Laboratory Guide Anatomy and Physiology TBME04 fall 2009 Name: Passed: 2008-08-25 Ingemar Fredriksson Department of Biomedical Engineering Linköpings universitet
Introduction This laboratory session is intended to increase the students knowledge of the physiology and anatomy of the nervous system. This is done by independent laboratory work in four steps, which are: 1. to decide the refractory period of the ulnar nerve. 2. to decide the time from a stimulus to a conscious response. 3. to decide the propagation speed of motor neuron in the median nerve 4. to decide the time from the release of the reflex of Achilles to the respond of the muscle, both theoretically and practically To take part in the laboratory session, the student must be prepared both by answering the questions in this document, and also by planning how the parameters above are to be decided. If the questions are not answered, the student is not allowed to carry out the laboratory session. There will be an oral test in the beginning of the session. The students are supposed to follow their own plan. A laboratory assistant will be present and answer specific questions, and the laboratory equipment will be presented at the start of the session. Four laboratory moments will be performed, each about 30-45 minutes long. At the end, a discussion of the results will take place. As an aid in this discussion please consider the following aspects: What is it that you measure? Are there parameters that affect the results that you didn t think of at first? Is the equipment influencing the results? Are the results reasonable? The laboratory session will be held at IMT, at the university hospital. A map can be found at the course home page. For further questions, please contact Johannes Johansson johjo@imt.liu.se. 1
Equipment This is a description of the equipment used in the laboratory tasks and not a comprehensive instruction on how to use them. The description is supposed to be a support when planning the laboratory work. At the lab session you will get a thorough user instruction. Reaction time indicator The equipment used for measuring the reaction time is a simple circuit as shown in Figure 1. Nervous stimulation By applying an electrical stimulation pulse over a nerve, an action potential is released in it. For the pulse to reach the nerve, the stimulation should be performed where the nerve is superficial. +5V Figure 1 Reaction time indicator. ut ECG amplifier The ECG amplifier is used to register an electromyogram (EMG). The ECG-amplifier uses the technique of differential amplifiers, see Figure 2, to amplify the EMG signal and to suppress disturbances. On body red black blue out EMG An electromyogram (EMG) is the Figure 2 Differential amplifyer action potentials of a muscle. By applying surface electrodes over the muscle, the activity over the entire muscle can be measured. The activity of a single motor unit can be measured by using electrode needles. (Not done in this course.) Reflex Hammer The reflex hammer used here is constructed so that it sends an impulse to an oscilloscope at the release of the reflex. An ECG amplifier is attached to the oscilloscope in order to measure the time from the release of the reflex to the response of the affected muscle. 2
Laboratory exercises It is important that you prior to the lab session have made a plan on how to complete the tasks. You won t have the time to do so during the lab session. Reaction time You are to experimentally decide the reaction time from an outer stimulus to a conscious reaction. Vary the stimulus between sight, hearing and sensation. Try to isolate the time it takes to process the signal within the brain. Also, try to isolate the nerve propagation velocity in a sensory nerve. Reaction time indicator with two buttons and a light emitting diod. Tape measure Refractory Period The refractory period of the ulnar nerve shall experimentally be decided. Nervous stimulator generating a series of pulses of adjustable interval ECG amplifier Nervous Propagation Speed The motor nerve propagation speed of the median nerve shall be decided. Nervous stimulator with single pulse ECG amplifier Tape measure Reflex First, calculate the time from the release of the Achilles reflex to the response of the muscle. Then experimentally decide this time. Reflex hammer ECG amplifier Tape measure 3
Figure 3 Example of how the Achilles reflex and the patella reflex can be released 4
Preparation exercises These exercises are to be completed prior to the lab session in order for you to participate. In addition to answering the questions, also try to relate them to the tasks described above. You also need to obtain anatomical and physiological knowledge relevant for this lab session. It is more important to know where to find the various muscles and nerves than their Latin names. Before the lab starts there will be an oral test and discussion concerning the questions below. 1. How does a nervous pulse propagate in a nerve? 2. Describe an action potential and its phases. Which channels are involved and how do the open/close relative to the different phases? 3. Why do myelinated nerve fibers propagate impulses faster then unmyelinated? 4. Why do wider nerve fibers propagate impulses faster then small ones? (Disregarding the fact that they often are myelinated.) 5. Explain the concepts of absolute and relative refraction period. 6. Describe the difference between sensory and motor nerve transmission. 7. Give examples of three types of nerve fibers, what is special for the various groups, where they are located, and their propagation speed. 8. Which muscles in the hand contract when the ulnar nerve is stimulated? 9. Which muscles in the hand contract when the median nerve is stimulated? 10. Describe the five components involved in the reflex arc. 11. What is the difference between a reflex and a conscious reaction to a stimulus? 12. What are reasonable reaction times for sight, hearing and sensation to a motoric response? 13. In what interval should the nerve propagation velocity be for the median nerve? 14. How long time should it take from a stimulus on the Achille s tendon until the Achille s reflex is released? 15. Give an estimate of how long the refractory period of the ulnar nerve should be. 5