Presentation on theme: "Physiology I (PHL 215) Physiology of Muscles Dr. Gamal Gabr."— Presentation transcript:
1 Physiology I (PHL 215)Physiology of MusclesDr. Gamal Gabr
2 Muscular System Functions Body movement (Locomotion)Maintenance of postureRespirationDiaphragm and intercostals contractionsCommunication (Verbal and Facial)Constriction of organs and vesselsHeart beatProduction of body heat (Thermogenesis)
4 Muscle cell structures not found in other cells Myofibrils: bundles of very fine fibersThick and thin myofilaments: very fine fibers that make up myofibrilsSarcomere: segment of myofibril between two Z lines; contractile unitT tubules: transmit electrical impulses through cell
6 Thin filaments: actin, tropomyosin, troponin Myofilaments4 protein molecules that make up myofilaments: Myosin, actin, tropomyosin, troponinThin filaments: actin, tropomyosin, troponinThick filaments: mostly myosin
7 Properties of MuscleExcitability: Capacity of muscle to respond to a stimulus Contractility: Ability of a muscle to shorten and generate pulling force Extensibility: Ability stretches when pulled Elasticity: Ability to return to original shape and length after contraction or extension
8 Muscle structure Connective Tissue Sheaths Connective Tissue (CT) of a MuscleEpimysium: Dense regular CT surrounding entire muscleSeparates muscle from surrounding tissues and organsPerimysium: Collagen and elastic fibers surrounding a group of muscle fibers called a fascicleContains blood vessels and nervesEndomysium: Loose CT that surrounds individual muscle fibersAlso contains blood vessels and nervesCollagen fibers of all 3 layers come together at each end of muscle to form a tendon or aponeurosis.
10 Motor neuronsStimulate muscle fibers to contractNeuron axons branch so that each muscle fiber (muscle cell) is innervatedForm a neuromuscular junctionCapillary beds surround muscle fibersMuscles require large amount of energyExtensive vascular network delivers necessary oxygen and nutrients and carries away metabolic waste produced by muscle fibers
11 Energy for Muscle Contractions ATP: adenosine triphosphateCP: creatine phosphateGlucose & OxygenGlucose stored in form of glycogen in muscleExcess oxygen molecules in sarcoplasm bound to myoglobin
12 Anaerobic respiration Allows body to avoid use of oxygen in short termProduces lactic acidAccumulation of lactic acid in muscles causes burning sensation
13 Types of Muscle Skeletal Attached to bones Makes up 40% of body weight (Women’s skeletal muscle makes up 36% of their body mass, Men’s skeletal muscle makes up 42% of their body mass)Responsible for locomotion, facial expressions, posture, respiratory movements, other types of body movementVoluntary in action; controlled by somatic motor neuronsSmoothIn the walls of hollow organs, blood vessels, eye, glands, uterus, skinFunctions: propel urine, mix food in digestive tract, regulating blood flowControlled involuntarily by endocrine and autonomic nervous systemsCardiacHeart: major source of movement of blood
14 Basic Features of a Skeletal Muscle Muscle attachmentsMost skeletal muscles run from one bone to anotherOne bone will move – other bone remains fixedOrigin – less movable attachmentInsertion – more movable attachmentMuscles attach to origins and insertions by connective tissueFleshy attachments – connective tissue fibers are shortIndirect attachments – connective tissue forms a tendon
15 Skeletal Muscle Structure Composed of muscle cells (fibers), connective tissue, blood vessels, nervesFibers are long, cylindrical, and multinucleatedTend to be smaller diameter in small muscles and larger in large muscles. 1 mm - 4 cm in lengthStriated appearanceNuclei are peripherally located
16 Muscle Fiber Anatomy Sarcolemma - cell membrane Surrounds the Sarcoplasm (cytoplasm of fiber)Punctuated by openings called the transverse tubules (T-tubules)Myofibrils -cylindrical structures within muscle fiberAre bundles of protein filaments (=myofilaments)Two types of myofilamentsActin filaments (thin filaments)Myosin filaments (thick filaments)When myofibril shortens, muscle shortens (contracts)
17 Sarcoplasmic Reticulum (SR) SR is an elaborate, smooth endoplasmic reticulumRuns longitudinally and surrounds each myofibrilSR stores Ca++ when muscle not contractingWhen stimulated, calcium released into sarcoplasmSR membrane has Ca++ pumps that function to pump Ca++ out of the sarcoplasm back into the SR after contraction
18 Smooth Muscle Cells are not striated Fibers smaller than those in skeletal muscleSpindle-shaped; single, central nucleusMore actin than myosinNo sarcomeresNot arranged as symmetrically as in skeletal muscle, thus no striations.
19 Smooth MuscleGrouped into sheets in walls of hollow organsLongitudinal layer: muscle fibers run parallel to organ’s long axisCircular layer: muscle fibers run around circumference of the organBoth layers participate in peristalsis
20 Cardiac MuscleFound only in heart where it forms a thick layer called the myocardiumStriated fibers that branchEach cell usually has one centrally-located nucleusFibers joined by intercalated disks
21 Disorders of Muscle Tissue Muscle FatigueLack of oxygen causes ATP deficitLactic acid builds up from anaerobic respirationMuscle Atrophya decrease in the mass of the muscleWeakening and shrinking of a muscleMay be causedImmobilizationLoss of neural stimulation
22 Disorders of Muscle Tissue Muscle HypertrophyEnlargement of a muscleMore capillariesMore mitochondriaCaused byStrenuous exerciseSteroid hormonesMuscle TonusTightness of a muscleSome fibers always contracted
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