Physiology: Muscle Tetanus

Question 1

What method is used to analyse muscle contraction?

Answer 1

myography

Question 2

What is myography?

Answer 2

the measurement of muscular phenomena, such as velocity and intensity of muscular contractions.

Question 3

What is a myogram?

Answer 3

a graphical recording of muscle activity

Question 4

What does the application of a single quick electrical stimulus cause in a muscle?

Answer 4

a single quick contraction and relaxation (a twitch)

Question 5

What is a twitch?

Answer 5

a single quick contraction and relaxation

Question 6

What periods/phases can a twitch be divided into?

Answer 6

1) latent period
2) contraction phase
3) relaxation phase

Question 7

Explain the latent period. How long does it usually last? When does it begin? What occurs during the latent period? What is the state of contraction?

Answer 7

• begins at stimulation
• lasts around 2msec
• action potential sweeps across the sarcolemma
• the sarcoplasmic reticulum releases calcium ions
• NO TENSION is produced (the contraction cycle doesnt begin yet).

Question 8

Explain the contraction phase. When does it usually end? What occurs during the latent period? What is the state of contraction?

Answer 8

• ends roughly 15 msec after stimulation
• calcium ions bind to troponin
• active sites are being exposed
• cross-bridge interactions are occurring
• TENSION rises to its PEAK!

Question 9

Explain the relaxation phase. When does it begin? How long does it last? What occurs during the relaxation phase? What is the state of contraction?

Answer 9

• begins after the contraction phase (15msec)
• lasts around 25 msecs
• calcium ion levels are falling
• tropomyosin covers active sites
• the number of cross-bridges is declining
• relaxation of muscle, decreasing contraction

Question 10

What does a single stimulation produce?

Answer 10

a single twitch

Question 11

What do twitches in skeletal muscles accomplish?

Answer 11

nothing useful

Question 12

What do all normal activities involve? What type of contractions?

Answer 12

sustained muscle contractions

Question 13

What happens if a second stimulus arrives before the relaxation phase has ended?

Answer 13

a second, more powerful contraction occurs.

Question 14

What does the addition of one twitch to another constitute to?

Answer 14

the summation of twitches - wave summation

Question 15

What is wave summation?

Answer 15

The summation of twitches.
- a secondary twitch begins before the primary twitche’s relaxation phase ends

Question 16

Which twitch, the primary or secondary is stronger?

Answer 16

The secondary twitch has a more powerful contraction.

Question 17

What is a tetanic contraction?

Answer 17

caused by a series of action potentials at short intervals.

Question 18

What are the two types of tetanic contractions?

Answer 18

1) Incomplete
2) Complete

Question 19

What is an incomplete tetanic contraction?

Answer 19

A muscle producing peak tension during rapid cycles of contraction and relaxation.
mmmmmm

Question 20

What is a tetanus?

Answer 20

• the stimulation continues (the muscle is never allowed to relax completely)
• tension rises to a peak

Question 21

What is a complete tetanus?

Answer 21

increasing the stimulation rate until the relaxation phase is eliminated.
- action potentials are so rapid, the sarcoplasmic reticulum does not have time to reclaim the calcium ions.
- contraction is continuous

Question 22

What do all normal muscular contractions involve?

Answer 22

a complete tetanus of the participating muscle fibers.