The Muscular System

ContinuedGrade 12 Exercise Science

Mr. MacMillan

ReviewO The characteristics of muscle

O IrritabilityO ContractilityO ExtendibilityO ElasticityO Conductibility

O Muscle fibre typesO Fast glycolytic, fast oxidative, slow

O Muscle typesO SkeletalO SmoothO cardiac

The Neuromuscular System

O The complex linkages between the muscular system and the nervous system

O Example: Preparing to Kick a Soccer Ball1. Messages needed to execute the action are

sent from brain or spinal cord.2. This causes a chemical reaction in the leg

muscle area3. 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 UnitO Nerves transmit impulses in waves that

ensure smooth movements.O Muscle Twitch

O A single nervous impulse and the resulting contraction

O Motor UnitO The motor neuron, its axon and the muscle fibre it

stimulates are together called the motor unit.

All-or-none PrincipleOWhether or not a motor unit activates

upon the arrival of an impulse depends upon the so called all-or-none principle

OAn impulse of a certain magnitude (or strength) is required to cause the innervated fibres to contract

OEvery motor unit has a specific threshold that must be reached for such activation to occur

Anatomy of Skeletal Muscle

O PerimysiumO Sheath of connective tissues that binds groups of muscle

fibres togetherO Epimysium

O Strong, connective sheath that envelopes the entire muscleO Endomysium

O Sheath of connective tissues that surrounds the muscle fibreO Tendon

O Attaches the muscle structure to the boneO 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 followingO A titleO Magnification listedO Labeled components of sketchO Each sketch should be on a separate piece

of paper

High microscope magnification of a single sarcomere within a single myofibril

HomeworkO Finish labeled sketches of skeletal

muscleO Read pages 2-37 of textbook

O Make any necessary notes if needed.