BIO 235 Lab Midterm Exam Questions and Answers with complete solution2024(Graded A+), Exams of Nursing

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Answers with complete solution2024(Graded A+)

The Isolated Stimulator passes a pulse of current through the volunteer's skin (for example, to make a muscle twitch). A green light indicates that the stimulator is delivering a pulse. What would it mean if the OOC light flashes yellow? - CORRECT ANSWERS The current is not flowing properly. The switch turns the Isolated Stimulator on and off. Can you connect stimulating electrodes to yourself? - CORRECT ANSWERS yes Which of the following electrical signals can be recorded with the Bip Amp and which cannot? - CORRECT ANSWERS ECG, EEG, EMG can all be used What signal does the pulse transducer "transduce" into an electrical signal? - CORRECT ANSWERS The changes in pressure from pulsatile blood flow in the arteries. Why would there be a lag between the raw data signal and the channel calculation signal that you see on screen? - CORRECT ANSWERS Time to calculate, need to collect pulses to make the calculation Based on what you have seen today, why do you think it would be advisable to record the heart rate for 60 seconds rather than for a shorter duration (for example, 15 or 30 seconds)? - CORRECT ANSWERS A shorter time frame leaves more room for error, breathing can change you heart rate A shorter time frame less more more for error, breathing can change you heart rate

• CORRECT ANSWERS A CAP is the average of all the action potentials. Action potentials are said to be "all or none" responses. Why does the frog sciatic nerve give a graded response? - CORRECT ANSWERS There is a graded response because there are different sized axons responding at different voltages. What was the smallest voltage required to produce the maximum (largest) CAP? What proportion of the nerve fibers were excited to produce this maximal response?
• CORRECT ANSWERS 90mV. Most of the nerves should have been excited at the maximum CAP.

Answers with complete solution2024(Graded A+)

In this activity, you examined the effect of increasing stimulus intensity on the nerve. What's another stimulus parameter that might also affect the nerve's tendency to generate a CAP? - CORRECT ANSWERS Temperature may effect nerve's tendency as well Explain the difference between the relative and absolute refractory periods. - CORRECT ANSWERS The relative refractory period is the interpulse interval at which there was the first decrease in the magnitude of the 2nd CAP, there is still ability to fire an AP if given enough stimulus to reach threshold again. Absolute refractory is the time at which the nerve can no longer fire an AP because there has not been enough time for the nerve to repolarize. Briefly describe the cellular events responsible for the refractory period. (Hint: Think about the mechanism of repolarization). - CORRECT ANSWERS At the peak of action potential, the voltage gated na+ channels are activated, and so are the delayed voltage gated k+ channels. As time goes on, voltage gated na+ channels close, and the delayed voltage k+ channels stay open, so that the cell hyperpolarizes. Due to the hyperpolarization, it will take more stimulus to reach threshold to get another AP. Based on your calculation for CAP conduction velocity, how long would it take the CAP to travel the length of the sciatic nerve? Assume a total length of 100 mm. - CORRECT ANSWERS By using the calculated conduction velocity at room temp, 25.97=.1m/x, where x is the time the CAP takes to travel the length of the sciatic nerve, time would be .00835s. The longer the length of the nerve, the more time it will take the CAP to travel. Now you have observed a muscle twitch, can you explain what you are seeing in the EMG and Force channels? - CORRECT ANSWERS As stimulus strength increased, you see more force being generated to the point of maximal stimulus, where force did not increase. What happened to the muscle contraction response as the current stimulus increased from 0 mA? What was the smallest current required to produce each of the following?a) a contraction (threshold current) b) the maximum contraction (maximal stimulus) - CORRECT ANSWERS The muscle contraction increased as the current stimulus increased. A- to achieve a contraction, threshold current was 8mA B- to achieve max contraction, the maximal stimulus was 14mA

Answers with complete solution2024(Graded A+)

When the current reached the following stages, what proportion of fibers in the muscle were contracting?a) at thresholdb) at the maximal stimulusc) above the maximal stimulus - CORRECT ANSWERS At threshold, the least amount of fibers were contracting- because of the smaller stimulus being delivered At maximal stimulus, the most amount of fibers were contracting to generate a larger force in response to the large stimulus Why does varying the stimulus strength affect the twitch force? - CORRECT ANSWERS Varying stimulus strength affects twitch force by recruiting the different sized motor units. What is the difference between incomplete tetanus and complete tetanus? - CORRECT ANSWERS incomplete tetanus has a relaxation period during contractions and Complete tetanus has no relaxation period during contractions The stimulus interval has a profound effect on the contraction force of the muscle. In your own words explain what happened when the muscle was stimulated in rapid succession. At which interval did the volunteer's muscle twitches begin to merge together (summate)? - CORRECT ANSWERS When muscle is stimulated in rapid succession, more residual calcium remains in the muscle, therefore allowing for more force to be generated when the muscle twitches summate. They began to merge together at 100ms, but at 50ms they completely merged. A short period of rapid electrical stimuli is used to observe muscle fibers contracting continuously (tetanus). Chemical agents can cause tetanus by interfering with the motor neurons. These agents include a toxin produced by the soil bacterium Clostridium tetani. One of the symptoms of these agents is called "spastic paralysis". Explain in your own words why these agents would have a negative effect on you and your muscles. - CORRECT ANSWERS The toxins may have negative effect because of the constant tetanus being delivered to the muscle. It would be constant force/contraction being generated, which can be painful and prevent from doing everyday activities due to intense spasms. Look at the latency for ulnar nerve stimulation at the wrist and at the elbow. How do these latencies differ? Why do you suppose this is? - CORRECT ANSWERS The

Answers with complete solution2024(Graded A+)

latency is much shorter at the wrist because it is closer to the muscle. The elbow latency takes longer because it must travel a longer distance to the muscle. Based on your results and calculations for nerve conduction velocity, how long would it take for a nerve impulse to travel from the spinal cord to the big toe? Assume that the distance traveled is 1 meter. - CORRECT ANSWERS distance = 1meter, velocity = 80m/s, it would take .8 seconds