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Muscle Tissue

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Muscle Tissue

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Muscle Tissue

  1. 1. What are the major functions of muscle tissue
  2. 2. There are four characteristics associated with muscle tissue: Excitability • Tissue can receive and respond to stimulation Contractility • Tissue can shorten and thicken Extensibility • Tissue can lengthen Elasticity • Tissue can return to its resting state
  3. 3. The characteristics of muscle tissue enable it to perform some important functions, including: Movement (both voluntarily and involuntarily) Maintaining posture Supporting soft tissues within body cavities Guarding entrance and exits of the body Maintaining body temperature
  4. 4. What are the 3 types of muscle tissue
  5. 5. Skeletal Muscle Tissue features and characteristics: Fibers are multinucleated with peripheral nuclei Actin and myosin filaments form distinct cross- striation patterns Muscle is surrounded by connective tissue epimysium Muscle fascicles surrounded by connective tissue perimysium Each muscle fiber surrounded by connective tissue endomysium Voluntary muscle under conscious control
  6. 6. Sensitive stretch receptors called neuromuscular spindles are present within nearly all skeletal muscles These spindles consist of a connective tissue capsule, in which are found modified muscle fibers called intrafusal fibers and numerous nerve endings Neuromuscular spindles monitor the changes in the muscle lengths and activate complex reflexes to regulate muscle activity
  7. 7. Functions of Skeletal Muscle Tissue Skeletal muscles function in pairs to bring about the coordinated movements of the limbs, trunk, jaws, eyeballs, etc. Skeletal muscles are directly involved in the breathing process.
  8. 8. Smooth Muscle Tissue features and characteristics: Found in hollow organs and blood vessels Fibers are fusiform in shape and contain single nuclei Each cell is filled with a specialized cytoplasm, the sarcoplasm and is surrounded by a thin cell membrane, the sarcolemma. Contain contractile actin and myosin filaments; however, they are not arranged in the regular, cross-striated patterns that are visible in both the skeletal and cardiac muscle fibers As a result, these muscle appear smooth or nonstriated Smooth muscle fibers are also involuntary muscles and are, therefore, under autonomic nervous system and hormonal control
  9. 9. Functions of Smooth Muscle Tissue Smooth muscle controls slow, involuntary movements such as the contraction of the smooth muscle tissue in the walls of the stomach and intestines. The muscle of the arteries contracts and relaxes to regulate the blood pressure and the flow of blood.
  10. 10. Cardiac Muscle Tissue features and characteristics: Primarily located in the walls and septa of the heart and in the walls of the large vessels attached to the heart(aorta and pulmonary trunk) Similar to skeletal muscle, cardiac muscle fibers exhibit distinct cross-striations as a result of the arrangement of actin and myosin filaments. Transmission electron microscopy reveals similar A bands, I bands, Z lines, and repeating sacromere units Exhibits only one or two central nuclei, are shorter, and are branched
  11. 11. The terminal ends of adjacent cardiac muscle fibers show characteristic and dense-staining, end-to-end junctional complexes called intercalated disks. Located in the intercalated disks are the gap junctions that enable ionic communication and continuity between adjacent cardiac muscle fibers. Exhibit autorhythmicity and spontaneously generate stimuli
  12. 12. Functions of Cardiac Muscle Tissue Cardiac muscle tissue plays the most important role in the contraction of the atria and ventricles of the heart. It causes the rhythmical beating of the heart, circulating the blood and its contents throughout the body as a consequence.
  13. 13. CONDUCTION SYSTEM
  14. 14. The heart is influenced by the autonomic nervous system which can increase or decrease the heart rate in line with the requirements of the body. However, due to an intrinsic regulating system, called the conduction system it is possible for the heart to go on beating without any direct stimulus from the nervous system. This system is composed of specialized muscle tissue that generates and distributes the conduction that causes contraction of the cardiac muscle. These tissues are found in the sinus (or sinoatrial) node, atrioventricular node, bundle of His, bundle branches, and conduction myofibers.
  15. 15. When stimulated by electrical activity, muscle fibers contract and produce motion. In the heart, this electrical activity is referred to as depolarization. The contraction causes the blood to be pumped around the body. Contracted chambers within the heart are termed systolic. Relaxation of the heart muscle is caused by electrical repolarisation. Relaxed chambers within the heart are termed diastolic.
  16. 16. Heartbeat Origination in the Sinus Node Atrial Depolarization Atrioventricular Nodal Depolarization Septal Depolarization Early Ventricular Depolarization Late Ventricular Depolarization
  17. 17. Ventricular Systole Ventricular Repolarization Atrial and Ventricular Relaxation
  18. 18. MUSCLE CONTRACTION
  19. 19. • Skeletal muscles require stimulation from the nervous system in order to contract • Motor neurons are the cells that cause muscle fibers to contract (motor neuron) cell body dendrites axon Synaptic terminals (synaptic end bulbs) telodendria axon hillock
  20. 20. Table 7-1 •Once an action potential (AP) is generated at the motor end plate it will spread like an electrical current along the sarcolemma of the muscle fiber • The AP will also spread into the T-tubules, exciting the terminal cisternae of the sarcoplasmic reticula •This will cause Calcium (Ca+2 ) gates in the SR to open, allowing Ca+2 to diffuse into the sarcoplasm •Calcium will bind to troponin (on the thin myofilament), causing it to change its shape. This then pulls tropomyosin away from the active sites of actin molecules. •The exposure of the active sites allow the sliding of the filaments
  21. 21. • If there are no longer APs generated on the motor neuron, no more Ach will be released • AchE will remove Ach from the motor end plate, and AP transmission on the muscle fiber will end • Ca+2 gates in the SR will close & Ca+2 will be actively transported back into the SR • With Ca+2 removed from the sarcoplasm (& from troponin), tropomyosin will re-cover the active sites of actin • No more cross-bridge interactions can form • Thin myofilaments slide back to their resting state Table 7-1
  22. 22. Skeletal muscle fibers shorten as thick filaments interact with thin filaments (“cross bridge”) and sliding occurs (“power stroke”). The trigger for contraction is the calcium ions released by the SR when the muscle fiber is stimulated by its motor neuron Contraction is an active process; relaxation and the return to resting length is entirely passive.
  23. 23. Calcium ions regulate contraction in smooth muscle, but they do it in a slightly different way than in skeletal muscle: Calcium ions come from outside of the cell. Calcium ions bind to an enzyme complex on myosin, called calmodulin-myosin light chain kinase. The enzyme complex breaks up ATP into ADP and transfers the Pi directly to myosin. This Pi transfer activates myosin. Myosin forms crossbridges with actin (as occurs in skeletal muscle) When calcium is pumped out of the cell, the Pi gets removed from myosin by another enzyme. The myosin becomes inactive, and the muscle relaxes. This process is called myosin-regulated contraction.
  24. 24. Cardiac-muscle contraction is actin-regulated, meaning that the calcium ions come both from the sarcoplasmic reticulum (as in skeletal muscle) and from outside the cell (as in smooth muscle). Otherwise, the chain of events that occurs in cardiac-muscle contraction is similar to that of skeletal muscle.
  25. 25. GROUP 4 DMD1E ASID, DEVIM NUCUM, JOSHUA BANGALISAN, KLYDDENE DE SAGUN, CRISTINE ANNE HORTIZUELA, JOYCE ANNE TAGLE, JHAIRA

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