Lecture 3: Muscular System

Question 1

Skeletal muscle

Answer 1

• 40% of human body mass

- ability to develop tension (defining characteristic)

Question 2

Skeletal muscle functions

Answer 2

Locomotion
Voluntary contraction
Relaxation

Question 3

Characteristics of skeletal muscle

Answer 3

Irritability
Contractility
Extensibility
Elasticity/flexibility

Question 4

Functions of muscle

Answer 4

Produce movement
Maintain postures/positions
Stabilize joints

Question 5

Anatomical cross section (ACS)

Answer 5

Measurement of cross-sectional area perpendicular to longitudinal axis of muscle

Question 6

Physiologic cross section (PCS)

Answer 6

Sum total of all the cross sections of fibers

*at largest point

Question 7

Fusiform muscle fibers

Answer 7

• Parallel fibers and fascicles
• high speed of contact force production
• ACS = PCS

Question 8

Penniform muscle fibers

Answer 8

PCS > ACS

Unipennate, bipennate, multipennate

Question 9

Type I muscle fibers

Answer 9

• Slow twitch, oxidative

- slow contraction times, well suited for long, low intensity work

Question 10

Type IIa muscle fibers

Answer 10

• intermediate fast twitch, oxidative glycolysis

- sustain activity for a long period of time OR contract with burst of force and then fatigue

Question 11

Type IIb muscle fibers

Answer 11

• fast twitch, glycolysis

- provide rapid force production and then fatigue quickly

Question 12

Myofibril

Answer 12

Contractile element of muscle fiber
Contains sarcomeres (found between Z lines, functional contractile unit)

Question 13

Sliding filament theory

Answer 13

• Explains production of tension in the muscle
• Myosin (thick filament) and actin (thin filament) create cross bridge, slide past one another, causing sarcomere to contract
• Force developed is sum of pulling forces that each myosin bridge exerts on actin filament

Question 14

Aponeurosis

Answer 14

Sheath of fibrous tissue

Can connect muscle to bone

Question 15

Tendons

Answer 15

• Connective tissue cord that connects muscle to bone
• transmits muscle force to bone
• can withstand high tensile loads
• viscoelastic stress-strain response

Question 16

Torque

Answer 16

Tendency of a force to produce rotation about a specific axis
- moment arm of a force is the perpendicular distance from the force’s line of action to the axis of rotation

Question 17

Isometric training modality

Answer 17

No visible movement

Used in rehabilitation

Question 18

Isotonic training modality

Answer 18

Same weight used throughout range of motion

Question 19

Isokinetic training modality

Answer 19

Same velocity, varied resistance

Question 20

Close-linked training modality

Answer 20

Isotonic movements where one segment is fixed in place

Question 21

Variable resistive training modality

Answer 21

Loads muscle throughout range of motion