The Muscular System

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

13. 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

14. 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

15. 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

16. 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

17. 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

18. The Nerve Stimulus and Action Potential

19. 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)

20. 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

21. 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

22. 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.

23. 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

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

26. 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

28. 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”)

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

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

34. 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

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

38. 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

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

42. 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)

43. (d) Circular a) Convergent

49. Muscles of the shoulder

50. Muscles of the shoulder