Diencephalon Flashcards
Inputs to the thalamus:
7 of them
Cerebral Cortex Hypothal Br. Stem Sp Cd Cerebellum BG Sensory inputs
Outputs of Thalamus (2 of them)
Cerebral Cortex
BG
DIENCEPHALON is embryologically located between the
telencephalon and the mesencephalon.
Diencephalon:
It is between the ______ and the _____.
It is________ to the internal capsule, and is divided in the midline by the_________
cerebral cortex and brainstem
medial
third ventricle
Three parts of Epithalamus
Habenula: involved in the limbic pathway
Pineal gland: synthesizes serotonin and converts it to melatonin
Posterior commissure: links pretectal and other nuclei of the two sides
Invovled in limbic pathway (part of epithalamus)
Habenula
Links pretectal and other nuclei of two sides (part of epithalamus)
Posterior Commissure
Dorsal thalamus structures:
Thalamic nuclei
Internal medullary lamina
External medullary lamina
provide a strong link to cerebral cortex (part of dorsal thalamus)
Thalamic nuclei (part of dorsal thalamus)
a band of myelinated fibers that subdivide thalamic nuclei into anterior, lateral, and medial nuclear groups
Internal medullary lamina (part of dorsal thalamus)
a narrow band of myelinated fibers lateral to thalamic nuclei
External medullary lamina (part of dorsal thalamus)
Ventral Thalamus structures (2 of them)
Reticular Nucleus of the Thalamus:
Ventral Lateral Geniculate Nucleus (vLGN)
between the external medullary lamina and the internal
capsule
Reticular Nucleus of the Thalamus
Structures of Subthalamus (2 of them)
Zona Incerta
Subthamamic Nucleus of Luys
located between hpyothatlamus and dorsal thalamus
Subthalamus
Controlling Center of ANS
Hypothalamus
Has neuorbehavioral functions and regulation of hormoes released by hypophysis
Hypothalamus
Structures in hypothalamus
hypothalmic nuclei
infundibulum
hypophysis (pituitary gland)
Hypophyseal protal system
vascular connection btwn hypothalamus and ant pituitary
Hypophyseal portal system
Thalamus is supplied by branches of Circle of Willis (5 of them)
Anterior Communicating artery Posterior Communicating artery ACA PCA Internal Carotid artery
Involved with basal ganglia and extrapyramidal activity
subthalamus
Medial to posterior limb of internal capsule and surrounds the third ventricle
Thalamus
Thalamus relays all sensory information to the cerebral cortex except…
olfactor input to the thalamus is from piriform cortex
Role of thalamus in motor and sensory information:
relays motor info to cerebral cortex
Integrates sensory info from different modalities and projects to association cortex
Where does sensory information from thalamus project to in the cortex?
Association cortex
Relays emotional and affective information to the cortex.
Thalamus
The thalamus is part of the “Papez circuit” of the Limbic System, projects to the
limbic cortex
intimately involved in the control of alertness, arousal, and sleep
Thalamus
Relationship between thalamus and cortex
It is under direct cortical feedback and control: reciprocal connections between the thalamus and the cortex.
Anterior Nuclear Group
Afferent Input
Efferent Output
Functions
Afferent input: mammilary body
Efferent Output: Cingulate Gyrus
limbic fnxs
Ventral Anterior (VA)
Afferent Input
Efferent Output
Functions
Afferent input: GP
Efferent Output: Premotor Cortex ~ area 6
motor functions
Ventral Lateral (VL)
Afferent Input
Efferent Output
Functions
Afferent input: Dentate nucleus of cerebellum
Efferent Output: Motor (4) and Premotor (6)
Motor functions
Ventral Posterior Lateral (VPL)
Afferent Input
Efferent Output
Functions
Afferent Input: Dorsal Column-medial lemniscus and spinothalmic
Efferent Output: Somatosensory (3,1,2)
Somatic sensation of Body
Ventral Posterior Medial (VPM)
Afferent Input
Efferent Output
Functions
Afferent INput: sensory nuclei of trigerminal nerve
Efferent Output: Somatosensory (3,1,2)
Somatic sensation of face
Lateral geniculate
Afferent Input
Efferent Output
Functions
Afferent Input: retinal ganglion cells
Efferent Output: primary visual cortex (area 17)
vision functions
Medial Geniculate
Afferent Input
Efferent Output
Functions
Afferent input: inferior colliculus
Efferent Output: Primary auditory cortex (41, 42)
Audition fnx
Lateral Dorsal (LD)
Afferent Input
Efferent Output
Functions
Afferent input: cingulate gyrus
Efferent output: cingulate gryrus
Emotional Expression
Lateral Posterior (LP)
Afferent Input
Efferent Output
Functions
Afferent input: parietal cortex
Efferent output: parietal cortex
Sensory integration
Pulvinar (Pul)
Afferent Input
Efferent Output
Functions
Afferent input: Superior colliculus, parietal, occipital, temporal lobes
Efferent output: parietal, occiptal and temporal (POT)
integrates senesory information
Medial Dorsal (MD)
Afferent input: amygdaloid nuclear complex, olfactory, hypothalamus
Efferent output: prefrontal cortex
Fnx: limbic
Midline nuclie
Afferent Input
Efferent Output
Functions
Afferent: reticular formation and hypothal
Efferent: Basal forebrain
limbic fnxs
Intralaminar nuclei: Centro-median (CM) Centro-lateral (CL) Parafascicularis (PF) Afferent Input Efferent Output Functions
Afferent: reticular formation, spinothalmic tract, GP and coritcal areas
Efferent: BG and wide areas of cortex
Role in pain, sleep and wakefullness
Reticular nucleus:
Afferent Input
Efferent Output
Functions
Afferent: cortex, thalamus, brain stem reticular formation
Efferent: thalmic nuclei
Modulates thalamic activity
Typical responses in sensory thalamic relay neurons:
• Single cell response in VPL of human during therapeutic surgery:
bursts of discharge in specific sensory relay nucleus of the VPL when a specific sensory periphery on the contralateral body is stimulated.
Causes of thalamic syndrome
Usually caused by a vascular lesion or tumor; relatively rare.
Thalamic syndome: Usually involves damage to the
lateral group of thalamic nuclei (VPL)
Progression of thalamic syndrome:
Initial
soon after
Later
initially, a transitory contralateral hemianalgesia.
• Soon, painful sensations appear with noxious stimuli.
• Later, pain is provoked by pressure, touch, and vibration.
Thalamic syndrome: In time, a state of spontaneous, constant or paroxysmal pain is evoked on the _________
without any external stimulus (Dysesthesia).
affected side (contralateral)
What happens to the threshold for pain/temp/tactile sensation on affected side of thalamic syndrome?
The threshold for pain, temperature, and tactile sensation, however, is usually lowered on the affected side.
What is unique about pain in pts with thalamic syndrome?
once the threshold is reached, pain has a strong emotional overtone to it
Reticular activating system is activated by
repetitive, low freq stimulation
Connections in the reticular activating system:
interconnected with each other and recipricolly with specific thalamic nuclei
Repetitive stimulation of non-specific thalamic nuclei evokes cortical recruitement which will
wax and wane
Controls level of excitability of neurons over wide areas of cortex
Reticular activating system
