2Introduction 600 muscles that make up 40-45% of your body weight Made up of bundles of muscle fibers (long, slender cells) held together by connective tissueWhen stimulated by nerves they contract (become short and thick) which causes movement
3PropertiesExcitability-the ability to receive and respond to a stimulusContractility-the ability to shortenExtensibility-the ability to be stretchedElasticity-the ability to resume resting length after being stretchedAutomaticity-the ability of a muscle to contract without a nerve supply
4Functions Movement To hold the body erect/posture Locomotion/manipulationHeartbeatMoving substances through hollow organsTo hold the body erect/postureBody heat – 85% of body heatJoint stabilizationSome Internal organ protection
5Types of MusclesCardiac, Visceral/smooth, & Skeletal
6Types of Muscle Skeletal Smooth – unstriated – involuntary - visceral Found in hollow organs like - digestive tract, blood vessels, and ducts leading from glands.Purpose is to move fluids through these structuresCardiacMyocardiumLike striated muscle in appearance but like smooth muscle in function.
8Cardiac Muscle Forms walls of the heart Contracts to circulate the bloodStriated with lots of mitochondriaInvoluntaryEfferent nerves control the rate of contractionAfferent nerves sense pain, spasm, & stretchContracts at a steady rate, except for brief, rapid bursts
9Visceral/Smooth muscle Found in the internal organsWalls of hollow, visceral organsNo striationsInvoluntaryEfferent neurons are less importantAfferent nerves are concerned with pain, spasm, and stretchSteadies constant contractions, automaticity
10Skeletal Muscles 40% of the body Attaches to and cover the bony skeletonLongest fibersStriatedVoluntaryEfferent nerves send impulses for contractionAfferent nerves send message to inform brain of degree of contractionContracts rapidly, tires easily; tremendous power, adaptableCauses body movement
16Origin & InsertionWhen muscles attach to bones, one end becomes the origin and one end becomes the insertionOrigin – the end that does not move; usually proximal to insertion. Where the muscle begins.Insertion – the end that moves when muscle contracts. Where the muscle ends.
18Muscle Tone Steady partial contraction is present at all times State of tension when awakeState of readiness to act; enables muscles for immediate responseDoes not produce an active movementKeeps muscles firm and healthyStabilizes the jointsMaintains posture
19Muscle Tone continued Loss of muscle tone Can occur in severe illnesses such as paralysis & palsyWhen muscles are not used for a long period of time – atrophy, waste away (degeneration & loss of mass)Complete immobilization of muscle (complete bed rest or in a cast or loss of neural stimulation) – strength decreases 5% per day; paralysis=atrophy to ¼ the initial size; muscle tissue is replaced by fibrous connective tissue – muscle rehab is impossible; delayed with electrical stimulation
20Muscle Tone continuedLack of use can result in contracture (permanent contraction of the muscle due to spasm or paralysis)Severe tightening of a flexor muscleResults in bending of a jointFingers, wrists, and knees, as well as other joints can be affected
21Muscle Tone continued Muscle fatigue Muscle is unable to contractTension drops to zeroSpasm – sudden involuntary contraction of a muscleClonic – a spasm alternating with relaxationTonic – sustained
22Muscle Tone continued Tetanus – a smooth, sustained contraction Tetany – the result of low calciumIncreases the excitability of neuronsLoss of sensation, muscles twitching, convulsionsIf untreated-spasms of the larynx, respiratory paralysis, and death can occur
23Characteristics Kinesiology Muscles work in antagonistic pairs Biceps brachii – elbow flexionTriceps brachii – elbow extensionContraction and relaxationMuscle innervationneuromuscular