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Muscular System Functions Muscle Tissue • Refers to all the contractile tissues of the body. • Skeletal=attached to skeleton. • Cardiac= heart muscles • Smooth= muscles of organs Smooth Muscle • Cells are small spindle shaped • Non-striated (striations are dark lines of tissue ) • Involuntary muscle • Found in organ groups..Example: intestinal, bladder, blood vessels. • Muscle contractions are rhythmic and slow. Cardiac Muscle • Requires continuous O2 • Only in the heart • Striated • Involuntary • Muscle contractions are rhythmic & automatic Skeletal Muscle • Attached to the bones of skeleton • Voluntary muscle…contains nerves • under voluntary control Composed of bundles of muscle cells – Each cell is Multinucleated. – Each cell is a muscle fiber – Cell membrane=SARCOLEMMA – Cytoplasm=SARCOPLASM Characteristics…. • Contractibility: muscles shorten and tighten…which in turn, brings the two ends of the bone closer together..which is movement.. Characteristics…cont’ • Excitability: or irritability.. The ability to respond to certain stimuli..producing signals called action potentials= impulses..(nerve impulses) • Extensibility: The ability of the muscle to be stretched. Characteristics…cont’ • Elasticity: The ability for a muscle to return to its original shape when relaxing. Attachments….. – Origin: point where muscle is attached to bone that moves very little – Insertion: point where muscle is attached to bone that moves. – Belly: muscle central part of the Contraction of Skeletal Muscle • Movement occurs as a result of 2 major events: • Nerve stimulation : message sent thru nerves to the muscle.. • Action potential: the muscle receives the stimuli, and contracts as a result. Muscle Groups • Head and Neck • Upper Extremities • Trunk –Thorax & Abdomen –Posterior & Anterior • Lower extremities Major Muscles of the Head & Neck….. • • • • • • • • • Temporalis: at the temple Frontalis: forehead Masseter: cheek Orbicularis oculi: around the eye Sternocleidomastoid: Behind the ear to the clavicle Trapezius: Back of the head (occipital) to the shoulder. Orbicularis oris: around the mouth Zygomaticus major: cheekbone to orbicularis oris Nasalis: muscles of the nose Intercostals More to come…..
