Muscular System

Question 1

Characteristics of Muscle

Answer 1

• Contractility
• Extensibility
• Elasticity
• Excitability
• Conductibility

Question 2

Contractility

Answer 2

The ability to apply tension when stimulated

Question 3

Extensibility

Answer 3

The ability to stretch

Question 4

Elasticity

Answer 4

The ability to return to resting length after stretch is removed (somewhat limited)

Question 5

Excitability

Answer 5

The ability to be excited by a stimulus

Question 6

Conductibility

Answer 6

The ability to move or transmit an impulse

Question 7

Muscle Types

Answer 7

• Smooth muscle
• Cardiac muscle
• Skeletal muscle

Question 8

Skeletal Muscle

Answer 8

• Is innervated (stimulated) by the somatic nervous system (voluntary nervous system), an efferent division of the PNS.
• Comprises 40-50% of total body weight
• Over 600 individual muscles.
• Responsible for movement, maintenance of posture and heat production.
• Striated and multinucleated.
• Muscle fibers vary in their content of myoglobin, the red-colored protein that binds oxygen in muscle fibers.
• Muscle fibers high in myoglobin content are termed red muscle fibers those low are termed white muscle fibers.

Question 9

Origin

Answer 9

The more stable end of the muscle attachment, usually proximal

Question 10

Insertion

Answer 10

The less stable end of the muscle attachment, usually distal

Question 11

Tendon

Answer 11

White glistening fibrous bands of connective tissue which attach the muscle to the bone

Question 12

Fascia

Answer 12

Gross term indicating all fibrous connective tissue not otherwise specifically named. It varies in thickness and density

Question 13

Aponeurosis

Answer 13

Fibrous or membranous, closely packed, parallel collagenous bundles which represent very much flattened tendons; provide strength and support to structures

Question 14

Composition of Skeletal Muscles

Answer 14

• Individual muscle cells called fibers
• Fibers are held together by fascia, this layer is called endomysium
• Bundles of muscle fibers are called fasciculi
• Fascia surrounding fasciculi are called perimysium
• Fascia covering the entire muscle is called epimysium

Question 15

Fusiform Muscle Shape

Answer 15

• Fibers run parallel to long axis of the muscle
• 100% of muscles contraction contributes to moving the attachments
• Has fewer fibers per unit area
• Has longer fibers and produces greater ROM but less force production

Question 16

Pennate Muscle Shape

Answer 16

• Fibers run obliquely to the muscle tendon
• Produces less ROM for a given shortening distance, but greater force
• Has shorter fibers, but more per unit area
• As the angle of the muscle fiber increases, the effective shortening component shrinks

Question 17

Muscle Shapes (named according to the arrangement of the fasciculi)

Answer 17

• Longitudinal (ex- sartorius)
• Unipennate (ex- EDL)
• Bipennate (ex- rectus femoris)
• Multipennate (ex- deltoid)
• Radiate (ex- pectoralis major)

Question 18

How muscles are named

Answer 18

• Shape
• Action
• Location
• Attachments
• Number of parts
• Size
• Fiber orientation

Question 19

What determines the action of a muscle?

Answer 19

• Where the muscle crosses the joint it is acting upon

- The relationship of the location of the joint crossing with the axis of rotation of the joint

Question 20

What determines how well a muscle performs its function?

Answer 20

• Size of the muscle

- Angle of pull

Question 21

Muscle Classification (due to articulations)

Answer 21

• Uniarticulate

- Bi/Multiarticulate

Question 22

Uniarticulate

Answer 22

Single joint muscles

Question 23

Bi/Multiarticulate

Answer 23

• 2+ joint muscles

- Tends to pull the bony attachments toward the center of the muscle.

Question 24

Advantages of Bi/Multiarticulate Muscles

Answer 24

• Produces motion in all the articulations that it passes. -
  Considered to be more efficient.
• They provide for the synchronous movement of multiple joints
• Less complex innervation
• Less muscle mass than if all muscles were single joint; this allows greater ROM
• Pulley action of muscles - Involves antagonistic muscles: movement in one joint puts a muscle on stretch so it can be more efficient in contraction in the other joint it passes.

Question 25

Disadvantages of Bi/Multiarticulate Muscles

Answer 25

• Active Insufficiency: inability of a muscle crossing two or more joints to shorten and produce enough force to cause full ROM in both joints at the same time. (hamstrings in knee flexion and hip extension)
• Passive Insufficiency: inability of muscle crossing two or more joints to be stretched enough to allow for full ROM in both joints at the same time (hamstrings in hip flexion and knee extension)

Question 26

Functions of a Muscular Contraction

Answer 26

• To act as a motive force
• To act as a resistive force
• To stabilize or fixate a body part

Question 27

What’s the opposite of contraction?

Answer 27

Relaxation

Question 28

Agonist

Answer 28

The worker muscle (causes the desired action)

Question 29

Antagonist

Answer 29

• Causes movement opposite to the agonist

- “True antagonist” has EXACTLY the opposite action(s) of the agonist

Question 30

Stabilizer

Answer 30

A muscle that fixes or holds a bone so the agonist can do the intended movement - eliminates undesirable movement – static or dynamic

Question 31

Synergist

Answer 31

A muscle that has at least one antagonistic action to the agonist and contracts to eliminate an undesirable movement, thus enabling the agonist to be more efficient. Sometimes called “true synergy”

Question 32

Neutralizer

Answer 32

A muscle that has a common and an antagonistic action with the agonist. The antagonistic actions cancel each other out and the common action results

Question 33

Co-contraction

Answer 33

The simultaneous contraction of antagonistic muscles