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 Vastus lateralis/medialis Shape Deltoid Size Gluteus maximus Direction of fibers Oblique, rectus abdominus or femoris Number of origins Triceps, biceps Location of attachments Sternocleidomastoid Action Adductors/abductors

Muscles comprise approx. 45% of our body weight 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