Diencephalon: Structure and Function

Question 1

Name the major subdivisions of the diencephalon:

Answer 1

1. Thalamus
2. Hypothalamus
3. Epithalamus
4. Ventral thalamus
5. Subthalamus

Question 2

Major thalamic input and output:

Answer 2

Cerebral cortex

Question 3

Diencephalon is divided medially by the:

Answer 3

3rd ventricle

Question 4

Thalamus is medial to the:

Answer 4

Posterior limb of the internal capsule

Question 5

Components of the epithalamus:

Answer 5

1. Habenular nuclear complex
2. Pineal gland
3. Posterior commissure

Question 6

Components of the thalamus:

Answer 6

1. Thalamic nuclei
2. External medullary lamina
3. Internal medullary lamina

Question 7

Components of the ventral thalamus:

Answer 7

Reticular nucleus of thalamus: the only nuclear group that does not project to the cortex.

Question 8

Components of the subthalamus:

Answer 8

1. Zona incerta

2. Subthalamic nucleus (of Luys)

Question 9

The ______ connects the pituitary gland to the hypothalamus.

Answer 9

Infundibulum

Question 10

What is the hypophyseal portal system?

Answer 10

Vascular system that connects the hypothalamus with the anterior pituitary gland.

Question 11

Blood supply to thalamus:

Answer 11

• Anterior communicating artery.
• Posterior communicating artery.
• ACA
• PCA
• Internal carotid (*anterior choroidal artery is most susceptible to thrombosis).

Question 12

Major functions of the thalamus:

Answer 12

1. Relays all sensory information to the cerebral cortex (except for olfactory input, which comes from the piriform cortex into the thalamus).
2. Relays information about motor activities to the cerebral cortex.
3. Integrates sensory information from different modalities and projects them to the association cortex.
4. Relays emotional and affective information to the cortex (part of limbic system).
5. Part of the “Papez circuit” of the limbic system.
6. Involved in the control of alertness, arousal, sleep.
7. Under direct cortical feedback and control: reciprocal connections between thalamus and cortex.

Question 13

Thalamic nuclei that have limbic functions:

Answer 13

1. Anterior nuclear group
2. LD
3. Medial group (MD)
4. Midline nuclei

Question 14

Thalamic nuclei that have motor functions:

Answer 14

1. VA

2. VL

Question 15

Thalamic nuclei that have SS functions for the body:

Answer 15

VPL

Question 16

Thalamic nuclei that have SS functions for the face:

Answer 16

VPM

Question 17

Thalamic nuclei that function in vision:

Answer 17

LGN

Question 18

Thalamic nuclei that function in audition:

Answer 18

MGN

Question 19

Thalamic nuclei that function in sensory integration:

Answer 19

1. Pulvinar

2. LP

Question 20

Thalamic nuclei that have a role in pain, sleep, wakefulness:

Answer 20

Intralaminar nuclei (CL, CM, PF)

Question 21

Thalamic nuclei that have a role in modulation of thalamic activity.

Answer 21

Reticular nucleus

Question 22

Thalamic syndrome:

Answer 22

• Usually caused by a vascular lesion or tumor.
• Usually involves damage to VPL.
• Initially causes a transitory contralateral hemianalgesia.
• Followed by painful sensations with noxious stimuli.
• Followed by pain provoked by pressure, touch, vibration.
• Followed by dysesthesia (pain evoked without any external stimulus).
• Threshold for pain is raised on the affected side (contralateral to the lesion). Once this threshold is reached pain has a strong emotional overtone to it.

Question 23

Characterisitics of reticular activating system:

Answer 23

• Activated by repetitive, low-frequency stimulation.
• Interconnected with thalamic nuclei.
• Controls the level of excitability of neurons over wide areas of cortex.