Response To Nerve Injury

Question 1

What is the function of the blood brain barrier?

Answer 1

Protests the CNS from imbalances in surrounding environment- electrolytes, hormones, metabolites

Question 2

Give the structure function of the blood brain barrier

Answer 2

Continuous capillaries

• complex tight junctions between endothelial cells
• continuous basal lamina
• no fenestrations in cytoplasmic membrane

Surrounded by foot processes of astrocytes

• characteristics of cerebral cortex
• Can lose effectiveness in certain brain diseases
  - loss of tight junctions and altered astrocytes
• Some parts of CNS have no barrier:
  
  • circumventricular organs (windows of the brain)
  • Important in regulating homeostasis

Question 3

What is the effect of Gillian Barre?

Answer 3

Post-infectious peripheral polyneuropathy

• Damage to Schwann cells
• Nerve fibers- large accumulation of lymphocytes, macrophages and plasma cells
• Ascending muscle, coordination & cutaneous sensation

Question 4

What is the effect of multiple sclerosis?

Answer 4

Selective Loss of myelin sheath with axon preservation

• multiple sites of demyelination occurring in the CNS
• Preferential damage to myelin-detach from axon and destroyed
• Damage to oligodendrocytes

Question 5

Explain the mechanism of multiple sclerosis ?

Answer 5

Target- autoimmune myelin basic protein

Three histological stages
1. Myelin breakdown associated with lymphocyte abs macrophage infiltration of affected area-plaque

2. Proliferation of astrocytes- gradual infiltration of astrocytes inti demyelination area
3. Reduced cellularity, astrocyte reduce in size

Question 6

What are the symptoms of multiple sclerosis?

Answer 6

Area of CNS where myelin is destroyed

Question 7

What is the general nerve response to injury?

Answer 7

Neurons and neuroglia mobilized in nerve injury

CNS

• Absent/slow regeneration- blood brain barrier
• ineffective phagocytosis
• Myelin debris persists
• Astricyte scarring

PNS

• rapid degeneration
• Macrophages migrate from blood
• Complete interruption of blood nerve barrier

Question 8

What complex procdesses occur in response to nerve injury?

Answer 8

Chromatolysis

Wallerian Degeneration (anterograde)

Question 9

What is wallerian degeneration?

Answer 9

Degeneration of axon distal to site of injury

PNS

• degeneration takes a few days
• dediferentiation of Schwann cells and alignment

CNS

• degeneration takes several weeks
• loss of axon contact initiate apoptotic cell death

Some anterograde degeneration Aldo occurs- traumatic degeneration-
-only extends fir several internodal segments

Question 10

What is chromatolysis?

Answer 10

-loss of Nissl substance from cell body
1-2 days after injury

• changes in cell bidy proportions to: amount axoplasm lost from injury
  
  • large amount= cell death

Motor fiber damage= muscle atrophy