Motor and Sensory Control Review

Question 1

What tract is responsible for motor control of the body.

Give its pathway, branches, and function

Answer 1

Corticospinal tract

primary motor cortex (precentral gyrus) → internal capsule → brainstem via cerebral peduncles → decussates mostly at caudal medulla

Lateral corticospinal tract crosses at the level of the pyramids
- Controls distal limb muscles

Anterior corticospinal tract don’t cross at the pyramids
- Controls axial trunk muscles (back)

Question 2

Describe the corticobulbar tract
- function
- pathway

Answer 2

governs volitional motor control of the head

primary motor cortex (precentral gyrus) → internal capsule → brain stem via the cerebral peduncles → synapses onto cranial nerve nuclei in the brainstem

Question 3

spastic vs flaccid paralysis

Answer 3

Spastic paralysis: muscle weakness. Spastic paralysis involves tight and hard muscles

Flaccid paralysis: reduced muscle tone and weakness/paralysis

Question 4

Describe the spinothalamic pathway and its function

Answer 4

Function: nociception, temperature, coarse touch

Primary sensory neuron enters the dorsal horn and synapses onto a secondary sensory neuron (aka second order neuron). This neuron becomes the spinothalamic axon. The spinothalamic axon crosses at the spinal cord segment right away and then ascends toward the brain and synapses onto the thalamus. From here, information regarding the stimulus is sent from the thalamus via the third order neuron (tertiary neuron), to the primary somatosensory cortex

Question 5

Describe the dorsal column - medial lemniscal pathway and its function

Answer 5

Function: Fine touch, proprioception, vibration information travels

Primary sensory neuron enters the dorsal horn and ascends ipsilaterally to synapse onto medulla. Information regarding the stimulus crosses to the opposite side at the medulla and synapses onto the thalamus via a secondary sensory neuron (aka second order neuron). From here, information regarding the stimulus is sent from the thalamus via the third order neuron (tertiary neuron), to the primary somatosensory cortex

Question 6

Describe the pathway for sensory input from cranial nerves

Answer 6

enter the dorsal column medial lemniscus system and spinothalamic tract in the brainstem to mediate somatosensation from the head

• Origin: primary sensory neurons in cranial nerve ganglia
• Crosses midline at brainstem
• Ascends through internal capsule to primary somatosensory cortex

Question 7

Bell’s palsy
- age
- time course
- upper face
- lower face
- associated symptoms

Answer 7

20s-50s

hours to few days

always affected

always affected

typically none; rare facial numbness

Question 8

Acute stroke
- age
- time course
- upper face
- lower face
- associated symptoms

Answer 8

> 60
seconds to minutes
+/- affected
always affected
weakness, numbness, speech difficulty, slurred speech, double vision, facial numbness, difficulty swallowing, vertigo, ataxia

Question 9

Describe the recovery time for Bell’s palsy and possible treatment and possible cause

Answer 9

Full recovery within 6 months (some have permanent facial paralysis)

Treatment: 10 course day of steroids and antiviral therapy (sometimes only)

Most common cause: reactivation of herpes simplex virus-1

Question 10

Describe the difference between a facial nerve lesion (Bell’s palsy) and a supranuclear lesion

Answer 10

Facial Nerve Lesion: Will affect sensation and motor control of upper and lower half of face on the same side of lesion

Supranuclear Lesion: will affect sensation and motor control of only lower half of face as the facial nerve nuclei have bilateral innervation from upper motor neurons to the upper face but only contralateral input into the lower face