Diencephalon

diencephalon

• midline structure with symmetrical right and left halves

• consists of the third ventricle and SHET

Hypothalamic Sulcus

• small groove on the lateral wall of the 3rd ventricle

• separates the thalamus and epithalamus dorsally and the hypothalamus and subthalamus inferiorly

Thalamus

• large mass of gray matter that lies on either side of the third ventricle

• Complex, highly organized and compartmentalized relay station for ascending tracts

• Reception of sensory information

Interthalamic adhesion

• connects the thalamus

Stratum Zonale

• covers the upper surface of the thalamus

• fiber bundles that emerge from lateral of the thalamus and terminate in the cerebral cortex

Internal Medullary Lamina

• thin vertical sheet of white matter that bifurcates ventrally

• divides the hypothalamus into lateral, medial, and anterior portions

External Medullary Lamina

• Layer of myelinated fibers on the lateral surface of the thalamus close to the internal capsule

Anterior Thalamic Nucleus

• counterpart: limbic area

• for episodic memory and emotions

Dorsomedial Thalamic Nucleus

• counterpart: limbic area and prefrontal lobe

• for memory association, integration of sensory, motor, visceral, and olfactory to emotions

Ventral Anterior

• counterpart: Area 6 and 8

• for motor relay

Ventral Lateral

• counterpart: Area 4

• for motor relay

Ventral Posterimedial

• counterpart: Area 3, 1, 2

• sensory nuclei

• trigeminal, gustatory

Ventral Posterolateral

• counterpart: Area 3, 1, 2

• sensory nuclei

• medial and spinal lemniscus

Lateral dorsal, lateral posterior, pulvinar

• counterpart: association areas

• multimodal nuclei

Medial geniculate body

• counterpart: areas 42 and 22

• Auditory functions

Lateral Geniculate body

• counterpart: area 17, 18, 19

• visual functions

Intralaminar nuclei

• activation of the cortex from brainstem reticular formation and sensorimotor integration

centromedian nuclei

• participates in sensorimotor coordination, cognition, and pain processing

Reticular nucleus

• subserves autonomic, motor, sensory, behavioral, cognitive, and mood-related functions

Thalamic Pain Syndrome

• Immediate C/L Hemiaamnesthesia

  • Abnormal nociception

  • Abnormal thermal sensation

Hypothalamus

• critical role in endocrine, metabolic, autonomic, and emotional function

• center of the limbic system

• sympathetic and parasympathetic functions (homeostasis)

• endocrine control

Anterior portion of hypothalamus

• temperature regulation

• dissipates heat

Posterior portion of the hypothalamus

• temperature regulation

• inhibit heat loss

Lateral region of the hypothalamus

• regulation of food intake

• hunger center

• initiates food/water intake

medial region of hypothalamus

• regulation of food intake

• satiety center

• inhibits food/water intake

Posterior lobe of hypothalamus

• water intake

• vasopressin to maintain water balance

Suprachiasmatic nucleus

• receives afferent fibers from the retina

• influence actvities of the hypothalamic nuclei

Hypothalamus

• A lesion in this area would cause:

  • Severe obesity and wasting

  • Hyperphagia

  • Problems with urination

  • Problems with sleep

  • Emotional disorders

  • Impaired temperature control

Epithalamus

• releases melatonin

• consists of the pineal gland and the habenular nuclei

• mainly secretory

Pineal body

• small mass that lies in the depression between the superior colliculi

• secretes melatonin

Habenular nucleus

• integrates somatic and olfactory sensation

• cross between the limbic system and basal gagnglia

habenular trigone

• small triangular area in fron of the superior colliculus

Parinaud’s Syndrome

• tumor in the pineal region obstructs the cerebral aqueduct and causes inability to move the eyes in the vertical plane

Germinoma

• type of tumor produces precocious sexual development

Subthalamus

• Between the tegmentum of the midbrain and dorsal thalamus

• Considered to be one of the extrapyramidal motor nuclei

• conected to corpus striatum

Interruption of the posterior commissure

• Abolishes the consensual light reflex

Hemiballismus

• motor disorder causes coarse flailing of the arm or leg; flailing of the affected extremities may lead to severe trauma or fractures