6 EMG Flashcards Preview

LCRS Neuroscience and Mental Health > 6 EMG > Flashcards

Flashcards in 6 EMG Deck (21):
1

Q: What is an EMG? What does it measure?

A: electromyogram

electrodiagnostic medicine technique for evaluating and recording the electrical activity produced by skeletal muscles

- recording of the action potentials occurring in skeletal muscle fibres

2

Q: Apart from EMG, give 2 other examples of extra cellular recordings. Include where the electrodes are placed.

A: ECG (EKG), electrocardiogram, recording action potentials from the heart. Electrodes on limbs, or chest.

EEG, electroencephalogram, recording action potentials from the brain. Electrodes on the scalp.

3

Q: What is an intracellular recording? Where are the electrodes? How does an extracellular recording compare?

A: one electrode inside the cell

Measure emf between inside and outside cell

both electrodes outside the muscle fibres-on membrane. Record the emf (potential) between 2 locations both outside the cells/fibres

4

Q: Draw a diagram that shows an example extracellular recording between 2 sites outside the fibres.

A: REFER

5

Q: Where do you place the electrodes to get ulnar nerve stimulation? (2)

A: fleshy pad of palm and below where you take radial pulse

6

Q: Draw a graph that shows gradually increasing then decreasing voluntary contraction. How is this conducted?

A: REFER. EMG line and force line

attach thumb to something that records force

person is asked to push something harder and harder then relax

result is increasing AP in muscle = more force applied

7

Q: Draw an EMG and twitch force graph for a stimulus of 3mA.

A: TF= -3 flat line
EMG= 0 with a single small line down twitch known as an artefact

8

Q: What causes an artefact? What is a delay on an EMG graph caused by?

A: interference between stimulating equipment and recording equipment

in relation to how far stimulus is from recording and how quickly nerve conducts

9

Q: Draw an EMG and twitch force graph for a stimulus of 5mA.

A: REFER

EMG= tiny delay then up down and flat line

TF= flat line at -3 but increases a little after EMG peak

10

Q: Draw an EMG and twitch force graph for a stimulus of 7mA.

A: REFER

EMG= tiny delay then up down and flat line (larger than 5mA and 2 of them in quick succession)

TF= flat line at -3 but increases a little after EMG peak (larger than at 5mA)

11

Q: Draw an EMG and twitch force graph for a stimulus of 9mA.

A: REFER

EMG= tiny delay then down up and flat line (larger than 7mA)

TF= flat line at -3 but increases a little after EMG peak (larger than at 7mA)

12

Q: Draw an EMG and twitch force graph for electrical stimulations (constant stimulus strength) at a frequency of 1/s.

A: REFER

13

Q: What happens when give a constant stimulation for a prolonged period? (2)

A: can cause pain

can cause tetanus

14

Q: Draw an EMG and twitch force graph for electrical stimulations (constant stimulus strength) at a frequency of 5/s.

A: REFER

5/s= 5 twitches of same size and close together

15

Q: Draw an EMG and twitch force graph for electrical stimulations (constant stimulus strength) at a frequency of 10/s.

A: REFER

10/s= frequency where muscle can't relax between= summation

16

Q: Draw an EMG and twitch force graph for electrical stimulations (constant stimulus strength) at a frequency of 20/s.

A: REFER

20/s= can almost reproduce voluntary force

17

Q: What is happening in the ulnar nerve and in the adductor pollicis as stimulus strength is increased?

A: stimulated

made to contract

18

Q: Define twitch.

A: give or cause to give a short, sudden jerking or convulsive movement

19

Q: Define tetanus

A: the prolonged contraction of a muscle caused by rapidly repeated stimuli

20

Q: How can you get summation in skeleton muscle?

A: If a skeletal muscle is stimulated and a second stimulus is applied before relaxation is complete, a second contraction, which develops a greater tension, is fused to the first contraction

21

Q: How long does the muscle force response last?

A: 1s