Place the following descriptions into the correct order to represent the sequence of events in a patellar reflex arc. Efferent signals in the motor nerve fiber stimulate the quadriceps femoris to contract. A primary afferent nerve fiber stimulates an alpha motor neuron in the spinal cord. Flexor muscles of the hamstrings relax to prevent antagonizing the quadriceps muscles. The alpha motor neuron to the hamstrings muscles is inhibited. A branch of the afferent nerve fiber stimulates an inhibitory motor neuron in the spinal cord. Stretch signals travel to the spinal cord via a primary afferent neuron. A tap on the patellar ligament excites nerve endings of muscle spindles in the quadriceps femoris.
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A tap on the patellar ligament excites nerve endings in muscle spindles in the quadriceps femoris. Show more…
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In the stretch reflex (knee jerk reflex), the muscle stretches and the muscle spindle is excited. The sensory neuron sends an afferent signal to the spinal cord.
Madhur L.
Using the list provided, complete the blanks in the following description of the stretch reflex associated with the knee. The patellar hammer is used to strike the patella of the quadriceps muscle group just below the knee. This results in a stretch of the muscle and the specialized receptor within the muscle called the muscle spindle. The resultant increase in length leads to an increased discharge of spindle afferents, particularly the Ia afferents. The discharge travels up the nerve to the spinal cord where the afferents make a monosynaptic excitatory contact onto alpha motoneurons from the same muscle group that the afferent information came from. The resultant excitation leads to action potentials being generated in the axon, which then travel down to the muscle and cause it to contract. This causes the lower limb to extend away from the body.
Activity 4: Analyzing a Spinal Reflex 1. What is a reflex? 2. Complete the following table to summarize the components of a reflex arc: Three major events Detection and delivery of stimulus Integration Delivery of motor response 3. Which specific component of the reflex arc is confined to the CNS? 4. In the patellar reflex, a. Which structure serves as the receptor? b. Which structure serves as the effector?
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