Hypothalamus & Limbic system Flashcards
Hypothalamus
Basic anatomy
▪ part of diencephalon
▪ inferior to the thalamus
▪ within floor and walls of the third ventricle
Surrounded by several structures
▪ infundibulum & median eminence
▪ optic chiasm
▪ circle of Willis
Hypothalamus
Summary of functions
Maintain homeostasis
▪ e.g., hunger, satiety, body temperature, sleep/wake cycle, etc.
Functional regions of hypothalamus
1 Autonomic function
Anterior hypothalamic nuclei
▪ promote parasympathetic system
Posterior hypothalamus nuclei
▪ promote sympathetic system
Functional regions of hypothalamus
2 Temperature regulation
Anterior hypothalamic nuclei
▪ regulate temperature in response to increased temperatures
▪ inhibit heat production
▪ lesion produces hyperthermia
Posterior hypothalamus nuclei
▪ regulate temperature in response to decreased temperatures
▪ promote heat production
▪ lesion produces hypothermia
Functional regions of hypothalamus
3 Water balance
▪ hypothalamus has blood osmolarity sensors
➢ lack blood-brain barrier
Paraventricular & Supraoptic nuclei
▪ production/release of posterior pituitary hormones (esp. ADH - vasopressin)
▪ destruction =diabetes insipidus (loss of ADH)
Functional regions of hypothalamus
4 Food intake
Ventromedial nuclei
▪ “satiety center” (fullness)
▪ role in feeding
▪ also role in expression of emotions (anger, etc…)
➢ destruction produces rage
Lateral hypothalamic nuclei
▪ “hunger” center
▪ role in feeding behavior
➢ destruction produces anorexia/starvation
Functional regions of hypothalamus
5 Pituitary control
▪ regulate pituitary hormone release
Arcuate nuclei (infundibular or tubular)
▪ major area of production of anterior releasing hormones
▪ control of anterior pituitary hormones
Paraventricular & Supraoptic nuclei
▪ production/release of posterior pituitary hormones (oxytocin and ADH -
vasopressin)
Functional regions of hypothalamus
6 Emotion
Ventromedial nuclei
▪ “satiety center” (fullness)
▪ also role in expression of emotions (anger, etc…)
➢ destruction produces rage
Dorsomedial nuclei
▪ role in expression of emotions (anger, etc…)
➢ stimulation produces rage
Functional regions of hypothalamus
7 Circadian Clock (sleep-wake cycle)
Suprachiasmatic nuclei
▪ role in circadian clock (receives input from retina)
Lateral preoptic nucleus
▪ plays role in non-REM sleep onset
Limbic system Overview
Areas of CNS controlling emotion and behavior “feel, feed, fight, flee, and f…., uh, sexual behavior”
Primary outputs to autonomic nervous system via the hypothalamus
Major components of limbic system: there is much disagreement about which structures to include (or exclude)
Amygdala
Critical connections between sensory association input and hypothalamus
▪ “sensory input ends at the amygdala” – connection between memory and
behavior
▪ receives a wide range sensory inputs (e.g., visual, auditory, somatosensory,
gustatory, pain, etc) directly & indirectly
➢ esp from insula, anterior cingulate cortex, & hypothalamus
Fear, rage/aggressiveness and feeding behavior
Connects to hypothalamus (mammillary bodies) via fornix
Bilateral damage
▪ may result in placidity, loss of fear, rage, and aggressiveness
➢ note: damage to one part of amygdala may modify, inhibit or promote these
behaviors
Hippocampus (and surrounding entorhinal cortex)
Plays role in learning and memory
▪ converting short term memory (< 1 hr) to long term memory
Large output via the fornix
▪ lies within lateral ventricles
Damage
▪ must be bilateral to see symptoms
▪ anterograde amnesia
➢ inability to create long term memories
▪ able to recall previous long term memory
Orbitofrontal cortex
Facilitate perception of smell
Hypothalamus
Midbrain
Raphe nuclei
Anterior tegmental area of midbrain (projects dopamine pathways to limbic areas
Thalamus
Mediodorsal nuclei of thalamus
▪ role in affective behavior and memory
b Anterior nucleus of thalamus
▪ critical link in Circuit of Papez
