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84 Cards in this Set
- Front
- Back
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Functions of thyroid gland
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Regulate tissue metabolism
Regulate tissue growth 2nd regulation of plasma Ca++ |
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Location of thyroid gland
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2nd and 3rd tracheal rings
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Origin of thyroid gland
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Downgrowth of the base of the tongue (thyroglossal duct)
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Cell type enclosing follicle of thyroid gland
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Simple cuboidal epithelial cells
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Main cell type of thyroid
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Follicular epithelial or principal cells
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Secondary cell type of thyroid
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Parafollicular or "C" cells
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Product of Parafollicular cells
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Calcitonin (regulate Ca 2+)
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Changes in thyroid epithelium due to activity
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Hyperactive = Columnar shape, colloid is reduced
Hypoactive = Squamous shape, colloid is increased |
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Product of follicular cells
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Thyroglobulin
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What is thyroglobulin?
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Glycoprotein
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Storage form of thyroid hormone
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Iodinated thyroglobulin
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Enzyme of follicular cells
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Thyroperoxidase, iodinates thyroglobulin close to microvilli of follicular cells
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Functional changes to make thyroid hormone
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Tyrosine residues added in golgi
Iodinated in lumen |
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Products in cytoplasm of follicular cells of thyroid gland
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Thyroglobulin= monoidotyrosine
di-iodotyrosine tri-iodothyronine Tetra-iodothyronine |
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Location of iodide pump?
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Basement membrane of follicular cells
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How iodine is produced?
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From oxidation of iodide
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Fate of T1, T2, T3, T4
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T3, T4 = active thyroid hormone and exocytosed out of basal surface into basket of fenestrated capillaries
T1, T2 = Deiodinated and recycled |
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How is thyroid activated?
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TSH from Basophilic thyrotrophs from anterior pituitary
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Location of TSH receptors
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Basal surface
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Responses to TSH
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Hypertrophy and hyperplasia of follicular cells
Increased production and iodination of thyroglobulin Increased re-uptake and lysosomal digestion of iodinated thyroglobulin Increased secretion of T3 and T4 |
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Monitors Plasma levels of T3/T4
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Neurosecretory neurons in the hypothalamus
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Functions of thyroid hormone
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Metabolic
Calorigenisis- increase energy production and oxygen consumption (basal metabolic rate) Regulation of water and ion transport Regulation of protein, fat, and carbohydrate metabolism Growth promoting effects Acts with Growth hormone to promote skeletal development |
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Symptoms of hypothyroid
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Mentally and physically sluggish
Low basal metabolism Mental retardation Decreased glucose absorption Weak heart beat |
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Symptoms of hyperthyroid
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Restless, irritable, anxious
Elevated basal metabolism Mentally alert Increased glucose absorbtion in GI tract Tachycardia |
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Cretinism
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Hypothyroidism
Stunting of physical and mental development |
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Myxedema
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Hypothyroidism
Lethargy Mental deficiency |
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Hashimoto's disease
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Hypothyroidism like,
Auto-immune response to thyroglobulin (destruction of follicular cells) |
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Gioter
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Enlargement of thyroid gland from hypertrophy and hyperplasia of follicular cells
Caused by Iodine deficiency Graves disease |
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Iodine deficiency
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Hyperthyroidism
Decreased T3/T4 output Increased TSH release by pituitary, follicular cell hyertrophy (parenchymatous goiter) |
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Graves disease
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Direct stimulation of follicular cells by plasma IgG (thyroid stimulating immunoglobulin)
Protrusion of the eyebolls (exopthalamos) due to build up of water in retroorbital tissues |
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Origin of parafollicular cells
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Neural crest
Amine precursor uptake and decarboxylation cell line |
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Structures shared/not shared between para/follicular cells
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Share basement membrane
Para do not touch lumen |
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Actions of calcitonin
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Decrease Ca++ through
Inhibit osteoclast activity Promoting Ca++ excretion from kidneys |
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Response of calcitonin
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Released in response to elevated plasma levels of Ca++
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Actions of Ca++
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Membrane permeability and excitability in muscles/nerves
Enzyme activity Blood clotting Receptor binding Maintenance of acid/base balance |
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Ca++ absorption
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From small intestine through vitamine D derivative 1,25 dihyroxycholecalciferol
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Hypercalcemia symptoms
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Ectopic calcification of soft tissues
Kidney stones |
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Hypocalcemia symptoms
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<9mg/100mL plasma
Hyperexcitablity of neurons Prolonged skeletal muscle contractions (tetany) Aberrant (abnormal)cardiac muscle contraction and rhytmicity |
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Origin of inferior parathyroids
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3rd pharyngeal arch descend with thymus
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Origin of superior parathyroids
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4th pharyngeal pouch descend with thyroid
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Chief cell product
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Parathyroid hormone from pro-parathyroid hormone
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Half life of parathyroid hormone
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18 min
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types of chief cells
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light = inative
dark = active PTH secreting |
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PTH effects
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Increase plasma calcium
Increase release of osteoclast stimulating factor Promote Kidney Ca++ resorption inf distal convoluted tubules Promote synthesis of 1,25 dihyroxycholecalciferol (Ca++ absorptive aid) |
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Oxyphil cells
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Parathyroid
Don't appera untill age 7 Unknown function Full of mitochondria |
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Location of most of islets
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Tail of pancreas
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cell types of pancratic islets
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Alpha, Beta, Delta, F cells, G cells?
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Alpha cells
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Located a periphery of islet
Nucleus indented Eccentrically placed electron dense core Secrete glucagon |
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Glucagon
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Raises blood glucose levels by promoting the ormation of glucose from glycogen stored in liver (glycogenolysis)
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Beta cells
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Small, most numerous cell
Center of islets Electron dense core Secrete insulin |
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Insulin
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Regulate blood glucose levels:
Promote glucose transfer from plasma to target tissues Stimulate conversion of glucose to glycogen in liver hepatocytes |
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Loss or hypo secretion of Beta cells
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Diabetes Mellitus
1) Hyperglycemia due to decrease uptake of glucose 2) Increase glucose in the urine (Glucosuria) 3) Increase water excretion (poly uria) |
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Type 1 vs. Type 2 diabetes
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Type 1 = reduced beta secretion
Type 2= Adult, defect in insulin receptors |
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Delta cells
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Larger than alpha/beta cells
Lightly electron dense secretory vesicles Secrete somatostatin |
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Somatostatin
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Neurotransmitter and a neurohormone in different tissues
1) in hypothalamus, somatostatin= inhibits growth hormone release 2) In the pancreas hromone acts in paracrine to inhibit glucagon and insulin release (secondary regulator) |
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F cells
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Pancreatic polypeptide secretors
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Pancreatic polypeptide
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Stimulate release of gastric secretion in gut
Inhibit bile secretion in the gall bladder |
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G cells
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Secret Gastrin
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Gastrin
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Increases HCL secretion in stomach
Increases gastric motility |
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A, B and D cells
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Connected by gap junctions and thus can effect each other through paracrine effects
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Regulation of glucagon and insulin
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Plasma glucose
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branches of inferior, middle, superior adrenal arteries
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Capsular arteries
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Branching of adrenal arteries
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Inferior, superior, middle adrenal arteries to
Capsular arteries to Cortical arterioles and medularry arterioles |
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Three major categories of steroid hormones of adrenal cortex and effects
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Glucocorticoids- effect carbohydrate metabolism
Mineralocorticoids- effect fluid and electrolyte balance Gonadal Steroids- similar to hormones secreted by testis |
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What controls adrenocortical hromone release?
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ACTH release from basophils in the anterior pituitary and Renin/angiotensin system
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3 layers of adrenal cortex
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Zona Glomerulosa
Zona Fasciculata Zona Reticularis |
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Cell type in zona glomerulosa
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Small pyramidal or columnar cells arranged in spherical aggregates
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Secretion of zona glomerulosa
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Aldosterone
Deoxycorticosterone |
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Action of Zona glomerulosa hormones?
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Promote resorption of Na+ from distal convoluted tubules of the kidney, sweatglands, and salivary glands
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Control of zona glomerulsosa
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Mainly renin/angiotensis system but also ACTH
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Zona fasciculata cells type
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Long radially oriented cords of secretory epithelial cells separated by capillaries
Apical cytoplasm has short microvilli that extend into the capillary sinusoids and numerous mitochondria |
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Zona fasciculata secretions
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Glucocorticoids (cortison, cortisone, corticosterone)
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Action of zone fasciculata secretions
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Down regulate immune response by inhibition of lymphocyte production and turnover
Modulation of carbohydrate metabolism by promoting the formation of glucose from protein Suppression of inflammatory response by decreasing production of T-cells and Plasma cells |
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Control of cortisol
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Negative feedback from:
Corticotrophs in the anterior pituitary (via ACTH release) Hypothalamic neurosecretory cells which release CRH |
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Zona reticularis cells
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Numerous secondary lysosomes, deeply staining nuclei, few lipid droplets evident
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Secretion of zona reticularis
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Cortisol
Steroidal androgens (continuously released) |
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Cinical siginificance of zona reticularis
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Andrenogenital syndrome
-male secondary sexual characteristics Precocious development in prepubertal males |
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Addison's Disease
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Hypo adrenalism- atrophy of adrenal cortex
Weakness and drowsiness due to low blood glucose (glucocorticoids) Increase ACTH secretion decreased blood pressure due to decreased extracellular fluid volume (minarlocorticoids) Decreased absorption of Na+ and Cl- ions in kidneys Darkening of exposed skin Low BP |
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Cushings disease
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Hyperadrenalism
-Can result from excessive synthetic glucocorticoid use -Redistribution of fat around the neck, face (moon face) and abdomen -Wasting of limb musculature and thinning of bones due to antianabolic effects of glucocorticoids on protein synthesis -Thining of skin and loss of fat causes redskin due to blood vessels shwoing through -Hyperglycemia |
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Origin of chromaffin cells
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From sympathetic ganglion cells of the celiac plexus that migrate into the adrenal cortex
(neurons that have lost axonal and dendritic processes and function as secretory cells) |
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2 types of catecholamine secreting cells and location
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Round, moderately electron dense granules that fill vesicles, they tend to cluster around the adrenal sinusoids (distant from BV)
Norepinephrine secreting cells- Flattened or ovoid granules with eccentrically located high electron dense core surrounded by a less electron dense ring, tend to cluster around the adrenal arteriols and away from sinusoids |
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Chemical difference between norepinephrine and epinephrine
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1 methyl group
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epinephrine to norepinephrine transformation
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Glucocorticoid induced
Cells closest to sinusoids are bathed in glucocorticoids from adrenal cortex. |
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Catecholamine function
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Respond to environmental and emotional stresses
Elevate plasma glucose levels (stimulate glycogenolysis) Increase BP and cardiac output Dilation of coronary and skeletal muscle blood vessels Cutaneous vasoconstriction |
