Hypothalamic and Limbic Systems Dr. Dennis Flashcards
Where is the hypothalamus and what is its relationship to the third ventricle?
Inferior to thte thalamus forms walls and floors of third ventricle
Where are the mammillary bodies located?
posterior part of hypothalamus and are adjacent to cerebral peduncles
Where is the Tuber Cinereum?
Small swelling between mammillary bodies and optic chiasm and tract
Where is the median eminence?
arisses from tuber cinereum and narrows into infundibulum attaches to pituitary gland
What is the lateral zone of the hypothalamus?
- Carries two way traffic through hypothalamus rostrally towards forebrain and caudally to brainstem
What is found in the medial zone of hypothalamus
- Conrtains majority of hypothalamic nuclei
- Has three fxnl areas:
- Anterior area
- Middle area
- Posterior area
What is the anterior area?
- Within medial zone
- Superior to optic chiasm
- contains pre optic suprachiasmatic supraoptic paraventricular and anterior nuclei
Middle area?
- Within Medial zone
- Superior to and including tuber cinereum
- contains dorsomedial ventromedial and arcuate nuclei
Posterior area
- Within medial zone
- Superior to and including mammillary bodies
- contains posterior nucleus and mammillary bodies
Describe the lateral nucleus
- Contains median forebrain bundle that carries info to and from hypothalamus
- Within the lateral zone
- Damage to this area results in decrease in feeding behavior with weight loss
Supraoptic & Paraventricular nuclei?
- Contain oxytocin (PVN) and ADH (SON)
- Lesionis can result in diabetes insipidus
- Within the anterior area of the medial zone of hypothalamus
Suprachiasmatic nucleus?
- Receives retinal input and involved in circadian trhythms
Anterior nucleus
- Range of visceral somatic functions, temp regulation
- Within the anterior area of medial zone
Ventromedial nucleus
- Satiety center
- Lesions causae excessive eating and weight gain
- Middle tuberal area of hypothalamus
Dorsomedial nucleus
- Emotional behavior, stimulation causes rage
- Destruction results in decreased aggression and feeding
- Middle tuberal area of hypothalamus
Arcuate nucleus
- Secretes releasing and inhibiting hormones
- Middle tuberal area of hypothalamus
Medial mammillary nucleus
- Part of posterior area
- Afferents from hippocampus via fornix
- Efferents to the thalamus and brainstem
- Lesions result in inability to process short term events into long term memories
What is the blood supply to hypothalamus?
- Anteromedial group from A1 and anterior communicating to preoptic area supraoptic nuclei and rostral part of lateral hypothalamus
- Posteromedial group perforating arteries from PoCoA and PCA P1
- Rostral portion of PoCoA tuberal region
- Caudal parts of PoCoA mammillary region
What does the fornix do?
Hippocampal fibers relaying afferents to the mammillary bodies
What does the stria terminalis and ventral amygdalofugal fibers do?
Afferent fibers from amygdala to hypothalamus
What is corticohypothalamic input?
- Afferents from orbitofrontal and cingulate areas, multiple assoc. areas and frontal lobe to lateral zone
Where do Retinohypothalamic fibers go?
Afferents that Target SCN
What is median forebrain bundle and Dorsal longitudinal fasciculus?
- Relay two way information to and from the hypothalamus
- Efferent
What are the efferents descending to PAG and RF?
- Hypothalamomedullary fibers
- Hypothalamospinal fibers
- Medial zone and mammillary bodies
- Enables hypothalamus to influence emotion aspects of behavior
What are the ascending routes of the efferents in hypothalamus? (4)
- Hypothalamocortical fibers ascend to forebrain target frontal lobe
- Mammillothalamic tract projects to anterior nucleus of thalamus
- Lateral zone projects to DM nucleus of thalamus
- Thalamic nuclei send projections to frontal lobe
What is the supraopticohypophysial tract?
- Made of axons of neurons in supraoptic nucleus and Paraventricular nucleus
- Produces oxytocin and ADH to be released by Post Pit.
- Stored in herring bodies and released into the capillary plexus of posterior pituitary
What is the tuberoinfundibular tract?
- Input from neurons located in periventricular zone, PVN
- Conveys releasing hormones to median eminence and infundibulum
How is the anterior area of the hypothalamus relate to ANS?
- Activates Parasympathetic activity
- Efferents to the brainstem parasympathetic neurons from CN III VII IX X and spinal S2-4
How does the posterior area of the hypothalamus relate to ANS?
- Activates sympathetic activity
- Efferents to sympathetic neurons in lateral horn of T1-L2
- Lesions in anterolateral medulla disrupt hypothalamomedullary fibers so the sympathetic output to the face and head or body resulting in hroners syndrome
What is the significance of the suprachiasmatic nucleus?
- Receives direct input from the retina to mediate circadian rhythms
- This coveys circadian info to other hypothalamic regions for sleep and wake cycles
- SCN activity opposes drive for sleep
In general what does the limbic system include and what does it do?
- Includes subcallosal area, cingulate gyrus, parahippocampal gyrus, uncus, hippocampal formation and subcortical nuclei
- between hypothalamus and neocortex
- Connections influence behavior, memory and pain perception
What is the hippocampal formation?
- Curved sheet of cortex for learning and memory folded into the medial part of temp lobe
- Made of Subiculum, Hippocampus propper, and Dentate nucleus
What is the parahippocampal gyrus?
- Cortex overlying the hippocampal formationi anterior part of parahippocampal gyrus is called the entorhinal cortex
What is the afferent pathway of the hippocampal formation?
- Dentate gyrus to CA3 to CA1 to the Subculum
What is the hippocampal formation efferent pathway?
- Fibers from cell bodies in the subiculum (CA2) and hippocampus proper (CA1) bundle into fibria making the fornix
- This terminates in the medial mammillary nucleus ventromedial nucleus and anterior nucleus
What is an Uncal Herniation and signs?
- Movement of the unus and potential the parahippocampal gyrus down over the tentorium cerebelli
- can compress midbrain and can damage lower brainstem if not caught
- Dialated pupil, abnormal eye movements, diplopia, weakness due to CST involvement, respiration eventually can be affected as well as abnormal reflexes
- eventual decline if not caught
What is Korsakoff’s syndrome?
- Progressive degeneration of mammillary bodies hippocampal complex and dorsomedial thalamic nucleus
- This impedes retention of new memories to create long term memories
- Difficulty constructing meaningful statements and confabulation occurs
- caused by thiamine deficiency caused by chronic alcoholism
What is hippocampal amnesia?
- Bilateral lesions of hippocampus
- Profound deficit in anterograde episodic memory cant learn new material combined with spared procedural and working memory
- IQ and formal reasoning are normal
What is Anosmia?
- Loss sof smell due to viral infection of olfactory mucosa obstruction of nasal passage or possibly congenital
- If lesion shearing CN1 or tumors in floor of anterior cranial fossa patients do not recover smell
Phantosomia?
- Olfactory hallucination
- distortion in smell or perception of it when none is present
- abnormal sequence of neuronal activity due to lesion of anterior medial temporal lobe hippocampus amygdala or medial dorsal thalamic nuclei
What is the amygdala?
- Attaches emotional significance to a stimulus
- Regulates visceral responses to emotional stimuli and pain
- emotional responses to food pleasant smells stimulate appetite and unpleasant smells suppreses appetite
What are the afferents of the amygdala?
- Sensory info from raphe nuclei, PAG, dorsal motor nucleus of X, nucleus ssolitarius and locus ceruleus
- Input from dorsomedial nucleus of thalamus and info from widespread cortical areas
What are the efferents of the amygdala?
- Stria terminalis and ventral amygdalofugal paths
- These target the hypothalamus ventral striatum and septal nuclei
- cerebral cortex including frontal prefrontal cingulate and inferior temproal cortical areas
What happens if tehre is a lesion in the amygdala?
- Lesion results in imparied recognition of fear, anger, and disgust in facial expressions and vocal affect
What is Kluver-Bucy syndrome?
- Bilateral temporal lobe lesions that abolish amygladoid complex
- results in behavioral changes such as:
- visual agnosia
- Hyperorality
- Hypermetamorphosis-compulsion to intensively expore environment
- Placidity
- Hyperphagia
- Hypersexuality
What is the ventral tegmental area?
- Medial to substantia nigra and houses dopaminergic neurons
- connects with ventral striatum amygdala and other limbic structures
- important for reward and motivation, may contribute to addiction
What is the septal nuclei?
- Small area rostral to anterior commissure
- Reciprocal connections with oolfactory bulub hippocampus throughthe fornix and amygdala
- Reole in reward/pleasure and control of rage
What is the nucleus accumbens?
- Located in forebrain near continuation of caudate and putamen
- Important in behaviors related to addiction and chronic pain
Papez circuit?
- emotional experience involves reciprocal interactions btw diencephalon and cerebal cortex
- fornix projects to mammillary bodies
- Amygdala is key in expression emotions emotional memory
- Inerconnectiosn btw limbic system and hypothalamus
- Assoc. areas of cortex prefrontal are important
Cingulate cortex–>cingulum–> hippocampus—>fornix–>mammiillary bodies–> mammilothalamic tracti–> thalamus anterior nuclei–>cingulate cortex
