Hypothalamus and brain homeostasis Flashcards
What is homeostasis?
The maintenance of the body’s internal environment within a narrow physiological range
How is the hypothalamus involved in homeostasis?
Endocrine function: signal to the pituitary via hormones
Hypothalamus release CHR –> Anterior pituitary release ACTH –>adrenal cortex release cortisol
What are the symptoms of lateral hypothalamic leison in mice?
Skinny
What are the symptom of ventromedial hypothalamic leision in mice?
Obese
Explain how the hypothalamus are involved in body fat homeostasis.
Normal body fat level: signal and target match –> intake/expenditure –> neutral energy balance
High body fat level: signal and target dont match (positive discrepancy to target) –> increase in expenditure, decrease in intake –> negative energy balance
Low body fat level: signal and target don’t match (negative discrepancy to target) –> increase in intake, decrease in expenditure –> positive energy balance
What is leptin?
A food intake regulating hormone: increased body weigth –> leptin release –> decreased food intake
Which three nuclei are important for the control of feeding?
The paraventricular-, the arcuate- and the lateral hypothalamic nucleus
Describe how the three nuclei are involved in feeding homeostasis: fasted state.
Excitatory: NPY/AgRP neurons of arcuate nucleus –> lateral hypothalamic area –> feeding behavior
Inhibitory: NPY/AgRP neurons of arcuate nucleus –I paraventricular nucleus –I secretion of hypophysiotropic hormones controlling ACTH and TSH
Describe how the three nuclei are involved in feeding homeostasis: leptin increase.
Excitatory: Alpha-MSH/CART neurons of arcuate nucleus –> paraventricular nucleus –> release of ACTH and thyrotropin from anterior pituitary + activate brainstem neurons and preganglionic neurons of sympathetic ANS
Inhibitory: Alpha-MSH/CART neurons of arcuate nucleus –I lateral hypothalamic area –I feeding behavior
Which nucleus are thought to be involved in obesity development?
Arcuate nucleus
What are the GABAergic neurons of the arcuate nucleus?
ARGP, TH and SST
What are the glutamatergic neurons of the arcuate nucleus?
POMC, TAC2, KISS1 and OXTR
How does leptin (a protein) enter the brain?
Through the circumventricular organs surrounding the 3rd and 4th ventricles, regulated by MCH neurons (activation promotes permeability, and enhance leptin action in the arcuate nucleus)
How does obesity and diabetes differ molecularly?
Ob: lacks a circulating factor
Db: lacks a receptor
