Upper Motor Neuron Control of the Brain and Spinal Cord

A 45-year-old woman presented to the neurology clinic with complaints of weakness and impaired fine motor control in her left hand following a stroke. Neurological examination revealed muscle weakness and loss of dexterity in her left upper extremity, particularly affecting her ability to grasp and manipulate objects. Which region of the primary motor cortex was likely damaged in this patient?

• A

• B

• C

• D

Mirror motor neurons are stimulated by what?

• By excessive stretching of muscles

• By excessive contraction of muscles

• Stimulation of the somatosensory cortex of the parietal lobe

• Observing another individual performing an action
• Stimulation of the primary motor cortex of frontal lobe

Lower motor neurons responsible for posture and locomotion are found in the _______ and primarily receive input from upper motor neurons in the _______.

• medial ventral horn; brainstem

• lateral ventral horn; brainstem

• medial ventral horn; cerebral cortex

• lateral ventral horn; cerebral cortex

• medial dorsal horn; brainstem

At which level of the nervous system does pyramidal decussation occur?

• Cerebral cortex

• Midbrain

• Pons

• Medulla

• Spinal cord

What percentage of pyramidal tract fibers decussate to form the lateral corticospinal tract?

• 10%

• 25%

• 50%

• 75%

• 90%

A man is rushed to the hospital after he has had a stroke involving his left middle cerebral artery. The man will likely lose his ability to

• raise both eyebrows.

• raise the right corner of his mouth.

• squint.

• push his tongue into his left cheek.

• furrow his brow.

Which of the following body areas listed has the greatest area of motor cortex devoted to it?

• Neck

• Lips

• Wrist

• Knee

• Brow

The vestibulospinal tract would play a role in which of the following activities?

• Contracting your abdominal muscles as you tackle an opponent in football.

• Shifting your weight to your right leg before you raise your left leg.

• Extending your arms to protect yourself after you trip.

• Contracting muscles in your left leg as you take a step with your right leg.

• Contracting your triceps as you do a push up.

Within the spinal cord, the neurons that innervate the proximal muscles are more ___ in the spinal cord, whereas the neurons innervating distal muscles are more ___.

• central, peripheral
• superior, inferior
• anterior, posterior
• medial, lateral
• dorsal, ventral

Lateral descending motor tracts in the spinal cord are responsible for ___ whereas medial tracts aid in ___.

• involuntary muscle contracts and posture/balance

• sensory perception and digestion
• voluntary movement and posture/balance
• heart rate regulation and respiration
• visual processing and auditory perception