The Muscular System Lessons 1-3

Cardiac Muscle Tissue

• Makes up the walls of the heart

• Cells are long and branch frequently

• Have striations (stripes)

• Involuntary control

• Contains intercalated discs that connect cardiac cells and synchronize contractions

Smooth Muscle Tissue

• Found in blood vessels and hollow organs

  • Ex. stomach and intestines

• Involuntary control

• Non-striated

Skeletal Muscle Tissue

• Muscles attach to bone

  • Ex. Biceps muscle

• Fibers are long and bundled

• 40-50% of body weight

• Voluntary control

• Striations

Excitability

Ability to respond to stimuli or nerve impulse

Contractility

Ability to contract or shorten its size

Extensibility

Ability of muscle to stretch

Elasticity

Ability of muscle to return to original length after stretching

Movement

Skeletal muscles contract to pull on the bones to produce movement and stabilize joints

Maintain posture

• Maintained through tonic contractions

• Helps to balance weight and counter gravity

Heat Production

• Muscles get energy (ATP) through cellular respiration which also produces heat

• Skeletal muscles are the main generator of heat in the body

  • Each time they contract, they produce heat

Whole Muscle

Made of a bundle of fascicles

Fascicles

Made of a bundle of muscle fibers (muscle cells or myocytes)

Muscle fibers

Made of bundles of myofibrils

Myofibrils

Composed of two types of long myofilaments, thick and thin

Sarcomeres

• Organized into repeating sections along the myofibril

• The functional unit of muscle fibers where contraction begins, that are separated by Z lines

Sliding Filament Theory

• When a muscle contracts, thick filaments pull on thin filaments causing them to slide past each other

• The distance between the Z lines is reduced causing the sarcomere to shorten

Nerve Impulse

Required for contraction

Motor Neuron

Nerve that transmits an impulse to muscle to cause contraction

Muscle Contraction

• Myofilaments move closer together causing every level to shorten

• Muscle shortens and pulls on bones causing movement

• Requires nerve impulse, calcium, and energy (ATP)

Isotonic

Contraction in which the length of the muscle changes to produce movement

Isometric

Contraction in which the length of the muscle doesn’t change and no movement occurs

Joint

Where bones join

Whole muscle

Muscle body

Tendons

Attach the muscle to bone

Origin

Stationary attachment site of a muscle

Insertion

The moveable attachment site of the muscle

Agonist/Prime Mover

Main muscle that contracts to produce movement

Synergist

Muscle assists agonist

Antagonist

Muscle that does opposite motion of agonist and relaxes when agonist contracts

Hypertrophy

Strength training, increase in muscle growth