Weight and WorkSkeletal Muscle

Definitions• Motor Unit: a motor neuron and all muscle fibers it

innervates.

• Twitch: single contraction in response to a single

stimulus/AP.

• Isotonic: muscular contraction where constant

tension continues while the length of the muscle

changes.

– Concentric

– Eccentric

• Isometric: muscular contraction against resistance

in which the length of the muscle remains the same.

Isotonic Contraction

Isometric Contraction

Work

• Work is accomplished only when an object is

moved.

• Work = Force X Distance

• Force = muscle tension required to overcome the

load (weight of the object).

• In an isometric contraction where no object is

moved (muscles do not change length) the work

done = zero.

Load/Velocity relationship

• Load is an important determinant of

shortening velocity. Load =

velocity

Load/Velocity Relationship

3 Muscle Fiber Types

Slow Oxidative

Fast Oxidative Fast Glycolytic

Postural muscles

Bird flight muscles

Mammal breast muscles

Lithobates pipiens• Referred to as Rana pipiens

also.

• Opportunistic feeders

• Occurs through much of US

and Canada (cosmopolitan)

• Status is controversial:

widespread, but most

populations throughout

range are decreasing rapidly.

• Commonly used in research.

HOMEWORK!!!!• Write an entire lab report, again.

• Include answers to ALL labscribe

questions WITHIN the body of the

paper.

• Follow my formatting

instructions!!!!!!

• Due on November 28/29.

Next Week…

• Have a GREAT Thanksgiving!!!