Upload
ethelbert-johnston
View
216
Download
0
Tags:
Embed Size (px)
Citation preview
The Muscular System
Part 2: Support & Movement
Muscle Tissue
Muscle: One of the 4 basic human tissuesDefined 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: 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:
Involuntary 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: Actin Myosin
Four Essential Ions Needed: Calcium Sodium Chloride Potassium
Common Characteristics: Excitability Conductivity Contractility Extensibility Elasticity
Skeletal Muscles: Function
Functions: MovementStabilityCommunication
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 musclesEnveloped by connective tissue
Fascia: Thin fibrous sheet of connective tissue that surrounds muscles & provides protectionSuperficial Fascia: Separates the skin from
muscle; subcutaneous layerDeep Fascia: Holds individual muscles
together
Skeletal Muscles: Connective Tissue
3 Types of Connective Tissue protecting muscles: Endomysium: Layer of areolar tissue
surrounding individual muscle fibersPerimysium: Sheath of connective tissue
surrounding the fasciclesEpimysium: 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 fasciaAttaches 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