Anatomy and Physiology ANP 201 PDF

Anatomy and Physiology ANP 201 Unit 2 - Principles of Support and Movement Part B – The Muscular System Objectives  Identify and describe the three types of muscle tissue: skeletal, cardiac, and smooth muscle.  Describe the microscopic structure of a skeletal...

Anatomy and Physiology ANP 201 Unit 2 - Principles of Support and Movement Part B – The Muscular System Objectives  Identify and describe the three types of muscle tissue: skeletal, cardiac, and smooth muscle.  Describe the microscopic structure of a skeletal muscle fiber.  Understand the sliding filament theory of muscle contraction.  Describe the roles of actin, myosin, troponin, and tropomyosin in muscle contraction.  Explain the process of excitation-contraction coupling, including the role of the neuromuscular junction and the release of calcium ions.  Identify the different energy systems used by muscles.  Explain the structure, location, and function of each type of muscle tissue and describe muscle movement.  List and describe common muscle disorders. Types of Muscle ❖ Types of Muscle: Three types of muscles are found in the human body.  Smooth muscle: In walls of hollow organs, vessels, and respiratory passageways Cells tapered, single nucleus, nonstriated Involuntary; produces peristalsis; contracts and relaxes slowly Types of Muscle  Cardiac muscle: Muscle of heart wall Cells branch; single nucleus; lightly striated Involuntary; self-excitatory Types of Muscle  Skeletal muscle: Most attached to bones and move skeleton Cells long, cylindrical; multiple nuclei; heavily striated Voluntary; contracts and relaxes rapidly Work in pairs (antagonist) Types of Muscle  Functions Movement of skeleton Maintenance of posture Generation of heat Structure of Muscles  Structure of muscles: Held by connective tissue The muscle is made up of individual cells called muscle fibers. A skeletal muscle fiber is a single cell of a muscle. Endomysium around individual fibers Perimysium around fascicles (bundles) Epimysium around whole muscle Structure of Muscles  Structure of a skeletal muscle. (A) Structure of a muscle showing the tendon that attaches it to a bone (B) Muscle tissue seen under a microscope. Muscular System &  Muscles cells in action: Neuromuscular junction Point where nerve fiber stimulates muscle cell Neurotransmitter is acetylcholine (Ach) ❖ Generates an action potential Motor end plate-membrane of muscle cell Neuromuscular Junction (continued) Neuromuscular Junction (continued) Neuromuscular Junction (continued) Muscle Fiber &  Muscle fiber: Myofibrils: A bundle of myofilaments that contracts. Sarcomeres: Units of myofibrils. Myofilaments: Actin and myosin filaments whose structure and function account for muscle contractions. When muscle fibers are stimulated to contract, myofilaments slide past one another, causing sarcomeres to shorten. Muscle Contraction & Contraction: Sliding together of filaments to shorten muscle ❖ Actin: Thin and light filaments ❖ Myosin: Thick and dark filaments with projecting head Muscle Contraction Muscle Contraction Muscle Contraction Muscle Contraction & Role of calcium: Uncovers binding sites so crossbridges can form between actin and myosin Muscle Contraction Muscle Contraction & Muscle Contraction  Summary-muscle contraction: 1. Acetylcholine (Ach) is released from a neuron ending into the synaptic cleft at the neuromuscular junction. 2. Ach binds to the motor end plate of the muscle and produces an action potential. 3. The action potential travels to the sarcoplasmic reticulum (SR). 4. The sarcoplasmic reticulum releases calcium into the cytoplasm. Muscle Contraction 5. Calcium shifts troponin and tropomyosin so that binding sites on actin are exposed. 6. Myosin heads bind to actin, forming cross-bridges. 7. Myosin heads pull actin filaments together within the sarcomeres and cell shorten. 8. ATP is used to detach myosin heads and move them back to position for another “power stroke”. 9. Muscle relaxes when stimulation ends and the calcium is pumped back into the SR.  - Muscular System  Energy sources: ATP-supplies energy Myoglobin-stores oxygen Glycogen-stores glucose Creatine phosphate -stores energy  Oxygen consumption: Oxygen debt-develops during strenuous exercise Anaerobic metabolism Yields lactic acid-causes muscle fatigue Recovery oxygen consumption: Removes lactic acid Replenishes energy-storing compounds Muscular System -  Effects of exercise: Changes in structure and function of muscle cells Vasodilation brings blood to tissue Heart strengthened Breathing improved  Types of muscle contractions: Tonus-partially contracted state Isotonic contractions-muscle shortens to produce movement Isometric contractions-tension increases, but muscle does not shorten Mechanics of Muscle Movement ❖ Mechanics of Muscle Movement:  Attachments of skeletal muscles Tendon-cord of connective tissue that attaches muscle to bone Origin-attached to more fixed part Insertion-attached to moving part Aponeurosis-broad band of connective tissue that attaches muscle to bone or other muscle Mechanics of Muscle Movement  Muscles work together: Prime mover-performs movement Antagonist-produces opposite movement Synergists-steady body parts and assist prime mover Mechanics of Muscle Movement  Levers and body mechanics- muscles function with skeleton as lever systems Components: Lever-bone Fulcrum-joint Force-muscle contraction Most muscles work as third class levers (fulcrum-effort- weight) Skeletal Muscles ❖ Skeletal Muscles Groups:  Naming of muscles-size, shape, attachment, action, location, direction of fibers, number of attachments (heads)  Name and Actions Size: Makes up the buttocks and is the largest muscle, e.g., Gluteus maximus Shape: shaped like a triangle, e.g., Deltoid Attachment: Attached to the sternum, e.g., Sternocleidomastoid Action: Extends the fingers, e.g., Extensor digitorum Location: Overlies the frontal bone, e.g., Frontalis Direction: Longitudinal muscle of the abdomen, e.g., Rectus abdominis Number of attachments: Biceps brachii has 2 attachments or origins, e.g., Biceps brachii Skeletal Muscles &  Head and Neck: Frontalis: Wrinkles forehead and lifts eyebrows. Orbicularis oculi: Closes eye (winking) Zygomaticus: Raises corner of mouth (smiling) Masseter: Closes jaw. Orbicularis oris: Closes and protrudes lips (kissing) Sternocleidomastoid: Turns head to side; flexes neck and head. Trapezius: Extends head; raises and abducts shoulders dorsally.  D Skeletal Muscles is (continued)  Upper Limb and Trunk: External oblique: Compresses abdomen; rotates trunk. Rectus abdominis: Flexes spine. Pectoralis major: Flexes and adducts shoulder and arm ventrally. (pulls arm across chest. Deltoid: Abducts and raises arm at shoulder joint. Skeletal Muscles (continued) &  Upper Limb and Trunk: Latissimus dorsi: Extends and adducts shoulder and arm dorsally. (pulls arm across back)  & Skeletal Muscles (continued)  Upper Limb and Trunk: Biceps branchii: Flexes forearm and supinates hand. Triceps branchii: Extends forearm.  Skeletal Muscles (continued) &  Lower Limb and Buttocks: Adductor longus: Adducts and flexes thigh. Sartorius: Rotates thigh. (sitting cross-legged)  Skeletal Muscles (continued) &  Lower Limb and Buttocks: Quadriceps femoris group: Extends leg. Peroneus longus: everts foot. Tibialis anterior: Dorsiflexes and inverts foot. Gastrocnemius: Flexes leg and foot. (tiptoeing) Skeletal Muscles (continued) D  Lower Limb and Buttocks: Gluteus medius: Abducts thigh. Gluteus maximus: Extends thigh. (forms buttocks) Hamstring group: Flexes leg and extends thigh at hip joint. Gastrocnemius: Flexes leg and foot. (tiptoeing) Skeletal Muscles (continued) &  Lower Limb and Buttocks: Gluteus medius: Abducts thigh. Gluteus maximus: Extends thigh.(forms buttocks) Gastrocnemius: Flexes leg and foot. (tiptoeing)