3Characteristics of muscles Muscle cells are elongated (muscle cell = muscle fiber)Contraction of muscles is due to the movement of microfilamentsAll muscles share some terminologyPrefix myo refers to musclePrefix mys refers to musclePrefix sarco refers to flesh
4Skeletal muscle Cardiac muscle Smooth muscle The Muscular system Muscles are responsible for all types of body movementThree basic muscle types are found in the bodySkeletal muscleCardiac muscleSmooth muscle
5Skeletal muscle Most are attached by tendons to bones Cells are multinucleateStriated – have visible bandingVoluntary – subject to conscious controlCells are surrounded and bundled by connective tissueSites of muscle attachmentBonesCartilagesConnective tissue coverings
6Smooth muscleHas no striationsSpindle-shaped cellsSingle nucleusInvoluntary – no conscious controlFound mainly in the walls of hollow organs
7Cardiac Muscle Has striations Usually has a single nucleus Joined to another muscle cell at an intercalated discInvoluntaryFound only in the heart
8Produce movement Maintain posture Stabilize joints Generate heat Functions of musclesProduce movementMaintain postureStabilize jointsGenerate heat
9Properties of skeletal muscle activity Irritability – ability to receive and respond to a stimulusContractility – ability to shorten when an adequate stimulus is receivedSkeletal muscles must be stimulated by a nerve to contract
11Nerve stimulus to muscles Motor unitOne neuronMuscle cells stimulated by that neuron
12Nerve stimulus to muscles Neuromuscular junctions – association site of nerve and muscleSynaptic cleft – gap between nerve and muscleNerve and muscle do not make contactArea between nerve and muscle is filled with interstitial fluidSodium rushing into the cell generates an action potentialOnce started, muscle contraction cannot be stopped
14Contraction of a skeletal muscle Muscle fiber contraction is “all or none”Within a skeletal muscle, not all fibers may be stimulated during the same intervalDifferent combinations of muscle fiber contractions may give differing responsesGraded responses – different degrees of skeletal muscle shortening
15Single, brief contraction Not a normal muscle function TwitchSingle, brief contractionNot a normal muscle functionTetanus (summing of contractions)One contraction is immediately followed by anotherThe muscle does not completely return to a resting stateThe effects are added
16Muscle response to strong stimuli Muscle force depends upon the number of fibers stimulatedMore fibers contracting results in greater muscle tensionMuscle can continue to contract unless they run out of energy
18Energy for muscle contraction Initially, muscles used stored ATP for energyBonds of ATP are broken to release energyOnly 4-6 seconds worth of ATP is stored by musclesAfter this initial time, other pathways must be utilized to produce ATP
19Aerobic RespirationSeries of metabolic pathways that occur in the mitochondriaGlucose is broken down to carbon dioxide and water, releasing energyThis is a slower reaction that requires continuous oxygen
20Anaerobic Respiration Reaction that breaks down glucose without oxygenGlucose is broken down to pyruvic acid to produce some ATPPyruvic acid is converted to lactic acidThis reaction is not as efficient, but is fastHuge amounts of glucose are neededLactic acid produces muscle fatigue
21Muscle fatigue and oxygen debt When a muscle is fatigued, it is unable to contractThe common reason for muscle fatigue is oxygen debtOxygen must be “repaid” to tissue to remove oxygen debtOxygen is required to get rid of accumulated lactic acidIncreasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less
22Types of muscle contractions Isotonic contractionsMyofilaments are able to slide past each other during contractionsThe muscle shortensIsometric contractionsTension in the muscles increasesThe muscle is unable to shorten
23Muscle tone Some fibers are contracted even in a relaxed muscle Different fibers contract at different times to provide muscle toneThe process of stimulating various fibers is under involuntary control
25Abnormal Muscle Tone Cramps and spasms are conditions of the muscles Spasticity, flaccidity and paralysis are conditions of the muscles usually caused by an underlying neurological injury or disease.
26CRAMPSCramps - A cramp is an involuntary and forcibly contracted muscle that does not relax.Cramps can affect any muscle under your voluntary control (skeletal muscle).Muscles that span two joints are most prone to cramping.Cramps can involve part or all of a muscle, or several muscles in a group.
27CRAMPS The most commonly affected muscle groups are: Back of lower leg/calf (gastrocnemius).Back of thigh (hamstrings).Front of thigh (quadriceps).The exact cause of muscle cramps is unknown (idiopathic)Factors may be exercising or working in intense heat, dehydration and depletion of salt and minerals (electrolytes).
28CRAMPSTreatment and prevention Cramps usually go away on their own without seeing a doctor. Self-care:Stop doing whatever activity triggered the cramp.Gently stretch and massage the cramping muscle, holding it in stretched position until the cramp stops.Apply heat to tense/tight muscles, or cold to sore/tender muscles.
29SPASMSA charley horse is the common name for a muscle spasm, particularly in the leg. Muscle spasms can occur in any muscle in the body. When a muscle is in spasm, it contracts involuntarily and does not relax.Muscle spasms commonly occur when a muscle is over-used or injured. The muscle may keep firing small contractions. It may be that nerves working with the muscle become irritated.
30SPASMSAt the first sign of a muscle spasm, stop your activity and try stretching and massaging the affected muscle. Heat will relax the muscle at first, although ice may be helpful after the initial spasm and pain has improved.
31SPASTICITYSpasticity: A state of increased tone of a muscle (and an increase in the deep tendon reflexes). For example, with spasticity of the legs (spastic paraplegia) there is an increase in tone of the leg muscles so they feel tight and rigid and the knee jerk reflex is exaggerated. It may interfere with gait, movement and speech. Spasticity is caused by neurological injuries and diseases.
32FLACCIDITYMuscle Flaccidity: Weak and soft muscles with decreased resistance to movement, increased mobility and greater than normal range of movements. Flaccidity is caused by neurological injuries and diseases.
33PARALYSISParalysis is the complete loss of muscle function for one or more muscle groups. Paralysis often includes loss of feeling in the affected area. Paralysis is caused by neurological injuries and diseases.
35SPRAINS A sprain is an injury to a ligament The ligaments can be injured by being stretched too far from their normal position.The most common symptoms of a sprain are: pain, swelling, and bruising of the affected joint. Symptoms will vary with the intensity of the sprain or strain.
36STRAINS A strain is an injury to a muscle or tendon. Strains are caused by pulling too far on a muscle, or by pulling a muscle in one direction while it is contracting in the other.Strains can also be caused by chronic activities that develop an overstretching of the muscle fibers.
41Can Strains and Sprains be prevented? Unfortunately, not all sprains and strain can be prevented. Some helpful hints on how to avoid strains and sprains are listed below.Stretch before you exercise or workout.Wear proper shoes for the activity.Warm up properly before activities.Do not run on icy or uneven surfaces.
42RUPTURED TENDONSA tendon is the fibrous tissue that attaches muscle to bone in the human body.The forces applied to a tendon may be more than 5 times your body weight.In some rare instances, tendons can snap or rupture.Ruptured tendons can be treated either surgically or medically depending on the severity of the rupture.
43RUPTURED TENDONSThe 4 most common areas of tendon rupture are as follows:QuadricepsAchillesRotator cuffBiceps
44Ruptured Tendon Symptoms A snap or pop you hear or feelSevere painRapid or immediate bruisingMarked weaknessInability to use the affected arm or legInability to move the area involvedInability to bear weightDeformity of the area
51PatellarTendon Disorders Patellar Tendonitis (jumper’s knee)Inflammation of the patellar tendonPatella-Femoral SyndromeIrritation on the underside of the patellaCan lead to softening or loss of the underside cartilage liningOsgood-Schlatter DiseaseIrritation where the patella tendon inserts on the tibiaMostly occurs in boys during a growth spurt
52Muscles and body movement Movement is attained due to a muscle moving an attached boneMuscles are attached to at least two pointsOrigin: attachment to an immoveable boneInsertion: attachment to a movable bone
53How to describe how muscles are used in motion Prime mover: muscle with the major responsibility for a certain movementAntagonist: muscle that opposes or reverses a prime moverSynergist: muscle that aids a prime mover in a movement and helps prevent rotationFixator: stabilizes the origin of a prime mover