Damage and Repair in the CNS

Question 1

Why is repair in the CNS less feasible than in the PNS?

Answer 1

The complexity of the CNS is at the expense of repairability.

Question 2

As a general rule, what functions will be affected after injury to a particular segment of the CNS?

Answer 2

Movement, sensation and autonomic control below the level of the injured segment will be affected.

Question 3

What do the functional consequences of CNS injury depend on?

Answer 3

The site and size of the injury only.

-Not the type of injury.

Question 4

Where is the energy consumed by the brain derived from?

Answer 4

Glucose metabolism; the brain has no energy stores of its own other than glycogen in astrocytes (small).

Question 5

What is the difference between a depression fracture and a compound fracture?

Answer 5

• A depression fracture is a break in cranial bone causing depression of the bone towards the brain.
• A compound fracture is a piercing or splintering of cranial bone.

Question 6

What is a haematoma?

Answer 6

Compression of the brain due to raised intracranial pressure.

Question 7

What is a contusion?

Answer 7

A region of injured tissue or skin in which blood capillaries have been ruptured; a bruise.

Question 8

What is traumatic brain injury?

Answer 8

• Movement of the brain inside the skull due to impact.

- Causing cerebral contusions, lacerations and subdural haematomas.

Question 9

Which cells of the brain will experience irreversible damage after ischaemia lasting 4-5 minutes?

Answer 9

• Hippocampal cells
• Pyramidal cells
• Striatal neurones
• Purkinje cells

Question 10

Which cells of the brain will experience irreversible damage after ischaemia lasting more than 4-5 minutes?

Answer 10

Thalamic and brainstem neurones.

Question 11

What does anoxic mean?

Answer 11

Without oxygen.

Question 12

What is oedema?

Answer 12

A condition where an excess of watery fluid collects in the cavities or tissues of the body.

Question 13

Why might an oedema occur after a traumatic brain injury?

Answer 13

As a result of an inflammatory response to an injury.

Question 14

List 5 consequences of severe traumatic brain injury.

Answer 14

– Seizures.

– Focal neurologic deficits.

– Dementia.

– Persistent vegetative state.

– Increased risk of Alzheimer’s disease.

Question 15

Why is there no axonal regeneration in the CNS?

Answer 15

• Due to the presence of inhibitory molecules such as:

• Nogo
• MAG
• OGmp
• CSPG
• Due to the lack of neurotrophic stimulation.
• Due to the formation of glial scars.
• Due to the demyelination of axons.

Question 16

What do glial scars consist of?

Answer 16

Primarily astrocytes and proteoglycans.

Question 17

What are the treatment options for CNS injury?

Answer 17

• Surgery:
– remove a hematoma
– repair skull fractures
– decompression

• Medication:
– Anti-seizure medication
– Reduce oedema using diuretics
– Induced coma - reduce oxygen and nutrient
requirements

• Rehabilitation

Question 18

What is neuroplasticity?

Answer 18

The brain’s ability to reorganise itself by forming new neural connections.

Question 19

Describe the mechanisms involved in neuroplasticity.

Answer 19

• Neuronal activity stimulates neurotrophin synthesis and secretion, causing:

• Change in postsynaptic responsiveness.
• Change in synaptic morphology.
• Change in presynaptic transmitter release.
• Change in membrane excitability.

•Contributes to the modification of synaptic transmission and connectivity.

Question 20

In the injured CNS environment, which ells up-regulate the inhibitory extracelluar matrix?

Answer 20

Astrocytes.