Muscle Facts The average human heart will beat 3,000 million times in its lifetime and pump 48 million gallons of blood. Muscle is about 15% more dense than fat. The tongue consists of 16 different muscles. The masseter is the strongest muscle in the human body. It can exert as much as 975lb of force. The human heart creates enough pressure when it pumps blood, that it could squirt blood 30 feet. The smallest muscle in the body is the stapedius attached to the stapes in the ear. It takes the interaction of 72 different muscles to produce human speech.

Why Muscles to pull against bones to produce movement. to maintain posture to stabilize joints to generate heat (mitochondria) to pump blood through the body (heart muscle).

3 Types of Muscle Tissue Involuntary Voluntary Involuntary

Skeletal Muscle Tissue Mostly voluntary (except-spinal, balance) Striated due to pattern of sarcomeres Multinucleate Attach to bones via tendons Found in appendicular skeleton, and spine Fast twitch-respond quickly to nerve impulses (like blinking) Slow twitch-respond slowly to nerve impulses Slow twitch muscle fibres are good for endurance activities like long distance running or cycling. They can work for a long time without getting tired. Fast twitch muscles are good for rapid movements like jumping to catch a ball or sprinting for the bus. They contract quickly, but get tired fast, as they consume lots of energy. Most of your muscles are made up of a mixture of both slow and fast twitch muscle fibres. But, your soleus muscle in your lower leg and muscles in your back involved in maintaining posture contain mainly slow twitch muscle fibres. And muscles that move your eyes are made up of fast twitch muscle fibres. Chickens have fast and slow twitch muscle, too. Dark meat, like in chicken legs, is mainly made up of slow twitch fibres. White meat, like in chicken wings and breasts, is largely made up of fast twitch muscle fibres. Chickens use their legs for walking and standing, which they do most of the time. This doesn't use much energy. They use their wings for brief bursts of flight. This requires lots of energy and the muscles involved tire very quickly. Muscles that contain a lot of slow twitch fibres are red, because they contain lots of blood vessels. Slow twitch muscle fibres rely on a rich supply of oxygenated blood as they use oxygen to produce energy for muscle contraction. Fast twitch muscle fibres don't use oxygen to make energy, so they don't need such a rich blood supply. This is why fast twitch muscles are lighter in colour than muscles that contain a lot of slow twitch muscle fibres. Fast twitch muscle fibres can produce small amounts of energy very quickly whereas slow twitch muscles can produce large amounts of energy slowly.

Smooth Muscle Tissue Found in walls of organs (peristalsis-moves food through digestive system) (vasoconstriction/vasodialtation-regulates diameter of blood vessels Involuntary-regulates by nerves and hormones. Single nuclei

Cardiac Muscle Tissue Found in heart only Striated Involuntary Multinucleate, many mitochondria per cell.

Gross Anatomy Skeletal Muscle

Origin and Insertion The origin of a muscle is a fixed bone for attachment. The insertion is the bone that the muscle moves when it contracts. The biceps and triceps are antagonistic muscles.

How Muscles Contract Voluntary muscle is stimulated by motor neurons (nerves). The point at which the nerve and muscle meet is the neuromuscular junction. Each branch of the neuron may stimulate a single muscle cell. Animation at http://entochem.tamu.edu/MuscleStrucContractswf/index.html

MYOSIN and ACTIN The motor neuron releases Ca++ which stimulates the myosin filaments. The myosin, like little hands, grabs onto the actin filaments pulling it to close, shortening the sarcomere. The contraction stops when the nervous system stops stimulating the muscle tissue. The myosin releases the actin. ALL or NOTHING If stimulated, the entire muscle fiber must contract. We use differing degrees of muscle when different number of muscle fibers are stimulated.

When a muscle contracts the Z-line shortens.

Frontalis-flexes forehead Orbicularis oculi-opens/closes the eye Temporalis pulls mandible up Orbicularis oris-lips Masseter-pulls mandible up Sternocleidomastoid-rotates head