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

5. Muscle cell vs. Muscle fiber Typical body cells are round with a single, central nucleus. 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. 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: Composed of several tissue types: Skeletal muscle tissue Skeletal muscle tissue Nervous tissue Nervous tissue Blood Blood Connective tissue Connective tissue Attached to bone through a tendon. Attached to bone through a tendon. Attached to other muscles or organs Attached to other muscles or organs through a sheet-like tendon called an through a sheet-like tendon called an aponeurosis. aponeurosis.

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

8. Structure of a Skeletal Muscle Sarcolemma

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

10. Make a muscle cell and organize into muscle bundle

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

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

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

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

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