Degeneration and regeneration

Question 1

What are the 4 neurone types

Answer 1

Bipolar
Unipolar
Multipolar
Pyrimidal cells

Question 2

What type of muscles can nerves supply

Answer 2

Skeletal
Smooth
Cardiac
Secretory glands

Question 3

What are Seddons three classification

Answer 3

• neuropaxia
• axonomotomesis
• neurotomesis

Question 4

What is neuropoxia

Answer 4

Disturbance at myelination

Question 5

What is axonotomesis

Answer 5

Injury at the level of the myelin sheath but the 3 layers are still intact

Question 6

What is neurotomesis

Answer 6

When the entire nerve is completely damaged (connective tissue and axon)

Question 7

What are the three connective tissue layers on a neurone

Answer 7

• endoneurium
• perineurium
• epineurium

Question 8

What happens after axonotmesis

Answer 8

Wallerian degeneration

Question 9

What is the most severe nerve damage according to Seddons classification

Answer 9

Neurotomesis

Question 10

Is it possible to get recovery in neurotomesis

Answer 10

Not if the injury is really close to the cell body of the nerve

Question 11

If a neurone is damaged in a neuronal chain what will happen

Answer 11

• The neurone that is innervating a damaged neurone will withdrawal
• the neurone after the damaged neurone will die as it is not being innervated

Question 12

When a neurone is damaged how does the environment change

Answer 12

• myelin forming cells: oligodendrocytes and Schwann cells
• microglia: immune cells
• astroycytes

Question 13

Where are oligodentroytes found

Answer 13

In the CNS

Question 14

Where are Schwann cells found

Answer 14

In the PNS

Question 15

What are oligodendrocytes

Answer 15

Myelinate more than one axon

Question 16

What are Schwann cells

Answer 16

Myelinate only one axon

Question 17

What is the role of microglia cells

Answer 17

Phagocytose damaged material

Question 18

What happens minutes after a nerve injury

Answer 18

• synaptic transmission cut off
• Two ends of the axon will leak into intracellular fluid
• Cut ends will swell apart

Question 19

What happens hours after a nerve injury

Answer 19

• synaptic terminal degenerates

- astroglia surround the synaptic terminal

Question 20

What happens days to weeks after a nerve injury

Answer 20

• cell body undergoes chromatolysis

- distal stump of axon undergoes wallerian degeneration

Question 21

What happens at chromatolysis

Answer 21

The cell body increases in metabolic activity and produces lots of proteins
Nucleus becomes displaced to the periphery margins

Question 22

What happens at wallerian degeneration

Answer 22

The axon is digested by phagocytes

Tissue that is preserved forms hallow tubules

Question 23

What happens to the axons at wallerian degeneration

Answer 23

Axon sprout into Schwann cells

Question 24

What happens when a type S motoneruone supplies as type FF muscle fibre

Answer 24

The FF muscle fibre changes to a type S muscle fibre to match the nerve supplying it

Question 25

What is the fate of a denervated and not reinnervated muscle in the acute phase

Answer 25

• muscle is paralysed
• muscle becomes areflexic (cannot get reflexes)
• muscle start to fasciculate

Question 26

What is the fate of a enervated muscle in the chronic phase

Answer 26

• fasciculations subside to give enervation atrophy and disuse atrophy
• muscle dies
• muscle tissue is replaced by connective tissue