1.1 The External Features of the Brainstem and Diencephalon

Question 1

What is the Brainstem?

Answer 1

The Part of the Brain which lies just Superior to the Spinal Cord

Question 2

What are the 3 parts of the Brainstem?

Superior to Inferior

Answer 2

1. The Midbrain
2. The Pons
3. The Medulla (Oblongata)

Question 3

Which Cranial Cavity does the Brainstem lie in?

Answer 3

The Posterior Cranial Fossa

Question 4

Embryologically, which 2 Vesicles of the Neural Tube give rise to the Brainstem?

Answer 4

1. The Mesencephalon (The Midbrain)

2. The Rhombencephalon (The Hindbrain)

Question 5

What are the Cavities (of the Ventricular System) which lie within the Brainstem?

Answer 5

1. The Cerebral Aqueduct

2. The 4th Ventricle (IV Ventricle)

Question 6

What is the name of the Groove which separates the Pons from the Medulla?

Answer 6

The Pontomedullary Junction

Question 7

What Cranial Nerves emerge from the Pontomedullary Junction?

Answer 7

1. The Abducens Nerve (Cranial Nerve VI)
2. The Facial Nerve (Cranial Nerve VII)
3. The Vestibulocochlear Nerve (Cranial Nerve VIII)

Question 8

Which Foramina do the Cranial Nerves which leave the Pontomedullary Junction, exit the Cranium?

Answer 8

The Abducens Nerve (Cranial Nerve VI) exits via the Superior Orbital Fissure
The Facial Nerve (Cranial Nerve VII) and the Vestibulocochlear Nerve (Cranial Nerve VIII) exit via the Internal Auditory Meatus

Question 9

Which of the Cranial Nerves which emerges from the Pontomedullary Junction, has the Longest Intracranial Course?
What is the Clinical Significance of this?

Answer 9

The Abducens Nerve (Cranial Nerve VI) is vulnerable to injury by raised Intracranial Pressure, and other mechanical factors. This can cause loss of motor innervation to the Lateral Rectus Muscle of the Eye

Question 10

What is the function of the Medullary Pyramids?

Answer 10

These are Descending Motor Fibers

Question 11

What is the function of the Decussation of the Pyramids?

Answer 11

This is where the Descending Motor Fibers cross over to the Contralateral side

Question 12

What is the function of the Superior Olive?

Answer 12

This contains the Olivary Nuclei associated with the Perception of Sound (This is part of the Pons)

Question 13

What is the function of the Inferior Olive?

Answer 13

This contains the Olivary Nuclei associated with Cerebellar Motor Learning and Function

Question 14

Is the Superior part of the Posterior Medulla the “Open” or the “Closed” part?

Answer 14

The Open Part

Question 15

Is the Inferior part of the Posterior Medulla the “Open” or the “Closed” part?

Answer 15

The Closed Part

Question 16

What structure does the “Open” part of the Posterior Medulla open onto?

Answer 16

The 4th Ventricle (IV Ventricle)

Question 17

Through which Foramen does the Medulla pass through to become the Spinal Cord?

Answer 17

The Foramen Magnum

Question 18

Which Cranial Nerve arises from the Pons?

Answer 18

The Trigeminal Nerve

Question 19

What connects the Pons to the Cerebellum?

Answer 19

The Cerebellar Peduncles

Question 20

What kind of fibers make up the Cerebellar Peduncles?

Answer 20

Centripital Fibers (Afferent Sensory fibers from the Pontine Nucleus)

Question 21

What lies immediately Superior to the Midbrain?

Answer 21

The Diencephalon

Question 22

What lies immediately Inferior to the Midbrain?

Answer 22

The Pons

Question 23

What connects the Midbrain to the Cerebrum?

Answer 23

The Cerebral Peduncles

Question 24

What kind of fibers make up the Cerebral Peduncles?

Answer 24

Motor Fibres (Efferent Motor Fibers destined for Lower Motor Neuron Synapses in the Spinal Cord)

Question 25

What is the Diencephalon made up of?

Answer 25

1. The Thalamus

2. The Hypothalamus

Question 26

What 2 parts of the Brain does the Diencephalon lie between?

Answer 26

Superiorly - The Fornix

Inferiorly - The Midbrain

Question 27

Can all of these structures be seen from the surface?

Answer 27

No, only a small part of the Hypothalamus can

Question 28

What are the surface projections visible on the surface of the Hypothalamus called?

Answer 28

Mamillary Bodies