Chapter 9 - The Muscular System

Fibers.

By converting chemical energy from food into mechanical energy

Three; skeletal, cardiac and smooth.

Skeletal muscle contraction

40-50% of the body weight

striated or voluntary muscle

It increases the efficiency of the heart muscle in pumping blood.

It comprises the bulk of the heart; branch frequently; characterized by intercalated disks

also known as non striated, involuntary or visceral muscle; lacks striations and appears smooth; found in walls of hollow visceral structures (i.e. digestive tract, blood vessels and ureters), contractions are involuntary.

single; tapered

All muscle cells specialize in contraction (shortening)

The origin of a muscle is its attachment to the more stationary bone. The insertion is the attachment to the more movable bone. When muscles contract, they pull on the more movable bone.

Each skeletal muscle is an organ composed daily of skeletal muscle cells and connective tissue; most skeletal muscles extend from one bone across a joint to another bone

tendons.

˜attachment to the bone that remains relatively stationary or fixed when movement at the joint occurs

˜point of attachment to the bone that moves when a muscle contracts

˜main part of the muscle

origin; insertion

˜tendons—strong cords of fibrous connective tissue; some tendons enclosed in synovial-lined tubes called tendon sheaths;tendons lubricated by synovial fluid;

Small, fluid-filled sacs between some tendons and the bones beneath them.

Bursaemake it easier for a tendon to slide over a bone when the muscle shortens

Thick myofilaments are formed from the protein myosin; thin myofilaments are composed of actin

composed of myofilaments and key players in the process of contraction

thin; sarcomere; shortening

overlapping; sarcomere; dark

The basic functional unit of muscle tissue; separated by dark bands - Z lines; has thick and thin myofilaments; contractile unit of the muscle

calcium and energy-rich ATP molecules

calcium

Muscles produce movement by pulling on bones. Contraction, or shortening, of the muscle pulls the insertion bone toward the origin bone. Movement occurs at the joint between the origin and insertion.

prime mover, synergist, and antagonist

muscle whose contraction is mainly responsible for producing a given movement

muscle whose contractions help the prime mover produce a given movement

muscle whose actions oppose the action of a prime mover in any given movement

Because skeletal muscles work in coordinated teams, not separately.

• Enables us to maintain body position
• Only a few muscle's fibers shorten at one time
• Tonic contractions produce no movement of body parts

• Good posture means that body parts are held in positions that favor best function
• skeletal muscle tone maintains posture by counteracting the pull of gravity

By the breakdown of ATP during contractions; survival depends on the body's ability to maintain a constant body temp

• fever - body temp too high 
• hypothermia - body temp too low

• muscle cells being repeatedly stimulated without adequate rest
• repeated muscular contraction depletes cellular ATP stores and outstrips the ability of the blood supply to replenish oxygen and nutrients

Reduced strength of muscle contraction

lactic acid

the metabolic effort required to burn excess lactic acid that may accumulate during prolonged periods of exercise

It is attempting to return the cells’ energy and oxygen reserves to pre-exercise levels.

skeletal system disorders, multiple sclerosis, brain hemorrhage, and spinal cord injury

motor neurons

acetylcholine [ACh]

The point of contact between a nerve ending and the muscle fiber it innervates

The combination of a motor neuron and the muscle cell or cells it innervates.

It is the minimal level of stimulation required to cause a muscle fiber to contract; once the threshold is reached a muscle fiber will contract completely, a response called all or none (individual muscle fibers not the whole muscle respond in this mode

Different motor units responding to different threshold stimuli permit a muscle as a whole to execute contractions of graded force.

quick, jerky responses to a stimulus; laboratory phenomena and do not play a significant role in normal muscle activity

˜sustained and steady muscular contractions caused by a series of stimuli bombarding a muscle in rapid succession

It is a contraction that produces movement at a joint. The muscle changes length, and the insertion end moves closer to the point of origin.

It is a muscle contraction that does not produce movement. It increases tension within a muscle but does not change the length of the muscle. (ex. pushing against a wall)

Isotonic contractions produce movement; isometric contractions increase tension within a muscle but do not change the length of the muscle.

The muscle lengthens

The muscle shortens

Some of the health benefits are: greatly improved muscle tone, better posture, more efficient heart and lung function, less fatigue, and looking and feeling better!

disuse atrophy, hypertrophy

• isometric exercises and weight lifting
• strength training increases the number of myofilaments not the number of muscle fibers

Strength training can produce muscle hypertrophy by contracting muscles against resistance. Endurance training, also called aerobic training, increases a muscle’s ability to sustain moderate exercise over a long period without muscle hypertrophy. It also allows a more efficient delivery of oxygen and nutrients to a muscle via increased blood flow.

˜movement that decreases the angle between two bones at their joint: bending

˜movement that increases the angle between two bones at their joint: straightening

When the lower arm is flexed at the elbow, the biceps brachiicontracts while its antagonist, the triceps brachii, relaxes.

When the lower arm is extended, the biceps brachiirelaxes while the triceps brachiicontracts.

when the leg flexes at the knee, muscles of the hamstring group contract while their antagonists in the quadriceps femorisgroup relax.

When the leg extends, the hamstring muscles relax while the quadriceps femorismuscle contracts.

Movement of a part away from the midline of the body

Movement of a part toward the midline of the body

Movement around a longitudinal axis

flexion: bending elbow or knee; extension: straightening elbow or knee; abduction: lowering arm; rotation: shaking head “no”

˜hand positions that result from rotation of the forearm; supination results in a hand position with the palm turned to the anterior position; pronation occurs when the palm faces posterior

supine, which means lying face up; prone, which means lying face down

elevation of the dorsum or top of the foot

Øthe bottom of the foot is directed downward

Standing on your toes

Orbicularisorisis the kissing muscle, and zygomaticusis the smiling muscle.

• orbicularis oculi
• orbicularis oris
• zygomaticus

• mastication muscles are amongst the strongest muscles in the body
• masseter and temporal
• large muscles of mastication stretch from the upper skull to the lower jaw.
• these powerful muscles produce chewing movements

It flexes the head

It elevates the shoulders and extends head

Around the eyes, nose and mouth.

The neck muscles connect the skull to the trunk of the body, rotating the head or bending the neck

• flexes the upper arm
• upper extremity is attached to the thorax by the pectoralis major

extends upper arm

abducts the upper arm

flexes the forearm

extends the forearm

• rectus abdominis (which flexes the spinal column)
• external oblique 
• internal oblique
• transversus abdominis

• intercostal muscles and the diaphragm
• they change the size of the chest during respiration

normally flexes the thigh, but it can flex the trunk if the thigh is fixed/immovable, as in sit-ups

extends the thigh

adduct thighs

• flex the leg
• semimembraneous 
• semitendinosus
• biceps femoris

• Extend the leg
• within the group: rectus femoris and vastus muscles

dorsiflexes the foot

• plantar flexes the foot
• toe dancer's muscle

flexes the foot

All muscle disorders; can range from mild to life threatening

• injury from overexertion or trauma 
• if injury is near a joint and involves ligament damage, it may be called a sprain

muscle pain

inflammation of muscle

inflammation of muscle and tendon

˜painful muscle spasms (involuntary twitches)

˜Crush injuries result from severe muscle trauma and may release cell contents that ultimately cause kidney failure

headaches and back pain

˜viral infection of motor nerves that ranges from mild to life threatening

A successful vaccination program has halted transmission of the disease.

It is still contracted in third world regions where the population has not been vaccinated, but it is becoming less and less of a threat.

It is a viral infection of the nerves that control skeletal muscle movement. It can cause paralysis that may progress to death because of the muscles affected

˜A group of genetic disorders characterized by muscle atrophy

• ˜Duchenne(pseudohypertrophic) muscular dystrophy (DMD) is the most common type
• Characterized by rapid progression of weakness and atrophy
• X-linked inherited disease, affecting mostly boys (b/c they only have one X chromosome)
• usually shows signs around the age of 3, getting much worse in the next 5 to 10 years

• An autoimmune muscle disease characterized by weakness and chronic fatigue
• A person in myasthenia crisis is in danger of dying from respiratory failure