Physiology muscular system

functions

• Movement – in conjunction with bones

• Posture – muscles always at work, keeping you upright

• Heat Generation – muscle action produces heat that we can circulate (aka shivering)

Skeletal Muscle

• Moves your bones, face, eyes, etc

• Voluntary

• Contractions are generally fast/short

Smooth Muscles

• muscles of your internal organs

• Involuntary

• Contractions are slow/extended

Cardiac Muscles

• Muscles of your heart

• Involuntary

• “never” stops

compositions of muscles

• Muscles as a whole are just bundles of smaller and smaller bundles

• The muscle unit we’ll focus on is the muscle fiber

• Muscle fibers contain important filaments called:

  • Actin (thin)

  • Myosin (thick)

muscle contraction

• When used, muscles will either shorten or become tense

1. Muscle fiber(s) stimulated by motor neuron(s)

2. Muscle fiber cells release Ca from their sarcoplasmic reticulum (SR)

3. Ca stimulates actin and myosin to interact with one another

4. Actin/Myosin slide “inward” towards one another, and cause muscle fibers (and muscle) to shorten

muscle contraction requirements

• Energy is required for muscles to contract

  • Our primary energy molecule is ATP

  • We get the most ATP aerobically, which requires oxygen

• When oxygen intake doesn’t keep up, we switch to anaerobic

  • Gives us less ATP, and produces lactic acid

• When muscles run out of ATP, accumulate too much lactic acid, and/or have an ion imbalance, they will become fatigued

  • A fatigued muscle cannot contract fully or at all