Muscular System The Power System

Muscle Facts Nearly half our weight comes from muscle tissue. There are 650 different muscles in the human body. Video

Three functions of muscle 1. Responsible for all body movement.

Three functions of muscle 2. Responsible for body form/shape and posture.

Three functions of muscle 3. Responsible for body heat and maintaining body temperature.

Types of muscles 1. Skeletal = attached to bone. Video Naming 2. Smooth = present in organs. 3. Cardiac = found only in the heart.

Skeletal Muscle Attached to bone. (Tendons) p. 125 Striated (striped) appearance Voluntary = you tell these muscles to move. Multinucleated muscle cell bundles Muscle cell = Muscle fiber Sarcolemma = muscle cell membrane. Contract quickly, fatigue easily, can’t maintain contraction for long.

Microscopic view of Skeletal Muscle

Smooth Muscle Visceral (organ) muscle. Found in walls of digestive system, uterus and blood vessels. Cells small and spindle-shaped. Involuntary = these muscles move on their own. Controlled by autonomic nervous system. Act slowly, do not tire easily, can remain contracted for a long time.

Microscopic view of Smooth Muscle

Cardiac Muscle Found only in the heart. Cells look striated (striped) and branched. Involuntary = muscle cells work on their own. Cells are fused – when one contracts, they all contract. Does not get tired.

Microscopic view of Cardiac Muscle

Sphincter Muscles A sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning.

Characteristics of Muscles (4) 1. Contractibility – the ability of a muscle to reduce the distance between the parts of its contents or the space it surrounds. Muscle-Contraction Contraction

Characteristics of Muscles 2. Extensibility – the ability of a muscle to be stretched.

Characteristics of Muscles 3. Exciteabillity – (irritability) the ability to respond to certain stimuli by producing impulses.

Characteristics of Muscle 4. Elasticity – ability of muscle to return to its original length when relaxing

How do muscles move? Muscles are attached to bones. When a muscle moves it pulls on the bone that it is attached to, causing the bone to move. Groups of muscles work together to create movement. Skeletal muscle movement

Motor Unit Motor unit = a motor neuron plus all the muscle fibers it stimulates. Motor unit

Neuromuscular junction Neuromuscular junction = the space between the neuron’s fibers and the muscle cells membrane. The Neuromuscular junction and the Synaptic cleft are the same thing.

Acetylcholine Acetylcholine = chemical neurotransmitter, it diffuses from the end of the neuron across the synaptic cleft/Neuromuscular junction. Acetylcholine carries a message from a neuron and delivers it to muscle cells. This message is usually, “MOVE!” Muscle Contraction

Muscle fatigue With movement of skeletal muscles you will get muscle fatigue. Muscle fatigue = inability of a muscle to maintain its strength of contraction or tension. When muscle activity is great, oxygen cannot be supplied to the muscles fast enough and lactic acid is produced.

Oxygen debt Oxygen is needed for muscle contraction. When muscle activity is great, there is not enough oxygen for things to happen normally. After exercise has stopped, extra oxygen is needed to get things back to normal. The additional oxygen that must be taken into the body after vigorous exercise to restore all systems to normal is called oxygen debt.

Muscle tone A sustained partial contraction of portions of a skeletal muscle in response to activation of stretch receptors results in muscle tone. Tone is essential for maintaining posture.

Common muscle disorders Atrophy = wasting away of muscle due to lack of use.

Hypertrophy Muscle hypertrophy = an increase in the size of the muscle cells.

Muscle Strain A muscle strain is a muscle tear. Symptoms = pain and swelling Remember the word RICE if you have an injury. R = rest I = ice C = compress E = elevate

Muscle spasm A muscle spasm is a sustained contraction of a muscle. These muscle contractions are involuntary. Spasms/Cramps Massage techniques

Myalgia Myalgia = muscle pain.

Tendonitis Tendons hold muscle to bones. Tendonitis is inflammation of a tendon. Inflammation = swelling and redness.

Muscular Dystrophies = muscle destroying diseases Dystrophy = degeneration. The most common form is Duchenne muscular dystrophy (DMD). Muscular dystrophies are due to genetic defects. This defect is usually X-linked recessive.

The End