THE MUSCULOSKELETAL SYSTEM 2015 Thompson Educational Publishing, Inc. 1
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. 2015 Thompson Educational Publishing, Inc. 2
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. 2015 Thompson Educational Publishing, Inc. 3
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. 2015 Thompson Educational Publishing, Inc. 4
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. 2015 Thompson Educational Publishing, Inc. 6
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. 2015 Thompson Educational Publishing, Inc. 8
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) 2015 Thompson Educational Publishing, Inc. 9
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. 2015 Thompson Educational Publishing, Inc. 11
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 2015 Thompson Educational Publishing, Inc. 14
Synergist Synergist The muscles surrounding the joint being moved; secondary muscles involved Eg. Hamstring curl-the popliteus muscle 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. 2015 Thompson Educational Publishing, Inc. 16
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 2015 Thompson Educational Publishing, Inc. 19
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). 2015 Thompson Educational Publishing, Inc. 20
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 2015 Thompson Educational Publishing, Inc. 22
Indirect Attachment