Multiple Choice
Which stage of a reflex arc would be significantly different in a reflex that is initiated by the brain compared to a reflex that is initiated by the spinal cord?
13. The Peripheral Nervous System
Introduction to Reflex Arcs
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Which of the following reflexes would test the integrity of L4 to S2?
A
downward curling of the toes as a blunt object is drawn downward along the lateral aspect of the foot
B
lifting a cut foot if you step on a piece of glass
C
striking the patellar ligament with a reflex hammer
D
contraction of the muscles of the anterior compartment of the thigh while the posterior compartment muscle relaxes
E
stroking the skin of the lateral abdomen
Verified step by step guidance1
Understand the spinal nerve roots involved in the reflexes listed. L4 to S2 are lumbar and sacral nerve roots that contribute to the innervation of the lower limb.
Identify the reflexes associated with these nerve roots. The Babinski reflex, which involves the downward curling of the toes, tests the integrity of the L4 to S2 nerve roots.
Consider the reflex arc involved in the Babinski reflex. This reflex is a plantar response that involves the corticospinal tract and is typically tested by drawing a blunt object along the lateral aspect of the foot.
Evaluate the other reflexes mentioned. Lifting a cut foot when stepping on glass is a withdrawal reflex, striking the patellar ligament tests the L2-L4 nerve roots, and contraction of thigh muscles involves different nerve roots.
Conclude that the downward curling of the toes as a blunt object is drawn along the foot is the reflex that tests the integrity of L4 to S2.
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