B-227_Lab_12_student notes

B-227_Lab_12_student notes - EXPERIMENT 14A Neuromuscular...

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EXPERIMENT 14A Neuromuscular Reflexes The automatic response of a muscle to a stimulus is called a reflex. The patellar reflex results from tapping the patellar tendon below the knee with a reflex hammer. This causes contraction of the quadriceps muscle and extension of the leg. Stretching of the muscle activates nerve impulses which travel to the spinal cord. Here the incoming impulses activate motor neurons, which travel back to the muscle and result in muscle contraction. This reflex arc is primarily a spinal reflex, but is influenced by other pathways to and from the brain (Figure 1). A reflex may be reinforced (a term used by neurologists) by slight voluntary contraction of muscles other than the one being tested. For example, voluntary activation of arm muscles by motor neurons in the central nervous system “spills over” to cause a slight activation of the leg muscles as well. This results in the enhancement of the patellar reflex. There are other examples of central nervous system influences on reflexes. Health care professionals use knowledge of these influences to aid in diagnosis of conditions such as acute stroke and herniated lumbar disk, where reflexes may be absent; and spinal cord injury and multiple sclerosis, which may result in exuberant reflexes. In this experiment, you will use an EKG Sensor to compare the speed of a voluntary vs . a reflex muscle action and to measure the relative strength (amplitude) of the impulse generated by a stimulus with and without reinforcement. You will make a rough calculation of nerve impulse speed using data generated by an Accelerometer used in conjunction with the EKG sensor. Important: Do not attempt this experiment if you have pain in or around the knee. Inform your instructor of any possible health problems that might be exacerbated if you participate in this exercise. Figure 1
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OBJECTIVES In this experiment, you will Graph the electrical activity of a muscle activated by a reflex arc through nerves to and from the spinal cord. Compare the relative speeds of voluntary and reflex muscle activation. Associate muscle activity with involuntary activation. Observe the effect of central nervous system influence on reflex amplitude. Calculate the approximate speed of a nerve impulse. Compare reflex response and electrical amplitude in different subjects. MATERIALS computer electrode tabs Vernier computer interface reflex hammer Logger Pro cable tie, 10 cm long Vernier EKG Sensor cloth tape measure Vernier 25- g Accelerometer pen PROCEDURE Each person in the group will take turns being subject and tester. Part I Voluntary Activation of the Quadriceps Muscle 1. Connect the EKG Sensor and the Accelerometer to the Vernier computer interface. 2.
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This note was uploaded on 09/14/2011 for the course BIO 227 taught by Professor Lonsdale during the Fall '10 term at Boise State.

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B-227_Lab_12_student notes - EXPERIMENT 14A Neuromuscular...

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