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Muscular system Anatomy & Physiology Functions • • • • • Movement, pumping/transport Breathing Posture Produce heat, regulate body temperature Protection,(of organs, stabilize joints, etc.) Muscle Types • Skeletal- voluntary (bones, face), over 400, long cells, many nuclei, striated • Cardiac- involuntary (heart and blood vessels), strongest, 1 nuclei per cell, some striations with gap junctions • Smooth- involuntary (intestines, internal organs), slow and smooth, 1 nuclei per cell, no striations Muscle Contraction • All or None! • Opposites contract! Muscles work in pairs • Bicep bends at the elbow (relaxed) → tricep straightens the arm (contracted) • muscle contraction animation video Sarcomere = contractile unit Muscle contraction • Actin (thin) filaments, with myosin, are responsible for cell movements • Myosin (thick) “molecular motor”—a protein that converts chemical energy (ATP) to mechanical energy, (force and movement) • Need Ca++ ions AND ATP to contract • Acetylcholine Types of Muscles • Slow Twitch- red fibers, oxygen storage, can build over time, used for aerobic exercise, long distance running • Fast Twitch- white fibers, used for short burst of energy, born with a certain amount, sprinters • Intermediate- most common, mixture of red and white Naming Muscles • Location • Shape • • • • • Size Direction of fibers Number of origins Location of attachments Action Vastus lateralis/medialis Deltoid Gluteus maximus Oblique, rectus abdominus or femoris Triceps, biceps Sternocleidomastoid Adductors/abductors • 600+ muscles in the body • Approx. 640 • Muscles comprise approx. 45% of our body weight • Smallest muscle = stapedius in ear • Largest muscle = gluteus maximus • Most active muscles are in the eye • Over 100,000 movements per day