Peripheral Nerve Damage

Question 1

Causes of peripheral nerve damage

Answer 1

1. Infections such as leprosy and HIV-AIDS
2. Nutritional deficiencies such as vitamin B12
3. Nerve injury sure to trauma
4. side effects of drugs such as some anticancer drug
5. disruption is blood supply to the nerve occurs with vasculitis, arteriosclerosis
6. Systemic diseases such as diabetes

Question 2

Chronaxie

Answer 2

Duration that a stimulus twice the strength of rheobase needs to be applied to elicit a response

Question 3

Denervation hypersensitivity

Answer 3

Also known as supersensitivity.
It is a heighten response of the target organ /tissue following Denervation due to an upregulation of receptors on the postsynaptic membrane

Question 4

Rheobase

Answer 4

It’s the minimum strength of stimulus that can elicit a biological response in the strength - duration curve

Question 5

Utilization time

Answer 5

Duration for which a stimulus of rheobase strength needs to be applied in order to elicit a biological response

Question 6

Types of nerve injuries

Answer 6

1. Neuropraxia
2. Axonotmesis
3. Neurotmesis

Question 7

Neuropraxia

Answer 7

1. Least serve form of nerve injury
2. Nerve is compressed or blood supply to the nerve is disrupted
3. Recovery rapid with a few hours
4. Serve forms need several months

Question 8

Axonotmesis

Answer 8

1. More serve form
2. Axon is disrupted, myelin sheath is intact
3. Wallerian degeneration takes place in Distal segment

Question 9

Neurotmesis

Answer 9

1. Most serve form
2. Axon, and surrounding encapsulating connective tissue is affected
3. Last chances of recovery

Question 10

Changes that occur in Wallerian degeneration

Is the Distal segment

Answer 10

Distal segment :

1. Formation of ovoids by schwann cells which fragment the myelin sheath and scavenge myelin debri
2. change in schwann cell properties from Myelinating to demyelinating
3. Infiltration of leukocytes into the Distal seg.

Question 11

Changes that occur in Wallerian degeneration

Is the proximate segment

Answer 11

1. The first node of ranvier is degenerated
2. Chromatolysis: breakup of the RER and shift of the nucleus from the center of the cell body. Changes in RER alter rRna synthesis, gene expression that supports neuronal recovery.

Question 12

What mediates Wallerian degeneration

Answer 12

Calcium influx and activation of axonal proteases

Question 13

Effect of nerve degeneration

Answer 13

1. Reduced /absence of neurotransmitters

2. Upregulation (increased number or affinity) of receptors on the postsynaptic membrane

Question 14

What brings about Denervation hypersensitivity

Answer 14

Nerve regeneration or Exogenous administration of neurotransmitter agonist

Question 15

How are motor nerves tested

Answer 15

Assessed clinically by evaluating the muscle strength of the muscles they supply

Question 16

How are sensory neurons tested

Answer 16

Assessed by testing for sensation in the area of the specific nerve supply

Question 17

strength and duration curve

Answer 17

Relies on the varying strength and duration of a stimulus applied to a nerve and evaluating the biological response

Question 18

How is the strength and duration curve formed

Answer 18

An electrode is placed over the point where a motor nerve is entering a muscle this point is called the motor point. And the strength and duration of the stimulus can be regulated until biological response is achieved

Question 19

Parameters of a strength duration curve

Answer 19

1. Rheobase
2. Chronaxie
3. Utilization time

Question 20

Damaged nerve SD curve

Answer 20

The Utilization time and Chronaxie are prolonged and rheobase is increase. Showing a right shift away from the normal curve

Question 21

Nerve regeneration is characterized by

Answer 21

1. Development and prolongation of a growth cone from the proximal nerve stump
2. Extension along the surfaces schwann cell column in the Distal segment

Question 22

Difference between nerve regeneration in PNS and CNS

Answer 22

Nerve regeneration occurs in PNS but not in CNS

Question 23

Differences in nerve degeneration and regeneration of neurons in PNS and CNS

Answer 23

The rate of removal of myelin debris, cytokins release, regeration association gene expression are relatively faster in PNS than in the CNS. Also there is a response from nonnueronal cells, in PNS schwann cells dedifferenciate into a “growth supporting” mode but CNS oligodentrocytes show no change