1. Anatomy & Physiology I Chapter 8
4/21/2017 2:11 AM
The Muscular System
Anatomy & Physiology I
Chapter 8
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2. Types of Muscle
Smooth
Cardiac
Skeletal

3. Smooth Muscle
Makes up walls of hollow body organs (digestive tract, blood vessel wall), respiratory passageways, uterus, iris
Involuntary movement
Cell structure
Tapered ends
Single, central nucleus
No visible bands (striations)
Stimulated by nerve impulses, hormones, stretching

4. Cardiac Muscle Makes up wall of heart Involuntary movement
Cell structure
Branching interconnections
Single, central nucleus
Striated
Membranes are intercalated disks
Stimulated by electrical impulses, nervous stimuli, hormones

5. Skeletal Muscle Attached to bones, muscles, or skin Voluntary movement
Cell structure
Long and cylindrical
Multiple nuclei per cell
Heavily striated
Stimulated by nervous system
Number of individual skeletal muscles in the body: 600+

6. The 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

7. Structure of a Muscle Muscle Fiber - one muscle cell
Fascicles - bundles of muscle fibers

8. Structure of a Muscle: Connective Tissue Components
Endomysium – deep layer of connective tissue surrounding indvidual muscle fibers
Perimysium – connective tissue surrounding each fascicle
Epimysium (deep fascia) – connective tissue sheath enclosing an entire muscle
the endomysium, perimysium and epimysium merge to form tendons
Tendon – the band of connective tissue that connect muscle to bone

9. Structure of a Skeletal Muscle Fiber
Nucleus
A band
I band
Z disc
Mitochondria
Openings into transverse tubules
Sarcoplasmic reticulum T
riad: T
erminal cisternae T
ransverse tubule
Myofibrils
Sarcolemma
Sarcoplasm
Myofilaments

10. Structure Of A Skeletal Muscle
Structure of a muscle showing the tendon that attaches it to a bone.
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?

11. Muscle Cells in Action
Motor 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.

12. Neuromuscular Junction (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 synapse
Receptors – specialized structures (on the muscle cell membranes) that can be excited by a stimulus
Motor end plate – muscle cell membrane that contains receptors

13. Neuromuscular Junction (NMJ)
The branched end of a motor neuron makes contact with the membrane of a muscle fiber (cell).
Enlarged view of the NMJ showing release of neurotransmitter acetylcholine (Ach) into the synaptic cleft.
Acetylcholine attaches to receptors in the motor end plate, whose folds increase surface area.
Electron microscope photograph of the neuromuscular junction.

14. Properties of Muscle Tissue
Excitability (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

15. Sliding Filament Mechanism of Skeletal Muscle Contraction
Muscle is relaxed and there is no contact between the actin and myosin filaments.
Cross-bridges form and the actin filaments are moved closer together as the muscle fiber contracts.
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?

16. The Role of Calcium Calcium
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.

17. Energy Sources
Muscle contraction requires energy (ATP), oxidized in muscle cells from
Oxygen
Glucose or other usable nutrient
Compounds in muscle cells that store oxygen, energy, or nutrients
Myoglobin – stores oxygen
Glycogen – stores glucose
Creatine phosphate – stores energy; can be used to make ATP

18. Oxygen Consumption
Aerobic glucose metabolism – cellular production of ATP in the presence of adequate oxygen
Anaerobic 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

19. Effects of Exercise Improved balance, joint flexibility
Increase in muscle size (hypertrophy)
Improvements in muscle tissue
Vasodilation
Strengthened heart muscle
Improved breathing and respiratory efficiency
Weight control
Stronger bones

20. Types of Muscle Contractions
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 action
Isotonic
No change in tension
Muscle length shortens
Movement
Isometric
Great increase in tension
Muscle length unchanged
No movement

21. Isometric and Isotonic Contractions
Muscle develops
tension but does
not shorten
Muscle shortens,
tension remains
constant
Muscle lengthens
while maintaining
tension
Movement
No movement
Movement
(a) Isometric contraction
(b) Isotonic concentric contraction
(c) Isotonic eccentric contraction

22. The Mechanics of Muscle Movement
Tendons attach muscles to bones
Origin—attached to more fixed part of skeleton
Insertion—attached to more moveable part of skeleton

23. Muscle Origins and Insertions
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
Origins
Origins
Humerus
Scapula
Bellies
Extensors:
Flexors:
Triceps brachii
Biceps brachii
Long head
Brachialis
Lateral head
Insertion
Radius
Insertion
Ulna

24. Muscles Work Together action – the effects produced by a muscle
to produce or prevent movement
prime mover (agonist) - muscle that produces most of force during a joint action
synergist - 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

25. Muscle Actions Across Elbow
prime mover - brachialis
synergist - biceps brachii
antagonist - triceps brachii
Origins
Origins
Humerus
Scapula
Bellies
Extensors:
Flexors:
Triceps brachii
Biceps brachii
Long head
Brachialis
Lateral head
Insertion
Radius
Insertion
Ulna

26. Skeletal Muscle Groups
Characteristics for naming muscles (often combined)
Location
Size
Shape
Direction of fibers
Number of heads (attachment points)
Action

27. Superficial Muscles (anterior view)
Associated structure is labeled in parentheses.

28. Superficial Muscles (posterior view)
Associated structures are labeled in parentheses.

29. Muscles of the Head Facial expression (orbicularis) muscles
Orbicularis oculi
Orbicularis oris
Levator palpebrae superioris
Buccinator
Mastication (chewing) muscles
Temporalis
Masseter
Intrinsic
Extrinsic

30. Muscles of the Head
Associated structure is labeled in parentheses. ZOOMING IN • Which of the muscles in this illustration is named for a bone it is near?

31. Muscles of the Neck Are ribbonlike Extend up, down, or obliquely
Extend in several layers in a complex manner
Most common is sternocleidomastoid

32. Muscles of the Upper Extremities
Position the shoulder
Move the arm
Move the forearm and hand

33. Muscles That Move the Shoulder and Arm
Trapezius
Latissimus dorsi
Pectoralis major
Serratus anterior
Deltoid
Rotator cuff
Supraspinatus
Infraspinatus
Teres minor
Subscapularis

34. Muscles That Move the Forearm and Hand
Brachialis
Biceps brachii
Brachioradialis
Triceps brachii
Flexor carpi
Extensor carpi
Flexor digitorum
Extensor digitorum

35. Muscles That Move The Forearm & Hand

36. Muscles of the Trunk Breathing muscles Abdominal muscles
Pelvic floor muscles
Deep back muscles

37. Muscles of Respiration
Diaphragm
Intercostal muscles

38. Muscles of Respiration
Associated structures are also shown.

39. Muscles of the Abdomen and Pelvis
External oblique
Internal oblique
Transversus abdominis
Rectus abdominis
Levator ani

40. Muscles of the abdominal wall
Surface tissue is removed on the right side to show deeper muscles. Associated structures are labeled in parentheses.

41. Muscles of the female perineum (pelvic floor)
Associated structures are labeled in parentheses.

42. Deep Muscles of the Back
Erector spinae
Deeper muscles in the lumbar area

43. Muscles of the Lower Extremities
Among the longest and strongest in the body
Specialized for locomotion and balance

44. Muscles That Move the Thigh and Leg
Gluteus maximus
Gluteus medius
Iliopsoas
Adductors
Sartorius
Iliotibial (IT) tract
Hamstrings

45. Associated structures are labeled in parentheses.
Muscles of the Thigh
Associated structures are labeled in parentheses.

46. Muscles That Move the Foot
Gastrocnemius
Achilles tendon
Soleus
Tibialis anterior
Peroneus longus
Flexor and extensor muscles

47. Muscles That Move The Foot
Associated structures are labeled in parentheses

48. Effects 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

49. Muscular Disorders Spasms Cramps Strains Sprains Atrophy Colic
Seizure or convulsion
Cramps
Strains
Sprains
Atrophy

50. Diseases of Muscles Muscular dystrophy Myasthenia gravis Myalgia
Myositis
Fibrositis
Fibromyositis
Fibromyalgia syndrome (FMS)

51. Disorders of Associated Structures
Bursitis – 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

52. End of Presentation