hypothalamus Flashcards
what is homeostasis
balanced functioning of physiological processes and maintenance of an organism’s internal environment within a narrow range
what is the hypothalamus and what does it do
- specialized sensory neurons measure the regulated parameter and deviations from optimal range are detected
- coordinates the necessary compensatory mechanims
what are the 3 things that the hypothalamus controls
- autonomic nervous system (sympathetic and parasympathetic)
- endocrine system (anterior and posterior pituitary gland)
- motivated homeostatic behaviors (feeding, drinking) (connections with forebrain, limbic system, brainstem and spinal cord)
what are the 3 divisions of the hypothalamic nuclei from medial to lateral
- periventricular area
- medial hypothalamic area
- lateral hypothalamic area
what are the 4 regions of the medial hypothalamic area from rostral to caudal
- preoptic area
- anterior (supraoptic) region
- middle (tuberal) region
- posterior (mammillary) region
magnocellular neurosecretory cells located in the supraoptic nucleus and paraventricular nucleus do what?
secrete two hormones into a capillary bed in the posterior pituitary
what are the two hormones that the magnocellular neurosecretory cells secrete
- oxytocin
- vasopressin
what does oxytocin do
- uterine contractions
- milk letdown reflex
- love hormon e
what does vasopressin do
- ADH
- regulated blood volume
- salt concentration
what do parocellular neurosecretory cells do and where are they located
- paraventricular nucleus
- secrete releasing hormones and inhibiting hormones into the hypothalamic-pituitary portal circulation
biological stress is created by the brain in response to real or imagined stimuli and this leads to:
the release of cortisol during “stress response”
what does cortisol do
- released glucose into your bloodstream
- increases blood pressure for increased physical activity such as running
- stimulates brain for more intense awareness
- immune system activity is reduced to save energy for physical activity
what are the 5 steps of the HPA axis
- stress (physiological stess or anxiety)
- parvocellular neurosecretory neurons
- anterior pituitary releases ACTH
- ACTH acts on adrenal cortex
- cortisol inhibits CRH release
what are the two NT of the sympathetic and parasympathetic system
preganglionic and postganglionic
sympathetic
- pre - ACh
- post - NE
parasympathetic
- pre -ACh
- post - ACh
what is anabolism
when blood is filled with nutrients
what are the two forms that energy is stored in
- glycogen in liver and skeletal muscle
- triglycerides in adipose tissue
what is catabolism
- during fasting; between meals
- stored glycogen and triglycerides are broken down to provide body with a continuous supply of molecules for fuel
what does the ob gene code for
a protein called leptin which is released by adipocytes
what is leptin
a hormone that communicates with the brain about fat reserves
elevated leptin levels in blood activates:
hypothalamus and decreases feeding behavior
decreased leptin leptin levels in blood activates:
hypothalamus and increases feeding behavior
what is parabiosis
anatomical and physiological union of two animals - share blood supply
leptin released by adipocytes activate leptin receptors in ____ ____ of the hypothalamus
arcuate nucleus
arcuate nucleus
- sense leptin levels
- controls paraventricular nuc
- controls lateral hypothalamus area
paraventricular nucleus
- ANS (increase sympathetic tone)
- endocrine system (leads to release of ACTH and TSH)
- both increase metabolism and energy expenditure
lat. hypothalamic area
activates homeostatic motivated behavior (feeding behavior)
arcuate neurons responding to elevated leptin release the peptide transmitters:
- alpha MSH
- CART
anoretic peptides
- increase alphaMSH and CART in arcuate nucleus
- inhibit feeding behavior
- increase metabolism
- increase energy expendature
arcuate neurons responding to decreased leptin release the peptide transmitters:
- NPY
- AgRP
orexigenic peptides
- increase NYP and AgRP in arcuate nucleus
- stimulate feeding behavior
- decrease metabolism
- decrease energy expenditure
what are the peptides involved in short term regulation of feeding bahvior
- ghrelin
- gastric distension
- cholecystokinin (CCK)
- insulin
what do serotonin levels in the hypothalamus do
- rise at the sight or smell of food
- peak during a meal, especially in reponse to carbs
- elevates mood - especially during stress
depression and anxiety are linked to:
lowered brain serotonin levels
low serotoning levels reduce ____
satiety
antidepressent drugs that elevate brain ____ levels, are and effective treatment for ____ ____
serotonin; bulimia nervosa
what are circumventricular organs
- highly vascularized structures located around the third and fourth ventricles lack of a blood-brain barrier (BBB)
- points of communication between the blood, the brain, and the CSF
what is drinking behavior stimulated by
hypovolemia and hypertonicity
what is hypovolemia
decrease in blood volume (volumetric thirst)
steps of hypovolemia
- detected by pressure receptors in the cardiovascular system
- signals ascend to nucleus of the solitary tract via vagus nerve
- solitary nucleus prokects to paraventricular nucleus of hyothalamus
- vasopressin (ADH) released by posterior pituitary
- ADH acts on kidney to increase water retention and inhibit urine production
- hypothalamus activates sympathetic division of ANS to constrict blood vessels
- reduced blood flow to kidneys causes release of renin to the blod
- in the liver, renin converts angiotensinogen to angiotensin I which breaks down to angiotensin II
what does angiotensin II do
- acts on the neurons of the subfornical organ, which stimulate neurons in the paraventriculat nucleus causing release of ADH by posterior pituitaty
- ADH acts on kidney to increase water retention and inhibit urine production
- subfornical organ projects to lateral hypothalamus which produces thirst that motivates drinking behavior
what is hypertonicity
increase in blood salt (osmometric thirst)
what are the steps in hypertonicity
- hypertonicity of the blood is sensed by neurons in the vascular organ of the lamina terminalis (OVLT)
- OVLT projects to the paraventricular nucleus of the hypothalamus
- posterior pit. secretes vasopressin
- ADH acts on kidney to increase water retention and inhibit urine production
- OVLT projects to the lateral hyothalamus
- lateral hyothalamus stimualtes osmometric thirst, the motivation to drink water when dehydrated
neurons in the ____ ____ transduce small changes in blood temperature to changes in firing rate
anterior hypothalamus
cold-sensitive neurons of the anterior hypothalamus project to:
medial preoptic area of the hypothalamus
medial preoptic area projects to parvocellular neruons of the:
paraventricular nucleus -> anterior pit.
thyroid stimulating hormone, TSH is released by:
and this leads to:
anterior pit; release of thyroid hormone thyroxin
what does thyroxin do
increases metabolism
medial preotpic nucleus activity activates sympathetic division of ANS and this causes:
blood vessels in skin to constrict and piloerection
cold-sensitive neurons of the anterior hypothalamus projects to:
this leads to:
lateral hypothalamus; shivering and to seek warmth
warm-sensitive neurons of the anterior hypothalamus projects to:
medial preoptic area of hypothalamus
medial preoptic area projects to parocellular neurons of the:
paraventriculat nucleus -> anterior pituitary
parvocellular neurons signal anterior pituirary to:
stop secreting TSH and metabolism is slowed
medial preoptic nucleus activity activates:
sympathetic divistion of ANS and blood is shunted to the periphery to dissipate heat
activity in the lateral hypothalamus causes behavior of:
seeking shade, panting, and in humans - sweating
