Module 3 Flashcards
(28 cards)
What is neuroendocrine Control?
1pt
- Secretion of hormones from the pituitary gland is closely controlled by the brain, especially by the hypothalamus
- Hypothalamus-pituitary unit is the central regulator of endocrine function
What tissues is the pituitary gland made of?
2 pt
Posterior pituitary: Brain tissue
Anterior pituitary: Glandular tissue
What hormones come from the hypothalamus?
4pt
- Releasing Hormones (+ Stimulation)
- GnRH, GHRH, CRH, PRH, and TRH
- Regulatory neuropeptides (- Stimulation)
- Somatostatin, Dopamine
What hormones are released from the anterior, posterior and intermediate pituitary gland?
3pt
- Anterior Lobe ⇒ PRL, GH, FSH, and LH, ACTH, TSH
- Intermediate Lobe ⇒ POMC (specifically αMSH, β-endorphin)
- Posterior Lobe ⇒ Oxytocin and vasopressin (=ADH)
What hormone is released from the pineal gland?
1pt
Melatonin
What hormone is released from the sympathoadrenal Medulla?
1pt
Catecholamines
What is the hypothalamus and what is it’s functions?
2pt
- Portion of the brain (diencephalon) that contain 12 small nuclei
- Endocrine, autonomic, somatic and emotional functions
- Control of body temperature
- Control of blood circulation/pressure
- Regulation of food and water intake
- MAINTAIN HOMEOSTASIS!!
What does the nuclei of the hypothalamus do?
1pt
The nuclei synthesize different hormones in
response to physiological changes
What are neural signals in the hypothalamus?
2pt
- Parasympathetic and sympathetic effects
- Allows control of heart rate, vasoconstriction, digestion, sweating, etc
What are endocrine signals in the hypothalamus?
2pt
- 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 the neuroendocrine cells of the hypothalamus and what do they do?
4pt
- Magnocellular neurons (large and long)
- Somas (cell bodies) in the supraoptic nucleus (SON) and paraventricular nucleus (PVN)
- Axons terminate in the aposterior pituitary
- Secrete antidiuretic hormone (ADH) and oxytocin
- Parvocellular neurons (small and short)
- Somas (cell bodies) in the in various nuclei
- Axons only reach the median eminence
- Secrete multiple Releasing Hormones
Know SON and PVN
What are the specific neuroendocrine functions of the hypothalamus?
3pt
- 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 medulla
What are the hypothalamic hormones? Give examples.
4pt
- Small Neurohormones (9 amino acids)
- Antidiuretic Hormone (ADH or VP)
- Oxytocin
- Releasing Hormones + Release-Inhibiting Hormones
- Stimulatory (usually small polypeptides)
- Corticotropin Releasing Hormone (CRH),
- Growth Hormone Releasing Hormone (GHRH)
- Gonadotropin Releasing Hormone (GnRH)
- Thyrotropin Releasing Hormone (TRH)
- Inhibitory:
- PRL-inhibitory hormone (= Dopamine)
- GH-inhibitory hormone (= Somatostatin)
- Stimulatory (usually small polypeptides)
Where is oxytocin and ADH synthesized and released?
2pt
- Both are synthesized as preprohormones 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 ADH?
2pt
Oxytocin: Uterus and mammary gland
ADH: Kidneys
What does ADH do?
2pt
- Conserves body water and regulates tonicity
- Stimulates insertion of “water channels” or aquaporins into the membranes of kidney tubules
- Channels transport solute-free water through tubular cells and back into blood, leading to a ↓ in plasma osmolarity and an ↑ urine osmolarity
- Water deprivation ↑ ADH secretion, ↓ water clearance and ↑ water conservation
- Water load ↓ ADH secretion and ↑ water clearance
What is diabetes insipidus?
3pt
- Lack of ADH secretion
- Kidneys make a lot of urine (up to 16 L/day!)
- Dehydration and excessive thirst
How is ADH secretion controlled?
3pt
- When plasma osmolarity is below a certain threshold, the osmoreceptors (in HYP) are not activated and secretion of ADH is suppressed
- The osmotic threshold for ADH secretion is considerably lower than for thirst
- Nausea and vomiting are also stimulators of ADH
What does oxytocin do?
3pt
- Ejects milk from lactating mammary glands in the breast via contraction of myoepithelial cells (in response to afferent suckling stimulation)
- Enhances contraction of smooth muscle of the uterus during parturition (in response to dilation of the cervix)
- Used clinically to induce labor and control postpartum hemorrhage
- Oxytocin levels are low during the initial labor but ↑ as labor progresses therefore oxytocin itself may not be responsible for initiating labor
what are characteristics of releasing hormones?
6pt
- Secretion in pulses
- Act on specific membrane receptors (G-protein coupled receptors)
- Transduce signals via second messengers
- Stimulate synthesis of pituitary hormones
- Stimulate release of stored pituitary hormones
- Stimulates hyperplasia and hypertophy of target cells in the pituitary gland
What is the hypophyseal portal system
3pt
- System of blood vessels in the median eminence connecting the hypothalamus with the AP
- Quickly transports hormones between the hypothalamic nuclei and AP
- Communication between two different tissue types
What happens to anterior pituitary hormones?
1pt
Hormones produced by the anterior pituitary (in response to releasing hormones) enter a secondary capillary system, and from there drain into the circulation
What are the direct and indirect effects of growth hormones? Give an example for each.
4pt
- Direct effects are the result of GH binding its
receptor on target cells.- E.g. Fat cells (adipocytes) have GH receptors, and GH stimulates them to break down triglyceride and supresses their ability to take up and accumulate circulating lipids.
- Indirect effects are mediated primarily by IGF-1
- IGF-1 secreted from the liver and other tissues in response to GH.
Anterior pituitary hormone
What is the most abundant pituitary hormone and what does it do?
2pt
Growth hormone is ~40-50% of pituitary cells
Growth promoting actions on muscle and the skeleton
