The Muscular System PDF

Human Anatomy and Physiology Topic 4 The Muscular System: Movement for the...

Human Anatomy and Physiology Topic 4 The Muscular System: Movement for the Journey Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  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. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Types of Muscles Muscle is a general term for all contractile tissues. The cells of a muscle tissue are called muscle fibers, each about the size of a human hair. Muscle tissue is constructed of bundles of these fibers. The body has three major types of muscles: – Skeletal – Smooth – Cardiac Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  The three types of muscle: skeletal, cardiac, and smooth. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved. Summary of Muscle Characteristics Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Characteristics of Muscles All muscle tissues display five physiological characteristics: 1- Excitability. A muscle cell can be stimulated by a nerve to contract. 2- Conductivity. The stimulation from the nerve moves quickly along the length of the muscle cell. 3- Contractility. A muscle cell can shorten with force. Muscles can only pull; they cannot push. 4- Extensibility. A muscle cell can be stretched. Muscles are stretched by the contraction of other muscles. E.g.: If the biceps brachii contracts to flex the arm, the triceps brachii needs to stretch to accommodate the motion. 5- Elasticity. If a muscle cell is stretched, it will return to its original shape. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Skeletal Muscle Skeletal muscles are voluntary muscles that attach to bones of the skeletal system. Muscle fibers appear striped à are called striated muscle. These muscles allow external movement and are developed through exercise. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Skeletal Muscle Also called voluntary because movement is controlled by conscious thought. Skeletal muscles are responsible for: – Movement – Maintaining of posture – Heat is also produced by skeletal muscles Skeletal muscles are attached to bones through tendons which are fibrous tissues. Ligaments attach bone to bone. Some muscles attach directly to a bone or soft tissue without a tendon. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Actions of the Skeletal Muscle Muscle actions are the motions caused by muscle contractions. Flexion: flexion describes a decrease in the angle of a joint, for example, a movement of the forearm that causes it to bend at the elbow. Extension: The term extension describes an increase in the angle of a joint, for example, a movement of the forearm that straightens the elbow. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Actions of the Skeletal Muscle Abduction: movement of a part of the body away from the midline. Adduction: movement of a part of the body toward the midline. Doing “jumping jacks” is to alternately abduct and adduct the arms and legs. Abduction Adduction Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Actions of the Skeletal Muscle Protraction: movement that brings part of the body forward. Retraction: movement that brings part of the body backward. For example, a chicken protracts and retracts its head as it walks. Protraction Retraction Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  The types of skeletal movement: flexion and extension of the leg. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Muscle Actions Movement of the body is the result of the contraction (shortening) of muscles called primary movers or agonist, and relaxation of opposing ones termed antagonist. – The agonist is the chief muscle causing movement. As the muscle contracts it pulls the bone, causing movement. – The antagonist muscle causes movement in the opposite direction of the agonist. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Coordination of antagonist muscles to perform movement. During contraction, the immovable end of a muscle is the origin (more proximal), while the movable end is the insertion (more distal). Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved. Anterior (left image) and posterior (right image) views of superficial Anatomy skeletal & Physiologymuscles. for Health Professions: An Interactive Journey, Second Edition Colbert Ankney Lee Copyright ©2011 by Pearson Education, Inc. All rights reserved.  The Diaphragm It is the primary mover of breathing. This dome-shaped muscle separates the abdominal cavity from the thoracic cavity. It is responsible for performing the major work of bringing atmospheric air into our lungs. This muscle is under both voluntary and involuntary control. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  The diaphragm: The major muscle of breathing. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Muscle Fibers Each muscle cell is an elongated fiber known as the muscle fiber and can be up to 12 inches (app. 30.5cm) in length. The cytoplasm of the muscle fiber is known as the sarcoplasm that contains many nuclei and mitochondria. Sarcoplasm is composed of several hundred to several thousand thread-like myofibrils. Several muscle fibers bundle together to form a specific muscle segment. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  (Muscle segment) (Muscle cell) Figure 7-6 (A) The muscle segment. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Sarcomeres Sarcomeres are the functional contractile units of a muscle fiber. Each sarcomere has two types of threadlike structures called: – Thick myofilaments made up of myosin. – Thin myofilaments made up of actin. Muscles appear to show bands: – I bands made up of thin actin – A bands made up of myosin – Z lines made up of thin actinin. They appear as dark lines and define the boundaries of sarcomeres. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Muscle Structure Details of the contractile machinery of the muscle cell. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  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. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  The muscle segment with sarcomere. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Relaxed and contracted sarcomeres. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  ATP and Calcium Energy is needed for contraction and relaxation. This energy comes from ATP (adenosine triphosphate) which helps the myosin heads form and break the cross- bridges with actin. Calcium triggers contraction by reacting with regulatory proteins that allow interaction of actin and myosin During relaxation, calcium is stored away from the actin and myosin in the sarcoplasmic reticulum (SR). The SR is an intracellular system of closed saclike membranes involved in the storage of calcium in skeletal muscle cells – equivalent to smooth endoplasmic reticulum. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  ATP and Calcium The motor neuron instructs a muscle to contract by releasing a neurotransmitter called acetylcholine (ACh). Acetylcholine is released at the neuromuscular junction and 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 will cause actin, myosin, and ATP to interact, which causes the contraction. When calcium is pumped back into the SR, the cross- bridge attachments are broken, and the muscle relaxes. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Muscular Fuel Muscles 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. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  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. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Smooth Muscles Smooth muscles are involuntary muscles. They are called smooth because they do not have a striped appearance. These muscles are found within certain organs, blood vessels, and airways, and allow for internal movement. – E.g.: change in blood vessel diameter. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Smooth Muscles Also called visceral muscles. Found in organs, blood vessels and bronchial airways – but not in the heart. The ability of a smooth muscle to contract and relax is essential to the internal processes of our body, like digestion and regulation of blood pressure. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Smooth Muscles Smooth muscles do not contract as rapidly as skeletal muscles (skeletal muscles contract 50 times faster). Smooth muscles receive a smaller blood supply, resulting in poor repair of injured tissue. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved. Vasodilation and Vasoconstriction Enlarging the diameter of a blood vessel is called vasodilation. Decreasing the diameter of a blood vessel is called vasoconstriction. Vasodilation can lead to a decrease in blood pressure due to smooth muscle relaxation in the blood vessel, while vasoconstriction increases blood pressure. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Respiratory Smooth Muscle Smooth muscle is also found in the airways of the respiratory system. – Excess constriction of smooth muscle in the respiratory system occurs during an asthma attack. A special type of smooth muscle is called a sphincter and can be found throughout the digestive system. – These donut shaped muscles act as doorways to let material in and out. Contraction closes the door while relaxation opens it. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Cardiac Muscle Cardiac muscle is a specialized striated and involuntary muscle – also called myocardium. It is located in the middle layer of the heart wall. Cells of the cardiac muscle are the cardiocytes. Cardiac muscle fibers are shorter and receive a richer supply of blood than any other muscle in the body. When muscle fibers contract, they force the blood to circulate from the heart through the blood vessels in the body. Contraction causes the heart to beat - it is an internal movement. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Figure 7-11 Heart and intercalated discs. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.  Cardiac Muscle Membranes of cardiac muscle cells are interlocking and linked by gap junctions, forming intercalated discs. When one fiber contracts, it pulls the next one into a contraction creating a domino effect. This wave of motion squeezes blood out efficiently. Cardiac muscle does not repair itself. – Damage to cardiac muscle always leaves a scar. – Scar tissue does not contract like normal tissue because it is rigid. – This decreases cardiac output. Anatomy & Physiology for Health Professions: An Interactive Journey, Second Edition Copyright ©2011 by Pearson Education, Inc. Colbert Ankney Lee All rights reserved.