Thalamus And Hypothalamus Flashcards
Where is the 3rd ventricle relative to the thalamus (diencephalon)
Medial to it
Where does the diencephalon run along
3rd ventricle
Thalamus and hypothalamus are deep (lateral) to
3rd ventricle wall
What is the thalamus superior to
Hypothalamus and midbrain
Hypothalamus is anterior to
Midbrain
Anterior border of diencephalon is marked by
The crossing of anterior commissure and optic chiasm
What runs right between the thalamus
3rd ventricle
What is the thalamus
A bunch of nuclei
Where are the LGN and MGN
Thalamus
What sits underneath the thalamus
LGN and MGN
What sits int he back near the bottom of the thalamus,us
Pineal body
Thin gray zone separating lateral vs anterior vs medial groups of nuclei on the thalamus
Intralaminar zone
Contains intralaminar nuclei, part of reticular activating system
Intralaminar zone
Midline nuclei
Single (un paired nuclei)
Means pillow. Posterior postion, related to visual system
Pulvinar
MD nucleus
- olfactory and emotional information
- amygdala, olfactory cortex, basal ganglia
Anterior nucleus of thalamus
- from hypothalamus talks to cortex and pays attention to stressful events
- mammillothalamic tract, fornix
VA/VL nucleus of thalamus
Substantia nigra pars reticulata, GPi
VL nucleus of thalamus
Medial leminscus, spinothalamic tracts
SOMATOSENSORY FOR BODY
VPM nucleus of thalamus
-trigeminal lemniscus, trigeminothalamic tract, gustatory inputs
SOMATOSENSORY FOR FACE
What are the two somatosensory nuclei of the thalamus
VPL and VPM
LGN
Visual, from optic tract
MGN
From inferior collilcus
-auditory
Where does the anterior thalamus project to
Cingulate gyrus
-respond to situations that are stressful or rewarding
Where does the MD nucleus project to?
Prefrontal cortex
-normal motivational state and learning about reward/stressful events
What are the two major systems that have a role in maintaining the conscious state
- reticular activating system
- sensory, motor, anterior and dorsomedial nuclei
What is the most important system for maintaining the conscious state
Reticular activating system
Reticular activating system
- involves the intralaminar nuclei
- project diffusely throughout cortex to maintain the conscious state and alertness
Disruption of the reticular activating system
Disruption at any level causes a loss of consciousness
Sensory, motor, anteiror and dorsomedial nuclei
Reciprocal connections with their cortical targets, creates a positive feedback loop that assists in maintaining alertness and the conscious state, but is less critical than the reticular activating system
What happens when the sensory, motor, anterior, and dorsomedial nuclei of the thalamus get disrupted
Just a reduced level of alertness
Anteiror nucleus and cognition
AN receives input from hypothalamus and projects to cingulate gyrus. Function not well understood, probably promotes working memory, or learning during stressful or rewarding moments
Mediodorsal nucleus and emotion
Receives input from amygdala and is part of the basal nuclei “motivational loop”. Possible role in regulating mood, motivation, and executive functions
What does the anterior nucleus have interactions with
Cingulate gyrus, indirect influence on working memory function
Proposed role for lesions in AN
Diencephalic amnesia
Infarct or alcoholism-associated degernation of AN
-thiamine deficiency
Korsakoff’s syndrome
-impaired info transfer from working memory to long term memory: AN projects to cingulate gyrus, which projects to hippocampus
Mediodorsal nucleus
Projections to prefrontal cortex support prefrontal functions, including working memory, intellectual functions, planning, behavioral regulation, and mood
Lesions to mediodorsal nucleus
Lead to disorientation in immediate environment or social situation, learning/memory impairment, possibly related to clinical depression (MDD)
Blood supply to diencephalon
Branches from circle of willis vessels penetrate DORSALLY into hypothalamus and continue to reach thalamus
-arterial branches also supply optic nerves, chiasm, tracts: could lead to VF defect if ischemia
What is the hypothalamus vulnerable to
Invading tumors
What are some arteries that supply the thalamus
- posterior medial choroidal artery (from PCA)
- thalamogeniculate artery (PCA)
- paramedian branches (from PCA)
- tuberothalamic branches (posteiror comm artery)
Key arteries for thalamus
Branches of proximal PCA and posterior comm artery
Does the thalamus have the same blood supply as the internal capsule and the basal ganglia
No. Can damage one of these areas and the other will remain intact
Damage to left LGN
Right homonomyous hemianopsia
Damage to MGN
Impaired binaural processing
Damage to VPL and VPM
Right face and body deficit
Damage to VPM
Spared. Fibers from each side ascend bilaterally with ALS
Damage to VA.VL
Impairment in motor coordination and fine-tuning
No motor strength loss!
Would you get motor strength loss if you damaged the left Va/VL?
Nope
Venous drainage of the thalamus
Thalamostriate vein and the internal cerebral vei
Venous accidents
Not likely in the thalamus
-elsewhere in larger vessels can result in back filling, increased ICP, and risk of hemorrhage
What is the main venous drainage for the thalamus
Thalamostriate vein
-then to the internal cerebral vein-great cerebral vein-straight sinus-confluence of sinuses
Anteiror boundaries of the hypothalamus
Lamina terminals
Preoptic area
Ventral anatomical borders of the hypothalamus
- optic chiasm
- infundibulum
- tuber cinereum
Posteiror/caudal anatomical boundaries of the hypothalamus
- midbrain
- mammillary bodies
Major functions of the hypothalamus
- endocrine regulation
- reproductive behavior
- thermoregulation
- conscious state
- feeding/appetite
- circadian rhythm
- autonomic NS regulation
What are structures that sit below the hypothalamus
The pituitary gland sitting in the cella tursica that is attached by the infundibulum
Major arterial supply to the hypthalamus
Branches from circle of willis vessels penetrate dorsally into hypothalamus
- has very high density of arteries, arterioles, and capillaries. This, small risk and incidence of ischemic or hemorrhagic infarcts in hypothalamus
- no defined vascular territories
Hypothalamic regulation of the autonomic nervous system
Nuclei with descending projections directly to sympathetic or parasympathetic pre-ganglionic neurons or with indirect effects via reciprocal interactions with projections brainstem regions
Anterior hypothalamic area and autonomic nervous system
- promotes sweating (sympathetic)
- promotes GI function (parasympathetic)
Autonomic function of paraventricular N (hypothalamic nuclei)
Can increase blood pressure and heart rate (symp)
Autonomic nervous system function of dorsomedial N (hypothalamic nuclei)
Can increase blood pressure and heart rate (symp)
Autonomic nervous system function of posterior hypothalamic nucleus/area
Vasoconstriction (symp)
Where does heat dissipation occur
Anterior hypothalamic area
Where does heat conservation occur
Posterior hypothalamic area/nucleus
Heat dissipation in the anterior hypothalamic area
- contains the rose story neurons (ambient hypothalamic temp)
- cold activated and heat activated neurons
- contributes to set point body temp, like thermostat
- hyperthermic-sensitive neurons activate sweating, vasodilation in skin
- pyrogens inhibit anterior H area
What contributes to set point of body temperature like a thermostat
Anterior hypothalamic area
Lesions to anterior hypothalamic area and heat regulation
Hyperthermia
What do hyperthermic-sensitive neurons in the anteiror hypothalamic area do
Activate sweating, vasodilation in skin
Pyrogens and anterior hypothalamic area
Inhibit it
- prostaglandins
- cytokines
- infectious pathogen molecules
Thermosensitive neurons in the anterior hypothalamic area are activated by what
Drop in body temperature
- mediates vasoconstriction in skin, shivering, and stimulation of TRH
- in infants, activates brown adipose tissue
Lesions to the posteiror H area
Produce loss of thermoregulation due to impaired heat conservation and collateral damage to descending projections from anterior H area
Histamine and hypothalamus
Promotes alertness/arousal
Where is the histamine system located
In posterior H nucleus and tuberomammillary nucleus
Targets of histamine system
Widespread projection targets include cerebral cortex and limbic system
What is the mechanism of drowsy side effects of early anti-histamine
Histamine system having widespread projection targets including cerebral cortex and limbic system
What does the hypocretin/orexin system promote
Wake state
Orexin
Part of a system that promotes wake state and has a role in promoting feeding
Where are the hypocretin/orexin neurons located
Diffuse population of neurons mostly located in lateral hypothalamic area
What are the projection targets of the hypocretin/orexin system
Cerebral cortex, limbic system, brainstem sites
Hypocretin/orexin deficiency
Narcolepsy
-sudden “sleep-attacks” no voluntary control, often begins with REM sleep
Feeding and ventromedial nucleus
Feeding suppressive
Lateral hypothalamic area (orexin neurons) and feeding
Feeding promoting
Lateral hypothalamic area lesions and feeding
Reduce body weight (temporarily )
What is the satiety center in the hypothalamus
VMN
What is the appetite center in the hypothalamius
LHA
What would VMN lesions disrupt
- impair signaling of stomach dissension
- impair signaling of adequate nutrients
- impair insulin regulation
- impair signals to brain from white adipose
- impair stress-induced suppression of feeding
Accurate nucleus of hypothalamus and feeding
Arcuate neurons detect nutrient in blood (glucose sensing, lipid sensing, amino acid sensing)
Released in response to porting/fat ingested, limits meal size
CCK (cholecytokinin)
Where is CCK released from
Arcuate nucleus
What do arcuate and VMH together typically do to feeding
Inhibit
What does LHA generally do
Promotes feeding
What is LHA activated by
Glucocorticoids, reduced levels of satiety signal, release of “craving” signals
Paraventricular N and feeding
Bidirectional effects on feeding
Stress and feeding
Can have bidirectional effects on feeding
- inhibitory mechanisms: stress-induced activation of brainstem norepi and serotonin systems with projections to feeding related nuclei act to suppress hunger/craving/eating
- stress induced release of glucocorticoids (from HPA axis) can act in the hypothalamus and other rain trigger hunger/eating
What nucleus regulates the circadian rhythm
Suprashiasmatic nucleus (SCN)
When does pineal release melatonin
Dark, inhibited by light
What does light to in pineal gland
Activates melanopsin ganglion cell neurons, which send excitatory projections to SCN via retina-hypothalamic tract
- SCN sends excitatory projections to PVN (PVH), which projects to pre-ganglionic sympathetic neurons and activates them
- postganglionic projections to pineal inhibits melatonin secretion
Targets and rhythms of circadian rhythm
Multiple targets, multiple rhythms
Experimental demonstration of 25 hour free running circadian rhythms in hamsters and humans and role of SCN
- 24/7 constant light
- activity beceoms 25 hour daily routine
- SCN lesions, daily rhythm is totally chaotic
Mammillary bodies role in memory function/deficits
Are indirectly connected to limbic structures that are critical for memory function
Maxillary body and Korsakoff’s syndrome
- damage due to thiamine deficiency (alcoholism or malnourishment)
- short term and long term memory impairment
- confabulation (making up memories)
- shorter term memory function also impacts language comprehension and ability to communicate during convo
- sometimes oculomotor deficit and ataxis (Wernicke-Korsakoff)
