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The Muscular System

The Muscular System. Mrs. Ashley. Functions of the Muscular System. Movement-responsible for all types of body movement both voluntary and involuntary Add in digestion Pump blood Supporting soft tissues in body cavities Maintaining body temperature Guarding entrances and exits to body.

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The Muscular System

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  1. The Muscular System Mrs. Ashley

  2. Functions of the Muscular System • Movement-responsible for all types of body movement both voluntary and involuntary • Add in digestion • Pump blood • Supporting soft tissues in body cavities • Maintaining body temperature • Guarding entrances and exits to body

  3. Three Types of Muscles • Skeletal Muscles • Cardiac Muscles • Smooth Muscles

  4. Comparison of Skeletal, Cardiac, and Smooth Muscles

  5. Comparison of Skeletal, Cardiac, and Smooth Muscles

  6. Characteristics of Muscles • Skeletal and smooth muscle cells are elongated (muscle cell = muscle fiber) • Contraction of muscles is due to the movement of microfilaments • All muscles share some terminology • Prefixes myo and mys refer to “muscle” • Prefix sarco refers to “flesh”

  7. Skeletal Muscles • Produce movement • Maintain posture • Stabilize joints • Generate heat • Skeletal muscle tissue • Associated with & attached to the skeleton • Under our conscious (voluntary) control • Microscopically the tissue appears striated • Cells are long, cylindrical & multinucleate

  8. Sites of Muscle Attachments • Sites of muscle attachment • Bones • Cartilages • Connective tissue coverings

  9. Microanatomy of a Muscle Fiber (cell)

  10. Microanatomy of a Muscle Fiber (cell)

  11. Cardiac Muscle Cardiac muscle tissue • Makes up myocardium of heart • Unconsciously (involuntarily) controlled • Microscopically appears striated • Cells are short, branching & have a single nucleus • Cells connect to each other at intercalated discs

  12. Smooth Muscle • Smooth (visceral) muscle tissue • Makes up walls of organs & blood vessels • Tissue is non-striated & involuntary • Cells are short, spindle-shaped & have a single nucleus • Tissue is extremely extensible, while still retaining ability to contract

  13. Physiology of skeletal muscle contraction • Skeletal muscles require stimulation from the nervous system in order to contract • Motor neuronsare the cells that cause muscle fibers to contract

  14. Stimulation and Contraction of Single Skeletal Muscle Cells • Excitability (also called responsiveness or irritability)—ability to receive and respond to a stimulus • Contractility—ability to shorten when an adequate stimulus is received • Extensibility—ability of muscle cells to be stretched • Elasticity—ability to recoil and resume resting length after stretching

  15. The Nerve Stimulus and Action Potential • Skeletal muscles must be stimulated by a motor neuron (nerve cell) to contract • Motor unit—one motor neuron and all the skeletal muscle cells stimulated by that neuron

  16. Control of Muscles • Skeletal muscles are made up of thousands of muscle fibers • A single motor neuron may directly control a few fibers within a muscle, or hundreds to thousands of muscle fibers • All of the muscle fibers controlled by a single motor neuron constitute a motor unit

  17. The Nerve Stimulus and Action Potential

  18. The size of the motor unit determines how fine the control of movement can be – • small motor units  precise control (e.g. eye muscles • large motor units gross control (e.g. leg muscles)

  19. Recruitmentis the ability to activate more motor units as more force (tension) needs to be generated • Hypertrophy – “stressing” a muscle (i.e. exercise) causes more myofilaments/myofibrils to be produced within muscle fibers; allows for more “cross bridges” resulting in more force (strength) as well as larger size • There are always some motor units active, even when at rest. This creates a resting tension known as muscle tone, which helps stabilize bones & joints, & prevents atrophy

  20. How Muscles Work • For muscles to create a movement, they can only pull, not push • Muscles in the body rarely work alone, & are usually arranged in groups surrounding a joint • A muscle that contracts to create the desired action is known as an agonist or prime mover • A muscle that helps the agonist is a synergist • A muscle that opposes the action of the agonist, therefore undoing the desired action is an antagonist

  21. Anatomy of the Muscular System • Origin • Muscle attachment that remains fixed • Insertion • Muscle attachment that moves • Action • What joint movement a muscle produces • i.e. flexion, extension, abduction, etc.

  22. Muscles and Body Movements • Movement is attained due to a muscle moving an attached bone • Muscles are attached to at least two points • Origin • Attachment to a moveable bone • Insertion • Attachment to an immovable bone

  23. Skeletal muscle movements • Flexion/extension • Abduction/adduction • Rotation – left/right; internal(medial)/external(lateral) • pronation/supination • Elevation/depression • Protraction/retraction • Dorsiflexion/plantarflexion • Inversion/eversion

  24. Types of Body Movements • Flexion • Decreases the angle of the joint • Brings two bones closer together • Typical of bending hinge joints like knee and elbow or ball-and-socket joints like the hip • Extension • Opposite of flexion • Increases angle between two bones • Typical of straightening the elbow or knee • Extension beyond 180° is hypertension

  25. Types of Body Movements • Rotation • Movement of a bone around its longitudinal axis • Common in ball-and-socket joints • Example is when you move atlas around the dens of axis (shake your head “no”)

  26. Types of Body Movements • Abduction • Movement of a limb away from the midline • Adduction • Opposite of abduction • Movement of a limb toward the midline

  27. Types of Body Movements • Circumduction • Combination of flexion, extension, abduction, and adduction • Common in ball-and-socket joints

  28. Types of Body Movements • Dorsiflexion • Lifting the foot so that the superior surface approaches the shin (toward the dorsum) • Plantar flexion • Depressing the foot (pointing the toes) • “Planting” the foot toward the sole

  29. Special Movements • Inversion • Turn sole of foot medially • Eversion • Turn sole of foot laterally

  30. Special Movements • Supination • Forearm rotates laterally so palm faces anteriorly • Radius and ulna are parallel • Pronation • Forearm rotates medially so palm faces posteriorly • Radius and ulna cross each other like an X

  31. Special Movements • Opposition • Move thumb to touch the tips of other fingers on the same hand

  32. Naming of Skeletal Muscles • By direction of muscle fibers • Example:Rectus (straight) • By relative size of the muscle • Example:Maximus (largest) • By location of the muscle • Example:Temporalis (temporal bone) • By number of origins • Example:Triceps (three heads) • By location of the muscle’s origin and insertion • Example:Sterno (on the sternum) • By shape of the muscle • Example:Deltoid (triangular) • By action of the muscle • Example:Flexor and extensor (flexes or extends a bone)

  33. (d) Circular a) Convergent

  34. Muscles of the shoulder

  35. Muscles of the shoulder

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