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The Muscular System The Muscular System
Anatomy & Physiology IChapter 8
Types of MuscleTypes of Muscle
SmoothCardiacSkeletal
Smooth MuscleSmooth MuscleMakes up walls of hollow body organs (digestive tract, blood vessel wall), respiratory passageways, uterus, irisInvoluntary movementCell structure
◦Tapered ends
◦Single, central nucleus
◦No visible bands (striations)
Stimulated by nerve impulses, hormones, stretching
Cardiac MuscleCardiac MuscleMakes up wall of heartInvoluntary movementCell structure
◦Branching interconnections◦Single, central nucleus◦Striated◦Membranes are intercalated disks
Stimulated by electrical impulses, nervous stimuli, hormones
Skeletal MuscleSkeletal MuscleAttached to bones, muscles, or skinVoluntary movementCell structure
◦Long and cylindrical◦Multiple nuclei per cell◦Heavily striated
Stimulated by nervous systemNumber of individual skeletal muscles in the body: 600+
The Muscular SystemThe Muscular System
Skeletal muscle has three primary functions Skeletal movement Posture maintenance
◦ muscles provided a steady partial contraction (muscle tone) of muscles of the thigh, abdomin, back, neck and shoulders
Heat generation ◦ heat is a natural by-product of muscle cell metabolism
Structure of a MuscleStructure of a MuscleMuscle Fiber - one muscle cellFascicles - bundles of muscle fibers
Structure of a Muscle: Structure of a Muscle: Connective Tissue Connective Tissue ComponentsComponentsEndomysium – deep layer of connective tissue surrounding indvidual muscle fibersPerimysium – connective tissue surrounding each fascicleEpimysium (deep fascia) – connective tissue sheath enclosing an entire musclethe endomysium, perimysium and epimysium merge to form tendonsTendon – the band of connective tissue that connect muscle to bone
SarcoplasmSarcolemma
Openings intotransverse tubules
Sarcoplasmicreticulum
Mitochondria
Myofibrils
Myofilaments
A band
I band
Z disc
Nucleus
Triad:Terminal cisternaeTransverse tubule
Musclefiber
Structure of a Skeletal Structure of a Skeletal Muscle FiberMuscle Fiber
(A)Structure of a muscle showing the tendon that attaches it to a bone.
(B)Muscle tissue seen under a microscope. Portions of several fascicles are shown with connective tissue coverings.
ZOOMING IN • What is the innermost layer of connective tissue in a muscle? • What layer of connective tissue surrounds a fascicle of muscle fibers?
Structure Of A Skeletal MuscleStructure Of A Skeletal Muscle
Muscle Cells in ActionMuscle Cells in ActionMotor unit is a single neuron and all the muscle fibers it
Skeletal muscle contraction requires stimulation by a neuron
◦Paralysis occurs when the damaged nervous system can’t get a signal to the muscles
Neuromuscular junction (NMJ) – the point of contact between a nerve fiber (axon) and a muscle fiber.
Neuromuscular Junction Neuromuscular Junction (NMJ)(NMJ)Neurotransmitter – chemical released
from neurons◦ Acetylcholine (Ach) is the neurotransmitter
released at the NMJ Synaptic cleft – tiny space between
two cells involved in a synapseReceptors – specialized structures
(on the muscle cell membranes) that can be excited by a stimulus
Motor end plate – muscle cell membrane that contains receptors
(A)The branched end of a motor neuron makes contact with the membrane of a muscle fiber (cell).
(B)Enlarged view of the NMJ showing release of neurotransmitter acetylcholine (Ach) into the synaptic cleft.
(C)Acetylcholine attaches to receptors in the motor end plate, whose folds increase surface area.
(D)Electron microscope photograph of the neuromuscular junction.
Neuromuscular Junction Neuromuscular Junction (NMJ)(NMJ)
Properties of Muscle TissueProperties of Muscle TissueExcitability (ability to respond to stimuli)
◦Action potential – spreading wave of electrical current
Contractility (ability to shorten when stimulated)
◦Actin – thin protein filament in muscle cells (light)
◦Myosin – thick protein filament in muscle cells (dark) Striations result from the alternating bundles of actin
(light) and myosin (dark) filaments Crossbridge – attachment between myosin head and
actin
◦Sarcomere – contracting subunit of skeletal muscle
(A)Muscle is relaxed and there is no contact between the actin and myosin filaments.
(B)Cross-bridges form and the actin filaments are moved closer together as the muscle fiber contracts.
(C)The cross-bridges return to their original position and attach to new sites to prepare for another pull on the actin filaments and further contraction.
ZOOMING IN • Do the actin or myosin filaments change in length as contraction proceeds?
Sliding Filament Mechanism of Sliding Filament Mechanism of Skeletal Muscle ContractionSkeletal Muscle Contraction
The Role of CalciumThe Role of CalciumCalcium
Is released when nerve fiber stimulates muscle cell
Attaches to proteins blocking receptor sites
Allows cross-bridges to form between actin and myosin
Returns to endoplasmic reticulum (ER), which is called “sarcoplasmic reticulum” in muscle cells.
Energy SourcesEnergy SourcesMuscle contraction requires energy (ATP), oxidized in muscle cells fromOxygenGlucose or other usable nutrient
Compounds in muscle cells that store oxygen, energy, or nutrients Myoglobin – stores oxygenGlycogen – stores glucoseCreatine phosphate – stores energy; can be used to make ATP
Oxygen ConsumptionOxygen ConsumptionAerobic glucose metabolism – cellular production of ATP in the presence of adequate oxygenAnaerobic glucose metabolism – cellular production of ATP in the presence of low, inadequate oxygen
◦Inefficient production of ATP◦Lactic acid accumulation◦Oxygen debt – rapid breathing after
exercise; replenishes oxygen stores; rid cells of lactic acid
◦Recovery oxygen consumption – the period after exercise when extra oxygen is needed
Effects of ExerciseEffects of ExerciseImproved balance, joint flexibilityIncrease in muscle size (hypertrophy)Improvements in muscle tissueVasodilationStrengthened heart muscleImproved breathing and respiratory efficiencyWeight controlStronger bones
Types of Muscle Types of Muscle ContractionsContractions
Muscle Tone (Tonus) – the normal state of balanced tension or partial contraction while a muscle is in a passive state; constant state of readiness for actionIsotonic ◦No change in tension ◦Muscle length shortens ◦Movement
Isometric◦Great increase in tension◦Muscle length unchanged◦No movement
Muscle shortens,tension remains
constant
Movement
Movement
Muscle developstension but does
not shorten
No movement
Muscle lengthenswhile maintaining
tension
(a) Isometric contraction (b) Isotonic concentric contraction (c) Isotonic eccentric contraction
Isometric and Isotonic ContractionsIsometric and Isotonic Contractions
The Mechanics of Muscle The Mechanics of Muscle MovementMovement
Tendons attach muscles to bonesOrigin—attached to more fixed part of skeletonInsertion—attached to more moveable part of skeleton
Muscle Origins and Muscle Origins and InsertionsInsertions
Origin◦ bony attachment at
stationary end of muscle
Belly◦ thicker, middle region
of muscle between origin and insertion
Insertion◦ bony attachment to
mobile end of muscle
Scapula
Bellies
RadiusInsertion
Humerus
UlnaInsertion
Origins Origins
Long head
Extensors:
Lateral head
Flexors:Biceps brachii
Brachialis
Triceps brachii
action – the effects produced by a muscle
◦to produce or prevent movement prime mover (agonist) - muscle that
produces most of force during a joint actionsynergist - muscle that aids the prime
mover
◦stabilizes the nearby joint
◦modifies the direction of movement antagonist - opposes the prime mover
◦preventing excessive movement and injury
Muscles Work TogetherMuscles Work TogetherMuscles Work TogetherMuscles Work Together
Muscle Actions Across Muscle Actions Across ElbowElbow
prime mover
- brachialissynergist
- biceps brachii
antagonist - triceps brachii
Scapula
Bellies
RadiusInsertion
Humerus
UlnaInsertion
Origins Origins
Extensors:
Lateral head
Flexors:Biceps brachii
BrachialisLong headTriceps brachii
Skeletal Muscle GroupsSkeletal Muscle Groups
Characteristics for naming muscles (often combined)LocationSizeShapeDirection of fibersNumber of heads (attachment points)Action
Associated structure is labeled in parentheses.
Superficial Muscles Superficial Muscles (anterior view)(anterior view)
Associated structures are labeled in parentheses.
Superficial Muscles (posterior Superficial Muscles (posterior view)view)
Muscles of the HeadMuscles of the Head
Facial expression (orbicularis) muscles◦Orbicularis oculi◦Orbicularis oris◦Levator palpebrae superioris◦Buccinator
Mastication (chewing) muscles◦Temporalis ◦Masseter ◦Intrinsic ◦Extrinsic
Associated structure is labeled in parentheses. ZOOMING IN • Which of the muscles in this illustration is named for a bone it is near?
Muscles of the Muscles of the Head Head
Muscles of the NeckMuscles of the Neck
Are ribbonlikeExtend up, down, or obliquelyExtend in several layers in a complex mannerMost common is sternocleidomastoid
Muscles of the Upper Muscles of the Upper ExtremitiesExtremitiesPosition the shoulderMove the armMove the forearm and hand
Muscles That Move the Muscles That Move the Shoulder and ArmShoulder and Arm
TrapeziusLatissimus dorsiPectoralis majorSerratus anteriorDeltoidRotator cuff
◦Supraspinatus◦Infraspinatus◦Teres minor◦Subscapularis
Muscles That Move the Muscles That Move the Forearm and HandForearm and HandBrachialisBiceps brachiiBrachioradialisTriceps brachiiFlexor carpiExtensor carpiFlexor digitorumExtensor digitorum
Muscles That Move The Forearm & HandMuscles That Move The Forearm & Hand
Muscles of the TrunkMuscles of the Trunk
Breathing muscles
Abdominal muscles
Pelvic floor muscles
Deep back muscles
Muscles of RespirationMuscles of Respiration
DiaphragmIntercostal muscles
Associated structures are also shown.
Muscles of Muscles of Respiration Respiration
Muscles of the Abdomen Muscles of the Abdomen and Pelvisand Pelvis
External obliqueInternal obliqueTransversus abdominisRectus abdominisLevator ani
Surface tissue is removed on the right side to show deeper muscles.
Associated structures are labeled in parentheses.
Muscles of the abdominal Muscles of the abdominal wallwall
Associated structures are labeled in parentheses.
Muscles of the female perineum (pelvic floor)Muscles of the female perineum (pelvic floor)
Deep Muscles of the BackDeep Muscles of the Back
Erector spinaeDeeper muscles in the lumbar area
Muscles of the Lower Muscles of the Lower ExtremitiesExtremities
Among the longest and strongest in the bodySpecialized for locomotion and balance
Muscles That Move the Thigh Muscles That Move the Thigh and Legand Leg
Gluteus maximusGluteus mediusIliopsoasAdductorsSartoriusIliotibial (IT) tractHamstrings
Associated structures are labeled in parentheses.
Muscles of the ThighMuscles of the Thigh
Muscles That Move the Muscles That Move the FootFootGastrocnemius
Achilles tendon
Soleus
Tibialis anterior
Peroneus longus
Flexor and extensor muscles
Associated structures are labeled in parentheses
Muscles That Move The FootMuscles That Move The Foot
Effects of Aging on MusclesEffects of Aging on Muscles
Beginning at about age 40
Gradual loss of muscle cells
Loss of power
Tendency to flex hips and knees
Decrease in height
Muscular DisordersMuscular Disorders
Spasms
◦Colic
◦Seizure or convulsion
Cramps
Strains
Sprains
Atrophy
Diseases of MusclesDiseases of MusclesMuscular dystrophy
Myasthenia gravis
Myalgia
Myositis
Fibrositis
Fibromyositis
Fibromyalgia syndrome (FMS)
Disorders of Associated Disorders of Associated StructuresStructuresBursitis – inflammation of a bursa
Bunions - unnatural, bony hump that forms at the base of the big toe
Tendinitis - inflammation in or around a tendon
Tenosynovitis – inflammation of the lubricating sheath surrounding tendons.
Shin Splints – pain most likely caused by repeated stress on the shin bone (tibia) and the tissue that connects the muscle to the tibia.
Carpal tunnel syndrome - caused by compression of peripheral nerves affecting one or both hands. C
haracterized by a sensation of numbness, tingling, burning and/or pain in the hand and wrist
End of PresentationEnd of Presentation