Introduction
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.
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.
Sensors and Equipment
This experiment features the following sensors and equipment. Additional equipment may be required.
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This experiment is #14A of Human Physiology with Vernier. The experiment in the book includes student instructions as well as instructor information for set up, helpful hints, and sample graphs and data.
