1. The Muscular System

2. Functions of Muscle Tissue
Movement Facilitation
Thermogenesis
Postural Support
Regulation of Organ Volume
Pumps Blood (HEART)

3. Characteristics of Muscle Tissue
Contractility
ability to become short and thick while producing movement

4. Characteristics of Muscle Tissue
Extensibility
The ability of muscle tissue to be elongated or stretched
Smooth muscle

5. Characteristics of Muscle Tissue
Elasticity
ability to return to its normal resting length
Skeletal: from being shorter
Smooth: from being extended

6. Characteristics of Muscle Tissue
Excitability (irritability)
ability to receive and respond to a stimulus

7. Cardiac Muscle Forms heart wall (myocardium) Striated Involuntary
Fibers quadrangular & branching
Centrally located nucleus
Sarcolemmas connected by intercalated discs
Gap junctions

8. Smooth (Visceral) Muscle
Walls of hollow internal surfaces such as:
Blood vessels/stomach
Urinary bladder/intestines
Non striated
Involuntary
Can be stretched to great lengths
Allows for tremendous size variability

9. Skeletal Muscle
Attached to bones
Striated
Voluntary
Multinucleated

10. Characteristics of Skeletal Muscle
Muscle origin: where muscle begins--tendon attaches to immovable bone (proximal)
Muscle insertion: where muscle ends--tendon attaches to moveable bone (distal)
Belly (gastr): fleshy portion of muscle between tendons

11. SKELETAL MUSCLE ORGANIZATION
Muscle fibers: elongated muscle cells
Endomysium: membrane around muscle fibers
Perimysium: membrane around fascicles
Epimysium: membrane around entire muscle (fascia)

12. Key terms Sarcolemma = muscle cell membrane
Sarcoplasm = muscle cell cytoplasm

13. Key terms Myofilaments --contain contractile elements of muscle fiber
Sarcomere: one section of contractile filaments

14. Actin Thin Myofilaments Receptor site for Ca+ Anchored to the Z line
2 regulatory proteins
Tropomyosin- follows contour of filament
Troponin = protein on tropomyosin

15. Myosin Thick myofilaments Globular head AKA cross bridges
Overlap free ends of actin myofilaments
Shaped like a golf club

16. Sliding Filament Theory of Muscular Contraction
Due to an action potential, the actin and myosin myofilaments slide past one another, shortening the sarcomere
No change in length of myofilaments
H Zone narrows or disappears
I Band narrows or may disappear
A Band remains the same length

17. SLIDING FILAMENT THEORY OF MUSCLE CONTRACTION
SEE HANDOUT

20. Muscle--Nerve Interaction
Motor Neuron = nerve cell that excites muscle fiber
Axon – long, threadlike structure that transmits the impulse away from the cell body.
Motor Unit = motor neuron & all the muscle fibers it can effect

21. Neuromuscular Junction
Neuromuscular Junction = place between nerve & muscle fiber
Motor End Plate - location on muscle fiber next to the nerve

22. Muscle Nerve Interaction
Synaptic End Bulb - distal end of axon terminal
Synaptic Vesicles - membrane enclosed sacs within the synaptic end bulbs that store neurotransmitters

23. Acetylcholine
Acetylcholine (Ach) = neurotransmitter released to begin muscle contraction (action potential)
Acetylcholine Receptors—on motor end plate-makes membrane more permeable to Na+

25. Muscle Contraction Events (refer to handout)

26. Muscle Response to Nervous Stimuli
All or None Principle
Once a threshold stimulus is applied to a motor unit the muscle fibers innervated by that motor unit will contract to their fullest potential
Threshold Stimulus - the weakest stimulus from a neuron that will initiate a muscular contraction

27. Roles of Skeletal Muscles Agonist--Antagonist
Agonist (Prime Mover)
Main muscle
Antagonist
opposite movement

28. Roles of Skeletal Muscles Synergist
Synergist—assists agonist
provides additional force

29. Roles of Skeletal Muscles Fixator
Fixator (Stabilizer)
stabilizes a body segment
prime mover can act more effectively

30. Selected Superficial Skeletal Muscles (Anterior View)
Deltoid
Location: “caps” the shoulder
Action: shoulder abduction
Biceps brachii
Location: front of upper arm
Action: elbow flexion
Pectoralis major
Location: front of chest
Action: shoulder adduction

31. More Anterior Muscles Sternocleidomastoid Quadriceps Diaphragm
Location: front of neck
Action: turn head to opposite side
Diaphragm
Location: beneath the ribs
Action: breathing
Quadriceps
rectus femoris
vastus medialis
vastus lateralis
vastus intermedius
Location: front of thigh
Action: hip flexion; knee extension

32. Anterior Skeletal Muscles

33. Selected Superficial Skeletal Muscles (Posterior View)
Trapezius
Location: top of shoulder/neck
Action: neck extension; elevation
Triceps brachii
Location: posterior upper arm
Action: elbow extension
Gastrocnemius
Location: calf
Action: plantarflexion

34. More Posterior Muscles
Hamstring Group
semimembranosus
biceps femoris
semitendinosus
Location: posterior thigh
Action: Hip extension; knee flexion
Gluteus maximus
Location: buttocks
Action: Hip extension
Latissimus dorsi
Location: mid back
Action: shoulder extension

35. Posterior Skeletal Muscles

36. Intramuscular Injections
Injections that penetrate the skin and subcutaneous tissue
Used for prompt absorption
Used when large doses are necessary
Preferred sites:
Gluteus medius muscle
Vastus lateralis muscle
Deltoid muscle

37. Muscle Diseases and Disorders

38. Fibromyalgia
Painful disorder of muscles, tendons, and surrounding soft tissue
Muscles feel like they have been pulled or overworked.
Sometimes muscles twitch & other times they burn.
Most patients say that they ache all over.

39. FIBROMYALGIA PAIN POINTS

40. Muscular Dystrophies Muscle destroying diseases
Degeneration of individual muscle fibers
Progressive atrophy of skeletal muscles
Due to a genetic defect

41. Muscular Dystrophy in lower limbs

42. Shinsplints Pain in the anterior lower leg
Tendonitis of tibialis posterior muscle
Inflammation of periosteum
Stress fracture of the tibia
Exaggerated enlargement of muscles within the epimysium
Pulling away of the periosteum from the underlying bone
Treatment:
RICE
Strengthen tibialis anterior muscle

43. Shinsplints

44. Abnormal Contractions
Unintended muscular contraction not stimulated by normal mechanisms
May be caused by dehydration, electrolyte imbalances or neurological disorders & abnormalities
Examples--tic, twitch, spasm, Charlie horse

45. Myasthenia Gravis (MG)
A weakness of skeletal muscle
An auto-immune disorder
Caused by antibodies that block the Ach receptors at the motor end plate

46. Myasthenis gravis eye droop

47. The End