Lab Muscle Physio

Front 1

Define myograph

Back 1

an input transducer (or “force transducer”) commonly used to record muscle contraction

Front 2

Define myogram

Back 2

a physiological recording of muscle contraction

Front 3

Define muscle twitch

Back 3

a rapid, jerky, contractile response of a skeletal muscle when given a single stimulus of sufficient strength

Front 4

Define threshold stimulus

Back 4

the smallest stimulus that first causes contraction

Front 5

Define maximal stimulus

Back 5

minimal stimulus that first causes a maximal contractile response

Front 6

Define motor unit

Back 6

a motor neuron plus all the muscle fibers (muscle cells) it innervates

motor units vary in # of muscle fibers and the size of the fibers

smaller motor units: have finer fibers; more easily stimulated

larger motor units: have thicker fibers, respond later, producing a more forceful contraction

Hint 6

None

Front 7

Define motor unit summation

Back 7

(recruitment): increasing the number of motor units contracting simultaneously producing a stronger contraction.

(Induced experimentally by increasing the amplitude of electrical stimulation).

Hint 7

None

Front 8

Define mechanical summation

Back 8

Mechanical Summation (wave summation): increasing the frequency of stimulation, thereby increasing the rapidity of contraction producing a stronger contraction.

Allows for smooth continuous contraction).

Both types of summation occur together in the grading of contractile responses.

Hint 8

None

Front 9

Define tetanus

Back 9

Tetanus: complete fusion of individual twitches, resulting in a continued state of contraction

Front 10

Define fatigue

Back 10

the decline in muscle tension as a result of previous contractile activity

Neuromuscular fatigue: caused by shortage of neurotransmitter (not likely to occur in our frog gastrocnemius lab exercise)

Mechanical fatigue: actual mechanism not totally clear.

May be caused by: - build-up of lactic acid, lowering pH and interfering with enzymatic activity - from a relative deficit of ATP which somehow affects the excitation- contraction coupling mechanism

Hint 10

None

Front 11

Define muscle tone

Back 11

a sustained partial contraction of portions of a skeletal muscle in response to activation of stretch receptors (due to asynchronous motor unit stimulation)

• stabilizes the position of bones and joints

• allows the skeletal muscles to act as a shock absorbers that cushion sudden bumps

Hint 11

None

Front 12

Define treppe

Back 12

when a skeletal muscle contracts more forcibly in response to the same strength of stimulation after it has contracted many times (not summation, relaxation occurs between each stimulation); May be caused by:

• priming the external cytosol with Ca++

• tightens up the slack due to the elastic series component (ESC)

• increase in temperature, increases enzymatic activity

Hint 12

None

Front 13

Define an isotonic contraction

Back 13

- in isotonic contractions, cross-bridge activity leads to a shortening of the sarcomeresIsotonic Contraction

1. Muscle shortens

2. Tension is constant

3. Energy is expended

4. Graph: Distance vs. Time

Hint 13

None

Front 14

Define an isometric contraction

Back 14

- in isometric contractions, cross-bridge activity leads to development of tension in the sarcomeresIsometric Contraction

1. Muscle does not shorten (change length)

2. Tension increases

3. Energy is expended

4. Graph: Tension vs. Time

Hint 14

None

Front 15

Describe the function of the myograph transducer and how it was calibrated.

Back 15

an input transducer used to record movement during muscle contraction

used a weight to calibrate

Hint 15

None