CogKnoSys

Knowledge you can walk. Read the idea below, then step up to the general, across to peers or down to the specific.

Physical

Muscular System

The muscular system is the body's skeletal, smooth and cardiac muscle, which moves the body, holds posture and pumps blood.

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The idea

The muscular system is an organ system made of three kinds of muscle: skeletal, smooth and cardiac. It lets the body move, keeps it upright and circulates blood. Muscles also give the body strength and balance, and they make heat that keeps it warm.

Skeletal muscles are the ones you move on purpose. Tendons connect them to bones, so when a muscle contracts it pulls on the skeleton and creates movement. The human body has over 600 skeletal muscles. Smooth muscle lines organs such as the gut and blood vessels, and cardiac muscle forms the heart; both work without conscious control.

Each muscle is built from long cells called muscle fibers. Inside them, the proteins actin and myosin pull past each other to make the muscle contract. This uses large amounts of ATP, the cell's energy source, so muscles must keep making more. Nerves control most muscle action, although heart muscle can keep working on its own. Together with the skeleton, the muscles form the musculoskeletal system.

Check yourself

Question 1 of 2

About how many skeletal muscles are in the human body?

Pick one. The first pick counts.

Composition

what it's made of

  • Skeletal Muscle — Striped muscle under voluntary control that moves the body.
  • Smooth Muscle — Involuntary muscle that keeps blood flowing and moves food through the digestive system.
  • Cardiac Muscle — Involuntary, striped heart muscle whose fibers are joined side to side.
  • Tendons — Connective tissue that links each skeletal muscle to a bone.
  • Muscle Fibers — Long cells packed with actin and myosin, the proteins that contract.

Connection

how it relates

Under Human Body

Related

  1. Autonomic Nervous Systemstrength 70 of 100

    The autonomic nervous system adjusts heart and smooth muscle without conscious thought.

  2. Fight or Flight Responsestrength 60 of 100

    During a fight-or-flight response, muscles tense and the heart beats faster to get the body ready for action.

  3. Motionstrength 50 of 100

    Muscles supply the pulling forces behind every movement the body makes.

Cause and effect

  1. Thermal Energystrength 50 of 100

    Working muscles release heat, which helps keep the body warm.

Change

how and why it evolves

Past
Muscle forms before birth, during embryonic development, in a process called myogenesis. Muscles then grow with the body and get stronger with use.
Now
Today scientists explain contraction with the sliding filament model, and doctors and coaches use that knowledge to treat injuries and build strength.
Next
Research on muscle loss in old age and on muscle diseases will likely lead to better exercise plans and treatments.

Knowledge you can walk. Read the idea, then step up, across or down.

Muscular System

The muscular system is the body's skeletal, smooth and cardiac muscle, which moves the body, holds posture and pumps blood.

Learn, discuss, create, buy or invest

The idea

The muscular system is an organ system made of three kinds of muscle: skeletal, smooth and cardiac. It lets the body move, keeps it upright and circulates blood. Muscles also give the body strength and balance, and they make heat that keeps it warm.

Skeletal muscles are the ones you move on purpose. Tendons connect them to bones, so when a muscle contracts it pulls on the skeleton and creates movement. The human body has over 600 skeletal muscles. Smooth muscle lines organs such as the gut and blood vessels, and cardiac muscle forms the heart; both work without conscious control.

Each muscle is built from long cells called muscle fibers. Inside them, the proteins actin and myosin pull past each other to make the muscle contract. This uses large amounts of ATP, the cell's energy source, so muscles must keep making more. Nerves control most muscle action, although heart muscle can keep working on its own. Together with the skeleton, the muscles form the musculoskeletal system.

Check yourself

2 quick questions, instant feedback.