Thalamus, Hypothalamus,Epithalamus

2. Thalamus, Hypothalamus,Epithalamus

3. Dr. NimirDr. Safaa • Describe the location of the thalamus . • List the different parts and nuclei of the thalamus . • List the afferent input to different nuclei of the thalamus. • List the efferent output from the different nuclei of the thalamus. • Describe the structure of hypothalamus, epithalamus , and subthalamus. • List the nuclei of the hypothalamus. • List the afferent connections of the hypothalamus. • List the efferent connections of the hypothalamus • List the functions of hypothalamus.

4. The thalamus is an egg-shaped gray matter situated rostral (superior) to brainstem, one in each cerebral hemisphere. • Between them is third ventricle. • They may connect with interthalamic connection (adhesion). • It is an important relay and integrative station for information passing to: • All areas of cerebral cortex. • Basal ganglia. • Hypothalamus. • Brainstem.

5. Subdivisions of the thalamus: • Internal medullary lamina is a Y shape sheet of white matter dividing the thalamus into 3 parts: • Anterior part that contains anterior thalamic nuclei which receive mammillothalamic tract & also receive reciprocal connections with the cingulate gyrus and hypothalamus. • Its function is concerned with emotion & recent memory.

6. Medial part that contains dorsomedial nucleus & several smaller nuclei. Dorsomedial nucleus has two-way connections with prefrontal cortex, hypothalamic nuclei & thalamic nuclei. • Its function is integration of somatic, visceral, and olfactory informations, and relating them to one's emotional feelings and subjectivestates.

7. Lateral Part which issubdivided into dorsal tier & ventral tier. • Dorsal tier includes lateral dorsal nucleus, lateral posterior nucleus, and pulvinar. They are interconnected with other thalamic nuclei , parietal lobe, cingulate gyrus, occipital and temporal lobes. • Their function is not well known & mostly associated with emotions, sensory integration& vision.

8. Ventral tier consists of the following nuclei in a craniocaudal sequence: • Ventral anterior nucleus which is connected to reticular formation, substantianigra, corpus striatum, premotor cortex and thalamic nuclei. • It influences motor activity. • Ventral lateral nucleus has similar connections to that of ventral anterior nucleus plus input from cerebellum & red nucleus. • It influences motor activity.

9. Ventral posterior nucleus is subdivided into ventral posteromedial nucleus and ventral posterolateralnucleus. • Ventral posteromedial receives ascending trigeminal and gustatory pathways. • Ventral posterolateral receives the important ascending sensory tracts, the medial and spinal lemnisci. • Both nuclei relay common sensations to consciousness.

10. Other Nuclei of the Thalamus: • Intralaminarnuclei are within the internal medullary lamina & they influence the levels of consciousness and alertness. • Midline nuclei adjacent to the third ventricle. • Reticular nucleus is between external medullary & internal capsule. • It regulates thalamus by cerebral cortex.

11. Medial geniculate body forms part of the auditory pathway. • Lateral geniculate body forms part of the visual pathway.

12. Hypothalamus: • Is the part of diencephalon that extends from the region of the optic chiasmato mammillary bodies. • When observed from below it is related to optic chiasma, tuber cinereum, infundibulum and mammillary bodies. • Hypothalamic nuclei are divided into medial and lateral zones.

14. Medial zone include from anterior to posterior: • Part of the preopticnucleus. • Anterior nucleus. • Part of suprachiasmaticnucleus. • Paraventricular nucleus. • Dorsomedial nucleus. • Ventromedial nucleus. • Infundibular(arcuate) nucleus. • Posteriornucleus.

15. Lateral zone include from anterior to posterior: • Part of the preopticnucleus. • Part of suprachiasmaticnucleus. • Supraoptic nucleus. • Lateral nucleus. • Tuberomammillarynucleus. • Lateral tuberalnuclei.

16. Hypothalamus receives information from the body through: • Nervous connections. • Bloodstream. • Cerebrospinal fluid. • Hypothalamic nuclei respond and exert their control via the same routes. • Afferents: • Somatic and visceral afferents. • Visual afferents. • Olfaction. • Auditory. • Corticohypothalamic from frontal lobe. • Hippocampohypothalamic • Amygdalohypothalamic. • Thalamohypothalamic. • Tegmental.

17. Efferent: • Descending fibers to the brainstem and spinal cord. • Mammillothalamic tract. • Mammillotegmental tract. • Multiple pathways to the limbic system.

19. The epithalamus consists of habenular nuclei and their connections and pineal gland. • Habenular nuclei are medial to the posterior surface of the thalamus. • Receive afferents from: • Amygdaloidnucleus through the striamedullaristhalami ( some cross form habenular commissure). • Hippocampal formation through the fornix. • Send effrents to: • Interpeduncular nucleus. • Tectum of the midbrain. • Thalamus. • Reticular formation of the midbrain.

20. Pineal gland is behind thalami & above superior colliculi. • Its stalk base contains habenular commissure above & posterior commissure below. • Receives afferents from superior cervical sympathetic ganglia. • Its secretions(melatonin) reach target organs (pituitary, pancreas, parathyroids, adrenals and gonads) via the bloodstream or through the cerebrospinal fluid.