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Definition of a hormone
chemical substance synthesized and secreted by a specific organ or tissue
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Characteristics of hormones
- -secreted in small amounts at variable but predictable rates
- -circulated through blood
- -bind to specific receptors on/inside cell
- -lipid-soluble or water-soluble
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Which hormones are lipid-soluble?
- Steroid hormones (all hormones produced by the adrenal cortex and sex glands)
- Thyroid hormones
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Which hormones are water soluble?
Protein-based hormones
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What are the common functions of hormones?
- reproduction
- response to stress and injury
- electrolyte balance
- energy metabolism
- growth
- maturation
- aging
- nervous system function
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How do hormones function in the nervous system?
- Regulatory effect on nervous tissue
- can function as hormones OR neurotransmitters
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What gland secretes Growth Hormone?
Anterior Pituitary (Adenohypophysis)
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What is the function and target of Growth Hormone?
- Target: all body cells
- Function: promotes protein anabolism (growth, tissue repair) and lipid mobilization and catabolism (breakdown)
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What gland secretes Thyroid-stimulating hormone (TSH or thyrotropin)?
Anterior Pituitary (Adenohypophysis)
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What is the target and function of TSH?
- Target: thyroid
- Function: stimulates synthesis and release of thyroid hormones, growth and function of thyroid gland
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What gland secretes Adrenocorticotropic hormone (ACTH)?
Anterior Pituitary (Adenohypophysis)
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What is the target and function of Adrenocorticotropic hormone (ACTH)?
- Target: adrenal cortex
- Function: fosters growth of adrenal cortex; stimulates secretion of corticosteroids
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What gland secretes Gonadotropic hormones (Follicle-stimulating and Luteinizing hormones)?
Anterior Pituitary (Adenohypophysis)
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What is the target and function of the gonadotropic hormones (FSH and LH)?
- Target: reproductive system
- Function: stimulate sex hormone secretion; reproductive organ growth, reproduction processes
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What gland secretes melanocyte-stimulating hormone (MSH)?
Anterior Pituitary (Adenohypophysis)
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What is the target and function of melanocyte stimulating hormone (MSH)?
- Target: melanocytes in skin
- Function: increases melanin production and melanocytes to make skin darker in color
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What gland secretes Prolactin?
Anterior Pituitary (Adenohypophysis)
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What is the target and function of Prolactin?
- Target: ovary and mammary glands
- Function: stimulates milk production in lactating women; increases response of follicles to LH and FSH; unclear function in men
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What gland secretes Oxytocin?
Posterior Pituitary (Neurohypophysis)
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What is the target and function of oxytocin?
- Target: uterus and mammary glands
- Function: stimulates milk secretion; uterine contractility
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What gland secretes Antidiuretic hormone (ADH)?
Posterior Pituitary (Neurohypophysis)
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What is the target and function of ADH?
- Target: renal tubules, vascular smooth muscle
- Function: promotes reabsorption of water, vasoconstriction
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What gland secretes Thyroxine (T4)?
Thyroid
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What is the target and function of thyroxine (T4)?
- Target: all body tissues
- Function: precursor to T3
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What gland secretes Triiodothyronine (T3)?
Thyroid
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What is the target and function of T3?
- Target: all body tissues
- Function: regulates metabolic rate of all cells and processes of cell growth and tissue differentiation
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What gland secretes calcitonin?
Thyroid
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What is the target and function of calcitonin?
- Target: bone tissue
- Function: regulates calcium and phosphorus blod levels; decreases serum Calcium levels
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What gland secretes Parathyroid hormone?
Parathyroid
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What is the target and function of PTH (Parathyroid hormone)?
- Target: bone, intestines, kidneys
- Function: regulates calcium and phosphorus blood levels, promotes bone demineralization and increases intestinal absorption of calcium, increases serum calcium levels
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What gland secretes Epinephrine (adrenaline)?
Adrenal Medulla
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What is the target and function of Epinephrine (adrenaline)?
- Target: sympathetic effectors
- Function: response to stress; enhances and prolongs effect of SNS
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What gland secretes norepinephrine?
Adrenal Medulla
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What is the target and function of norepinephrine?
- Target: sympathetic effectors
- Function: response to stress; enhances and prolongs effects of SNS
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What gland secretes Corticosteroids (cortisol, hydrocortisone)?
Adrenal Cortex
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What is the target and function of corticosteroids?
- Target: all body tissues
- Function: promotes metabolism; response to stress
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What gland secretes androgens (testosterone, androsterone) and estrogen?
Adrenal Cortex
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What is the target and function of androgens and estrogen?
- Target: reproductive organs
- Function: masculinization in men; growth and sexual activity in women
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What gland secretes mineralocorticoids (aldosterone)?
Adrenal Cortex
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What is the target and function of mineralocorticoids?
- Target: kidneys
- Function: regulates Potassium and Sodium balance and thus water balance
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What secretes insulin?
Beta cells of pancreas
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What is the target and function of insulin?
- Target: general
- Function: promotes movement of glucose out of blood and into cells
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What secretes glucagon?
Alpha cells of pancreas
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What is the target and function of glucagon?
- Target: general
- Function: promotes movement of glucose from glycogen (glycogenolysis) and into blood
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What secretes Somatostatin?
Pancreas
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What is the target and function of somatostatin?
- Target: pancreas
- Function: inhibits insulin and glucagon secretion
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What secretes pancreatic polypeptide?
Pancreas
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What is the target and function of pancreatic polypeptide?
- Target: general
- Function: influences regulation of pancreatic exocrine function and metabolism of absorbed nutrients
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What secretes estrogen?
ovaries
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What is the target and function of estrogen?
- Target: reproductive system, breasts
- Function: stimulates development of secondary sex characteristics, preparation of uterus for fertilization and fetal development; stimulates bone growth
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What secretes progesterone?
Ovaries
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What is the target and function of progesterone?
- Target: reproductive system
- Function: maintains lining of uterus necessary for successful pregnancy
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What secretes testosterone?
Testes
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What is the target and function of testosterone?
- Target: reproductive system
- Function: stimulates development of secondary sex characteristics; spermatogenesis
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What are the characteristics and roles of hormone receptors?
- located within cells of target tissues
- specificity of hormone-target interation is determined by receptors in a "lock and key" type of mechanism
- hormone only acts on cells that have receptors specific to that hormone
- location of receptor sites affect the hormones mechanism of action
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Where are steroid hormone receptors located?
inside the cell
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What happens once lipid-soluble (steroid and thyroid) hormones enter into the cell?
They diffuse through the membrane and bind to receptor sites in the cytoplasm or nucleus. The complexes bind to DNA to stimulate or inhibit synthesis of mRNA. This can stimulate the synthesis of a new protein which has specific effects on the target cell.
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Where are protein hormone receptors located?
target cell membrane
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Which hormone-receptor complex is a two step process?
Protein
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What occurs when protein hormones activate receptors on the cell membrane?
The interaction stimulates the production of a second messenger which activates enzymes to regulate intracellular activity
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Which feedback system involves communication via hormones among several glands to turn on or turn off target organ hormone secretion?
complex feedback
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Which feedback system involves a gland that responds to a stimulus by increasing or decreasing the secretion of a hormone based on feedback from various factors?
Negative feedback
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What feedback system increases target organ action beyond normal?
Positive feedback
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What sort of stimuli cause the nervous system to modulate hormone secretion?
Pain, emotion, sexual excitement, and stress
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Neural involvement is initiated by the CNS and implemented by the ______
Sympathetic nervous system
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What is an example of neural involvement in the endocrine system?
Stress is sensed by CNS, the SNS secretes catecholamines that increase BP and HR to deal w/stress more effectively
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Oxytosin release causes an increase in uterine contractions. The pressure sensors in the vagina then stimulate more oxytocin to be released which causes stronger contractions. What feedback is this an example of?
Positive feedback
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Example of negative feedback
Increased blood glucose stimulates insulin secreation which decreases blood glucose, then the stimulation decreases.
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Example of complex feedback
regulation of thyroid hormones - synthesis and release of TSH from anterior pituitary is stimulated by thyrotropin-releasing hormone (TRH) which is secreted by the hypothalamus, T3 and T4 have an inhibitory effect on secretion of TRH and TSH
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What is the effect of aging on the thyroid gland?
Atrophy of the thyroid gland, TSH and T3 secretion is decreased
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What is the effect of aging on the parathyroid glands?
Increased basal level of PTH and increased secretion
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What are the effects of aging on the adrenal cortex?
- Adrenal cortex becoms more fibrotic and slightly smaller
- higher plasma levels of cortisol
- decreased plasma levels of adrenal androgens and aldosterone
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What are some effects of aging on the adrenal medulla?
- increased secretion and basal level of norepinephrine; no change in plasma epinephrine levels with aging
- decreased beta adrenergic receptor response to norepinephrine
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What are the effects of aging on the pancreas?
- Increase in fibrosis and fatty deposits in pancreas
- Increased glucose intolerance and decreased sensitivity to insulin
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What is the purpose of an MRI for evaluating the pituitary gland?
Identifies tumors involving the hypothalamus or pituitary
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What is the purpose of a TSH test?
measures levels for TSH. considered the most sensitive method fro evaluating thyroid disease. generally recommended as first diagnostic test for thyroid dysfunction
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What is the purpose of a Thyroxine (T4) total?
Measures total serum level of T4, useful in evaluating thyroid function and monitoring thyroid therapy.
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What is the purpose of measuring T3?
Measures serum levels of T3, helpful in diagnosing hyperthyroidism if T4 levels are normal
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What is the purpose of measuring readioactive iodoine uptake?
provides direct mesure of thyroid activity. useful for evaluation of functional activity of solitary thyroid nodules
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How is the procedure done for radioactive iodine uptake (RAIU)
Patient is given radioactive iodine either orally or IV, the uptake by the thyroid gland is measured with a scanner at several time intervals such as 2-4 hours and at 24 hours
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What is the purpose of measuring total serum calcium?
Helps detect bone and parathyroid disorders. Hypercalcemia = hyperparathyroidism. Hypocalcemia = hypoparathyroidism.
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What is the purpose of a thyroid scan?
Used to evaluate nodules of the thyroid. Radioactive isotopes are given orally or IV. Scanner passes over thyroid and makes graphic record of radiation emitted. Malignant tumors appear as cold spots because they tend not to toake up the radionuclide
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What is the purpose of measuring serum phosphate?
Measures inorganic phosphorus. Hyperphosphatemia =hypoparathyroidism. Hypophosphatemia = hyperparathyroidism
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What is the purpose of measuring cortisol levels?
evaluates status of adrenal cortex function
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What is the purpose of measuiring 17-ketosteroids?
It measures androgen metabolites in urine and evaluates adronocortical and gonadal function
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What is the purpose of measuring vanillylmandelic acid?
measures urinary excretion of catecholamine metabolite and is helpful in diagnosing pheochromocytoma
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What is the purpose of measuring ketones?
Measures amount of acetone excreted in urine as a result of incomplete fat metabolism. Normal value is negative or trace ketone. Positive result can indicate lack of insulin and diabetic acidosis
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