Neurophysiology

Question 1

What is the conus medullaris of the spinal chord?

Answer 1

Its termination

Question 2

Where is the conus medullaris given off?

Answer 2

at level of 2nd lumbar vertebrae

Question 3

What filament is given off by the conus medullaris?

Answer 3

a non-nervous filament; filum terminate

Question 4

Differentiate the cauda equina from the conus medullaris.

Answer 4

Cauda equina are spinal nerves that ARISE from the conus medullaris and are bundled together

Question 5

How many enlargements does the spinal chord have?

Answer 5

2; Cervical and Lumbar enlargement

Question 6

How many pairs of spinal nerves does the spinal chord have?

Answer 6

31

Question 7

What are the 5 segments of the spinal chord?

Answer 7

Cervical (8)
Thoracic (12) 
Lumbar (5)
Sacral (5) 
 Coccygeal (1)

Question 8

Where do the ventral and dorsal roots leaving the spinal chord reunite to form a spinal nerve?

Answer 8

At the intervertebral foramina

Question 9

True or false: The anterior root is purely sensory and the posterior root is purely motor.

Answer 9

False: Anterior root is motor; Posterior root is sensory

Question 10

Which ramus (anterior and posterior) gives fibers to synovial joints of vertebral column, muscles of the back, and the back’s skin?

Answer 10

Posterior ramus

Question 11

True or false: The cervical and thoracic roots are shorter than the lumbar and sacral roots

Answer 11

True

Question 12

Name the two types of multipolar neurons found in the spinal chord’s grey matter.

Answer 12

Golgi Type 1

Golgi type 2

Question 13

How can the neurons in the grey matter be organized?

Answer 13

Columns/Nuclei

Layers/Laminae

Question 14

What are the two types of long tracts?

Answer 14

Ascending (carry sensory info to brain) and descending (carry motor info from brain)

Question 15

Differentiate a receptor potential from a generator potential

Answer 15

Receptor potential is produced when the receptor is the primary afferent neuron

Generator potential is produced when the receptor and the primary afferent neuron are separate

Question 16

True of false: Receptor potentials always result in action potentials.

Answer 16

False.

Question 17

Which stimulus always results in an action potential?

Answer 17

Adequate stimulus

Question 18

Which parts of the reflex arc show a graded response?

Answer 18

At the receptor

At the neuromuscular junction

Question 19

Endplate potential

Answer 19

depolarization of skeletal muscle fibers

Question 20

Which part of the reflex arc shows all or none action potentials?

Answer 20

Those specialized for transmission (afferent and efferent fibers + interneurons)

Question 21

Name the brain system that provides short-term relief from pain

Answer 21

Analgesia system/Endogenous Analgesic system

Question 22

Enumerate the pathway for the analgesic system.

Answer 22

1. Starts in the frontal cortex and the hypothalamus
2. Terminates in gray matter around 3rd ventricle and aqueduct of sylvius
3. From here fibers descend down the lateral white column
4. Terminate where there’s synapse between fast and slow pain fibers to marginal nucleus and substantia gelatinosa of rolando respectively
5. Prevent signals from being sent to marginal nucleus and substantia gelatinosa of rolando

Question 23

State the neurotransmitters of analgesic fibers.

Answer 23

*SEED
Endorphin
Dynorphin
Enkephalins

Serotonin

Question 24

How does activity in other neurons close the ‘gate’ to result in pain relief? Example, rubbing, ice packs, massages

Answer 24

When pain stimulus applied, other receptors like vibration and temperature activated
Their fibers run through the posterior gray horn and they send collaterals to marginal nucleus and substantia gelatinosa of rolando
Their signals then inhibit the release of glutamate and substance P from fast and slow pain fibers

Question 25

What is phantom pain? Describe its mechanism.

Answer 25

perceptions that an individual experiences relating to a limb or an organ that is not physically part of the body

When a limb is amputated, the stump has endings of C and A fibers which show increased spontaneous activity caused by
1. new neuronal connections that were not present before
2. downregulation of potassium channels
3. upregulation of sodium channels
The dorsal root ganglion cells also show increased activity.
The ends of C and A fibers form new connections with secondary pain fibers
Finally there is the concept of cortical reorganization. the brain is capable of remapping itself such that if an area is no longer being represented, another part of the brain moves to occupy that area so its stimulation causes phantom pain.

Question 26

Suggest management of phantom limb pain.

Answer 26

Anticonvulsants - the most popular is GABAPENTIN by binding to calcium channels in the brain to slow down firing of action potentials

Antidepressants - act as inhibitors of the reuptake of serotonin and norepinephrine neurotransmitters

Non-steroidal inflammatory drugs block the action of enzymes that synthesize prostaglandins = decrease in nociception

TENS (Transcutaneous electrical nerve stimulation) - electrical current passed over skin, interfering with impulses being sent to brain

Mirror box therapy

Question 27

Lignocain mechanism of pain relief

Answer 27

blocks conduction of nerve impulses in pain fibers

Question 28

Enumerate CORDOCTOMY

Answer 28

surgical procedure done to disrupt lateral spinothalamic tract and relieve pain in patients suffering from severe pain

Question 29

Define RECEPTOR

Answer 29

a nerve ending that terminates in the periphery as myelinated or naked