Muscular System PDF

The Muscular System Dr. Naim Kittana Department of Biomedical Sciences Faculty of Human Medicine & Health Sciences An-Najah National University 1  The Muscular System Muscles are responsible for all types...

The Muscular System Dr. Naim Kittana Department of Biomedical Sciences Faculty of Human Medicine & Health Sciences An-Najah National University 1  The Muscular System Muscles are responsible for all types of body movement – they contract or shorten and are the machine of the body Three basic muscle types are found in the body 1. Skeletal muscle 2. Cardiac muscle 3. Smooth muscle 2  Function of Skeletal Muscles Produce movement Maintain posture Stabilize joints Generate heat 3 Skeletal Muscle Wrapping 4 Connective tissue sheaths of skeletal muscle: epimysium, perimysium, and endomysium. (Cell) 5 6 Microscopic anatomy of a skeletal muscle fiber 7 8 9 icroscopic anatomy of a skeletal muscle fiber 10 Sarcomere structure 11  Skeletal Muscle Activity Properties of Skeletal Muscle Activity (single cells or fibers) Irritability – ability to receive and respond to a stimulus Contractility – ability to shorten when an adequate stimulus is received 12 Motor Unit 13 The phases leading to muscle fiber contraction 14 The Neuromuscular Junction 15 Transmission of Nerve Impulse to Muscle 16  Channels Involved in Initiating Muscle Contraction 1. The process begins when the nerve impulse reaches the axon terminal and opens voltage-gated calcium channels in the axonal membrane. Calcium entry triggers release of ACh into the synaptic cleft. 2. Released ACh binds to ACh receptors in the sarcolemma, opening chemically gated Na+-K+ channels. Greater influx of Na+ causes a local voltage change (the end plate potential). 3. Local depolarization opens voltage-gated sodium channels in the neighboring region of the sarcolemma. This allows more sodium to enter, which further depolarizes the sarcolemma, generating and propagating an AP. 4. Transmission of the AP along the T tubules changes the shape 18 of voltage-sensitive proteins in the T tubules, which in turn 19  Steps in E-C Coupling: 20  The Sliding Filament Theory of Muscle Contraction Activation by nerve causes myosin heads (cross bridges) to attach to binding sites on the thin filament Myosin heads then bind to the next site of the thin filament This continued action causes a sliding of the myosin along the actin The result is that the muscle 21 is shortened (contracted)  Contraction of a Skeletal Muscle Muscle fiber contraction is “all or none” Graded responses : different degrees of skeletal muscle shortening, Muscle force depends upon the number of fibers stimulated Muscles can continue to contract unless they run out of energy  Types of Muscle Contractions 1. Isotonic contractions Myofilaments are able to slide past each other during contractions The muscle shortens 2. Isometric contractions Tension in the muscles increases The muscle is unable to shorten 23  Muscles and Body Movements Muscles are attached to at least two points: 1. Origin – attachment to a immoveable bone 2. Insertion – attachment to an movable bone 24 Energy for Muscle Contraction 25 26 27 28 29 Smooth Muscles Arrangement 30 Cardiac Muscles Arrangement 31 32 Types of Body Movements 33 Types of Body Movements 34  Types of Skeletal Muscles Prime mover – muscle with the major responsibility for a certain movement Antagonist – muscle that opposes or reverses a prime mover Synergist – muscle that aids a prime mover in a movement and helps prevent rotation 35  Naming of Skeletal Muscles 1. Direction of muscle fibers Example: rectus (straight) 2. Relative size of the muscle Example: maximus (largest) 3. Location of the muscle Example: many muscles are named for bones (e.g., temporalis) 4. Number of origins Example: triceps (three heads) 36  Naming of Skeletal Muscles 5. Location of the muscles origin and insertion Example: sterno (on the sternum) 6. Shape of the muscle Example: deltoid (triangular) 7. Action of the muscle Example: flexor and extensor (flexes or extends a bone) 37 Head and Neck Muscles 38 39 Muscles of the abdominal wall 40 Superficial muscles of the thorax and shoulder acting on the scapula and arm 41  Superficial muscles of the thorax and shoulder acting on the scapula and arm 42  Muscles crossing the shoulder and elbow joints, causing movements of the arm and forearm, respectively 43 Muscles crossing the shoulder and elbow joints, causing movements of the arm and forearm, respectively 44 Muscles of the anterior fascial compartment of the forearm acting on the right wrist and fingers 45  Muscles of the posterior fascial compartment of the right forearm acting on the wrist and fingers 46 47 48 49 50 Superficial Muscles: Anterior 51 Superficial Muscles: Posterior 52