Lab 2

Question 1

What are EMGs measuring?

Answer 1

the APs that muscles generate before contraction
- electrical activity

Question 2

Which data is biphasic? What does this mean?

Answer 2

• the raw data
• seeing both pos and neg fluctuations

Question 3

Which data is monophasic? What does this mean?

Answer 3

• RMS
• does not have a negative deflection
• rectifying the data by taking the absolute value of the neg and avg it with the pos

Question 4

What is rectifying data?

Answer 4

• getting rid of the negative value
• done by squaring the data, then taking the square root of that, and then taking the average

Question 5

Which muscles were being recorded during this experiment? What kind of muscles are they?

Answer 5

• biceps and triceps
• antagonistic muscles
• opposing actions across a joint - when they are activated at the same time, the antagonist is coactivated, and the agonist muscle is activated, resulting in isometric contraction

Question 6

What data on the graph shows coactivation?

Answer 6

• high pos deflection in one graph and low pos deflection in corresponding graph
• high pos deflection shows willing activation of the muscle

Question 7

Where was the node placed in this experiment?

Answer 7

• median nerve, which innervates the abductor pollicis muscle

Question 8

What is a stimulus artifact?

Answer 8

• electrical wave that is measured, but we are not interested in it
• caused by low latency - the stimulus is very fast, which makes it very small

Question 9

Latency period

Answer 9

period in which the action potential can be measured

Question 10

The _________ of APs are being measured

Answer 10

summation

Question 11

The movement of the electrode from the wrist to the elbow does what to the latency period?

Answer 11

increases it, and decreases the conduction velocity

Question 12

What can EMGs be used for?

Answer 12

• can help detect the presence, location and extent of diseases that damage muscle tissue or nerves

Question 13

What does skeletal muscle do?

Answer 13

• produce movement, maintain posture, and assist with body temp maintenance

Question 14

What does skeletal muscle attach to? How?

Answer 14

• bones
• tendons, aponeuroses, and fascia

Question 15

What is a motor unit?

Answer 15

• a motor neuron and all of the individual muscle fibers that it innervates

Question 16

What is the activation process of a motor unit?

Answer 16

1 - initiation of an AP, either voluntarily or as a result of electrical stimulation
2 - conduction of the AP along the nerve fiber
3 - release of NT at the NM junction
4 - depol of the muscle membrane, causes contraction of the muscle fibers

Question 17

What is the physiological significance of coactivation?

Answer 17

Believed to help stabilize the joint

Question 18

What is the range of normal conduction velocities?

Answer 18

50-60 meters per second

Question 19

Exercise 1

Answer 19

• volunteer flexes both biceps and triceps, and also recordings are taken when additional weights are being added to the volunteer’s arm
• Raw data is shown

Question 20

Exercise 2

Answer 20

• volunteer holds wrist of other hand, while pushing and pulling to activate the triceps and biceps
• coactivation is seen

Question 21

Exercise 3

Answer 21

• median nerve is stimulated at both the wrist and the elbow
• ulnar nerve is also stimulated at the elbow

Question 22

Exercise 4

Answer 22

• median nerve is stimulated at wrist again, but with increased voltage
• distance btwn wrist and elbow is recorded and the highest latency is taken from both readings in order to get the conduction velocity

Question 23

Exercise