Hypothalamus Flashcards
What does stimulation of a ventromedial satiety center do?
Inhibits the urge to eat.
What is the result of bilateral destruction of the ventromedial satiety center?
Overeating and gross obesity.
Where does the hormone act in the kidney?
Distal convoluted tubules and collecting ducts.
What maintains osmolarity in the blood?
Regulating water reuptake in the distal convoluted tubules.
What happens with a 1% increase in osmotic pressure?
Plasma is diluted to normal levels by increased water uptake.
What condition results from reduced production of ADH?
Diabetes insipidus.
How much urine can a patient with diabetes insipidus urinate per day?
18 to 20L.
What is the principal function of oxytocin?
To participate in a neurohumoral reflex to release milk during suckling.
What hormones are secreted by magnocellular neurons in the hypothalamus?
- Antidiuretic hormone (ADH) * Oxytocin
What is the role of the hypothalamo-hypophyseal tract?
Conveys hormones to the posterior pituitary.
What stimulates the release of oxytocin?
Suckling.
What does oxytocin stimulate in the breast?
Expression of milk.
What effect does oxytocin have during labor?
Stimulates uterine muscle contractions.
What is the appestat?
The interplay between the lateral and ventromedial nuclei regulating caloric and nutrient intake.
What reactions occur to conserve body heat?
- Peripheral vasoconstriction * Increased body metabolism * Shivering * Decreased respiratory rate
What mechanisms facilitate heat loss when body temperature increases?
- Dilation of peripheral blood vessels * Increased sweating * Increased respiratory rate
What hormone stimulates the release of adrenal cortical steroids?
Adrenocorticotropic hormone (ACTH).
What is the function of growth hormone (GH)?
Promotes growth of long bones and possibly other tissues.
What does prolactin do?
Stimulates development of mammary glands and lactation.
Where do hormones from the anterior pituitary drain?
Into capillaries that drain into the cavernous sinus.
What is the hypothalamus’s role in body homeostasis?
- Reproduction * Growth and metabolism * Food and fluid intake * Attack and defense * Temperature control * Sleep-wake cycle * Memory
What is the effect of stimulating the anterior hypothalamic area?
Produces parasympathetic effects.
What is the effect of stimulating the posterior hypothalamic area?
Produces sympathetic effects.
What type of neurons produce neurosecretion to control the anterior pituitary?
Parvocellular neuroendocrine cells.
What is the vascular system that carries neurosecretion to the anterior lobe of the pituitary?
Pituitary portal system.
What hormone shares the same releasing factor as LH?
Follicle stimulating hormone (FSH).
What is the axonal transport mechanism used by ADH?
Transport to the capillaries of the posterior pituitary.
What are Herring bodies?
Axonal swellings containing secretory granules for hormone release.
hypothalamus location
occupies the side walls and floor of the third ventricle
homeostatic functions the hypothalamus controls
reproduction
growth and metabolism
food and fluid intake
attack and defence
temperature control
sleep-wake cycle
memory
which cells of the hypothalamus are sensitive to blood concentration of hormones from the ant pit
parvocellular (small) neuroendocrine cells of the preoptic and tuberal regions
tuberoinfundibular tract
what do APs of these neurons cause
hypothalamic neurons produce secretions that pass down their axons to reach the stalk of the pit gland
calcium dependent exocytosis of releasing or inhibitory hormones (trophic)
control of release hypothalamic neurons
axonal connections of hypothalamus and other brain areas
pituitary portal system
vascular system that carries neurosecretions to ant pit
capillaries of infundibulum drain into portal vessels which pass into ant pit
break up to form a second capillary bed which bathes endocrine cells
arterial supply of the pit gland
comes from branches of internal carotid artery
one set of branches supplies a capillary bed in infundibulum
hormones secreted by ant pit and their functions
prolactin: development of mammary glands and lactation
TSH: stimulates thyroid to synthesise and release thyroxine and triiodothyronine
adrenocorticotrophic hormone: stimulates adrenal cortex
GH: growth of long bones and possibly other tissues
FSH: growth of ovaries/seminiferous tubules and section of estrogen/production of spermatozoa
LH: together with FSH induces ovulation
what give rise to the hypothalamo-hypophyseal tract
where does it terminate
magnocellular (large) neurons in the supraoptic and paraventricular nuclei
terminates in the pos pit
Herring bodies
axonal swellings containing secretory granules
provide local depot of granules for release by smaller swellings into capillary bed
arterial supply of pit gland
receives a direct supply from another set of hypophyseal arteries
route of hormone release from pituitary gland
from both ant and pos pit drain into capillaries
drain into cavernous sinus
into general circulaiton
how is osmolarity in the blood maintained by ADH
regulating water uptake in DCTs
result of reduced production of ADH
diabetes insipidus
patient can urinate 18 to 20L per day
principal function of oxytocin
participates in neurohumoral reflex to cause release of milk, when an infant is suckling
afferent limb of lactation reflex
impulses travel from nipple to hypothalamus via spinoreticular tract
oxytocin is liberated by magnocellular neurons in supraoptic and paraventricular nuclei
effect of oxytocin at breast
stimulates myoepithelial cells surrounding lactiferous ducts
effect of oxytocin during labour
stimulates uterine muscle contraction
how is heat sensed by hypothalamus
how is cold sensed by hypothalamus
when there is increased temperature the heated blood passes through the ant hypothalamic area
heat sensitive neurons activate
cool blood passes through pos hypothalamic area area
reactions to reduce body temperature
dilation of peripheral blood vessels beneath skin
increased sweating
increased resp rate
reactions to conserve heat
peripheral vasoconstriction
increased metabolism
shivering of voluntary muscles
decreased resp rate
what determines the appestat
baseline for caloric and nutrient intake by interplay between lateral and ventromedial nuclei
stimulation of lateral hypothalamic satiety centre
destruction
excessive eating
refusal to eat
stimulation of ventromedial satiety centre
destruction
inhibits urge to eat
overeating and obesity
autonomic effects of ant and pos hypothalamic areas
ant: parasympathetic effects
pos: sympathetic effects
