9A.4

Question 1

Twitch=

Answer 1

contractile response of a single muscle fiber to a muscle fiber to a muscle impulse

Question 2

Threshold stimulus

Answer 2

minimal strength required to cause contraction

Question 3

Latent period

Answer 3

brief delay between time of stimulation and the beginning of contraction (2 msec)

Question 4

Period of contraction

Answer 4

muscle contracts reaction time is 40 msec

Question 5

Period of relaxation

Answer 5

muscle relaxes reaction time is 50 msec

Question 6

Refractory period

Answer 6

period of lost excitability (time in which you cant make another action potential) reaction time is 5 msec

Question 7

Myogram=

Answer 7

recording of a twitch contraction

Question 8

All or none principle

Answer 8

• whole muscle fiber contracts or not (no halfsies)
• each muscle fiber generates same force in a contraction
  -whole muscles though, have varying size of contractions

Question 9

Strength of Contraction (reasons why some muscles are stronger than others)

Answer 9

• Frequency of stimulation of individual fiber
• Number of muscle fibers making up whole muscle

Question 10

Summation

Answer 10

• application of a series of stimuli of increasing frequency
• complete relaxation cannot occur combining individual twitches
• contraction becomes sustained

Question 11

Tetanic contraction

Answer 11

• frequency of stimulation occurs often enough that partial relaxation cannot even take place
• most common and used for usual body movements
• also accounts for muscle tone
  
  • small, sustained contractions not causing body movements
  • Mostly helps to maintain posture

Question 12

What are the different types of contractions

Answer 12

• Isotonic
• Eccentric
• Isometric

Question 13

Isotonic (def)

Answer 13

muscle contracts and changes length

Question 14

Isotonic

Answer 14

• Most common type moving bones
• Muscle tension is constant and muscle shortens

Question 15

Eccentric (def)

Answer 15

“lengthening” contraction

Question 16

Eccentric

Answer 16

• type of isotonic
• cross bridges are not generating enough force to shorten the muscle (resistance is stronger)
• tension is not constant

Question 17

Isometric (def)

Answer 17

muscle contracts but does not change length

Question 18

Isometric

Answer 18

• no body movement, just stabilizing positions
• pushing on a wall
• tension is constant

Question 19

Cramps

Answer 19

= painful spasmodic contraction
- caused by prolonged physical activity or prolonged cold
- insufficient amount of ATP/ lactic acid build up
- Ca^2+ does not return properly to the sarcoplasmic reticulum prevents muscle from relaxing

Question 20

Muscle strain/ Pull/ Tear

Answer 20

• overstretched of muscle fibers causing tearing
• can also tear fascia
• severity is determined by tear and amount of lost usage

Question 21

Atrophy

Answer 21

= muscle fibers decrease in size
- due to extreme inactivity
- can decrease muscle strength by 5% each day
- eventually is replaced by fibrous connective tissue
and cannot be rehabilitated -> muscle cannot divide
- takes about 2 years immobilization

Question 22

Rigor Mortis

Answer 22

= few hours after death
- loss of ATP (because u ded) and excessive leakage of Ca^2+ -> SR no longer controlling flow
- cross bridges do not let go of actin causing stiffening
- can continue for 72 hours until tissue starts to decompose