The Muscular System Continued Grade 12 Exercise Science Mr. MacMillan

Review O The characteristics of muscle O Irritability O Contractility O Extendibility O Elasticity O Conductibility O Muscle fibre types O Fast glycolytic, fast oxidative, slow O Muscle types O Skeletal O Smooth O cardiac

The Neuromuscular System O The complex linkages between the muscular system and the nervous system O Example: Preparing to Kick a Soccer Ball 1. Messages needed to execute the action are sent from brain or spinal cord. 2. This causes a chemical reaction in the leg muscle area 3. Muscles produce the force and you kick the ball All of this happens in an instant with many nerves and muscles being affected, yet kicking a soccer ball seems so effortless

The Neuromuscular Junction

Motor Unit O Nerves transmit impulses in waves that ensure smooth movements. O Muscle Twitch O A single nervous impulse and the resulting contraction O Motor Unit O The motor neuron, its axon and the muscle fibre it stimulates are together called the motor unit.

All-or-none Principle O Whether or not a motor unit activates upon the arrival of an impulse depends upon the so called all-or-none principle O An impulse of a certain magnitude (or strength) is required to cause the innervated fibres to contract O Every motor unit has a specific threshold that must be reached for such activation to occur

Anatomy of Skeletal Muscle

O Perimysium O Sheath of connective tissues that binds groups of muscle fibres together O Epimysium O Strong, connective sheath that envelopes the entire muscle O Endomysium O Sheath of connective tissues that surrounds the muscle fibre O Tendon O Attaches the muscle structure to the bone O Blood vessel O Supplies the muscle with blood and other nutrients

Microscopic Skeletal Muscle O Using the microscopes in the back cupboard, you will be examining skeletal muscle under a light microscope O Your task is to sketch what you see under all three magnifications O Your 3 sketches need the following O A title O Magnification listed O Labeled components of sketch O Each sketch should be on a separate piece of paper

High microscope magnification of a single sarcomere within a single myofibril

Homework O Finish labeled sketches of skeletal muscle O Read pages 2-37 of textbook O Make any necessary notes if needed.