7 The Muscular System: Movement for the Journey
Multimedia Asset Directory Slide 42 Muscle Contraction Animation Slide 51 Forearm and Hand Muscles Animation Slide 52 Head and Neck Muscles Animation Slide 53 Hip and Thigh Muscles Animation Slide 54 Leg and Foot Muscles Animation Slide 55 Lower Limb Muscles Animation Slide 56 Female Pelvic Muscles Animation Slide 57 Shoulder and Arm Muscles Animation Slide 58 Trunk and Abdominal Muscles Animation Slide 59 Upper Arm Muscles Animation Slide 82 Myofacial Massage Video Slide 83 Neuromuscular Massage Video
Multimedia Asset Directory Slide 84 Western Massage Video Slide 87 Physical Therapy Video Slide 88 Occupational Therapy Video Slide 89 Massage Therapy Video Slide 90 Kinesiology Video
Introduction • The skeletal system provides the framework for the body; the system that allows for movement and locomotion is the muscular system. • In addition to external motion of the arms and legs, the muscular system also moves things inside the body. This internal motion includes the movement of the digestive system, the cardiovascular system, and the respiratory system. • Different types of muscles allow for both external and internal movement.
Learning Objectives • Differentiate the three major muscle types. • Explain the difference between voluntary and involuntary muscles. • Identify and explain the components of a muscle cell. • Describe the cellular activities required for muscle movement. • Identify specific skeletal muscles.
acetylcholine (AS eh till KOH leen) actin (ak TIN) adenosine triphosphate (ah DEN oh sin) ataxia (ah TAK see uh) atrophy (AT roh fee) diaphragm (DYE ah fram) electromyography (ee LEK troh my OG rah fee) fibromyalgia (FIE broh my AL jee uh) flaccid (FLAS sid) Pronunciation Guide Click on the megaphone icon before each item to hear the pronunciation.
flexion (FLEK shun) glycogen (GLIE co jin) Guillian-Barré syndrome (GEY yan bar RAY) hypertrophy (high PER troh fee) intercalated discs (in TER kuh LATE ed) muscular dystrophy (MUS kyoo lahr DISS troh fee) myalgia (my AL jee uh) myasthenia gravis (my as THEE nee uh) myofibril (my oh FIE bril) Pronunciation Guide Click on the megaphone icon before each item to hear the pronunciation.
myosin (MY oh sin) rigor mortis (RIG er MORE tiss) sarcomeres (SAR koh meres) sphinters (SFING terz) tetanus (TET ah nuss) tonus (TONE us) Pronunciation Guide Click on the megaphone icon before each item to hear the pronunciation.
Overview • Muscle is a general term for all contractile tissue. • The contractile property of muscle tissue allows it to become short and thick as a result of a nerve impulse and then to relax once that impulse is removed. This alternative contraction and relaxation causes movement. • The cells of muscle tissue are called muscle fibers. • Muscle tissue is constructed of bundles of these fibers, each approximately the size of a human hair.
Types of Muscles • The body has three major types of muscles • Skeletal • Smooth • Cardiac
Skeletal Muscle • Skeletal muscles are voluntary muscles that attach to bones of the skeletal system. • The fibers appear striped, so they are sometimes called striated muscle. • These muscles allow external movement and are developed through exercise.
Smooth Muscle • Smooth muscles are involuntary muscles. • They are called smooth because they don’t have the striped appearance of skeletal muscles. • These muscles are found within certain organs, blood vessels, and airways, and allow for internal movement. • Change in blood vessel diameter is one example.
Cardiac Muscle • Cardiac muscle is a specialized muscle with a striated appearance. • It is found solely in the heart. • Cardiac muscle is completely involuntary. • The contraction of this muscle causes your heart beat, an internal movement.
Skeletal Muscles • Skeletal muscles are attached to bones and provide movement for your body. • Tendons are fibrous tissues that attach skeletal muscles to bones, while ligaments attach bone to bone. Some muscles attach directly to a bone or soft tissue without a tendon.
Skeletal Muscles • Skeletal muscle is also called voluntary because movement is controlled by conscious thought. • The numerous skeletal muscles are responsible for movement and maintaining posture. • Heat is also produced by skeletal muscles.
Contraction and Relaxation • Movement of the body is the result of contraction (shortening) of certain muscles while there is relaxation of others. • The primary mover (or agonist) is the chief muscle causing movement. As the muscle contracts it pulls the bone, causing movement. • Point of origin – The end of the muscle that is attached to the stationary bone • Point of insertion – Muscle end attached to the moving bone
Contraction and Relaxation • Synergistic muscles assist the primary mover. • Antagonist muscles cause movement in the opposite direction of the agonist. • All movement is a result of contraction of primary movers and relaxation of opposing muscles.
The Diaphragm • The primary mover of breathing is the diaphragm. • This dome-shaped muscle separates the abdominal cavity from the thoracic cavity and is responsible for performing the major work of bringing atmospheric air into our lungs. • This muscle is under both voluntary and involuntary control.
Movement Terminology • Rotation describes circular movement that occurs around an axis. • Circumduction describes circular movement of the end of a limb. • Abduction means to move away from the midline of the body. • Adduction occurs when you produce a movement toward the midline.
Movement Terminology • Extension is a term used for increasing the angle between two bones connected at a joint. The muscle that straightens a joint is called the extensor muscle. • Flexion is the opposite of extension, decreasing the angle between two bones. The muscle that bends the joint is called the flexor muscle.
Figure 7-5 The types of skeletal movement. (A) Flexion and extension of left forearm.
Figure 7-5 (continued) The types of skeletal movement. (B) Flexion and extension of the leg.
Muscle Fibers • Each muscle cell is an elongated fiber known as the muscle fiber, and can be up to 12 inches in length. • Several muscle fibers can be bundled together to form a specific muscle segment. • Each muscle fiber is composed of several myofibrils.
Sarcomeres • Sarcomeres are the functional contractile units of each fiber. • Each sarcomere has two types of threadlike structures called thick and thin myofilaments. • Thick myofilaments are made up of the protein myosin.
Sarcomeres • Thin myofilaments are made up of the protein actin. • The sarcomere has actin and myosin filaments arranged in repeating units separated from each other by dark bands called Z lines which give the striated appearance to skeletal muscle. • Z lines are the borders of each sarcomere.
Muscle Contraction • Contraction of a muscle causes the two types of myofilaments to slide toward each other and shorten each sarcomere, and therefore the entire muscle. • Muscle contraction requires that temporary connections of cross-bridges are formed between the myosin head and the actin. These pull the sarcomere together.
ATP and Calcium • Energy is needed for contraction and relaxation. This energy comes from ATP (adenosine triphosphate) which help the myosin heads form and break the cross-bridges with actin. • Calcium is stored away from the actin and myosin in the sarcoplasmic reticulum (SR) during relaxation of the muscle.
ATP and Calcium • During contraction, the calcium is released from the SR and causes actin, myosin, and ATP to interact, which causes the contraction. When calcium leaves the muscle and returns to the SR, the cross-bridge attachments are broken and the muscle relaxes.
ATP and Calcium • When the nervous system tells a muscle to contract, the signal causes the muscle fiber to open sodium ion channels. • Sodium ions flow into the muscle fiber, exciting it. • When the muscle becomes excited, calcium is released from the SR. • It is the calcium that causes the muscles to contract. • Calcium is then pumped back into the SR.
Applied Science: Inter-Relatedness of the Neuromuscular System • Contraction of skeletal muscle requires the coordination of both the muscular and nervous systems. • The initiation of a skeletal muscular contraction requires an impulse from a motor neuron of the nervous system to cause a release of a neurotransmitter substance called acetylcholine, which sets the process of muscle contraction into motion.
Applied Science: Inter-Relatedness of the Neuromuscular System • It is the acetylcholine which opens sodium channels, exciting the muscle fibers. • This all occurs at the neuromuscular junction.
From the Streets:Neuromuscular Blockade • Rapid Intubation Sequence (RSI) • A procedure used in emergency situations to place an ET tube. • Involves use of medications that act on the neuromuscular junction. • There are two ways to block neuromuscular junction.
Muscular Fuel • Muscles, like all tissue, need fuel in the form of food and oxygen to survive and function. • The body stores glycogen in the muscle, where it waits to be converted to a useable energy source. When needed, glycogen is converted to glucose which releases energy. • Muscles with very high demands also store fat and use it as energy. Energy release causes heat production. That is why an exercising athlete gets overheated.
Muscular Fuel • Higher demand muscles also have a greater blood supply to carry much-needed oxygen. • The greater blood supply gives them a darker color. • An example of this is a chicken which has white and dark meat.
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Rules for Naming Muscles • Muscles can be named based on any of the following criteria • Muscle location (Example: Biceps brachii is in the arm. Brachii = arm.) • Number of origins (Example: Biceps brachii has two origins. Biceps = two heads.) • Action (Example: Adductor longus adducts the thigh.) • Size (Example: Gluteus maximus. Maximus = biggest.)
Rules for Naming Muscles • Muscles can be named based on any of the following criteria • Location of attachments (Example: Brachioradialis. Radialis refers to the radius.) • Shape (Example: Deltoid is triangular. Delta = triangle.) • Direction of fibers (Example: Rectus abdominis. Rectus = straight.) • Combination (Example: Pectoralis major. Pectoral = shoulder, major = big.)