SPORT MED 20L Mr. Giesbrecht How a Muscle Works SPORT MED 20L Mr. Giesbrecht

MOTOR UNIT A Motor unit consists of the motor neuron and the muscle fibers it connects to Some motor units consist of only one muscle fiber while others consist of hundreds of muscle fibers

MUSCLE STRUCTURE AND SARCOMERES

https://www.youtube.com/watch?v=Ktv-CaOt6UQ

MUSCLE CONTRACTION – SLIDING FILAMENT THEORY Resting Phase Very little calcium is present so few myosin cross-bridges are formed

MUSCLE CONTRACTION – SLIDING FILAMENT THEORY Excitation-Contraction Coupling Phase A signal (Action Potential) comes from the motor neuron to the muscle causing the release of calcium Calcium stimulates the connection of the mysosin (Thick Filaments) cross bridges to the actin (Thin Filaments)

MUSCLE CONTRACTION – SLIDING FILAMENT THEORY Contraction Phase The cross bridges pull on the thin filaments bringing the ends of the sarcomere closer together The energy for the puling action of the cross-bridges comes from the breakdown of adenosine triphosphate (ATP) In order for contraction to continue calcium must be present and the cross bridge needs ATP

MUSCLE CONTRACTION – SLIDING FILAMENT THEORY Relaxation Phase Stimulus from motor neuron stops Calcium is “pumped” back to storage Cross-bridges release

MUSCLE TWITCH https://www.youtube.com/watc h?v=3xTjnwo2S2A

MUSCLE FIBER TYPES Fast Twitch Muscle Fibers Develop force fast Relax fast Fatigue quickly Type IIx

MUSCLE FIBER TYPES Slow Twitch Muscle Fibers Develop force slowly Relax slowly Fatigue slowly Type I

MUSCLE FIBER TYPE AND SPORT PERFORMANCE Fast Twitch Strength/Power/Speed sports Slow Twitch Endurance based sports

MUSCLE FIBER TYPE AND SPORT PERFORMANCE Assignment – Classify the sporting events on the sheet provided as being either fast twitch or slow twitch activities.