Download A&P Chapter 8

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:

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:



Four Essential Ions Needed:





Actin
Myosin
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:

E.g. gluteus maximus
 Minimus:

Long muscles
E.g. adductor longus
 Major:

Smallest muscles
E.g. gluteus minimus
 Longus:

Largest muscles
Larger muscles
E.g. pectoralis major
Skeletal Muscle Names

Named by Shape:
 Trapezius:

Trapezoid shaped
E.g. Trapezius muscle
 Rhomboid:

E.g. Rhomboid major
 Quadratus:

Diamond shaped
Square shaped
E.g. Quadratus femoris
Skeletal Muscle Names

Named by Action:
 Flexor:

Decreases angle
E.g. flexor carpi radialis
 Levator:

E.g. levator scapulae
 Tensor:

Elevates
Makes rigid
E.g. tensor fasciae latae
Skeletal Muscle Names

Named by Number of Origins:
 Biceps:

E.g. biceps brachii
 Triceps:

Two origins
Three origins
E.g. triceps brachii
 Quadriceps:

Four origins
E.g. quadriceps femori