Neuroendocrine control Flashcards by Robyn Schenk

how are secretions of hormones form the pituitary gland closely controlled

-secretion of hormones form the pituitary gland is closely controlled by the brain especially by the hypothalamus

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what is the central regulator of the endocrine function

the hypothalamus-pituitary unit

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infundibulum

the stock that connects the pituitary to the brain

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sphenoid bone

the pituitary is surrounded by this bone for protection

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posterior pituitary tissue

-an extension of the neural tissue
-neural ectoderm
-brain tissue
-pars nervosa
-ectoderm of the floor of the brain

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anterior pituitary tissue

-true endocrine gland of epithelial origin
-oropharynx ectoderm
-glandular tissue
-pars distalis
-ectoderm of roof of mouth

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how does the pituitary gland form

-mouth tissue forms rathkes pouch
-it invanginates
-Wraps around the infundibulum
-developing sphenoid bone cuts off the glandular tissue and surround the two tissues
-results in anteriour pituitary “hugging” the posterior pituitary

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what does the infundibulum stock do

-carries axons form the neurosecretory cells of the hypothalamus down to the posterior pituitary where they release their hormones into the blood

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pars tuberalis

portal vessels of the portal systems pass near of through the pars tuberalis en route to the capillary beds on the pars distalis

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pars intermedia

-portion of the AP that makes contact with the pars nervosa of the PP
-in human fetus produces melanocyte-stimulating hormone (MSH)

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neuroendocrine hormones of the hypothalamus

-releasing hormones (+stimulation)
-GnRH, GHRH, CRH, PRH, TRH
-regulatory neuropeptides (-stimulation)
-somatostatin, dopamine

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neuroendocrine hormones of the pituitary

-anterior lobe= PRL, GH, FSH, LH, ACTH, TSH
-intermediate lobe= POMC
-posterior lobe= oxytocin snd vasodepressent

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neuroendocrine hormones of the pineal

melatonin

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neuroendocrine hormones of the sympathoadrenal medulla

catecholamines (cells in middle of adrenal that cause flight and fight)

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what is the role of the hypothalamus

-portion of the brain that contains 12 small nuclei with a variety of functions
-endocrine, autonomic, stomatic, and emotional functions:
-control of body temp
-control of blood circulation/pressure
-regulation of food and water intake
-all these things help maintain homeostasis

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who has a hypothalamus

all vertebrate

nuclei of the hypothalamus

-composed mainly of different nuclei
-discrete masses of grey matter in the CNS
-they synthesize different hormones in response to physiological changes

what are the functions of the 12 small nuclei in the hypothalamus

two important for this class:
-paraventricular nucleus (water balance/stress)
-supra-optic nucleus (water balance)
-other:
-anterior hypothalamic area (body temp)
-medial preoptic (blood pressure)
-lateral hypothalamic area
-dorsal hypothalamic area
-posterior hypothalamic area (shivering)
-dorsomedial (GI tract)
-ventromedial neucleus (satiety)
-mammillary body (feeding)

functional mechanisms of the hypothalamus

-neural signals
-endocrine signals

neural signals of the hypothalamus

-parasympathetic and sympathetic effects
-allows control of heart rate, vasoconstriction, digestion, sweating, etc

endocrine signals of the hypothalamus

-releases neurohormones into general circulation via the posterior pituitary
-releases neurohormones into blood portal system (releasing hormones) to regulate function of the anterior pituitary

what are some specific neuroendocrine functions of the hypothalamus

-production of ADH and oxytocin
-secretion of regulatory hormones to control activity of the anterior lobe of the pituitary gland
-control of sympathetic output to adrenal medullae

neuroendocrine cells of the hypothalamus

-magnocellular neurons (L&L)
-parvocellular neurons (S&S)

neuroendocrine cells of the hypothalamus magnocellular neurons

-large and long
-somas (cell bodies) in the supraoptic nucleus (SON) and paraventricular nucleus (PVN)
-axons terminate in the posterior pituitary
-secrets antidiureticc hormones and oxytosin

neuroendocrine cells of the hypothalamus parvocellular neurons

-small and short -somas (cell bodies) in the various neuclei -axons only reach the median eminence -secretes multiple releasing hormones -small so that it only goes half way to where the blood is to carry away releasing hormones

what are the hypothalamic hormones

-small neurohormones (9 AA): -antidiuretic hormones (ADH) also called vasopressin (VP) -oxytocin -releasing hormones + release-inhibiting hormones -A. stimulatory (usually small peptides): -corticotrophin releasing hormone -growth hormone releasing hormone -gonadotrophin releasing hormone -thyrotrophin releasing hormone -B. inhibitory: -PRL-inhibitory hormone (dope) -GH-inhibitory hormone (somatostatin)

hypo hormones: small neurohormones (9aas)

-antidiuretic hormones (ADH or VP) -oxytocin -both are synthesized as prehormones in the cell bodies of hypothalamic neurons -released from the termini in response to an action potential

what are the target organs for oxytocin and vasopressin

-Vasopressin is the kidney -Oxytocin is the mammary gland or uterus

how does either oxytocin or vasopressin make there way to the target tissue

-neurohormone is made and packed in cell body of neuron -vessicles are transported down the cell -vesicles containing neurohormone are stored in posterior pituitary -neurohormones are released into blood

what does ADH/vasopressin do

-conserves water and regulates tonicity -inserts aquaporins in the nephrons of kidneys and takes water from the filtrate -channels transport solute free water through tubular cells and back into blood leading to an dec in plasma osmolarity and an increase in urine osmolarity -water deprivation = inc ADH secretion=decrease water clearence and inc in water conservation -Lack of ADH secretion = diabetes

what happens with a Lack of ADH secretion

-diabetes insipidus -kidneys make lots of urine (up to 16L/day -dehydration and excessive thirst -can be treated with exogenous ADH

control of ADH secretion

-when plasma osmolarity is below certin threshold the osmoreceptors in (HYP) are not activated and secretion of ADH is supressed -the osmotic threshold for ADH secretion is considrably lower than for thirst -nausea and vomiting are also stimulators of ADH (loss of electrolytes and water)

oxytocin

-ejects milk from lactating mammary glands in the breast via contraction of myoepithelial cells (in response to sound or afferent suckling stimulation) -enhances contraction of smooth muscles of the uterus during parturition (in response to dilation of the cervix) -used clinically to induce labor and control postpartum hemorrhage -oxy levels are low during the initial labor but inc as labor progresses -oxy itself may not be responsible for initiating labour