Descending motor control pathways

Question 1

Spastic paralysis define

Answer 1

Damage to upper motor neurons

Question 2

Spastic paralysis

Answer 2

Voluntary movement is not possible due to muscle spasms in the affected muscles
Reflexes can be elicited but will be altered (hyperactive)
Pathological reflexes can be elicited (e.g. Babinski’s sign, which is normally not seen in adults)

Question 3

Flaccid paralysis define

Answer 3

Damage to lower motor neurons

Question 4

Flaccid paralysis

Answer 4

No movement of any kind, including reflexes, is possible in the affected muscles (the extent of the paralysis depends on the site and extent of the injury)
Affected muscles will atrophy

Question 5

Localization of lateral corticospinal tract injuries - If the injury to the pathway is above the pyramidal decussation (i.e., in the brain), the paralysis will be seen on

Answer 5

the side of the body opposite the site of the injury (contralateral side)

Question 6

Localization of lateral corticospinal tract injuries - If the injury to the pathway is below the pyramidal decussation (i.e., in the spinal cord or peripheral nerve) the paralysis will be seen

Answer 6

on the same side of the body as the injury (ipsilateral side)

Question 7

Localization of ventral corticospinal tract injuries - Because ventral corticospinal tract axons don’t decussate until they reach the spinal cord segment where they terminate,

Answer 7

injury to the upper motor neurons will always be above the level of the decussation, so the paralysis will be seen on the side of the body opposite the site of the injury (contralateral side)

Question 8

Only injury to lower motor neurons in a peripheral nerve would be

Answer 8

below the decussation and the paralysis will be seen on the same side of the body as the injury (ipsilateral side)

Question 9

Ipsilateral

Answer 9

the same side as some point of reference

Question 10

Contralateral

Answer 10

• the opposite side as some point of reference

Question 11

the anatomical course of a group of axons that carry similar information; also called a fiber tract

Answer 11

pathway

the anatomical course of a group of axons that carry similar information; also called a fiber tract

Question 12

a group of nerve fibers that carry information from a higher area of the CNS to a lower area; for example, from the cerebral cortex to the spinal cord

Answer 12

descending pathways
a group of nerve fibers that carry information from a higher area of the CNS to a lower area; for example, from the cerebral cortex to the spinal cord

Question 13

Decussation

Answer 13

the crossing the midline by a pathway

Question 14

Lateral corticospinal tract

Answer 14

Lateral corticospinal tract
cell body-upper and medial portion of precentral gyrus (primary motor area)
decussates- Pyramidal tracts caudal medulla
lateral white column spinal cord

lower motor
cell body-lateral part of ventral horn
NMJ SKM upper and lower limb

Question 15

Ventral corticospinal tract

Answer 15

Ventral corticospinal tract

• cell body-upper and medial portion of precentral gyrus (primary motor area) near longitudinal fissure
• ventral white column spinal cord
• decussates-in the spinal cord segment where they exit on lower motor neurons

cell body-medial part of ventral horn
NMJ SKM neck or trunk

Question 16

• connects the primary motor area of the cerebral cortex with skeletal muscles that are innervated by cranial nerves in order to execute voluntary movements in the head and neck

Answer 16

Corticobulbar tract
- connects the primary motor area of the cerebral cortex with skeletal muscles that are innervated by cranial nerves in order to execute voluntary movements in the head and neck

Question 17

a neuron in a descending pathway with a cell body in the spinal cord or brain stem and an axon that exits the CNS, travels through a peripheral nerve, and terminates at a neuromuscular junction on a skeletal muscle

Answer 17

Lower motor neuron

a neuron in a descending pathway with a cell body in the spinal cord or brain stem and an axon that exits the CNS, travels through a peripheral nerve, and terminates at a neuromuscular junction on a skeletal muscle

Question 18

What are the three motor control pathways that descend from the cerebral cortex that are responsible for voluntary movement of certain skeletal muscles

Answer 18

1. Lateral corticospinal tract
2. Ventral corticospinal tract
3. Corticobulbar tract

Question 19

Every cranial nerve except the ____, ____, and ____ innervate skeletal muscles

Answer 19

olfactory (I), optic (II), vestibulocochlear (VIII)

Question 20

Corticobulbar tract

Answer 20

cell body-precentral gyrus nearest lateral fissure
upper motor portion terminates -in cranial nerve somatic motor nuclei in the midbrain, pons, and, medulla
lower motor neuron-motor nucleus in the brain stem
axon travels to cranial nerve to a SKM in head or neck

3&4 midbrain
5 pons
rest of em medulla

Question 21

bulbar refers to

Answer 21

brainstem

Question 22

Most of the neurons of the lateral corticospinal tract are distributed

Answer 22

to the hand (for manual dexterity)

Question 23

Most of the neurons of the corticobulbar tract are distributed _____

Answer 23

Most of the neurons of the corticobulbar tract are distributed to the lower face and tongue (for speech)

Question 24

Function of Corticospinal Tracts (a.k.a. Pyramidal Tracts)

Answer 24

Function of Corticospinal Tracts (a.k.a. Pyramidal Tracts) connect the primary motor area of the cerebral cortex with
skeletal muscles that are innervated by spinal nerves in order to execute
voluntary movements