the musculoskeletalsystem - mrs. wilson's...

© 2015 Thompson Educational Publishing, Inc. 1

THE MUSCULOSKELETAL SYSTEM

The Musculoskeletal System


• The musculoskeletal

system consists of bones,

joints, and muscles that

provide support, and

stability to a body, thus

giving humans (and many

other animal species) the

ability to move.

• There are approximately

640 muscles in the

human body.

• Composes half our body

weight.

Types of Muscle Tissue

Below are diagrams and electron micrographs of each type

of muscle tissue, differentiated by structure and function:

(A) smooth muscle, (B) cardiac muscle, and (C) skeletal

muscle.


Smooth Muscles and Cardiac Muscles


Muscle tissue refers to a collection of cells that shorten during

contraction.

• Smooth Muscles. Surrounding the body’s internal organs,

including the blood vessels, hair follicles, and the urinary, genital,

and digestive tracts, are smooth muscles. Smooth (non-striated)

muscle tissue contracts more slowly than skeletal muscles, but

can remain contracted for longer periods of time. They are also

involuntary.

• Cardiac Muscles. As the name suggests, cardiac muscles are

found in only one place in the body—the heart. They are

responsible for creating the action that pumps blood from the

heart to the rest of the body. Cardiac muscles are involuntary

muscles because they are not controlled consciously, and are

instead directed to act by the autonomic nervous system.

Striated.

Skeletal Muscles


Skeletal Muscles. These muscles are the type of

muscles that are attached to the bones (by tendons

and other tissues).

• They are the most prevalent muscle type in the human

body—they comprise 30 to 40 percent of human body

weight.

• Skeletal muscles are “voluntary”—humans have conscious

control over their skeletal muscles; that is, the brain can

tell them what to do.

• Skeletal muscle tissue is referred to as striated, or

striped, because of its appearance under a microscope

as a series of alternating light and dark stripes.

3 Types of Human Muscles

How Skeletal Muscles Are Named


Muscles are typically named after their action, location,

shape, direction of the fibres, number of divisions/heads, or

the points of attachment.

Types of Muscle Contraction


There are three types of

muscle contraction, as

shown in the diagram (top

to bottom):

•A: Concentric contraction

(shortening)

•B: Eccentric contraction

(lengthening)

•C: Isometric contraction

(static)

Isometric Contraction

The muscle remains the same length. An example would be holding an object up without moving it; the muscular force precisely matches the load, and no movement results.

Agonist and Antagonist Muscle Pairs


Muscles pull. They never push.

Skeletal muscles are typically arranged

as opposing pairs.

•The muscle primarily responsible for

movement of a body part is referred to as

the agonist muscle.

•The muscle that counteracts the agonist,

lengthening when the agonist muscle

contracts, is called the antagonist muscle.

Muscle Teamwork

Agonist (prime mover)

The muscle or group of muscles producing the desired effect

Eg. Bicep curl-biceps brachii is the agonist

Antagonist

• The muscle or group of

muscles opposing the action

• Eg. Bicep curl-triceps brachii is

the antagonist

Agonist/Antagonist

Eg. Leg extension-

What is the agonist?

quadriceps

Eg. Leg extension-

What is the antagonist?

hamstrings

Opposing Muscles and Muscle Groups


Synergist

Synergist The muscles surrounding the joint

being moved; secondary muscles involved

Eg. Hamstring curl-the popliteusmuscle aids the hamstrings in leg flexion

The bicep is the prime mover in elbow joint movement and the

brachioradialis acts as a

synergistic muscle to stabilize the joint, thus aiding in the motion

Muscle Origins and Insertions


When skeletal muscle contracts, it causes

movement of the attached bones. The point

where the muscle attaches to the more

stationary of the bones of the axial skeleton

is known as the origin.

The other end, the point where the

muscle attaches to the bone that is

moved most, is known as the insertion.

• For example, when you contract your

biceps, you pull your forearm towards

your shoulder, so you are pulling towards

the origin. The insertion is on one of the

bones of the forearm (the radius), called

the radial tuberosity, and it is the forearm

that moves during contraction.

Delayed Onset Muscle Soreness (DOMS)

• Microscopic tearing deep within the muscle fibres

• Most frequent when you begin a wt tr program, change

routine, dramatically increase the duration or intensity of

xcise routine

• May last several hours to several days after xcise session

• Felt in first 24 hours, peak 24-72 hours, disappears 5-7

days later

Lesson 6.3


THE NEUROMUSCULAR SYSTEM

~ ~ ~

TOPICS COVERED IN THIS LESSON

• The Anatomy of Skeletal Muscle

• The Sliding Filament Theory

How Muscles Attach to Bones


Skeletal muscle is attached to the

bone either indirectly (via tendons)

or directly (when the outer

membrane of the muscle attaches

to the outer membrane of the bone).

•The most common of the two

ways in which muscles attach

to bones is the indirect method

(i.e., via tendons).

Attachments

Direct attachment

Collagen fibers of epimysium are continuous with periosteum of bone

Indirect attachment

Collagen fibers of epimysium continue as a strong, fibrous tendon that merges with the periosteum

How Muscle Attaches to Bones


Indirect Attachment

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