Hypothalamus and Limbic Systems (Dennis) Flashcards
The hypothalamus is inferior to the _____, forms walls & floor
of _______. Anatomically, part of the ______, but
functionally, part of the ______.
Inferior to the thalamus, forms walls & floor
of 3rd ventricle. Anatomically, part of the diencephalon, but
functionally, part of the limbic system.
What does the Hypothalamus regulate
- Basic drives (motivated, goal-directed behavior)
- Emotional or affective behavior
- Homeostasis
- ANS
- Has endocrine function
Food intake/body weight, fluid &
electrolyte balance, body temperature
- Sexual & reproductive behavior*
- Sleep–wake cycles/circadian rhythms*
What is the anterior (rostral) border of the hypothalamus?
Optic Chiasm
What is the posterior (caudal) border of the hypothalamus?
Midbrain (tegmentum/PAG)
What does the hypothalamus continue into?
Infundibular stalk and posterior pituitary
Are mammillary bodies found on the anterior or posterior part of the hypothalamus?
Posterior
What is the tuber cinereum?
Small swelling between optic chiasm and mammillary bodies & tract
What is the median eminence?
Arises from tuber cinereum and eventually becomes infundibulum, attached to pituitary gland
What divides the hypothalamus into functional medial and lateral zones
Fornix
Which hypothalamic zone contains scattered neurons which carry two-way traffic?
Lateral zone
Which of the hypothalamic zone contains the majority of hypothalamic nuclei?
Medial zone
What are the functional areas within the medial zone aof the hypothalamus?
Anterior area
Middle/Tuberal area
Posterior area
Where is the median forebrain bundle located
Lateral zone of the hypothalamus
Damage to what structure leads to a decrease in feeding behavior with a loss in weight
Median forebrain bundle
What are the nuclei located in the Anterior Area of the hypothalamus
- Supraoptic/paraventricular nucleus
- Suprachiasmatic nucleus
- Anterior nucleus
Lesion to what nuclei can result in diabetes insipidus, increased water intake and increase in urination
Supraoptic/paraventricular nucleus
Lesion to what nuclei may modify or abolish circadian rhythms
Suprachiasmatic nucelus
What are the nuclei found in the Middle/Tuberal Area of the hypothalamus
- Ventromedial nucleus
- Dorsomedial nucleus
- Arcuate nucleus
Lesion to what nuclei would cause excessibe eating and abnormal weight gain
Ventromedial nucleus
Lesion to what nuclei would result in decreased aggression and feeding
Dorsomedial nucleus
What nucleus is found in the Posterior Area of the hypothalamus
Medial mammillary nucleus
Lesion to what nuclei would reult in an inability to process short-term events to long term memory
Medial mammillary nucleus
What is the limbic system
Bridge connecting endocrine, visceral, emotional and voluntary responses to the environment
What constitutes the limbic system
- Subcallosal Area
- Cingulate gyrus
- Parahippocampal gyrus
- uncus
- hippocampal formation
- subcortical structures (hippocampus, amygdala and septal nuclei)
What structures are the anatomical basis for emotional, drive-related and motivated aspects of behavior
Hypothalamus & limbic system
What makes up the hippocampal formation aka Hippocampus
Subiculum
Hippocampus proper (ammon horn)
Dentate gyrus
What is the hippocampal formation important for
Learning & memory
What is the afferent pathway of the hippocampal formation
Dentate gyrus –> CA3 –> CA1 –> Subiculum
What is the fferent pathway of the hippocampal formation
Fibers of the subiculum & hippocampus proper –> fimbria –> fornix
Where does the fornix project information from the hippocampus, specific to learning & memory
- Medial mammillary nucleus
- Ventromedial nucleus (dorsal thalamus)
- anterior nucleus (dorsal thamalmus)
- Septal nuclei
- Frontal cortex
- Preoptic & anterior nuclei (hypothalamus)
- nucleus accumbems
What is an uncal herniation
Movement of the uncus and possibly the parahippocampal gyrus downward over the edge of the tentorium cerebelli leading to hemorrhagis lesion or tumor in the hemisphere
What are signs of uncal herniation
- Dilates pupil and abnormal eye movements (CN III) with double vision ipsilateral to the herniation
- Weakness of the extremities oppsite to the dilated pupil
- Respiration affected as it progresses, abnormal reflex appear & there is a potentially rapid decline
What is the neuroanatomical basis of Korsakoff’s Syndrome
Progressive degernation of the mammillary bodies, hippocampal complex & dorsamedial thalamic nucelus
What are the clinical manifestations of Korsakoff’s Syndrome
- Impedes the retention of newly acquired memory (short term memory does not become 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.
What can cause Korsakoff’s Syndrome
Thiamine deficiency, typically associates with chronic alcoholism
What is the neuroanatomical basis of hippocampal amnesia
Bilateral lesions of the hippocamp
What are the clinical manifestations of hippocampal amnesia
Profound deficit in anterograde episodic memory (cannot learn new material), combined with spared procedural and working memory
What is Anosmia
Loss of smell due to viral infetion of the olfactory mucosa, obstruction of the nasal passages or may be congenital
What is the neuroanatomical basis for ansomia
Lesions due to shearing of CN1 or tumors in the floor of the anterior cranial fossa
What is Phantosmia (olfactory hallucination)
Distortion in a smell experience or the perception of a smell when no odor is present
What is the neuroanatomical basis of Phantosmia (olfactory hallucination)
Lesions of anterior/medial temporal lobe. Can also be a result of lesions to the hippocampus, amygdala or medial dorsal thalamic nuclei
What are the anatomical connections bewteen the olfactory and limbic system
Hippocampus
amygdala
meial dorsal thalamic nuclei
What is the role of the amygdala
- Attaches emotional significance to a stimulus
- Regulates visceral responses to emotional stimuli, including pain
- Regulates emotional responses to food (pleasant smell stimulate appetite & unpleasent smells suppress appetite)
Lesion to the amygdala results in what
Impared recognition of fear, anger & dsigust in facial expressions as well as vocal affect (fear, anger)
What are the efferent pathways of the amygdala and what do they target
Stria Terminalis: Target hypothalamus, Ventral Striatum & Septal Nuclei
Amygdalofugal Pathway: Target hypothalamus, Ventral Striatum, Septal Nuclei & cerebral cortex, including the frontal, prefrontal, cingulate & inferior temporal cortical areas
What is the neuroanatomical basis of Kluver-Bucy Syndrome
Bilateral temporal lobe lesions that abolish amygdaloid complex
What are the clinical manifestations of Kluver-Bucy Syndrome
- Visual agnosia, inability to recognize an object by sight
- Hyperorality, tendency to examine objects by mouth
- Hypermetamorphosis, compulsion to intensively explore the immediate environment or overreact to visual stimuli
- Placidity, may not show fear or anger even when such a reaction is appropriate
- Hyperphagia, eating excessive amounts even when not hungry or when objects are not actually food
- Hypersexuality, suggestive behavior and talk with vague or ill-conceived attempts at sexual contact
Where is the ventral tegmental area located
In the midbrain, medial to the substantia nigra
What is the role of the VTA & what neurons does it house
Important in reward and motivation, may contribute to addiction.
Houses doapminergic neurons
What does the VTA makes connections with
Ventral Striatum
Amygdala
Other limbic structures
What is the nucleus accumbens and where is it located
Important in behaviors related to addcition and chronic pain
Located in forebrain, near continuation of causate and putamen
What is the Septal Nuclei and where is it located
Plays a role in reward/pleasure as well as control of rage.
Located rostral to anterior commissure
What is the Papez circuit
The neuroanatomical basis for emotional attachments to memory and emotional experiences which involve reciprocal interactions between the diencephalon and cerebral cortex
