Chapter 13 Homework Interactive Questi- Help Save &Exit; Submit Place the follow

Question

Chapter 13 Homework Interactive Questi- Help Save &Exit; Submit Place the following descriptions into the correct order to represent the sequence of events in a patellar reflex arc. A branch of the aterent ber simulates an inhibihory motor neuron in the spinal points A primary aterent nerve fiber strulates alpha elook spinal cord The alpha motor neuron to the hamstrings muscles is inhibted on the patellar endings of muscle spindies 3 Stretch signals travel to the spinal cord via a primary afferent neuron Efferent signals in the motor nerve tiber somulale the quadriceps temoris to contract. hamstrings relax to prevent antagonizing the quadriceps muscles

Explanation / Answer

Any circuit must start from the stimulation. So:

1. A tap on the petellar ligament excites nerve enddings of muscle spindles in the quadriceps femoris.

Any excitation is taken by afferent neurons and actions are done by efferent neurons. So, afferent neurons come before efferent neurons.

2. Stretch signals travel to the spinal cord via a primary afferent neuron.

The afferent neuron stimulates motor neuron in the spinal cord. In this case, it stimulates alpha and inhibitory motor neuron. So,

3. A primary afferent nerve fibre stimulates an alpha motor neuron in the spinal cord.

4. A branch of the afferent nerve fibre stimulates an inhibitory motor neuron in the spinal cord.

The signal to the inhibitory motor neuron inhibits alpha motor neuron to hamstrings muscles

5. The alpha motor neuron to hamstrings muscles is inhibited

Now, these 2 signals will travel through efferent neurons to their respective positions.

6. Efferent signals in the motor nerve fibre stimulate the quadriceps femoris to contract.

7. Flexor muscles of the hamstring relax to prevent antagonizing the quadriceps muscles.

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