The Muscular System 9 BIOLOGY The Muscular System

The Muscular System 9 BIOLOGY

The Muscular System • 3 Types of muscle: – 1. Smooth- involuntary, lines internal organs, no striping, one nucleus per cell – 2. Cardiac- involuntary, in the heart only, network arrangement for proper contraction, striped appearance, multi-nucleate – 3. Skeletal- voluntary, attached to bones by tendons.

Skeletal Muscle Contraction • Muscles arranged in antagonistic pairs – When one contracts, one is relaxed and vice versa. – Muscle fibers: • Arranged in myofibrils of actin and myosin • Sarcomere: functional unit of muscle • Sliding Filament Theory: – 1. Once nerve signal reaches muscle, actin filaments slide toward each other causing contraction – 2. Nerve signal release of calcium for relaxation of contraction – 3. ATP needed

Muscle Contraction

Energy for Muscle Contraction • Oxygen available aerobic respiration • Oxygen not available anaerobic – Causes lactic acid build- up, fatigue & soreness

Rigor Mortis: State of prolonged muscle contraction * Upon death, ATP is no longer released to relax contraction, so stiffness occurs. After 24 hours, tissue degradation begins Used to determine time of death in forensics

Myoglobin • Special kind of hemoglobin that is only in muscle cells • Binds only one O 2 instead of 4 O 2 in hemoglobin • Gives extra oxygen reserves to muscle tissue

Myoglobin in Food • Dark meat has more myoglobin, thus more iron than white meat. • Dark meat is generally more nutritious as a result

Skeletal Muscle Strength • Slow twitch: Slow Endurance Resist fatigue Lots of mitochondria Have myoglobin which gives oxygen reserve – Exercise causes increase of mitochondria, but not size of muscle – – – • Fast twitch: – Fatigue easily – Great strength – For short rapid movements – No myoglobin – Fewer mitochondria – Exercise increases diameter of muscle