Term
| What is the function of the hypothalamus? |
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Definition
Major Integration Center
-regulates ANS & most of endocrine system
-processes most sensory info |
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Term
| What is the structure of the pituitary? |
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Definition
Posterior lobe = neurons from hypothalamus
Anterior lobe = major endocrine part
Intermediate lobe = function in amphibians & fish |
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Term
| Describe the structure of the hypothalamus |
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Definition
Composed of neuroendocrine cells
-some project axons down post. pit. lobe
-some release factors to feed anterior pituitary |
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Term
| What is the role of the intermediate pituitary? (2) |
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Definition
-produces melanocyte stimulating hormone (increases skin pigment)
-produces B-LPH which is degraded to B-endorphin, acting as an analgesic during stress |
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Term
| What is the role of the posterior pituitary? (3) |
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Definition
-releases ADH & oxytocin produced by hypothalamus neurons & transported along axons in vesicles
-stores in nerve endings until AP is fired triggering release
-hormones will then diffuse into blood vessels |
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Term
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Definition
Anti Diuretic Hormone
-most important regulator of extracellular fluid
-regulates density of water channels in distal tubule & collecting duct of kidneys
-causes reabsorption of water |
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Term
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Definition
| hypothalamic osmoreceptors & stretch receptors in blood vessels |
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Term
| Which organs does oxytocin act on? What receptor does it use? What regulates the secretion of oxytocin? |
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Definition
-uterus smooth muscle (parturition contractions)
-mammary gland (contraction to drive milk to excretory ducts)
-G coupled receptor with activation of PLC
-regulated by several reflexes e.g. milk ejection reflex |
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Term
| Describe the milk ejection reflex |
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Definition
1. Suckling stimulates sensory cell in teat, transduces signal into an AP
2. Sensory nerve carries AP to hypothalamus for integration
3. AP is interpreted, transferred to motor nerve
4. Motor nerve carries AP to posterior & anterior pituitary
5. Effector receives the AP. Post. pit produces oxytocin, triggering milk ejection. Ant Pit produces prolactin triggering milk production. |
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Term
| What is the critical link between the endocrine & nervous system? |
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Definition
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Term
| Describe the endocrine part of the anterior pituitary |
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Definition
5 different cell types producing 6 different hormones
Thyrotropes prod TSH
Gonadotropes prod LH & FSH
Corticotropes prod ACTH
Somatotropes prod GH
Lactotropes prod PRL (prolactin) |
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Term
| What controls the tropic effects of hormones produces by the anterior pituitary? |
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Definition
| direct control from the hypothalamus |
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Term
| What is the function of Growth Hormone (somatotropin) |
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Definition
DIRECT
catabolic: stimulates lipolysis, reduces lipogenesis
anabolic: promotes protein synthesis
INDIRECT
-stimulate synth of IGF1 in liver, which stimulates proliferation of cartilage cells
-stimulates satellite cells in muscle
-stimulates AA uptake & protein synthesis |
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Term
| What is the function of TSH |
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Definition
-binds to G-coupled receptor on follicular cells of thyroid gland
-stimulates cAMP pathway which stimulates thyroid hormone synthesis |
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Term
| What is the function of ACTH |
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Definition
-binds to G-coupled receptor to stimulate cAMP pathway
-stimulates mobilization of cholesterol in adrenal cortex
-provides more substrate to increase release of corticosteroids |
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Term
| What is the function of LH |
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Definition
Males: stimulates testosterone production in Leydig cells
Females: creates a surge triggering ovulation |
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Term
| What is the function of FSH |
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Definition
Males: stimulates secretion of inhibin by sertoli cells
Females: development of follicles & secretion of estradiol by granulosa cells |
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Term
| What is the function of PRL (prolactin) |
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Definition
-stimulates milk protein synthesis (casein & lactalbumin)
-initiates incubation behaviour in chickens |
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Term
| Which anterior pituitary hormones use cytokine receptors? |
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Definition
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Term
True or False
Hypothalamic neurohormones use portal systems to bypass general circulation and reach the anterior pituitary |
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Definition
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Term
True or False
Prolactin is under perpetual inhibition by dopamine until lactation begins |
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Definition
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Term
| Which hormones are under tonic inhibition? |
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Definition
GH, MSH & PRL
-secretion decreases as animal matures |
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Term
| How does the hypothalamus receive a message from the CNS and then communicate with the anterior pituitary? |
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Definition
1. Environmental/internal signal sends AP to CNS
2. Electrical chemical signal is sent to limbic system
3. Electrical chemical is sent to hypothalamus
4. Hypothalamus sends releasing factor via portal system to pituitary
5. Ant Pituitary sends corresponding hormone to target gland
6. Target gland will release the ultimate hormone which will have systemic effects |
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Term
| Why is the portal system important? |
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Definition
| only very small amounts of hormone are produced by the hypothalamus, which would be diluted in regular circulatory system |
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Term
| What is pulsatility? (4 points) |
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Definition
-many hormones from hypothalamus & pituitary are released in pulses
-biological clock of hypothalamus regulates them
-prevents the downregulation of receptors due to desensitization
-can trigger actions specific to the frequency of the pulse |
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Term
| Describe feedback control |
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Definition
-circulating hormones from endocrine glands provide negative feedback to hypothalamus & pituitary
-regulates the secretion of hormones through 2 major feedback loops |
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Term
| What are the 2 major feedback loops? |
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Definition
Short Loop
-pituitary hormones feed back to hypothalamus
Long Loop
-hormones from target glands feed back to pituitary and hypothalamus |
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