Final Exam ReviewTerminologyBelly of the Muscle- Refers to the actual working or contracting portion of the muscle- Commonly red- Some muscles have more than one bellyo Bicep is a muscle with two belliesTendon- Tendons are at either end of the belly- They are made of dense regular connective tissue- They anchor muscle to bone- Attach to every muscle to their insertion (moving bone) and origin (non-moving bone)Anatomy of the Muscle- Epimysium – dense layer of collagen that surrounds the entire muscle- Perimysium – divides the skeletal muscle into a series of compartments, each compartment is called a fascicle - Endomysium – within each fascicle there are individual muscle fibers which are surrounded by a third layer of collagen fibers/ delicate connective tissue called endomysium. The endomysium contains capillaries, myosatellite cells, and nerve fibers - Epimysium  perimysium  endomysium- Fascicles  muscle fibers- Muscle fiber (myocytes) – surrounded by endomysium- Multinucleated – during development of muscle fibers, groups of embryonic cells called myoblasts fuse together forming a muscle fiber- Some myoblasts do not fuse with the developing muscle fibers and are called myosatellite cells- After injury myosatellite cells enlarge and divide, they then fuse with the damaged muscle fibers assisting with repair of the tissue- Sarcolemma – underneath the endomysium, connective tissue that surrounds muscle fibers, the plasma membrane of the muscle fiber- Sarcoplasm – cytoplasm of the muscle fiber, surrounded by the sarcolemma- T-tubules – narrow tubes that are continuous with the sarcolemma and extend deep into the sarcoplasm, surrounding each myofibril. They allow the quick signal distribution of an action potential - Tropomyosin – cover the active sites on the g-actin to prevent myosin interaction- Troponin – attached midway to the protein Tropomyosin and lies within the groove between the actin filaments. Blocks the attachment site for the myosin crosses bridge, thus preventing contraction. When muscle cell is stimulated to contract by an actin potential, calcium channels open in the sarcoplasmic membrane and release calcium into the sarcoplasm. Some calcium attaches to the troponin which causes it to change shape exposing binding sites for myosin on the actin filaments. Myosin binding to actin forms cross bridges and the contraction of muscle begins. - Terminal cisternae – enlarged areas of the sarcoplasmic reticulum that surround the t-tubuleso Where calcium is storedo Released the calcium when an action potential stimulates muscle contractiono Because they ensure rapid calcium delivery, they are well developed in muscles that contract quickly- Triad – T-tubule + 2 terminal cisternae, they are connected by a series of proteins that trigger calcium releaseMyofibrils- Smaller fibers within each muscle cell- Can actively shorten and are responsible for skeletal muscle fiber contraction - Cylindrical structures- Each myofibril has a mesh-like membrane complex surrounding it called the sarcoplasmic reticulum (major calcium storage in muscle cells)- Myofibrils have two protein filamentso Thin filament primarily composed of myosin G-actin are beads which contain a binding site for the myosin heads F –actin is a twisted stranded composed of two rows of g-actino Thick filaments – primarily composed of myosin- Have functional units called sarcomeres which are the actual contractile unit of the muscle – each myofibril has thousands of sarcomeres (a repeating unit of striated muscle)o A-band does not change length during muscle contraction and is composed of myosin (thick filaments) M-line the center line, connects the thick filaments, help with stabilization H-band the middle area of myosin where there is no overlap with actin changes size depending on if the muscle is relaxed or contractedo I band changes length during muscle contraction and is composed of only actin (thin filaments) Z-lines mark the boundary between adjacent sarcomeres Titin – extends from the tips of the thing filaments to attach to sites at the z-line- Helps keep thick and thin filaments in proper alignment- Aids in restoring resting sarcomere length after contraction- Regenerationo Skeletal cells can regenerate because of myosatellite cellso Cardiac muscle can also regenerate- Rigor Mortis – after death, muscles remain contracted because the body no longer releases AChETypes of Muscular Tissue- Skeletal muscle tissueo Striated and attached to boneso Voluntary contraction (subconsciously to a certain extent)o Innervated by somatic nerves- Cardiac muscle tissueo Striated and located in heart wallo Involuntary, it exhibits autorhythmicityo Innervated by autonomic nervous system (ANS)o Capable of regeneration Stem cells can come from remote location and enter heart to lay down more cells- Smooth muscle tissueo Non striated!o Located in walls of hollow organs/structureso Involuntary, exhibits autorhythmicity o Innervated by autonomic nervous system (ANS)o Capable of dividing and making more of itselfMuscle Contraction/RelaxationContraction steps1. ACh released by the synaptic terminal at the neuromuscular junction binds to receptors on the sarcolemma2. The resulting change in transmembrane potential of the muscle fiber leads to the production of an action potential3. Sarcoplasmic reticulum releases stored calcium. Calcium binds to troponin, causing the troponin to change shape pulling the Tropomyosin molecule away from the active site on actin and allowing interaction with the energized myosin heads4. Once the active sites are exposed the energized myosin heads bind to them forming cross bridges5. The contraction begins as repeated cycles of cross bridge binding, pivoting and detachment occurs, powered by the hydrolysis of ATP. These events produce filament sliding, and the muscle fiber shortensRelaxation steps1. ACh is broken down by AChE2. The Sarcoplasmic reticulum recaptures the calcium3. Active sites are recovered by Tropomyosin4. Contraction ends5. Muscle relaxation occurs, muscle returns passively to its resting lengthComponents- Interneuron – receives the message and alerts the motor neuron about which specific muscle needs to be moves- Effector – a peripheral gland or muscle cell stimulated by a neuron- Motor unit – all of the muscle cells controlled by a single motor neuron- Motor neuron – hundreds of skeletal fibers are innervated by