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Hypothalamus control pituitary secretion via releasing these 4 hormones
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Thyroid hormones require what for synthesis?
Iodine
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T3 & T4 stimulate transcription of:
numerous genes
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What is the major form of thyroid hormone used for transport in the blood?
T4
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What is the most potent form of thyroid hormone?
T3
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How do you get goiters?
Lack of iodine. Results in high levels of TSH and constant stimulation of thyroid gland
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What disease can cause goiters?
Graves' disease
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What are some actions of thyroid hormone?
- Increased oxygen consumption which ups BMR
- Stimulates glucose absorption in GI tract
- Stimulates lipolysis and proteolysis
- Stimulates muscle uptake/use of glycogen
- Increased CO
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_______ is required for normal growth to adult stature
TH
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How does TH promote normal growth?
- Promotes bone formation
- Promote ossification, bone maturation, fusion of epiphyseal plates
- Necessary for prenatal CNS development
- Increases GI motility
- Maintains sexual function
- Promotes growth of cartilage, teeth, hair, nails, and epidermis
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What are some other stimuli of TRH-TSH-TH?
- Exposure to cold
- Excitement
- Anxiety
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Increased levels of TH create negative feedback for what hormones?
TSH and TRH
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What releases growth hormone?
Pituitary gland
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How is GH released?
pulsatile with secretory bursts every 2 hours
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How does GH act?
Directly on target tissues or stimulates liver production of somatomedins (IGF-1)
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What are some conditions that stimulate secretion of GH?
- Starvation/fasting
- Trauma
- Puberty hormones
- Exercise
- Excitement
- Deep sleep
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What are some inhibitors of GH?
- Negative feedback on hypothalamus
- Somatostatin
- Somatomedin
- Increased levels of blood glucose and fatty acids
- Obesity
- Aging
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Somatomedin has a feedback loop on:
Hypothalamus and pituitary
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GH has multiple metabolic affects on:
Muscle, liver, adipose tissue, and bone
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What are the general actions of GH?
- Linear growth
- Protein synthesis
- Organ growth
- Carbohydrate and lipid metabolism
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What is the Diabetogenic effect?
- Increases insulin resistance
- Reduces glucose uptake and utilization
- Increases lipolysis in adipose tissue
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What happens when growth hormone increases protein synthesis?
- Stimulates increased protein and nucleic acid synthesis
- Promotes tissue growth
- Increased lean body mass, increased organ size
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What are the two sections of the adrenal gland?
- Adrenal medulla
- Adrenal cortex
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What does the adrenal medulla release?
Releases catecholamines
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What does the renal cortex release?
Corticosteroids
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What are the three zones of the adrenal gland?
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
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What is the Zona Glomerulosa?
- Outer most layer
- secretes mainly aldosterone
- controlled by angiotensin II and extracellular fluid volume
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What is the Zona Fasciculata?
- Secretes gluccocorticoids
- Controlled by ACTH (pituitary) and CRH (hypothalamus)
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What is the Zona Reticularis
- Secretes androgens
- Controlled by ACTH (pituitary) and CRH (hypothalamus)
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The adrenal medulla is under direct neural control of what?
Sympathetic nervous system as part of the "fight or flight" response
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What causes cortisol secretion?
- Trauma, infection, debilitating dieases
- Intense heat/cold, surgery, full restraint
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What are some actions of cortisol?
- Increases gluconeogenesis and glycogen storage in the liver
- Increases mobilization of fats from adipose
- Reduces inflammatory processes; speeds resolution of inflammation
- Maintains vascular responsiveness to EPI and NOREPI
- Inihibits bone formation
- Increases GFR
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What are some cortisol actions on sleep?
- Decreases REM sleep, increases slow wave sleep
- Increases wake time (burst of release just prior to waking up)
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Aldosterone is the major ________
mineralcorticoid
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What is aldosterone released in response to?
low ECF, low BP mainly due to renin-angiotensin II system and serum K+
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How does Aldosterone affect ECF and BP?
Enhances sodium reabsorption in GI tract and from sweat and saliva
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What controls release of aldosterone?
Hypothalamic-pituitary axis
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Where are androgens secreted?
Zona Reticularis
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What androgens important for in females?
Axillary and pubic hair and for libido
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What regulates blood calcium and phosphate levels?
PTH and calcitonin
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PTH secretion is stimulated by what?
hypocalcemia
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What releases calcitonin?
Thyroid gland
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Vitamin D is necessary for what?
bone deposition and resorption
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Vitamin D increases calcium absorption where?
kidneys
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What are the three cells types of the Islets of Langerhans?
- alpha cells - glucagon
- beta cells - insulin
- dela cells - somatostatin
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What are some islet characteristics?
- Gap junctions between cell types to allow communication
- Blood flow allows cells of islets to recognize secretion levels
- Adrenergic and cholinergic input
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What sitmulates insulin secretion?
- Increased blood glucose concentration
- Increased amino acid & fatty acid concentration
- Release of glucagon
- GH, cortisol, K+
- Obesity
- Parasympathetics
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What inhibits secretion of insulin?
- Decreased blood glucose concentration
- Fasting
- Exercise
- Sympathetics
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What does the presence of insulin increase?
- Glucose uptake into cells
- Glycogen formation
- Protein synthesis
- Fat deposition
- K+ uptake into cells
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What does the presence of insulin decrease?
- Glycogenolysis
- Gluconeogensis
- Lipolysis
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What stimulates secretion of glucagon?
- Fasting
- Decreased blood glucose
- Increased amino acid
- CCK
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What inhibits secretion of glucagon?
- Insulin
- Somatostatin
- Increased fatty acid
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What does glucagon increase?
- Glycogenolysis
- Gluconeogenesis
- Lipolysis
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What is the general function of glucagon?
Liberate stored nutrients for energy utilization
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What does somatostatin do?
- Provides over-riding control of glucagon and insulin secretion
- Inhibits release of insulin and glucagon
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What stimulates release of somatostatin?
- Ingestion of a meal
- GI hormones
- Glucagon
- Sympathetic system
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What inhibits release of somatostatin?
Insulin
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