Term
What are the two broad classes of vesicles for neurotransmitters? |
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Definition
large dense core vesicles - generally house peptide hormones
small synaptic vesicles - generally contain non-peptide transmitters |
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Term
Describe some characteristics of the postsynaptic actions of classical peptide transmitters. |
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Definition
slow transmission - tend to have longer range effects
act via G-protein --> indirectly modulate ion channels
generally have longer response |
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Term
What is the function of the hypothalamus? |
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Definition
Integrate sensory input and control body response through output. |
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Term
Compare the control of the central nervous system of autonomic functions between the ANS vs. pituitary. |
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Definition
ANS: direct nerve connections from the CNS to peripheral organs, classic neurotransmitters, immediate moment-to-moment control
Pit: relies on hormonal release into circulation to affect peripheral target organs, peptide transmitters, slower developing control and feedback |
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Term
What is another name for the pituitary gland? |
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Definition
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Term
Where is the pituitary located? |
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Definition
In a bony structure call the "sella turcica" at the base of the brain. |
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Term
How is the pituitary connected to the CNS? |
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Definition
pituiatry stalk - receives input from the hypothalamus |
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Term
What are the two sections of the pituitary and what is the tissue make-up of each? |
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Definition
Anterior pituitary (aka adenohypophysis): non-neural tissue, makes up 80% of pituitary
Posterior pituitary (aka neurohypophysis): neural tissue, makes up 20% of pituitary |
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Term
How is the anterior pituitary activated causing the release of hormones? |
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Definition
Activation of neurons in the hypothalamus result in increase of releasing hromones in portal circulation |
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Term
What causes the release of hormones in the anterior pituitary and where do they come from? |
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Definition
Binding of releasing hormones to cells in the anterior pituitary causes release of hormones from secretory granules into the general circulation. |
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Term
What makes up the hypothalamus-pituitary axis? |
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Definition
hypothalamus --> anterior pituitary --> peripheral endocrin gland --> effector cell |
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Term
Name the 5 hormone releasing cells in the anterior pituitary. |
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Definition
Corticotrophs
Somatotrophs
Thyrotrophs
Gonadotrophs
Lactotrophs |
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Term
What are the hormones involved in the hypothalamus-pituitary-adrenal axis? |
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Definition
CRH (corticotropin releasing hormone)
ACTH (adrenocorticotropin hormone aka corticotropin)
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Term
What are the characteristics/properties of CRH? |
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Definition
Glycoprotein released from hypothalamic neurons (paraventricular neurons)
41 amino acid peptide |
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Term
What is the precursor to ACTH and where is it synthesized? |
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Definition
POMC (proopiomelanocortin)
Produced in basal ganglia, cortex, and pituitary
39 amino acid peptide
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Term
What are the characteristics/properties of ACTH? |
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Definition
Peptide fragment cleaved from larger protein precursor, POMC |
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Term
What are three important proteins that POMC can be cleaved into? |
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Definition
ACTH: acts on adrenal cortex
alpha, beta-melanocortin: increases skin pigmentation
beta-lipotropin (LPH): stimulates release of fatty acids from adipose tissue |
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Term
What causes the release of ACTH? |
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Definition
CRH and vasopressin (AVP)
stress
hypoglycemia |
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Term
Where is CRH and AVP synthesized? |
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Definition
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Term
Where is AVP released, and how does it reach the anterior pituitary? |
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Definition
AVP released by posterior pituitary
Reaches anterior pituitary via inferior hypophyseal artery |
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Term
Describe the ciracadian patter of ACTH release. |
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Definition
Highest levels in the morning but dependent on sleep-wake cycle (ie. jet-lag can alter pattern)
Opposes circadian patter of growth hormone secretion |
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Term
What is the target of ACTH? What are its effects? |
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Definition
Acts on adrenal cortex
Stimulates steroid hormone synthesis and growth of cortex (trophic action) |
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Term
Describe the effects of a lack of negative feedback system from cortisol. |
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Definition
Result in high ACTH levels and adrenal hormones --> inc. in size of cortex
Androgenital syndrome: masculization of femal fetus |
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Term
Describe the negative feedback loop in ACTH regulation. |
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Definition
ACTH negatively feedsback to the hypothalamus.
Cortisol negatively feedsback to both the hypothalamus and the anterior pituitary. |
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Term
Describe what happens to the negative feedback system during chronic stress. |
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Definition
Chronic stress overrides negative feedback of CRH and ACTH leading to hyperactivity of adrenals. |
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Term
Where are the adrenal glands located, and what are the two distinct regions? |
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Definition
Located on top of each kidney.
Medulla: inner region, neural tissue
Cortex: outer region, non-neural tissue |
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Term
What are the three zones of the adrenal cortex? |
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Definition
zona glomerulosa
zona fasiculata
zona reticularis |
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Term
What are steroid hormones derived from? |
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Definition
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Term
What is the function of adrenocortical cells? |
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Definition
Synthesize and secrete steroid hormones. |
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Term
Where are the only places in the body where steroid hormone synthesis occurs? |
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Definition
Adrenal coretx
Ovaries
Testes |
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Term
What are the three classes of steroid hormones released by the adrenal cortex? |
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Definition
Glucocorticoids
Mineralocorticoids
Adrenal androgens (androgenic steroids) |
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Term
Name the three regions of the adrenal cortex and the class of steroid hormone secreted. |
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Definition
zona glomerulosa - mineralocorticoids
zona fasiculata - glucocorticoids, adrenal androgens
zona reticularis - glucocorticoids, adrenal androgens |
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Term
What are the two glucocorticoids secreted? |
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Definition
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Term
Describe the effects of cortisol. |
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Definition
Stimulates breakdown of muscle and other organs - inceases release of amino acids
Stimulates lipolysis - breakdown of fat
Stimulates gluconeogenesis - production of glucose from amino acids and lipids
Conserves glucose for use by CNS - inhibits uptake into muscle and fat cells
Exerts stron anti-inflammatory effects - large doses decrease production of antibodies
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Term
Describe the effects of corticosterone. |
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Definition
Works with cortisol to suppress immune function and inflammatory reactions. |
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Term
What is the mineralocorticoid released by the adrenal cortex? |
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Definition
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Term
What causes the release of aldosterone? |
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Definition
Increased serum potassium levels and lowered sodium levels
Decreased blood flow to kidneys
Weakly responsive to ACTH |
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Term
How does aldosterone maintain blood volume and blood pressure? |
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Definition
Increases potassium secretion
Promotes sodium reabsorption by kidneys
Increases water reabsorption through osmosis |
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Term
Where does aldosterone act in the kidneys, and what is a possible side effect? |
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Definition
Sodium reabsorption in the distal tubules of the kidney in increased water reabsorption
May results in hypertension (high blood pressure) |
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Term
Describe the release of androgens before and at puberty. |
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Definition
Expression is low before puberty.
Increased expression at puberty contributing to developmental changes in both genders |
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Term
What are some examples of weak androgen and strong androgens. |
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Definition
Androstenedione, dehydroepiandrosterone (DHEA) - weak but can be converted into strong such as testosterone |
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Term
Does ACTH stimulate all three classes of adrenal steroids? |
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Definition
ACTH stimulates zona reticularis and zona fasiculata - glucocorticoids and adrenal androgens only |
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Term
What is Addison's disease? |
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Definition
Patients lack cortisol from the zona fasiculata: patients lack negative feedback of ACTH, aldosterone levels can be low
Results in overproduction of ACTH and cause skin to darken due to increase release of MSH (a bioactive peptide from POMC) |
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Term
What is Cushing's Syndrome? |
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Definition
Prolonged exposure of the body's tissue to high levels of cortisol: aldosterone levels can also be high
Symptoms: obesity, weak muscles, fatigue
Most cases caused by pituitary tumors: benign tumors may secerte increased amounts of ACTH |
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Term
What is the relationship between ACTH and beta-endorphins? |
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Definition
Overproduction of ACTH may accompany increased beta-endorphin production
High stress --> high ACTH --> beta-endorphin --> blunt pain |
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Term
What are the receptors for beta-endorphins? |
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Definition
Beta-endorphins bind to opiate receptors to mediate pain relief |
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Term
Describe the pain-stress phenomenon. |
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Definition
Severely traumatized individual appear to be free from pain.
Due to simulatenous release of beta-endorphins along with corticotrophin in response to stressful stimulus of injury |
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Term
What stimulates GH release and what inhibits its release? |
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Definition
GH releasing hormone
Inhibited by somatostatin |
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Term
What kind of hormone is GH and in what specialized cell in the anterior pitutary is it synthesized? |
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Definition
Peptide hormone
Somatotroph |
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Term
What are the direct effects of GH? |
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Definition
Adipose tissue: causes breakdown of triglycerides and suppresses ability of fat cells to take up lipids form circulation
Metabolism: stimulates the formation of proteins form amino acids (anabolism), maintain blood glucose levels by inhibiting insulin activity |
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Term
What are the indirect effects of GH? |
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Definition
Stimulates release of IGF-1 (insulin-like growth factor) from the liver.
IGF-1: 70 amino acid peptide comprised of two chains connected by a disulfide bond |
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Term
What is the function of IGF-1? |
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Definition
Stimulates bone growth by increasing proliferation of chondrocytes
Stimulates muscle growth: proliferation and differentiation of myoblasts, uptake of amino acids and protein synthesis in muscle |
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Term
What are the the stimuli for GH release? |
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Definition
Exercise
Stress
Low blood glucose
Fasting
Sleeping |
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Term
Describe how levels of GH change with circadian rythm |
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Definition
Highest levels occur just after onset of sleep (more intese during puberty) |
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Term
Describe how IGF-1 levels change with age. |
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Definition
Rise progessively with age in children
Greater increase at onset of puberty then decreases to adult levels |
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Term
What is the result of GH deficiency, and what are possible treatments? |
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Definition
Deficiency: dwarfism - severity of growth retardation is linked to age of onset of disease
Human growth hormone (hGH) can be used to promote growth |
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Term
What is the result of elevated GH? |
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Definition
Before puberty: gigantism - normal body proportions
After puberty: Acromegaly - enlargement of distal body parts (hands, feet, skull, jaw, nose)
Pituitary tumors may increase GH levels
May cause diabetes: GH effects on metabolism atntagonize those of insulin
High blood pressure, heart disease, arthritis
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Term
What are possible treatments to prevent the symptoms of elevated GH? |
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Definition
X-ray therapy, surgery, syntheti somatostatin agonists |
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Term
Describe the negative feedback system in GH regulation. |
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Definition
GH negatively feedsback to the hypothalamus.
IGF-1 negatively feedsback to the hypothalamus. |
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Term
Describe the characteristics/properties of TRH. |
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Definition
Tripeptide (3 AA)
Stimulates release of thrytoid stimulating hormone (TSH) and prolactin |
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Term
Describe the properties/characteristics of TSH. |
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Definition
Binds receptors on thyroid gland to induce T3 and T4 secretion
Stimulates thryoid cell growth
Increasess synthesis of thyroid hormones
Increases blood flwo to thyroid gland
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Term
What are three actions that the thyroid hormones are responsible for? |
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Definition
Cellular differentiation
Growth
Metabolism |
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Term
How do thyroid hormones modulate gene transciption? |
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Definition
T3 and T4 bind to intracellular receptors (txn factors) which leads to protein expression |
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Term
Explain why thyroid hormones are important in increasing basal metabolic rate. |
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Definition
Increase lipolysis
Increase carbohydrate metabolism: inc. insulin-mediated stimulation of glucose uptake by cells, inc. gluconeogenesis and glycogenlysis (inc. blood glucose levels) |
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Term
Explain the role of thyroid hormones in normal development. |
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Definition
Thyroid hormones are critical for development of the mammalian CNS.
Thyroid hormones are required for normal growth in immature animals. |
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Term
Explain the importance of thyroid hormones cardiovascular, CNS, and reproductive functions. |
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Definition
Cardiovascular: inc. HR, cardiac contractility, and cardiac output, promote vasodilation
CNS: dec. thyroid hormones cause mental clouding, inc. causes anxiety
Repro: dec. thyroid hormones is associated with infertility |
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Term
What are the effects of decreased thyroid function? |
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Definition
Iodine deficiency: I required for T3 and T4 synthesis
Damage to thyroid gland
Hypothyroidism: lethargy, fatigue, intolerance of cold; can be treated with synthetic thyroid hormone |
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Term
What are the effects of increased thyroid function? |
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Definition
Pituitary tumors
Grave's disease: autoimmune disorder in which antibodies are expressed which bind to and activate TSH receptors
Hyperthyroidism: anxiety, insomnia, increased HR; treat with drugs blocking thyroid hormone synthesis |
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Term
Describe the feedback system in thyroid hormone regulation. |
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Definition
T3 and T4 negatively feedback to both the anterior pituitary and the hypothalamus. |
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Term
The posterior pituitary receives axonal projections from neurons with cell bodies located in what part of the hypothalamus? |
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Definition
Paraventricular nucleus (PVN)
Supraoptic nucleus (SON) |
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Term
Explain the path a peptide hormone travels when the hypothalamic neurons become activated. |
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Definition
Peptide hormones are synthesized in the cell body, packaged, and axonally transported from the hypothalamus to the posterior pituitary and released directly into general circulation |
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Term
What are the two hormones released from the posterior pituitary? |
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Definition
Oxytocin
Arginine vasopression (Anti-diuretic hormone) |
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Term
Describe the characteristics/properties of oxytocin. |
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Definition
9 amino acid peptide hormone
Synthesized by magnocellular cells of the PVN and SON
Stimulates uterine contractions during and after childbirth
Leads to milk letdown (lactation) |
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Term
Explain how oxytocin leads to milk letdown. |
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Definition
Milk is stored in alveoli of the mammary glands.
Alveoli are line by smooth muscle cells (myopeithelial cells)
Myoepithelial cells express oxytocin receptors -> binding causes contraction of myopeithelial cells -> milk ejection |
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Term
Explain how oxytocin leads to uterine contractions. |
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Definition
Smooth muscel cells of uterus increase expression of oxytocin receptors during gestation
Oxytocin is released during labor causing contraction of smooth muscle cells
Oxytocin analogs (ie. Pitocin) can be administered to induce labor
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Term
Describe the characteristics/properties of vasopressin. |
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Definition
9 amino acid peptide
Synthesized by magnocellular cells of the PVN and SON
Stimulated water conservation
Causes vasoconstriction in response to severe hemorrhage |
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Term
What stimulates vasopressin release? |
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Definition
Dec. BP: baroreceptors of the carotid sinus simtulate neurons in SON and PVN -> hypothalamic neurons release vasopressin from posterior pituitary
Binds to receptors in kidney and promote reabsorption of water back into circulation
Inc. plasma osmolarity: inc [salt] in bloodstream
Cicrumventricular organs and vasopressin neurons are osmosensitive: neurons transmit signal to PVN and SON causing water retention
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Term
Describe the relationship bewteen vasopressin and thirst. |
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Definition
Vasopressin secretion is increased before thirst is physiologically evident. |
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