Lecture 4- Diencephalon

Question 1

External features of diencephalon

Answer 1

Optic chiasm
Mamillary bodies
Lateral geniculate bodies
Medial geniculate bodies
Tuber cinereum
Infundibulum (pituitary stalk)
Cerebral peduncle

Question 2

Surfaces of diencephalon

Answer 2

Medial: 3rd ventricle with interthalamic adhesion
Dorsal: Fornix
Lateral: Internal capsule
Ventral: front- optic chiasm
              sides- optic tracts

Question 3

Subdivisions of diencephalon

Answer 3

Thalamus
Epithalamus
Subthalamus
Hypothalamus

Question 4

Functional classification of thalamus

Answer 4

Specific nuclei
Association/relay nuclei
Non-specific nuclei

Question 5

Structural classification of thalamus

Answer 5

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

Question 6

Specific nuclei and examples

Answer 6

Have a reciprocal connection to specific motor or sensory areas of cerebral cortex
Ventral anterior nucleus
Ventral lateral nucleus
Ventral posterior nucleus
Metathalamus

Question 7

Ventral anterior nucleus goes to

Answer 7

Prefrontal cortex (motor)

Question 8

Ventral lateral nucleus goes to

Answer 8

Posterior portion goes to primary motor area

Anterior portion goes to secondary motor area

Question 9

Ventral posterior nucleus goes to

Answer 9

Somatosensory area
Sensations from the skin, muscles and internal viscera
ONLY the consciously perceived parts
Special senses of position awareness, movements and taste

Question 10

Metathalamus

Answer 10

Medial geniculate nuclei: primary auditory cortical areas

Lateral geniculate nulcei: Primary visual cortical area

Question 11

Association nuclei and examples

Answer 11

Reciprocally connected to association areas of cerebral cortex
Anterior nucleus
Mediodorsal nucleus
Pulvinar

Question 12

Anterior nucleus goes to

Answer 12

Limbic system (cingulate gyrus)
Memory and behavioural functions
(reproductive and defense)

Question 13

Mediodorsal nucleus goes to

Answer 13

Limbic system and frontal lobe

Cognition (thinking) and judgement

Question 14

Pulvinar goes to

Answer 14

Nuclear complex

Function not well understood but connects to parietal, temporal and occipital cortices

Question 15

Non-Specific nuclei and examples

Answer 15

Involved in different levels of consciousness and degree of alertness
Reticular nucleus
Intralaminar nucleus

Question 16

Epithalamus consists of

Answer 16

Habenular nucleus
Habenular commissure
Striae medullaris
Epiphysis (pineal gland)
Posterior commissure

Question 17

Habenular nucleus

Answer 17

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

Question 18

Habenular commissure

Answer 18

Formed by lateral striae medullaris that cross the midline and reach habenular nucleus of opposite side

Question 19

Pineal gland

Answer 19

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

Question 20

2 cell types of pineal gland

Answer 20

Principal pinealocytes: synthesize melatonin from serotonin; implicated in sleep-wake cycle (secreted mostly at night and inhibited in daytime)

Neuroglia: support cells

Question 21

Functional roles of Epithalamus

Answer 21

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

Question 22

Subthalamus

Answer 22

Wedged between thalamus and hypothalamus
Consists of
- Subthalamic nuclei and zona incerta

Question 23

Ventral thalamic nucleus characteristics

Answer 23

Biconvex
Lies against internal capsule
5 distinct nuclei
Ventral to the dorsal thalamus and dorsal to the basis pedunculi/crus cerebri

Question 24

Nuclei of the ventral thalamus (subthalamus)

Answer 24

Subthalamic nucleus
Zona incerta
Nucleus of field H of Forel (subthalamic reticular nucleus)
Subthalamic reticular nucleus
Ventral lateral geniculate nucleus
Thalamic reticular nucleus

Question 25

Subthalamic nucleus

Answer 25

Reciprocal connections with globus pallidus
Serves as a relay from globus pallidus to substantia nigra and vice versa
Projects upon the cordate-putamen

Question 26

Zona incerta projections

Answer 26

Receives projections from

• sensory and motor cortex
• ventral lateral geniculate nucleus
• trigeminal nucleus
• cerebellar nuclei
• spinal cord

Projects to

• pretectum
• posterior lobe of epiphysis
• spinal cord

Question 27

Function of subthalamic fasciculus

Answer 27

Control of skeletal muscle activity

Lesion causes motor disturbances (hemiballismus, sudden, involuntary purposeless movement) on opposite side

Question 28

Zona incerta

Answer 28

Rostral extension of reticular formation
Lies between thalamus and subthalamic nucleus
Associated with regulation of thirst

Question 29

Hypothalamus and boundaries

Answer 29

Occupies a small amount of weight
Superior: Hypothalamic sulcus
Inferior: Optic chiasm, tuber cinereum, mamillary bodies
Anterior: Lamina terminalis
Posterior: Tegmentum of midbrain
Medial: 3rd ventricle
Lateral: Internal capsule

Question 30

Hypothalamic nuclear groups

Answer 30

Anterior group
Intermediate group
Posterior group
Mostly ill-defined boundaries

Question 31

Functions of hypothalamus

Answer 31

Control of hypophysis (pituitary gland)
Control of autonomic centres
Temperature regulation
Regulation of food and water intake
Emotions and behaviour
Control of circadian rhythms
Memory

Question 32

Hypothalamic control over autonomic centres

Answer 32

Anterior hypothalamic area for parasympathetic effects

Question 33

Hypothalamic control over temp regulation

Answer 33

Ant area: Responds to increase in temp

Post area: Responds to decrease in temp