Session 4 - CNS Basics

Question 1

What are the basic components of the CNS?

Answer 1

• Cerebral Hemispheres
• Brainstem and cerebellum
• Spinal Cord

Question 2

What are the main components of the Peripheral Nervous System (PNS)?

Answer 2

• Dorsal and ventral roots
• Spinal Nerves
• Peripheral Nerves

Question 3

Describe the dorsal and ventral surfaces of the brain.

Answer 3

Inferior brain is ventral (due to right angle curve)

Superior brain is dorsal

Question 4

What is the main immune cell of the brain?

Answer 4

Microglia - make up 10-15% of cells of brain.

Macrophages for the CNS.

Question 5

Which cells are responsible for myelination in the CNS and PNS?

Answer 5

CNS - Oligodendrocyte - cell which gives of arms which myelinate many neurones, insulating the CNS.

PNS - Schwann Cells

Question 6

Which nervous system cells can regenerate?

Answer 6

CNS - cannot regenerate

PNS - can regenerate to en extent.

Question 7

What is the difference between tumours in the CNS and PNS?

Answer 7

CNS- tumours can be benign OR malignant.

PNS- tumours tend to be benign.

Question 8

What are the parts of the brainstem?

Answer 8

1) Midbrain = Eye movements and reflex responses.
2) Pons = Feeding, Sleep
3) Medulla Oblongata = CVS and Resp centres, contains major motor pathway (Medullary Pyramids)

Question 9

Where do the trigeminal nerves originate?

Answer 9

The lateral surface of the Pons.

Question 10

What is decussation?

Answer 10

When the motor fibres from the brain cross over in the medulla oblongata. (medullary pyramids)

Question 11

What is a sulcus, and a gyrus?

Answer 11

Sulcus - A groove or furrow in the brain (seperated by adjacent gyrus).

Gyrus - A ridge or fold in the brain.

Question 12

What is a brain fissure?

Answer 12

A large ‘crack’ or ‘split’ between adjacent large areas of the brain.

Question 13

Name the lobes/ parts of the brain, and their function.

Answer 13

Frontal Lobe
-Higher cognition, Motor function, speech

Parietal Lobe
-Sensation, spatial awareness

Temporal Lobe
-Memory, smell, hearing

Cerebellum
-Coordination and motor learning.

Question 14

Why is the optic chiasm clinically significant, where is it located?

Answer 14

Inferior aspect of the brain.

Located very close to pituitary, pituitary tumours can cause visual disturbance. (compression)

Question 15

Where is the uncus located? What is its clinical importance?

Answer 15

Inferior brain.
If there is increased intracranial pressure, the uncus can herniate into the brainstem.
(Fixed dilated pupil on contralateral side - no constriction with torch)

Question 16

What is the location of the corpus callosum?

Answer 16

Fibres connecting the two cerebral hemispheres.

Question 17

Describe the clinical importance of the corpus callosum. In which condition?

Answer 17

Epilepsy in the brain (misfiring of neurons)
If sever can travel between hemispheres of the brain via the corpus callosum.
Clinically can be cut/disconnected, to reduce severity and travel to other side.

Question 18

Where are the thalamus and hypothalamus?

Answer 18

Thalamus Inferior to Fornix (inferor to corpus callosum)

Thalamus is superio-posterior to hypothalamus.

Question 19

What are the functions of the thalamus and hypothalamus?

Answer 19

Thalamus = Sensory relay station projecing to sensory cortex. 
Hypothalamus = Essential centre for homeostasis.

Question 20

How would an embolus from an internal carotid atheroma cause temporary loss of vision?

Answer 20

Internal carotid gives the ophthalmic branch which supplies the ORBIT and RETINA.
TIA - transient ischaemic attack - ischaemia to retina.
Temporary blindness (monocular blindess)

Question 21

What is the location of the primary motor cortex, and the primary somatosensory cortex?

Answer 21

Primary motor cortex - anterior to the central sulcus.

Primary somatosensory cortex - posterior to central sulcus.

Question 22

A man has motor weakness and paraesthesia involving the left half of the face, and left arm.
A stroke is suspected. Which part of the brain would the stroke have occured in?

Answer 22

RIGHT side.
Frontal and Parietal Lobe.
(around the primary motor and somatosensory cortexes)
(Look at homunculus)

Question 23

A scan of a patient shows a right cerebellar tumour. What would be some clinical signs she potentially presented with?

Answer 23

Impairment of RIGHT sided motor control, coordination or fine tune of movements.
(Remember cerebellar control is IPSILATERAL)