli
secretion of hormones in response to changing blood levels of critical issues (ions, nutrients)
parathyroid gland respond to humoral stimulus of low calcium in the blood (called PTH)
neural stimuli
nerve fibers stimulate hormone release
adrenal medulla (inner layer)
gland that releases epinephrine and norepinephrine and secretes catecholamines
hormonal stimuli
release of hormones in response to hormones from other endocrine glands
multistep hormonal release
steroid hormones
synthesized from cholesterol, 4 hydrocarbon rings
gonadal and adrenocortical hormones
lipid soluble and can cross plasma membrane
(cholesterol, progesterone, testosterone, cortisol, aldosterone, estradiol)
amino acid based hormones
amine(one single amino acid)
peptide(several aminoacids)
protein(chain of amino acids)
not lipid soluble and cannot cross plasma membrane
(thyroxine, ephinephrine)
water soluble hormones
all amino acid based hormones except thyroid hormone, cannot enter target cells, act on plasma membrane receptors
lipid soluble hormones
steroid and thryoid hormones, act on intracellular receptors inside the cell
Epinephrine mechanism steps (water soluble)
1. hormone binds to receptor
2. receptor activates G protein
3. G protein activates adenylate cyclase
4. Adenylate cyclase convert ATP to cAMP
5. cAMP activates protein kinases which trigger responses of target cell
1 molecule>100cAMP>1 million product molecules
target cell must have specific receptors to which the hormone binds
epinephrine>glucose release
lipid soluble hormone mechanism steps
1. steroid hormones diffuses through the plasma membrane and binds to an intracellular receptor
2. the receptor hormone complex enters the nucleus
3. the receptor hormone complex binds a hormone response element (a specific DNA sequence)
4. Binding initiates transcription of the gene to mRNA
5. The mRNA directs protein synthesis
How do hormones affect target cells?
1. change plasma membrane permeability or membrane potential
2. stimulate synthesis of proteins
3. Activate or deactivate enzyme systems
4. Induce secretory activity
5. Stimulate mitosis>progesterone acting on uterine lining
anterior pituitary gland
an up growth from the back of the mouth (Rathke's pouch) (adenohypophysis)
posterior pituitary gland
a down growth from the brain (neurohypophysis)
oxytocin release process
1. Hypothalamic neurons synthesize oxytocin and ADH
2. Oxytocin and ADH are transported along the hypothalamic-hypophyseal tract to the posterior pituitary gland
3. Oxytocin and ADH are stored in axon terminals in the posterior pituitary
4. Oxytocin and ADH are released into the blood when hyopthalamic neurons fire
Thyroid stimulating hormone (TSH)
anterior pituitary hormone that stimulates the thyroid gland to release thyroid hormones
prolactin (PRL)
anterior pituitary hormone that promotes lactation in breast secretory tissue
adrenocorticotropic hormone (ACTH)
anterior pituitary hormone that promotes release of glucocorticoids and androgens in the adrenal cortex
growth hormone (GH)
anterior pituitary hormone that stimulates liver, muscle, bone, cartilage and other tissues, anabolic hormone, stimulates somatic growth, mobilizes fats, spares glucose
growth promoting effects
follicle stimulating hormone (FSH) and luteinizing hormone (LH)
anterior pituitary hormone that stimulates ovarian follicle maturation, estrogen production, and sperm production
melanocyte stimulating hormone (MSH)
anterior pituitary hormone that stimulate the release of melanin in the skin and hair
anterior pituitary process
1. When appropriately stimulated, hypothalamix neurons secrete releasing and inhibiting hormones into the primary capillary plexus
2. Hypothalamic hormones travel through the portal veins to the anterior pituitary where they stimulate or inhibit release of hormones from the anterior pituitary
3. Anterior pituitary hormones are secreted into the secondary capillary plexus
oxytocin
a posterior pituitary hormone that stimulates labor contractions in the uterus and initiates milk ejection
antidiuretic hormone (ADH)
posterior pituitary hormone that stimulates kidney tubule cells to reabsorb water (limits water loss/gain)
pineal gland
produces melatonin, productions increases at night and decreases during the day (circadian rhythm)
thyroid
located in front of the trachea, hormones regulate metabolism
calcitonin
Decreases blood calcium levels by inhibiting osteoclasts, released by parafollicular cells in the thyroid gland
osteoclasts
A type of bone cell that removes bone tissue
hyperthyroid
jittery, losing weight, thin, increased metabolism
hypothyroid
tired, gained weight, slow metabolism
thyroid gland
follicles produce thyroglobulin
colloid fills lumen of follicles and is precursor of thyroid hormone
lumen
Central cavity of a tubular of hollow structure in an organism or cell (follicles and blood vessels)
parafollicular cells
produce the hormone calcitonin
Synthesis of thyroid hormone
1. thyroglobulin is synthesized and discharged into the follicle lumen
2. iodide is trapped (actively transported in)
3. iodide is oxidized to iodine
4. iodine is attached to tyrosine in colloid, forming DIT and MIT
5. iodinated tyrosines are linked together to form T3 and T4
6. thyroglobulin colloid is endocytosed and combined with a lysosome
7.Lysosomal enzymes cleave T4 and T3 from thyroglobulin and hormones diffuse into the bloodstrea
thyroid hormone
major metabolic hormone-increase basal metabolic rate (BMR), promotes glucose catabolism
regulation of tissue growth and development
maintenance of blood pressure
inhibits the hypothalamus and anterior pituitary
goiter
enlarged thyroid due to a lack of iodine
colloid produced but cannot make thyroid hormone due to a lack of iodine, the colloid continues to come in, swelling the thyroid
grave's disease
most common form of hypersecretion of thyroid hormone
parathyroid
increases calcium in the blood
not under control of the pituitary gland
adrenal cortex
releases corticosteroids which include
mineralocorticoids (aldosterone)
glucocorticoid (cortisol)
gonadocorticoids (sex hormones)
adrenal medulla
releases epinephrine (80%) norepinephrine(20%)
pancreas
pancreatic islets (islets of Langerhans) contain endocrine cells
-alpha cells produce glucagon, gram negative > pink
-beta cells produce insulin, gram positive>blue
glucagon
A hormone secreted by the pancreatic alpha cells that increases blood glucose concentration
major target is the liver
insulin
lowers blood glucose levels
enhances membrane transport of glucose into fat and muscle cells and liver
inhibits glycogenolysis and gluconeogenesis
promotes glycogen storage in liver and muscle
glycogenolysis
breakdown of glycogen to glucose
gluconeogenesis
synthesis of glucose, released into the blood