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

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 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.

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

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

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

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

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

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

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.

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.

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.

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.

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.

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

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

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

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

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