In the knee-jerk reflex, a . spinal interneurons inhibit the...

In the knee-jerk reflex, $a .$ spinal interneurons inhibit the motor neuron of the antagonistic muscle. $b$. activity in the stretch receptor neuron causes contraction of the leg flexor muscles. $c .$ the cell body of the motor neuron is in the dorsal horn of the spinal cord. $d$. action potentials in the sensory neuron release inhibitory neurotransmitter onto the motor neurons. $e .$ the sensory neuron forms a monosynaptic loop with the motor neuron to the antagonistic muscle.

In the knee-jerk reflex,
$a .$ spinal interneurons inhibit the motor neuron of the antagonistic muscle.
$b$. activity in the stretch receptor neuron causes contraction of the leg flexor muscles.
$c .$ the cell body of the motor neuron is in the dorsal horn of the spinal cord.
$d$. action potentials in the sensory neuron release inhibitory neurotransmitter onto the motor neurons.
$e .$ the sensory neuron forms a monosynaptic loop with the motor neuron to the antagonistic muscle.

Key Concepts

Reflex Arc

A reflex arc is a neural pathway that mediates a reflex action. This pathway typically includes a sensory receptor, an afferent pathway carrying the signal to the spinal cord, an integration center (which may be as simple as a single synapse in a monosynaptic reflex), an efferent pathway, and an effector organ such as a muscle. It enables rapid, involuntary responses to stimuli.

Monosynaptic Reflex

A monosynaptic reflex involves a direct synaptic connection between a sensory neuron and a motor neuron, allowing for a very quick response. This is exemplified by the knee-jerk reflex, where the direct connection minimizes delays in the reaction to muscle stretch.

Reciprocal Inhibition

Reciprocal inhibition is the process by which the activation of one muscle group is accompanied by the inhibition of its antagonistic muscle group. This is mediated by inhibitory interneurons in the spinal cord and ensures that while one muscle contracts, the opposing muscle is inhibited, allowing for smooth and coordinated movement.

Spinal Cord Organization

The spinal cord is anatomically divided into dorsal and ventral horns. The dorsal horn primarily processes sensory information, while the ventral horn contains the motor neuron cell bodies responsible for sending signals to muscles. Understanding this organization is crucial for mapping neural pathways in reflex actions like the knee-jerk response.

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