Reflexes and sensations handout

Reflexes and sensations handout - PSIO 201 Required Handout...

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PSIO 201 Required Handout Department of Physiology REFLEX PHYSIOLOGY Somatic reflex tests In this laboratory session you will be testing for the presence of several somatic and autonomic reflexes. The first set of tests are designed to examine a few reflexes that involve the activation of skeletal muscle. Somatic reflexes that are integrated at the level of the spinal cord are considered spinal reflexes , and those integrated in the brain are called cranial reflexes . Note that although spinal reflexes are processed in the spinal cord, the brain is ultimately informed of the events taking place by signals not considered part of the reflex arc. You will be testing both spinal and cranial somatic reflexes in this section. Spinal reflexes 1. Patellar reflex - The patellar, or knee-jerk reflex is an example of a stretch reflex, in which stretch of the quadriceps muscles activates stretch receptors called muscle spindles . This reflex is processed at the level of the spinal cord (L2-L4). To test the patellar reflex, have a partner sit on the laboratory bench with his/her legs bent and relaxed. Using a reflex hammer, strike the patellar tendon (just below the knee) and record what happens. What muscles contracted to produce this response? ______________________________________________________________________________ Now test the reflex again, while the subject contracts muscles elsewhere in the body. Have the subject grab the lab bench and try to pull it upward with much effort. How does the reflex compare to the result tested above? Why do you think so? ______________________________________________________________________________ 2. Achilles reflex - The Achilles reflex is another example of a stretch reflex, in which the Achilles tendon is tapped with a reflex hammer to elicit the reflex response. Have your subject sit on the lab bench with his/her shoe removed and foot slightly dorsiflexed. Support the subject’s foot with one hand and tap the Achilles tendon with the other. Record your response. What muscles contracted to produce this response? ______________________________________________________________________________ 3. Flexor and Crossed extensor reflexes* - The flexor reflex occurs in response to a painful stimulus. The crossed extensor reflex is often paired with the flexor reflex in the lower limbs. The response involves both sides of the body--the side at which the stimulus is sensed called the ipsilateral side (flexor reflex), and the opposite side called the contralateral side (crossed extensor reflex). To test the flexor reflex, have the subject stand with eyes closed. Suddenly grab the subject’s right wrist. Record your observations. ______________________________________________________________________________ * This reflex may be hard to observe in the laboratory since a painful stimulus is usually required to elicit a response.
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PSIO 201 Required Handout Department of Physiology In response to the painful stimulus, the subject will withdraw (flex) the effected limb. For the
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Reflexes and sensations handout - PSIO 201 Required Handout...

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