Neurophysiology - ENC

Question 1

What is the normal CBF?

Answer 1

1. 50-55 ml/100g/min.

Question 2

Decreases in CBF below what level result in deficits of neural function?

Answer 2

1. 23 ml/100g/min.

Question 3

What factors can increase CBF?

Answer 3

1. Increases in paCO2 (acidosis) or serum H.

2. Decreases in pH or paO2.

Question 4

How are body fluid levels regulated by the CNS?

Answer 4

1. ADH secreted from the supraoptic nucleus of the anterior hypothalamus decreases renal excretion of water.
2. The lateral hypothalamus increases water intake by the sensation of thirst.
3. Both ways are activated or inhibited in response to decreases or increases in serum osmolarity sensed by two circumventricular organs: subforniceal organ and the vascular organ of the lamina terminalis.

Question 5

Which cells are the primary synaptic contributors of the synaptic potentials measured in an EEG?

Answer 5

1. Pyramidal cells.

Question 6

What are alpha waves on EEG?

Answer 6

1. Observed in an awake and resting adult with eyes closed.

2. Rhythm is suppressed by eye opening or thought.

Question 7

What are beta waves on EEG?

Answer 7

1. Seen primarily in the frontal region of the brain.

2. Seen during drowsiness, light sleep and with mental activation.

Question 8

What are slow waves on EEG?

Answer 8

1. Theta waves - seen with drowsiness and sleep, also present in normal, awake young adults and with focus concentration.
2. Delta waves - seen during slow-wave sleep.

Question 9

EEG changes during different stages of sleep?

Answer 9

1. Awake, alert adult - beta rhythm.
2. Awake, resting (eyes closed) adult - alpha waves.
3. Stage 1 sleep - theta waves.
4. Stage 2 sleep - sleep spindles and K complexes.
5. Slow wave sleep (stages 3 and 4) - delta waves
6. REM - beta rhythm.

Question 10

A delay between the stimulus point and the Erb point (for the upper limbs) or lumbar spine (lower limbs) on SSEPs may indicate what pathology?

Answer 10

1. Peripheral nerve disease.

Question 11

A delay between the Erb point (upper limbs) or lumbar spine (lower limbs) to the C2 vertebra on SSEPs may indicate what pathology?

Answer 11

1. Nerve root or posterior column disease.

Question 12

A delay between C2 and the parietal cortex on SSEPs may indicate what pathology?

Answer 12

1. Medial lemniscal or thalamoparietal tract disease.

Question 13

What structure is each of the seven BAER waves thought to be associated with?

Answer 13

1. Nerve: CN VIII.
2. Cochlear nuclei (medulla).
3. Superior olivary complex (pons).
4. Lateral lemniscus (pons).
5. Inferior colliculus (midbrain).
6. Medial geniculate body (thalamus).
7. Auditory radiations (thalamocortical tract).