1. Part 2: Support & Movement
The Muscular System
Part 2: Support & Movement

2. Muscle Tissue Muscle: One of the 4 basic human tissues
Defined by its ability to contract & provide movement
Composition of muscle tissue will be discussed in next chapter
Current chapter will cover location, function, & classification

3. 3 Types of Muscle Tissue Skeletal Muscle: Smooth Muscle:
Striated - associated with unstriated muscle
Voluntary
Attaches to the bones of the skeleton Multinucleated
Smooth Muscle:
Involuntary
Found in digestive system, blood vessel walls, urinary & reproductive systems
Cardiac Muscle:
Only found in the heart
Has rhythmicity – will beat without outside stimulation
Sources of energy that moves blood through the blood vessels
Smooth & Cardiac Muscle are controlled by the autonomic nervous system.

5. Common Traits Proteins Needed: Four Essential Ions Needed:
Actin
Myosin
Four Essential Ions Needed:
Calcium
Sodium
Chloride
Potassium
Common Characteristics:
Excitability
Conductivity
Contractility
Extensibility
Elasticity

6. Skeletal Muscles: Function
Functions:
Movement
Stability
Communication
Expressions, Speech
Provides primary source of body heat
Through muscle contractions – thermogenesis
Roughly 600 skeletal muscles in the human body

7. Skeletal Muscles: Properties
Contractility: Ability to forcefully contract when stimulated
Extensibility: Ability of the tissue to stretch without damage
Elasticity: Ability to return to its original shape after contraction or extension
Excitability: Ability to respond to stimuli
Action Potentials: Electrical signals prompted by neurotransmitters or by autorhythmic signals arising within the muscle tissue

8. Skeletal Muscles: Connective Tissue Components
Fascicles: Bundles of muscle fiber that make up skeletal muscles
Enveloped by connective tissue
Fascia: Thin fibrous sheet of connective tissue that surrounds muscles & provides protection
Superficial Fascia: Separates the skin from muscle; subcutaneous layer
Deep Fascia: Holds individual muscles together

10. Skeletal Muscles: Connective Tissue
3 Types of Connective Tissue protecting muscles:
Endomysium: Layer of areolar tissue surrounding individual muscle fibers
Perimysium: Sheath of connective tissue surrounding the fascicles
Epimysium: Outer layer of connective tissue covering the entire muscle & blending into the fascia

12. Skeletal Muscles: Attachment
Collagen Fibers: Connects muscle directly to bone
Attaches using epimysium & periosteum
Tendons: Extensions of connective tissue, primarily from the deep fascia
Attaches to the periosteum of the bone

14. Skeletal Muscles: General Anatomy
Points of Attachment:
Origin: Point of attachment at the stationary end of an individual muscle.
Usually medial
Insertion: Point of attachment at the more mobile end of the muscle.
Belly: Middle region of the muscle; very thick.

16. Skeletal Muscles: Classification
Intrinsic Muscles: Entirely contained within a particular region, e.g. the tongue.
Extrinsic Muscles: Act upon a certain region, but their origin is elsewhere.

17. Skeletal Muscles: Classification
Classification based on the orientation of fascicles: 5 Types
Circular: Surround body openings; e.g. sphincter muscles
Convergent: Fan shaped; e.g. pectoralis major
Fusiform: Tapered at the ends but thicker in the middle; e.g. digrastric muscles
Parallel: Relatively long & uniform in width, look like straps with parallel fascicles; e.g. stylohyoid muscle.
Pennate: Short, feather-shaped bundles with tendons running almost the entire length; have unipennate, bipennate, multipennate forms; e.g. deltoid muscles.

18. Muscle Action & Coordination
Muscles act together as coordinated groups to produce movement
Muscles are often paired against muscles of an opposing joint.
Prime Mover or Agonist: The muscle that produces the most force.
Antagonist: The muscle that yields to the effects of the prime mover; acts opposite to it.
Synergist: A muscle that aids the prime mover and prevents unwanted movement at the joints.
Fixator: A muscle that prevents bone from moving and stabilizes the movement itself.
Example: Flexing the forearm at the elbow – biceps brachii is the prime mover & triceps brachii is the antagonist.

20. Muscle Innervation
Innervation: Every muscle fiber has a single motor neuron which innervates several other muscle fibers.
Threshold: The level of stimulus needed for the neuron to fire… It will not fire until this is reached, and will instantly fire once it is reached.
Without nerves, skeletal muscles will not move.
Atrophy: Without innervation & movement, muscles will waste away & form scar tissue.

21. Skeletal Muscle Names
Skeletal muscles are named according to their distinctive features!
Named for size, shape, action, & number of origins.

22. Skeletal Muscle Names Named by Size: Maximus: Largest muscles
E.g. gluteus maximus
Minimus: Smallest muscles
E.g. gluteus minimus
Longus: Long muscles
E.g. adductor longus
Major: Larger muscles
E.g. pectoralis major

23. Skeletal Muscle Names Named by Shape: Trapezius: Trapezoid shaped
E.g. Trapezius muscle
Rhomboid: Diamond shaped
E.g. Rhomboid major
Quadratus: Square shaped
E.g. Quadratus femoris

24. Skeletal Muscle Names Named by Action: Flexor: Decreases angle
E.g. flexor carpi radialis
Levator: Elevates
E.g. levator scapulae
Tensor: Makes rigid
E.g. tensor fasciae latae

25. Skeletal Muscle Names Named by Number of Origins: Biceps: Two origins
E.g. biceps brachii
Triceps: Three origins
E.g. triceps brachii
Quadriceps: Four origins
E.g. quadriceps femori