Muscular System

CATEGORY:

• Biology

DEFINITION:

•The muscular system is an organ system consisting of Skeletal (connected to the skeleton to form part of the mechanical system which moves the limbs and other parts of the body), smooth and Cardiac muscles

FUNCTION:

•Permits movement of the body, strength, maintains posture and balance, and circulates blood throughout the body and provides heat

-Together with the skeletal system it forms the Musculoskeletal System, which is responsible for movement of the body

ACTION:

•Controlled by the nervous system

-Some muscles (e.g. Cardiac muscle) can be completely autonomous

•Skeletal muscles perform coordinated contractions by shortening (Concentric) and lengthening (Eccentric) using ATP

-Muscles store little ATP so must continuously recycle the discharged Adenosine Diphosphate (ADP) into ATP rapidly

-Muscle tissue also contains stores of a fast acting recharge chemical, Creatine Phosphate which initially assists in producing the rapid regeneration of ADP into ATP

•Muscle force is proportional to physiologic cross-sectional area (PCSA), and muscle velocity is proportional to muscle fiber length

FACTS:

•Approximately 639 skeletal muscles in the human body

•Muscle fibres consist of two main types...

-Type I (Slow Twitch Oxidative)...

—Lower-intensity exercise...light resistance work aimed at muscular endurance and long-duration aerobic activities e.g. 5K and 10K runs

—Slow contraction times and a high resistance to fatigue

—Small motor neuron and fiber diameter

—High mitochondrial and capillary density

—High myoglobin content

—Low supply of creatine phosphate

—Low glycogen content

—High store of triglycerides

—Contain few of the enzymes involved in glycolysis, but contain many of the enzymes involved in the oxidative pathways (Krebs cycle, electron transport chain)

-Type II (Fast Twitch)...further categorized into Type IIa and Type IIb...

-Type IIa (Fast Twitch Oxidative)...

—Low force, power, speed production and high endurance

—Sustained power activities as more resistant to fatigue than Type IIb

-Type IIb (Fast Twitch Glycolytic)...

—High force, power, speed production and low endurance

—High-intensity bursts of power...maximal and near-maximal lifts and short sprints

MANIPULATION:

•It is possible to transform Type IIB to Type IIAB to Type IIA with exercise training

DIETING:

•Increasing the mass or size of Type II muscle fibres leads to a significant decrease in Fat mass

-For this to occur, weight training becomes more important than cardio training

-Nutrition Protocol must be adjusted to place the body in to an Anabolic state

—Increasing levels of Testosterone aids in the building of Muscle Mass

RELATED TO:

•Exercise Protocol

•Nutrition Protocol

NOTES:

•Body shape is determined by percentage of present Type I and Type IIa & Type IIb muscle fibres...comparing an athletic sprinter with an athletic endurance runner

•Major muscles of the Muscular System