Hypothalamic and Limbic Systems Flashcards
What is the function of the hypothalamus?
Integrates information from forebrain, brainstem, and spinal cord; primary role is maintenance of homeostasis (water/electrolyte balance, food intake, temperature, BP, circadian rhythm, stress responses, and body metabolism)
Where are mammillary bodies found?
Form posterior part of the hypothalamus and are adjacent to cerebral peduncles
What is the tuber cinereum?
Small swelling between the mammillary bodies and the optic chiasm and tract
What is the median eminence?
Arises from the tuber cinereum and narrows into the infundibulum, attaches to pituitary gland
What are the longitudinal divisions of the hypothalamic nuclei?
Anterior region, tuberal region, mammillary/posterior region
What are the medial to lateral divisions of the hypothalamic nuclei?
Periventricular zone and fornix
Where is the anterior region of the hypothalamus?
Superior to optic chiasm, extending anteriorly to the lamina terminalis
Where is the tuberal region of the hypothalamus?
Superior to and including the tuber cinereum
Where is the mammillary/posterior region of the hypothalamus?
Superior to and including the mammillary bodies
Where is the periventricular zone of the hypothalamus?
Periaqueductal gray (midbrain) through the wall of the 3rd ventricle
What is the fornix of the hypothalamus?
Used to divide the remainder of hypothalamus into medial and lateral zones
What is the lateral zone of the hypothalamus?
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
What is the medial zone of the hypothalamus?
Medial zone overlaps with anterior —–> posterior regions, where neurons are arranged in distinct nuclei
What is the supraoptic/paraventricular nucleus in the hypothalamus? What do lesions result in?
Contains oxytocin and ADH (PVN) —-> posterior pituitary; lesions can result in diabetes insipidus (DI), increased H2O intake, and increased urination
What is the suprachiasmatic nucleus in the hypothalamus?
Receives retinal input and is involved in circadian rhythms; damage to this area may modify, or abolish, these rhythms
What is the function of the anterior nucleus of the hypothalamus?
Range of visceral/somatic functions, temperature regulation
What is the function of the medial mammillary nucleus of the hypothalamus? What do lesions cause?
Afferents from the hippocampus via the fornix; efferents to the thalamus & brainstem; lesions result in an inability to process short-term events —-> long-term memory
What is the function of the ventromedial nucleus of the hypothalamus? What do lesions cause?
Considered to be a “satiety center”; lesions causes excessive eating and abnormal weight gain
What is the function of the dorsomedial nucleus of the hypothalamus? What does destruction cause?
Subserves functions of emotional behavior; stimulation causes sham rage; destruction results in less aggression and feeding
What is the blood supply to the hypothalamus?
Perforating branches from circle of willis (from anterior communicating, A1, posterior communicating, P1)
What is the suprachiasmatic nucleus?
Receives direct input from the retina to mediate circadian rhythms, hormonal fluctuations secondary to light-dark cycles; conveys circadian info to other hypothalamic regions, influencing sleep-wake transitions
What does suprachiasmatic nucleus activity cause?
Opposes drive for sleep, is essential for timing of rest vs activity
What is the function of the limbic system?
Connections influence behavior, memory, and pain perception
What is the function of the hippocampal formation?
Important in learning and memory
What is the function of the amygdala?
Vital to the motivational and emotional connotations of experience
What is the function of the Papez circuit?
Oversimplification of the role of limbic system plays in modulating feelings (fear, anxiety, sadness, happiness, etc)
What is the septal region?
Small area just rostral to the anterior commissure thought to control of rage behavior
What is the medial forebrain bundle?
Diffuse group of dopaminergic fibers that courses rostrocaudally through the lateral hypothalamic area; major conduit for septal nuclei and hypothalamus to communicate with the brainstem
What is the nucleus accumbens?
Receives input from the amygdala and hippocampus; play an important role in behaviors related to addiction and chronic pain; efferents include hypothalamus, brainstem, and globus pallidus
What is hippocampal amnesia?
Bilateral lesions of the hippocampi; causes profound deficit in anterograde episodic memory (cannot learn new material), combined with spared procedural and working memory; patients IQ and formal reasoning were fairly normal
What is Korsakoff’s Syndrome?
Progressive degeneration of the mammillary bodies, hippocampal complex and dorsomedial thalamic nucleus; impedes retention of newly acquired memory; can’t take short-term to long-term memory; difficulty in understanding written material and conducting meaningful conversations; patient will confabulate, combine fragmented memories into a synthesized memory of an “event” that never occurred; caused by a thiamine deficiency, typically associated with chronic alcoholism
What is anosmia?
Loss of smell due to a viral infection of the olfactory mucosa, obstruction of the nasal passages, or may be congenital; patients do NOT recover the sense of smell
What is phantosmia?
Distortion in a smell experience or the perception of a smell wen no odor is present; results from a lesion of anterior/medial temporal lobe
What is Kluver-Bucy Syndrome?
Bilateral temporal lobe lesions that abolish amygdaloid complex; results in visual agnosia, hyperorality, hypermetamorphosis, placidity, hyperphagia, hypersexuality
What are the signs of an uncal herniation?
Dilated pupil and abnormal eye movements (CN III involvment) with double vision ipsilateral to the herniation; weakness of the extremities (CST involvement) opposite dilated pupil; as it progresses, respiration is affected, abnormal reflexes appear, and there is a potentially rapid decline
