Chapter 3 Paralysis and Weakness

Question 1

Percent of fibers of the corticospinal tract that decussate/cross?

Answer 1

75-80%

Question 2

Percentage of corticospinal tract arising from the

Parietal lobe :
motor area 4 :
premotor area 6:

Answer 2

Parietal lobe - 40%
motor area 4 - 31%
premotor area 6-29%

Question 3

Law that states for flexion to be smooth and forceful, the extensor muscles must relax at the same rate as the flexors contract

Answer 3

Sherringtons Law/ Law of Reciprocal Innervation

Question 4

The Neurotransmitter released by Renshaw cells, which are responsible for recurrent inhibition, and by interneurons that mediate reciprocal inhibition during reflex action

Answer 4

Glycine

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Question 5

This serves as an inhibitory neurotransmitter of interneurons in the posterior horn

Answer 5

GABA

Question 6

Main neurotransmitter of the descending corticospinal tract [2]

Answer 6

Aspartate and Glutamate

Question 7

The one place where corticospinal fibers are entirely isolated is the pyrimadal tract in the __________

Answer 7

Medulla

Question 8

Lesions of the upper motor neuron has a predilection for certain muscles groups. Antigravity muscles are usually affected: (choose the following)

a. flexors of the arm
b. extensors of the arm
c. flexors of the leg
d. extensors of the leg

Answer 8

A and D

Question 9

Velocity dependent

a. rigidity
b. spasticity
c. cogwheeling rigidity
d. flaccidity

Answer 9

B. spasticity

The essential feature of spasticity is a velocity dependent increase in the resistance of muscles to passive stretch stimulus.

Question 10

The pathophysiology of spasticity is dependent on 2 more refined descending tracts which are:

Answer 10

1. dorsal reticulospinal tract - inhibitory effects on stretch reflexes
2. medial reticulospinal tract and vestibulospinal tracts - facilitates extensor tone

Question 11

A series of rhythmic involuntary muscle contractions occurring at a frequency of 5-7 hz in reponse to an abruptly applied and sustained stretch stimulus

Answer 11

CLONUS

Question 12

The following are the major inhibitory neurotransmitters of the spinal cord (2)

Answer 12

GABA and Glycine

Question 13

inability to execute previously learned activities in the absence of weakness, ataxia, sensory loss or extrapyramidal derangement that would be adequate to explain the deficit

Answer 13

Apraxia