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133 Cards in this Set

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Why is communication vital for any multicellular oranism? (4 reasons)
Maintain homeostasis; coordinate growth and development; adapt to internal and external stresses; contribute to the processes of sexual reproduction
Two communication systems
nervous and endocrine
Where is interaction between the nervous and endocrine system coordinated?
hypothalamus
Neuroendocrine signaling mechanism
neuron releases a chemical mediator not into a synapse but into one or both of the vascular systems. The mediator then affects a cell at some distance.
What type of vasculature is typical for the endocrine system?
fenestrated and sinusoidal blood capillaries
CT of fibrous capsule around endocrine glands
dense irregular connective tissue (type I collagen)
4 parenchymal arrangements of endocrine system
unicellular, cords, follicular pattern, multipolar neurons
what do steroid secreting glands store?
the hormone precursor cholesterol
pro-opiomelanocortin (POMC)
a prohormone made in several tissues in the body including the brain and pituitary that is broken down into ACTH
positive feedback system (loop)
the response enhances or intensifies the original stimulus
Are most feedback systems in the body positive or negative?
negative
examples of negative feedback loops
blood pressure, body temperature and blood glucose level
examples of positive feedback loops
blood clotting, labor contractions during childbirth and immune response that provide defence against pathogens
What is the source of hormones that are derivatives of tyrosine?
adrenal medulla, thyroid gland, and pineal gland
What is the source of small peptide hormones?
posterior pituitary, heart atria
What is the source of small protein hormones?
pancreas, anterior pituitary and parathyroid glands
What is the source of steroid hormones
adrenal cortex, ovaries and testes
What are examples of Eicosanoid hormones? And what is the source of them?
prostaglandins and leukotrienes; all cells except red blood cells
What does binding to plasma proteins do to circulating hormones?
makes them inactive
Endocrine organs
pineal, brain, ituitary, thyroid, parathyroid, thymus, adrenal gland, islets of langerhans of pancreas, parts of the ovary, testis, kidney, placenta, and heart
2 parts of the pituitary gland
neurohypophysis and adenohypophysis
2 parts of the neurohypophysis
pars nervosa and infundibulum (w/ infundibular stem and median eminence)
3 parts of the adenohypophysis
pars distalis, pars intermedia, and pars tuberalis
What is the embryological origin of the pituitary gland?
neural ectoderm (neurohypophysis) and ectoderm lining the oral cavity (adenohypophysis)
Two main parencymal cell types of the pars distalis of the pituitary gland
chromophobes and cormophils
Chromophobes
degranulated chromophil that is a parenchymal cell of the pars distalis of the pituitary gland (adenohypophysis) that is found in clusters away from the capillaries
chromophils
granulated hormone secreting cells of the adenohypophysis that are either acidophils or basophils
What do the acidophil type of chromophils secrete?
growth hormone and prolactin
What do the basophil type of chromophils secrete?
FSH, LH, TSH and ACTH
what is the purpose of the hypophyseal portal system
transport hormones from the hypothalamus to the adenohypophysis
2 types of small peptide hormones synthesized in the neuron cell bodies of the hypothalamic nuclei:
Releasing hormones and inhibiting hormones
GnRH
small peptide releasing hormone of the hypothalamic nuclei that stimulates gonadotrophs to release FSH and LH
CRH
small peptide releasing hormone of the hypothalamic nuclei that stimulates corticotrophs to release ACTH
TRH
small peptide releasing hormone of the hypothalamic nuclei that stimulates thyrotrophs to release TSH
GHRH (somatotropin)
small peptide releasing hormone of the hypothalamic nuclei that stimulates somatotrophs to release GH
Somatostatin
small peptide inhibiting hormone of the hypothalamic nuclei that inhibits growth hormone release from somatotrophs; inhibits gastrin release and is produced by δ cells of the pancreatic islets
Dopamin
small peptide inhibiting hormone of the hypothalamic nuclei that inhibits prolactin release from mammotrophs
Pars intermedia
thin layer of cells and colloid cyts next to the neural lobe of the pituitary. This region atrophies in adults
Pars nervosa
nervous tissue down-growth of the hypothalamus that makes up the posterior lobe of the pituitary gland and connects to the infundibulum. Consists of modified multipolor neurons with unmyelinated axons
What do the unmyelinated axons of the hypothalamohypophyseal tract contain
large granule-filled dilations called herring bodis along their length
What do the granules of herring bodies contain?
either oxytocin or ADH, ATP and neurophisins
function of neurophysins
low-affinity carriers for the hormones as they travel down the axon to the nerve terminal
Pituitcytes
higly branched astrocytes whose processes surround and support the axons of the hypothalamo-hypophyseal tract
Oxytocin
small peptide hormone of the posterior pituitary that stimulates milk ejection by the mammary glands and stimulates uterine smooth muscle contraction during copulation and childbirth
arginine vasopressin (AVP) or antidiuretic hormone (ADH)
small peptide hormone of the posterior pituitary that stimulates water resorption by the renal medulalary collecting duct. Regulated by the supraoptic nucleus
APUD cells or the diffuse neuroendocrine system cells
unicellular glands scattered among epithelial cells derived from neural crest that are polypeptide secreting with concentrated bioactive amines in secretory granules in their bases
DNES polypeptides mechanism of signalling
paracrine and endocrine
gastrin
digestive hormone that promotes secretion of gastric juice, increases gastric motility and promotes growth of gastric mucosa
secretin
digestive hormone that stimulates secretion of pancreatic juice and bil
cholecystokinin
digestive hormone that stimulates secretion of pancreatic juice rich in digestive enzymes and causes opening of sphincter of oddi which ejects bile from the gall bladder
Embryological origin of thyroid gland
endoderm
2 cell types of thyroid gland
follicular cells and parafollicular cells
What fills the lumen of the follicle of the thyroid gland?
colloid (mainly consists of the glycoprotein thyroglobulin)
What is functional activity of follicular cells stimulated by?
TSH from the anterior pituitary and by sympathetic nerves
when is TSH increased?
low environmental temperatures, puberty and pregnancy
when is TSH decreased?
emotional stress and systemic stress
What stimulates iodide uptake by follicular cells?
TSH
When endosomes combine with lysosomes in follicular cells, what is iodothyroglobulin broken down into?
2 hormones, T3 and T4.
Function of T3 and T4
increase basal metabolic rate (the rate at which cells use glucose), promote cell growth, increase HR, raise body temp, and enhance all energy-requiring cell functions
parafollicular cells
APUD cells of the thyroid gland that are derived from neural crest and secrete the peptide hormone colcitonin in response to high blood Ca
Calcitonin
peptide hormone secreted by parafollicular cells of the thyroid gland that inhibits bne resoprption by inhibiting osteoclasts and threby lowering blood calcium.
What is the embryological origin of the parathyroid glands?
endoderm of the 3rd and 4th pharyngeal pouches
2 cell types of the parathyroid gland
chief cells and oxyphil cells
What is the vasculature of the parathyroid glands
broad, irregular fenestrated capillaries channel the parenchymal cells
Chif Cells
most abundant parenchymal cells of the parathyroid glands that secrete parathyroid hormone
parathyroid hormone
peptide hormone that increases blood calcium by acting on bone, in kidneys and in the intestines
What causes activation of a vitamin D precursor in the kidney?
parathyroid hormone
Oxyphil cells
large parencymal cells of the parathyroid gland with many mitochondria and an unknown function
What shape are the adrenal glands?
Right: pyramid; Left: crescent shaped
Embryological origin of cortex of the adrenal gland
mesoderm
what does the cortex of the adrenal gland secrete?
3 classes of ssteroid hormones: mineralocorticoids, glucocorticoids and androgens
What are the 3 zones of the cortex and their primary secretion?
zona glomerulosa (mineralocorticoid: aldosterone); fasciculata (glucocorticoids); zona reticularis (androgens and glucocorticoids)
function of mineralocorticoids
osmotic balance and blood pressure regulation by affecting the function of renal tubules
Atrial natriuretic peptide
hormone released by the atrial cells of the heart in response to high BP and inhibits aldosterone release from the zona glomerulosa.
what is the vasculature of the zona fasciculata of the adrenal glands?
sinusoidal capillaries run between cords
Spongiocytes
cells in the zona fasciculata arranged in cords with large lipid droplets in their cytoplasm
What stimulates the secretion of glucocorticoids to raise BP?
ACTH from the anterior pituitary stimulates the zona fasciculata and zona reticularis
2 types of cells in the medulla of the adrenal glands
chromaffin and ganglion cells
Chromaffin cells
parenchymal cells of the medulla of the adrenal glands that are modified postganglionic sympathetic neurons that release epinephrine and norepinephrine
function of epinephrine
increases blood glucose, alertness, cardiac output and HR
function of norepinephrine
increases blood pressure by vasoconstriction
What is the physiological role of the fetal adrenal in the fetal life?
oto synthesize estrogen precursors which are converted in the placenta to estrogens.
What is the endocrine component of the pancreas called
islets of Langerhans
What is the embryological origin of the islets of langerhans?
endoderm and part of the DNES
β cells
parenchymal cells of the islets of langerhans that are concentrated in the center. They produce insulin in response to high blood glucose
α cells
parencymal cells that are in the periphery of the islets of langerhans and produce glucagon in response to low blood glucose
δ cells
parenchymal cells in the islets of langerhans that produce somatostatin to inhibit α cells and β cells.
F cells (or PP cells)
parenchymal cells located in the periphery of the islets of langerhan that produces pancreatic polypeptide that inhibit pancreatic exocrine secretion of enzymes and bicarbonate
What is the embryological origin of the pineal gland?
ectoderm
2 cell types of pineal gland
pinealocytes and astrocytes
What is the secretion of pinealocytes?
serotonin during the day and melatonin at night
What are circadian rhythms controlled by?
periodic release of NE by postganglionic sympathetic fibers which in turn is controlled by light perceived by the retina.
What is the primary site of action for melatonin?
hypothalamus
Melatonin's functions:
immune response, tep regulation, and possibly aging and senescence
What is the primary target for FSH?
testes
What does diabetes insipidus result from?
hyposecretion of ADH
What is responsible for regulating hormone release and function throughout the body?
the neuroendocrine system (hypothalamus, pituitary and adrenal gland)
Two mechanisms for inactivating hormones
removal of receptor area, inactivate hormone by enzyme
3 types of dysfunction that diseasaes associated with hormone defects cause:
overproduction (from tumor formation?), underproduction, or target cell insensitivity
None
Which glands produce peptide hormones?
anterior pituitary, posterior pituitary, hypothalamus and pancreas
Where is ACTH produced and what does it do?
anterior pituitary; stimulates synthesis and secretion of adrenal cortical hormones (cortisol, androgens, and aldosterone)
Where is prolactin produced and what does it do?
anterior pituitary; stimulates milk production and secretion in breast
Where is growth hormone produced and what does it do?
anterior pituitary; stimulates protein synthesis and overall growth
Where is Luteinizing hormone (LH) produced and what does it do?
anterior pituitary; stimulates testosterone synthesis, and ovulation, formation of corpus luteum, estrogen and progesterone synthesis in ovaries
Where is Follicle stimulating hormone (FSH) produced and what does it do?
anterior pituitary; stimulates sperm maturation of testes and follicular development and estrogen synthesis in ovaries
Where is thyroid stimulating hormone (TSH) produced and what does it do?
anterior pituitary; stimulates synthesis and secretion of thyroid hormones
Where is oxytocin produced and what does it do?
posterior pituitary; stimulates milk ejection from breasts and uterine contractions
Where is AVP or ADH produced and what does it do?
posterior pituitary; stimulates water reabsorption in principal cells of collecting ducts and constriction of arterioles
Where is calcitonin produced and what does it do?
thyroid (parafollicular cells); decreases serum Ca2+
What does PTH do?
parathyroid hormone increases serum Ca2+
Where is insulin produced and what does it do?
β cells of pancreas; decreases blood glucose
Where is glucagon produced and what does it do?
α cells of pancreas; increases blood glucose
Where is renin produced and what does it do?
kidney; catalyzes conversion of angionesinogen to angiotensin I
What does a pre-prohormone contain at it's N-terminus and why?
a 15-25 residue signal sequence of mostly hydrophobic aa that allows entry of the pre-prohormone into the ER
How are peptide hormones received by cells?
receptor mediated endocytosis and then hormone and receptor are degraded by lysosomal proteases
What does POMC become?
ACTH
How are peptide hormones released?
by the regulated secretory pathway; requires stimulus (releasing hormone that causes depolarization of PM, then an influx of Ca2+ for the release of hormone)
What are prohormones packaged in?
immature secretory granules (IMG)
How is ACTH inhibitted (and where)
feedback inhibition by cortisol (anterior pituitary, hypothalamus) and negative inhibition by dopamine (anterior pituitary)
Cushing's syndrome
a peptide hormone disease that is an adenoma of the adrenal cortex that releases excess cortisol
Cushing's disease
pituitary-acth secreting tumors, most common form of cushings syndrome
what are the 4 types of diabetes insipidus?
nephrogenic, gestational, dipsogenic, and neurogenic (most common)
what is diabetes insipidus characterized by?
polyuria and polydipsia,
What does iodination of tyrosine residues in thyroglobulin produce?
monoiodoyrosine (MIT) and diiodotyrosine (DIT)
Is T3 or T4 more active?
T3
Where are MIT and DIT synthesized? And by what?
the follicular cells of the thyroid gland, by the enzyme thyroidal peroxidase
How are MIT and DIT stored?
thyroglobulin
Where is thyroglobulin iodinated?
colloid space of follicular cells
What is the major site of degradation of T4 and T3?
liver
Exophthalmos
protruding eyes, caused by hyperthyroidism
None
What are the symptoms of hypothyroidism?
lowered basal metabolic rate, diastolic hypertension, and goiter
levothyroxine
treatment for hypothyroidism
what is the cause of hyperthyroidism
autoimmune. There are antibodies to TSH receptors