hypothalmus Flashcards
function of hypothalamus
- Homeostasis
- maintenance of the body’s internal environment within normal physiological parameters
- carries out the function through interconnections with areas of the brain related to emtions, Sleep/awakenings, hormones and autonomic activity
- MONITORS blood glucose levels, blood osmolarity, body temperature and various hormone levels
blood supply to hypothalamus
- Perforating branches of circle of willis
Boundaries of hypothalamus
- Superior = hypothalamic sulcus
- anterior = lamina terminalis
- posterior = midbrain (interpeduncular fossa)
- inferior = optic chiasma, tuber cinereum, mammillary bodies
overview of hypothalamus
- hypothalamus is nodal point of interconnecting structures relating to autonomic, endocrine, emotional and somatic functions
- ALL FUNCTIONS relate to MAINTAINING homeostasis
–> stable internal environment, including temperature, hydration, glucose and monitoring hormone levels
describe the major INPUTS
- cerebrum = thoughts and decision
- Limbic system = organizes appropriate behavioral responses associated with basic drives, “feeling”, motivation
- Retina = light information (amount/duration of day/night)
- Branstem and spinal cord = info from viscera
- Intrinsic neurons = monitoring blood temp, osmolarity, hormone levels, glucose concentration
describe major outputs
- To brainstem and spinal cord = influences viscera, especially AUTONOMIC FUNCTION
–> VII, IX, X, T1-L2, S2-4
- To PITUITARY = produces secretions (hormones and releasing factors)
Suprachiasmatic nucleus
- RECEIVES: light information from retina via RETINOHYPOTHALAMIC TRACT (retinosuprachiasmatic)
- NUCLEUS contains MELATONIN RECEPTORS
- Pineal secretes melatonin varying with light levels
- melatonin helps SET and SYNCHRONIZE the “clock”
- NUCLEUS CORRDINATES SLEEP/WAKEFULNESS CYCLES in the RETICULAR FOMRATION and other CIRCADIAN RHYTHMS
Mammillary bodies (nuclei)
- PROCESSES EMOTIONAL INFORMATION
- INPUT: from hippocampus and amygdala (largest INPUT pathway is FORNIX)
- OUTPUT: mammillothalamic, mammillotegmental tracts
- HYPOTHALAMUS TRIGGERS APPROPRIATE VISCERAL RESPONSES:
–> brainstem parasympathetic nuclei (VII, IX, X)
–> spinal cord sympathetic and parasympathetic segments (T1-L2, S2-S4)
Why is memory so important to hypothalamic function
REMEMBERING AND LEARNING
- location of food sources increases chances of feeding
- location of water sources increases changes of maintaining hydration
- location of and tactics for avoiding predators increases chances of long-term survival
- location of warmer climate associated with changing daylight length triggers migration for survival
- location and status of receptivity of potential mates increases chances for procreation
describe the autonomic control and integration of hypothalamus
- INPUT: Ascending visceral info from internal organs (pain, empty stomach, drysness in mouth, enviornmental factors) and limbic system (emotional info)
- OUTPUT: Parasympathetic and sympathetic
- Fibers from various nuclei converge on PARAVENTRICULAR NUCLEUS and then via dorsal longitudinal fasciculas and mammillotegmental tracts to brainstem and spinal cord
describe Parasympathetic control and integration of hypothalamus
- Nuclei = PREOPTIC and ANTERIOR
- Response = pupillary constriction, increased salivation, decreased BP and HR, increased GI peristalsis
describe sympathetic control and integration of hypothalamus
- Nuclei = POSTERIOR and LATERAL
- RESPONSE = pupillary dilation, decreased salivation, INCREASED HR and BP, decreased GI peristalsis, VASOCONSTRICTION
Anterior hypothalamus function in thermostat
- NUCLEI: Preoptic and anterior nuclei initiate HEAT LOSS
- VISCERAL RESPONSE: Sweating and vasodilation
- decreased motor activity
- BEHAVIOR: seek cooler environment, fan yourself
- ASPIRIN causes antipyretic (fever reducing) effect by acting DIRECTLY on HYPOTHALAMUS
Posterior hypothalmus function in thermostat
- NUCLEI: posterior nuclei activate heat production
- VASOCONSTRICTION
- increased muscular activity (including shivering)
- TH increases metabolic heat production
- BEHAVIOR: put on more clothes
describe the hypothalmus function of regulating food intact
- LATERAL NUCLEUS = Stimulation INDUCES eating, “feeding or hunger” center
- VENTROMEDIAL NUCLEUS = stimulation INHIBITS eating, “satiety” center
Osmoreceptors
- Monitor the concentration/hydration of blood
- Stimulation of the lateral hypothalamus (zona incerta) STIMULATES DRINKING
Glucoreceptors
- monitor glucose levels
- Affects feeding and satiety centers
describe hormonal control of Posterior pituitary
- hypothalamus synthesizes and releases the hormones of posterior pituitary (neurohypophysis)
- Nuclei: supraoptic and paraventricular
- Pathway: hypothalamo(supraoptico)hypophyseal tract
- Hormones:
–> ADH(antidiuretic hormone, vasopressin) = water conservation, increase blood pressure
–> oxytocin = uterus contractions, milk let down
- Intrinsic osmoreceptors sense and TRIGGER ADH to CONSERVE water
What is the result of damage to posterior pituitary
- INTERRUPT SYNTHESIS OF ADH leading to copious URINE FORMATION and CONSTANT THIRST
–> called DIABETES INSIPIDUS (tasteless)
- Blood and urine sugar levels are within normal limits
describe the hormonal control of anterior pituitary
- hypothalamus produces releasing factors that STIMULATE or INHIBIT release of hormoens from anterior pituitary (adenohypophysis)
- NUCLEI = ARCUATE, medial preoptic, preoptic, PERIVENTRICULAR nuclei
- Pathway: tuberohypophysial (-infundibular) tract then vascular, hypothalmo-hypphyseal portal system to adenohypophysis (anterior pituitary)
- Hormones: affect BODY GROWTH, thyroid secretion, gonadal function, adrenocortical secretion and mammary gland secretion
describe visceral response to CONSCIOUS THOUGHT
- thoughts, feelings, emotions can elicit:
- SYMPATHETIC RESPONSE = sweating and blanching, accelerated HR, constipation, increased or decreased frequency of urination when WORRIED OR SCARRED
- PARASYMPATHETIC RESPONSE = sexual dysfunction when depressed
- INTERRUPTION of NORMAL CYCLING OF gonadotrophic hormones = skipped or delayed menstration with worry or depression
describe Somatic response to CONSCIOUS and unconscious thoughts
- Slouching and moving slowly when depressed (Limbic)
- quick, agitated movements when STRESSED or ANXIOUS
- thoughts and emotions DRIVE facial movements appropriate to those thoughts and emotions
–> sad face, happy face, frightened face
describe the clinical correlation of direct connections between frontal lobs and hypothalmus
- Stroke victums can still move otherwise paralyzed muscles with EMOTIONAL RESPONSE
–> ex: smiling at a joke (duchenne smile)
- The muscles are ONLY PARALYZED for VOLUNTARY MOVEMENT (pyramid pathway, corticonuclear, is interrupted)
- pathway from cerebrum to hypothalamus takes DIFFERENT ROUTE (not well defined
function of suprachiasmatic
- circadian cycles, the clock
