Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Muscular System Facts about muscles… • A skeleton cannot move by itself • > 40% of the mass of the average human body is muscle • Found everywhere in your body • Power every movement from moving your lips to blinking your eyes Types of Muscle Tissue: • Skeletal • Smooth • Cardiac 3 Types of Muscle Tissue: Type Skeletal Smooth Cardiac Voluntary/ Involuntary Found Striations Structure Nucleus (stripes) Skeletal Muscles • • • • • Voluntary Found attached to bones Yes, striations Cells are long and thin Many Nuclei Smooth Muscles • Usually involuntary • Found in hollow organs (i.e. stomach, blood vessels, sm & lrg intestine) • No striations • Spindle-shaped (draw a spindle) • One nucleus Cardiac Muscle • Involuntary • Cardio= –Greek word for Heart • • • • Found in the Heart Striations Intercalated Discs One to two nuclei Type of muscle? Type of muscle? Type of muscle? Type of muscle? Type of muscle? Type of muscle? Skeletal Muscle Breakdown • Muscle • Bundle • Fibers (cells) • Myofibril • Filaments –Actin –Myosin Closer look at the filaments: • Actin: • Myosin: Closer look at the filaments: • Actin: thin filaments on outside • Myosin: Closer look at the filaments: • Actin: thin filaments on outside • Myosin: thick filaments in the middle Closer look at the filaments: • Z lines: Closer look at the filaments: • Z lines: attach the actin together Z lines Myosin Actin Muscle contraction: • Myosin heads grab and pull on actin Muscle contraction • Myosin heads grab and pull on actin Draw a picture of this in your notes Muscle relaxed: Muscle contracted: Muscles work in pairs Superficial muscles of the face Anterior superficial muscles Posterior superficial muscles Superficial muscles of the thigh Muscle Contraction • Myofibrils are made of filaments • Striations are formed by a pattern of thick and thin filaments made of protein • Thick filaments are made of the protein myosin • Thin filaments are made of the protein actin • Filaments are arranges in units called sarcomeres • Sarcomeres are separated by from eachother by regions called Z discs Actin and Myosin: Cause muscles to contract • A muscle contracts when thin filaments slide over thick filaments • Myosin forms a cross-bridge with actin • The cross bridge changes shape pulling the actin filament toward the center of the sarcomere • The distance between the Z discs decreases • The cross-bridge then detaches Control of Muscle Contraction • An enzyme produces an impulse causes the release of Calcium ions (Ca+) allowing actin and myosin to interact • The muscle remains contracted until the impulse ceases • Calcium ions pumped back into storage and contraction ends • Contraction of a single muscle fiber is an all-ornone process! • Most skeletal muscles work in opposing pairswhen one contracts the other relaxes