Which of the following statements . about the knee-jerk reflex is true? 2 pts Tr

Question

Which of the following statements . about the knee-jerk reflex is true? 2 pts True False It is a polysynaptic reflex. Muscle stretch receptors are activated by the hammer tap. The afferent (sensory) nerve travels from the receptor to the spinal cord. The leg extends in response to a hammer tap. The reflex involves only three neurons - a sensory neuron, an intermediate neuron, and a motor neuron. In a healthy adult, what happens when the sole of the foot is stroked? 1 pt O The big toe does not move. O The big toe dorsiflexes (extends upwards. O The big toe flexes (curls downwards)

Explanation / Answer

Patella reflex or knee jerk reflex is a monosynaptic stretch reflex involving the L2, L3, and L4 segments of spinal cord. It is a simple reflex involving the flow of information from a sensory neuron to the appropriate motor neuron via a single synapse. It only involves one sensory an done motor neuron. In this reflex, if a hammer taps the tendon, it stretches the muscle spindle in the quadriceps femoris muscle, making it longer. This stimulates the stretch receptors in the muscle. The signal that is produced is sent to the L3 segment of the spinal cord (L3). Here, an alpha motor neuron conducts an efferent impulse to the quadriceps femoris muscle. The contraction in the quadriceps femoris muscle causes the jerking/extending the foot upwards.

Options 2nd, 3rd and 4th are right.

When the sole of the foot is stroked, all toes including big toe should curl downwards the top surface of the foot. If the big toe dorsiflexes, then it is sign of neurological disorder.

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