Lecture 4- Diencephalon Flashcards
External features of diencephalon
Optic chiasm Mamillary bodies Lateral geniculate bodies Medial geniculate bodies Tuber cinereum Infundibulum (pituitary stalk) Cerebral peduncle
Surfaces of diencephalon
Medial: 3rd ventricle with interthalamic adhesion
Dorsal: Fornix
Lateral: Internal capsule
Ventral: front- optic chiasm
sides- optic tractsSubdivisions of diencephalon
Thalamus
Epithalamus
Subthalamus
Hypothalamus
Functional classification of thalamus
Specific nuclei
Association/relay nuclei
Non-specific nuclei
Structural classification of thalamus
Divided into 3 cell groups by y-shaped internal medullary lamina
Anterior
Lateral:
Dorsal- lateral dorsal, lateral posterior, pulvinar
Ventral- ventral anterior, Ventral lateral, ventral
posterior
Medial
Others
Specific nuclei and examples
Have a reciprocal connection to specific motor or sensory areas of cerebral cortex Ventral anterior nucleus Ventral lateral nucleus Ventral posterior nucleus Metathalamus
Ventral anterior nucleus goes to
Prefrontal cortex (motor)
Ventral lateral nucleus goes to
Posterior portion goes to primary motor area
Anterior portion goes to secondary motor area
Ventral posterior nucleus goes to
Somatosensory area
Sensations from the skin, muscles and internal viscera
ONLY the consciously perceived parts
Special senses of position awareness, movements and taste
Metathalamus
Medial geniculate nuclei: primary auditory cortical areas
Lateral geniculate nulcei: Primary visual cortical area
Association nuclei and examples
Reciprocally connected to association areas of cerebral cortex
Anterior nucleus
Mediodorsal nucleus
Pulvinar
Anterior nucleus goes to
Limbic system (cingulate gyrus) Memory and behavioural functions (reproductive and defense)
Mediodorsal nucleus goes to
Limbic system and frontal lobe
Cognition (thinking) and judgement
Pulvinar goes to
Nuclear complex
Function not well understood but connects to parietal, temporal and occipital cortices
Non-Specific nuclei and examples
Involved in different levels of consciousness and degree of alertness
Reticular nucleus
Intralaminar nucleus
Epithalamus consists of
Habenular nucleus Habenular commissure Striae medullaris Epiphysis (pineal gland) Posterior commissure
Habenular nucleus
Slight swelling in the habenular trigone medial to posterior surface of thalamus
Integration of olfactory, visceral and somatic pathways and sleep mechanisms
Link the limbic system to the brainstem via afferent fibres that pass through striae medullaris thalami
Habenular commissure
Formed by lateral striae medullaris that cross the midline and reach habenular nucleus of opposite side
Pineal gland
Small, reddish conical endocrine gland
Attached to diencephalon by pineal stalk
Calcification results in brain sands (corpora arenacae @ 30 years old)
Usually lies slightly to the left
2 cell types of pineal gland
Principal pinealocytes: synthesize melatonin from serotonin; implicated in sleep-wake cycle (secreted mostly at night and inhibited in daytime)
Neuroglia: support cells
Functional roles of Epithalamus
Regulation of cyclic behaviours - circadian rhythm - reproductive cycles - day/night cycle Modulation of other systems in the brain - limbic system - hypothalamus - raphe - some motor-related pathways
Subthalamus
Wedged between thalamus and hypothalamus
Consists of
- Subthalamic nuclei and zona incerta
Ventral thalamic nucleus characteristics
Biconvex
Lies against internal capsule
5 distinct nuclei
Ventral to the dorsal thalamus and dorsal to the basis pedunculi/crus cerebri
Nuclei of the ventral thalamus (subthalamus)
Subthalamic nucleus Zona incerta Nucleus of field H of Forel (subthalamic reticular nucleus) Subthalamic reticular nucleus Ventral lateral geniculate nucleus Thalamic reticular nucleus
