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Muscular System

Muscular System. Honors Anatomy & Physiology. Skeletal, Smooth, or Cardiac?. SKELETAL Striated Voluntary Multinucleated Bound to bones to move skeleton. SMOOTH Not striated Involuntary Single nucleus In hollow organs like stomach Moves food. CARDIAC Striated Involuntary

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Muscular System

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  1. Muscular System Honors Anatomy & Physiology

  2. Skeletal, Smooth, or Cardiac? SKELETAL • Striated • Voluntary • Multinucleated • Bound to bones to move skeleton SMOOTH • Not striated • Involuntary • Single nucleus • In hollow organs like stomach • Moves food CARDIAC • Striated • Involuntary • Single nucleus • Heart muscle • Moves blood

  3. The remainder of the chapter will focus on SKELETAL MUSCLE • Smooth/Visceral muscle will be covered in the DIGESTIVE system • Cardiac muscle will be covered in the CARDIOVASCULAR system.

  4. Introduction • Muscles are organs made of specialized cells that use nutrients for energy to contract. • Skeletal Muscle action provide: • Movement of skeleton • Muscle tone and posture • Stabilizes joints • Generate body heat • Protect abdominal organs

  5. Muscle cell vs. Muscle fiber • Typical body cells are round with a single, central nucleus. • Muscle cells/FIBERS are elongated often with several nuclei pushed to the outside of the cytoplasm.

  6. Skeletal Muscle Structure • Composed of several tissue types: • Skeletal muscle tissue • Nervous tissue • Blood • Connective tissue • Attached to bone through a tendon. • Attached to other muscles or organs through a sheet-like tendon called an aponeurosis.

  7. Connective Tissue • Used to separate individual skeletal muscles and hold in position. • Insulates and bundles individual skeletal muscle cells, aka muscle fibers. • Allows for blood vessels and nerves to pass into the muscle fiber. • Allows different parts of the muscle to move independently.

  8. Structure of a Skeletal Muscle Sarcolemma

  9. Skeletal Muscle Fiber • An individual muscle cell. • Contracts in response to stimulation. • Composed of: • Cell membrane = sarcolemma • Cytoplasm = sarcoplasm • Several small nuclei • Mitochondria = possibly HUNDREDS depending on demand placed on the muscle. • Myofilaments that allow for contraction

  10. Make a muscle cell and organize into muscle bundle

  11. Functional Unit of Muscle = Sarcomere • Actin – THIN myofilament • Myosin – THICK myofilament • It is the overlapping nature of the ACTIN and Myosin and the connection made between them that allows muscles to contract.

  12. Skeletal Muscle Activity FUNCTIONAL PROPERTIES • Excitability – can receive message from the brain. • Contractility – can contract. • Extensibility – can stretch through use of connective tissues like tendons. • Elasticity – can return to original position following contraction.

  13. How do Muscles KNOW to Contract? • A motor neuron communicates the signal to move from the brain to the muscle. • A motor neuron is an EFFERENT neuron. • The connection between a motor neuron and a muscle fiber is called the NEUROMUSCULAR JUNCTION.

  14. What do muscles NEED to contract? • Blood supply containing: • Oxygen • Glucose • Water • Electrolytes • Innervation: information • Brain – spinal cord – spinal nerve – nerve • Neuromuscular junction and neurotransmitter

  15. How do Muscles Contract? Sliding Filament Theory • Mitochondria convert carbohydrates and oxygen to ATP. • ATP is the energy muscles use to contract. • With this energy, the myofilaments ACTIN and MYOSIN inside the muscle fiber slide across one another. • This causes the muscle to CONTRACT (shorten) and RELAX (lengthen).

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