Physiology Chapter 2-Regeneration of nerve fibres

Question 1

In the case of a severed axon, where do the latter regenerate?

Answer 1

Cut axons in the peripheral nervous system can regenerate whereas those in the CNS cannot.

Question 2

What happens when an axon is cut in the peripheral nervous system?

Answer 2

The portion of the axon farthest from the cell body degenerates, and the surrounding Schwann cells phagocytize the debris.
The Schwann cells remain and form a regeneration tube to guide the regenerative nerve fibre to its proper destination.
The remaining portion fo the axon starts to grow by amoeboid movement.
This is guided by chemotaxis from the Schwann cells.

Question 3

What happens to cut axons in the CNS?

Answer 3

The axon themselves have the ability to regenerate but the oligodendrocytes synthesize proteins that inhibit axonal growth.

Question 4

Nerve growth in the brain and spinal cord is controlled by what?

Answer 4

A delicate balance between nerve growth-enhancing and inhibiting proteins.

Question 5

What do researchers speculate is the reason for the proteins that inhibit axonal growth?

Answer 5

To serve as guardrails during fetal development to keep new nerve endings from straying outside their proper paths.