Week 6: Diencephalon

Question 1

The diencephalon develops from which primary brain vesicle?

Answer 1

Prosencephalon (forebrain)

Question 2

The junction of the midbrain and diencephalon is represented by:

a. the slit-like third ventricle
b. a line that passes through the posterior commissure and is immediately caudal to the mamillary body
c. a line that traverses the interventricular foramen (foramen of Monro) and the optic chiasma
d. The inter-thalamic adhesion or massa intermedia
e. the fornix

Answer 2

b. a line that passes through the posterior commissure and is immediately caudal to the mamillary body

a splits The diencephalon into symmetrical halves
c is The boundary between the diencephalon and the telencephalon

Question 3

List the four major parts identified on each side of the diencephalon.

Answer 3

• The thalamus
• The subthalamus
• The epithalamus, and
• The hypothalamus

Question 4

The diencephalon and the telencephalon form the ___?

Answer 4

The cerebrum

Question 5

Which of the following is CORRECT regarding the thalamus:

a. Certain thalamic nuclei receive input from the pathways for all the senses
b. Certain thalamic nuclei participate in memory, sleep, and mental activities.
c. Every nucleus of the thalamus sends axons to the cerebellum
d. Is the second largest component of the diencephalon

Answer 5

b. Certain thalamic nuclei participate in memory, sleep, and mental activities.

a is wrong: all senses except smell
d: it is the largest
c: Every nucleus of the thalamus sends axons to the cerebral cortex (except the reticular nucleus)
Probably only one non-cortical structure (the striatum) receives afferent fibers from the thalamus

Question 6

A line that traverses the interventricular foramen (foramen of Monro) and the
optic chiasma represents:

a. The boundary between the diencephalon and the telencephalon
b. The junction of the midbrain and diencephalon
c. The division of the diencephalon into symmetrical halves
d. The division between the thalamus and the hypothalamus
e. The division between the subthalamus and the epithalamus

Answer 6

a. The boundary between the diencephalon and the telencephalon

Question 7

Which surface of the diencephalon is exposed to view?

Answer 7

Only the ventral surface

Question 8

In about 70% of brains, the left and right thalami are joined by a bridge of grey matter, called the:

a. the fornix
b. inter-thalamic adhesion or massa intermedia
c. tela choroidea
d. the internal capsule
e. stria medullaris thalami

Answer 8

b. inter-thalamic adhesion or massa intermedia

Question 9

True/false: Every nucleus of the thalamus sends axons to the cerebral cortex

Answer 9

FALSE:

Every nucleus of the thalamus sends axons to the cerebral cortex EXCEPT the reticular nucleus

Question 10

The subthalamus is a complex region ____ to the thalamus.

Answer 10

VENTRAL

The subthalamus is a complex region ventral to the thalamus

Question 11

The subthalamus includes (select all that apply):

a. sensory fasciculi
b. tracts from the cerebellum, and corpus striatum.
c. tracts from the brain stem
d. the habenular nuclei and their connections
e. a nucleus with motor functions (the subthalamic nucleus)
f. nuclei and tracts concerned with autonomic
and behavioral responses to emotional changes.

Answer 11

a. sensory fasciculi
b. tracts from the cerebellum, and corpus striatum.
c. tracts from the brain stem
e. a nucleus with motor functions (the subthalamic nucleus)

Corrections:
d and f are in the epithalamus

Question 12

True/false: The habenular commissure in the dorsal wall of the stalk includes fibers of the stria medullaris thalami that terminate in the opposite habenular nuclei.

Answer 12

TRUE

Question 13

Which of the following is NOT TRUE regarding the habenular nuclei?

a. Its position is marked by the slight swelling in the habenular
trigone
b. No clearly defined function is attributed to the habenular nuclei
c. It is in the hypothalamus
d. Afferent fibers are received through the stria medullaris thalami, which runs along the dorsomedial border of the thalamus
e. The habenular nuclei give rise to a well-defined bundle of fibers known as the habenulointerpeduncular tract

Answer 13

c. It is in the hypothalamus

Question 14

Which of the following is CORRECT regarding the fornix?

a. It marks the boundary between the diencephalon and the telencephalon
b. It participates in memory, sleep, and mental activities.
c. It is a robust bundle of fibers that originates in the hippocampal formation of the temporal lobe, curves over the thalamus, and ends mainly in the mamillary body
d. It is subdivided into nuclei that have different afferent and efferent connections.

Answer 14

c. It is a robust bundle of fibers that originates in the hippocampal formation of the temporal lobe, curves over the thalamus, and ends mainly in the mamillary body

Question 15

True/false: The ventral wall of the pineal stalk is attached to the posterior commissure, which carries axons involved in pupillary reflexes and eye
movements.

Answer 15

TRUE

Question 16

What does the epithalamus consist of?

Answer 16

– the habenular nuclei and their connections
– the pineal gland and
– nuclei and tracts concerned with autonomic
and behavioral responses to emotional changes.

Question 17

What is the stratum zonale?

a. a thin layer of gray matter that constitutes the reticular nucleus of the thalamus
b. a reciprocal corticothalamic connection
c. a thin sheet of
inhibitory (α-aminobutyrate-ergic) neurons between the external medullary lamina and the internal capsule.
d. a thin laminae of white matter on the dorsal surface of the thalamus
e. Cerebellothalamic fibers from the dentate and interposed nuclei have crossed the midline in the decussation of the superior cerebellar peduncles.

Answer 17

d. thin laminae of white matter on the dorsal surface of the thalamus

Question 18

The medial lemniscus, spinothalamic tract, and
trigeminothalamic tracts form the:

a. The ventral thalamus
b. The reticular nucleus
c. The subthalamic nucleus
d. The sensory fasciculi in the subthalamus
e. The dorsal thalamus

Answer 18

d. The sensory fasciculi in the subthalamus

Corrections:
the ventral thalamus is The reticular nucleus, together with a few small
thalamic nuclei
the dorsal are the other thalamic nuclei

Question 19

Which of the following is NOT true regarding the reticular nucleus?

a. It is a thin sheet of inhibitory (α-aminobutyrate-ergic) neurons
b. It receives collateral branches of some of the excitatory corticothalamic and thalamocortical fibers.
c. Activity of neurons in it can suppress the transmission of signals through the thalamic nuclei of the ascending sensory pathways
d. It is between the external
medullary lamina and the internal capsule of the thalamus
e. It is connected with the reticular formation of the brain stem.
f. Certain features of the electroencephalogram (EEG) in normal sleep depend on it

Answer 19

e. It is connected with the reticular formation of the brain stem.