Hypothalamus Flashcards
Describe the location and structure of the hypothalamus
Inferior to thalamus
Forms walls and floor of 3rd ventricle
Anatomically part of the diencephalon but functionally part of the limbic system
What are some functions of the hypothalamus?
Regulates basic drives (motivated goal-directed behaviors) as well as emotional or affective behavior
Regulator of homeostasis, ANS and endocrine function
Food intake/body weight, fluid and electrolyte balance, body temperature
Sexual and reproductive behavior
Sleep-wake cycles/circadian rhythms
What is the rostral/anterior boundary of the hypothalamus?
Optic chiasm
What is the caudal/posterior boundary of the hypothalamus?
Merges into tegmentum and PAG (midbrain)
What do the mammillary bodies form?
Posterior part of the hypothalamus and are adjacent to the cerebral peduncles
What is the tuber cinereum?
Small swelling between the mammillary bodies and the optic chiasm + tract
What is the median eminence?
Arises from the tuber cinereum and narrows into the infundibulum
Attaches to pituitary gland
What are the hypothalamic zones?
Divided into functional areas of nuclei along the lateral -> medial and anterior -> posterior axes
Columns of the fornix cut through the hypothalamus en route to the mammillary bodies -> divide hypothalamus into lateral and medial zones
What does the lateral zone contain?
Scattered neurons interspersed among major bundles of fibers, which carry two-way traffic through the hypothalamus, rostrally toward the forebrain and caudally toward the brainstem
What does the medial zone contain?
The majority of hypothalamic nuclei
What are the hypothalamic areas?
Three functional areas exist within the medial zone along the AP axis
Includes the anterior, middle (tuberal) and posterior area
Where is the anterior area of the hypothalamus and what nuclei does it contain?
Superior to optic chiasm
Contains the preoptic, suprachiasmatic, supraoptic (medial and lateral), pareventricular and anterior nuclei
Where is the middle (tuberal) area and which nuclei does it contain?
Superior to and including the tuber cinereum
Contains the dorsomedial, ventromedial and arcuate nuclei
Where is the posterior area and which nuclei does it contain?
Superior to and including the mammillary bodies
Contains the posterior nucleus and mammillary bodies
Describe the nucleus of the lateral zone
Diffusely arranged neurons with few named nuclei
Contains the median forebrain bundle
Damage results in a decrease in feeding behavior with a resultant weight loss
Describe the supraoptic/pareventricular nucleus of the anterior area
Contain oxytocin (PVN) and ADH (SON) —> posterior pituitary Lesions result in diabetes insipidus (DI), increased H2O intake and increased urination
Describe the suprachiasmatic nucleus of the anterior area
Receives input and is involved in circadian rhythms
Damage to this area may modify or abolish these rhythms
Describe the anterior nucleus of the anterior area
Range of visceral/somatic functions
Temperature regulation
Describe the ventromedial nucleus of the middle (tuberal) area
Satiety center
Lesions cause excessive eating and abnormal weight gain
Describe the dorsomedial nucleus of the middle area
Subserves emotional behavior
Stimulation causes sham rage
Destruction results in decreased aggression and feeding
What is the function of the arcuate nucleus of the middle area?
Secretes releasing/inhibiting hormones
Describe the medial mammillary nucleus of the posterior area
Afferents from the hippocampus via the fornix
Efferents to the thalamus and brainstem
Lesions result in an inability to process short term events into long term memory
What provides blood supply to the hypothalamus?
Served by small perforating arteries from the circle of Willis
What does the anteromedial group of the circle of Willis supply?
Branches from anterior communicating and anterior cerebral arteries (A1)
Serve preoptic area and supraoptic region, septal nuclei and rostral portions of lateral hypothalamic area
