Hypothalamus Flashcards
Two general classes of hypothalamic function
- Homeostasis: maintains balance of functions within a narrow range
- Allostasis: attempts to maintain balance in the face of changing conditions, often leading to variable responses
Major subdivisons of the hypothalamus
- Anterior region–lateral and medial preoptic nuclei, SCN
- Tuberal region–PVN, arcuate, supraoptic, anterior, ventromedial, and dorsomedial nuclei
- Lateral-posterior region–posterior area and mammilary bodies
Hyperthermia
-Affects anterior hypothalamus which controls the heat-loss mechanism
Hypothermia
-Affects posterior hypothalamus which controls the heat-conservation mechanism
Genital dystrophy and abnormalities in sexual development
-Tuberal region
Feeding, obesity, and emaciation
- Obesity: lesions of ventromedial hypothalamus
- Emaciation: lesions of lateral hypothalamus
Diabetes insipidus
-Supraoptic and paraventricular nuclei (from which ADH is synthesized)
Hypertension
-Excess release of corticotropin-releasing factor in medial hypothalamus
Sleep disorders
-Lesions of posterior hypothalamus-midbrain border
Aggression and rage behavior
-Tumors in medial hypothalamus
Superior hypophysial artery
-Supplies portal system in the median eminence from which drain the long portal veins to the adenohypophysis
Inferior hypophysial artery
- Supplies the portal system in the intermediate lobe which empties via the short portal veins into the adenohypophysis
- Also supplies a portal system in the neurohypophysis
Main hypothalamic functions
- Limbic
- Autonomic
- Neuroendocrine
- Body temperature
- Energy metabolism/food intake
Hypothalamus role in neuroendocrine function
-Regulates hormone release from the pituitary gland by axons that either project onto it or secrete releasing factors into the portal systems
Hypothalamus role in temperature regulation
- Temperature signals sent via spinohypothalamic tract
- Anterior hypothalamus (ahhh) regulates sweating to reduce body temp
- Posterior hypothalamus (p-p-please) regulates shivering to increase body temp
- Pre-optic nucleus compares input with internal set-point temperature
Determinants of hunger
- Physiological signals
- Adrenergic receptors in medial hypothalamus
- Serotonergic, dopinergic, and beta adrenergic receptors in the lateral hypothalamus
Neurotransmitters involved in eating
- Opiods: involved in pleasure and pain
- Corticotropic releasing factor: stress related
- Monoamines: involved in moods
- Gaba: involved in anxiety
Factors that inhibit food intake
- Serotonin
- Dopamine
- Leptin
- Corticotrophin-releasing factor
- MSH
- CART
- Calcitonin gene related peptide
- Amylin
- Glucagon
- Glucagon-like peptide 1
Factors that stimulate food intake
- Ghrelin
- NPY
- Cholecystokinin
- Neurotensin
- Bombesin
- Agouti-related protein
Orexigenic signals
- Feed me!
- Empty stomach releases ghrelin–>NPY increases in the arcuate nucleus within 6 hours of food deprivation
- Lateral hypothalamus area and paraventricular nucleus stimulate food intake
- AGRP increases in the arcuate nucleus and blocks action of anorexigenic MSH and MC3 and MC4 receptors
- NPY expressing neurons in the arcuate nucleus also express receptors for leptin and insulin and are inhibited by these satiety signals
Anorexigenic signals
- No thank you!
- Leptin, insulin, MSH, cocaine and amphetamine regulated transcript, POMC, and glucagon like peptides 1 and 2 fall with food deprivation and rise with overfeeding
- Key signals are gamma and alpha MSH acting at MC3 and MC4 receptors.
- CART is an antagonist of orexigenic NPY
Disorders producing diminished appetite-Anorexia
- Lateral hypothalamic lesions
- Advanced degenerative brain disease
- Systemic medical illnesses
- Psychiatric disorders: depression, anorexia nervosa
Disorders producing increased appetite- Hyperphagia
- Medial hypothalamic lesions
- Bilateral temporal lobe injury (kluver-bucy)
- Psychiatric disorders: mania, depression, bulimia
- Prader Willi
Prader Willi Syndrome
- Paternal genes are not expressed on chromosome 15
- Disrupts normal function of the hypothalamus
- Uncontrollable hunger, stunted growth, sexual underdevelopment, slowed mental/motor development
