The legs of an accident victim with a fractured vertebral column and injured spinal cord could not be raised because

Analyze the question The victim has a fractured vertebral column and an injured spinal cord. The question asks why the legs could not be raised. Raising the legs is a voluntary action, so the focus is on how the command to move reaches the legs.

Concept

• The spinal cord is the pathway connecting the brain to the rest of the body.
• Sensory (afferent) neurons carry impulses from receptors to the CNS.
• Motor (efferent) neurons carry impulses from the CNS to effectors (muscles).
• A voluntary movement starts in the brain. The impulse travels down the spinal cord, then along motor neurons to the leg muscles.

Step-by-step solution

1. To raise the leg, the brain must send a motor impulse down the spinal cord.
2. If the cord is injured, that impulse is blocked at the damaged region.
3. The leg muscles never receive the command, so the leg cannot be lifted (paralysis).

Checking the options

• A. Impulses from leg receptors not reaching the brain would cause loss of sensation (feeling), not inability to move the legs. This is not what the question asks.
• B. Impulses from the brain not reaching the legs explains the loss of voluntary movement. This is correct.
• C. Chemical release at synapses is normal nerve function and does not explain paralysis.
• D. Reflex actions may still occur in the legs, because simple reflex arcs only need the spinal cord below the injury. So this is not the reason.

Answer: B, impulses from the brain cannot travel to the legs.

Exam tip Match the problem to the pathway:

• Can't feel → sensory pathway (receptor → brain) is blocked.
• Can't move → motor pathway (brain → muscle) is blocked.

Cord injuries often affect both, but the question here asks about raising the legs, which is movement.