Muscular System
Honors Anatomy & Physiology
Susan Chabot Lemon Bay High School Skeletal, Smooth, or Cardiac
SKELETAL SMOOTH CARDIAC Striated Not striated Striated Voluntary Involuntary Involuntary
Multinucleated Single nucleus Single nucleus Bound to bones In hollow Heart muscle organs/ stomach
Moves skeleton Moves food Moves blood • 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. 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 Not included in book BUT important Protect abdominal organs Make a Cell
Using the clay provided, construct a typical cell. Cell vs. Muscle cell/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. Skeletal Muscle Structure Composed of several tissue types: Skeletal muscle tissue Nervous tissue Blood (Connective tissue) Dense Connective tissue
Attached to bone through a tendon.
Attached to other muscles or organs through a sheet-like tendon called an aponeuroses. 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. TENDON
EPImysium
ENDOmysium
Bone MYOFIBRIL PERImysium MUSCLE FIBER/cell FASCICLE Transform your cell into a muscle fiber 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/Myofibrils that allow for contraction 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.
FUNCTIONAL PROPERTIES Skeletal Muscle Activity 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. How do Muscles A motor neuron KNOW to communicates the signal Contract? 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. 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 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).