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Block 4
Hypophysis (pituitary) II and Pineal Gland
| Question | Answer |
|---|---|
| The posterior pituitary consists of what 2 things? | 1. pars nervosa (neurosecretory axons and endings) 2. infundibulum (neurosecretory axons that form the hypothalamohypophyseal tracts) |
| Cell bodies of neurons in the pars nervosa reside in the _____** and ______** of the hypothalamus. | SUPRAOPTIC, PARAVENTRICULAR NUCLEI |
| Axons of the pars nervosa neurons form the ________ ______** | hypothalamohypophyseal tract |
| Pars nervosa axons end near what? | fenestrated capillaries |
| Where are secretory vesicles of the pars nervosa neurons found? | all parts |
| pars nervosa neurons have a well developed? | Nissl substance |
| The posterior pituitary is not an endocrine gland. It is a _____ site for secretions of the neurons of the _____ and _____ nuclei** | storage site, supraoptic, paraoptic |
| What are the 3 distinct vesicles in nerve endings of the pars nervosa? | 1. vesicles w/ diameters 10-30nm accumulate in axon terminals, form dilations in portions of axons called HERRING BODIES 2. 30nm vesicles that contain ACETYLCHOLINE (play part in release of neurosecretory vesicles) 3. larger 50-80nm vesicles |
| What to membrane bound vesicles that form Herring bodies contain? | oxytocin or ADH (antidiuretic hormone; vasopressin; arginine vasopressin AVP), 9 amino acids each.... ATP... neurophysin |
| what is the function of neurophysins? | not clear |
| dilations near axon terminals are called? | herring bodies |
| what are the only cells specific to the posterior pituitary | pituicytes |
| what are pituicytes? | similar to astrocytes, contain GFAP, associated with fenestrated capillaries |
| what are other cell types found in the posterior pituitary?** | FIBROBLASTS and MAST CELLS ** |
| What is the effect of ADH? | increase permeability of distal portion of nephron, the distal convoluted tubule and collecting ducts, by acting on ADH regulated water channels to cause rapid reabsorption of water across tubule epithelium |
| What are aquaporins (AQP-2) | hourglass shaped water channels inserted into cell membrane that allow water to cross cell membrane |
| what can large nonphysiologic doses of ADH do? | increase blood pressure by promoting contraction of smooth muscles in small arteries... VASOPRESSIN |
| what effect do physiological levels of ADH have on blood pressure? | minimal effects |
| What SHORT TERM effect does ADH have on AQP-2 | causes translocation of AQP-2 containing vesicles into the apical cell surface of tubular epithelial cells |
| What LONG TERM effect does ADH have on AQP-2? | causes synthesis of AQP-2 and insertion into apical cell membrane |
| What stimulates the release of ADH? | increase in plasma osmolality or decrease in blood volume, also pain, trauma, emotional stress, drugs such as nicotine... **INADEQUATE WATER CONSUMPTION, SWEATING, VOMITING, and DIARRHEA |
| what does an absence of ADH cause? | large quantities of dilute urine |
| absence or reduced production of ADH causes what condition? | CENTRAL DIABETES INSIPIDUS, suffer extreme thirst due to fluid loss |
| What does central diabetes insipidus commonly result from? | head injury, tumor, other lesions that may damage posterior pituitary or hypothalamus |
| what is diabetes insipidus usually treated with? | synthetic analogs of ADH |
| What gene mutations cause the condition NEPHROGENIC DIABETES INSIPIDUS? | AQP-2 and ADH receptor mutations |
| In nephrogenic diabetes insipidus, the kidney is unable to respond to what? | ADH |
| What may abnormally high levels of ADH be the result of? What happens to individuals with this? | ADH-secreting tumors of hypothalamus, retain water and have highly concentrated urine |
| What is a more potent promoter of smooth muscle contraction than ADH? | oxytocin |
| What is the primary effect of oxytocin? | promote smooth muscle contraction in uterus and the myoepithelial cells of secretory alveoli and alveolar ducts of mammary gland |
| What is the function of the pineal gland? | regulate circadian rhythm |
| where is the pineal gland located and what is it shaped like? | roof of third ventricle, pine cone shaped |
| What are the chief cells of the pineal gland? | PINEALOCYTES |
| what cells that resemble astrocytes are found in the pineal gland? | INTERSTITIAL (GLIAL) CELLS |
| What does the pineal gland secrete? | melatonin |
| What are coropora arenacea? | brain sand... calcified concretions, derived from precipitation of calcium phosphates and carbonates on carrier proteins released into cytoplasm when pineal secretions are exocytosed, increase with age, may serve as landmark on CT |
| what gland is photosensitive? | pineal gland |
| How does the pineal gland receive information on light and dark cycles? | from retina via REINTOHYPOTHALAMIC TRACT |
| Light impulses _____ the production of melatonin. | inhibit |
| at night, plasma levels of melatonin ____ | rise |
| function of the pineal gland and secretion of melatonin may play a part in what conditions? | Jet lag, seasonal affective disorder (SAD) |
Created by:
shuckybean
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