Download FASCIA, MUSCLES, TENDONS

FASCIA, MUSCLES,
TENDONS
Skeletal Muscle Structure

Origin:
Proximal attachment

Insertion:
Distal attachment

Tendons:
Peritendineum

Aponeurosis
Skeletal Muscle Hierarchy

Myofilament:
Thick filaments
Myosin
Thin filaments
Actin

Myofibril:
Bundle of myofilaments
Segmentally arranged into sarcomeres
Skeletal Muscle Hierarchy

Myofiber
Made up of many myofibrils
Multinucleated in skeletal muscles
= muscle cell

Fascicle
Bundle of myofibers

Muscle
Composed of several to several hundred
fascicles
Connective Tissues

Endomysium:
Surrounds a myofiber

Perimysium:
Surrounds a fascicle
Connective Tissues

Epimysium:
Covers entire muscle
Blends in with deep fascia

Connective tissue supports provide
physical support and a pathway for nerves
and vessels.
Myofilaments

Actin myofilaments (F-actin):
Polymers of G-actin
Tropomyosin
Troponin

Myosin filaments:
ATPase
Sarcomeres

Z-line (Z-actin):
Composed of Z-actin
Marks ends of Z-actin

I bands:
Part of a sarcomere composed entirely of
actin
Sarcomeres

A band:
Part of a sarcomere composed of both actin
and myosin

H band:
Part of a sarcomere composed entirely of
myosin
Sliding Filament Theory

During a contraction:
I band and H band shorten
A band remains the same length

Sliding occurs when ATPase heads of
myosin attach to actin via troponin and
swivel.
Myofiber

Sarcoplasmic reticulum:
Equivalent to endoplasmic reticulum of most
cells.

T-tubules:
Tubular extensions of the muscle fiber
membrane that extend down into the
cytoplasm (saracoplasm).
Conduct action potential from cell membrane
surface to interior.
Myofiber

Cisternae:
Saccular extensions of the sarcoplasmic
reticulum that release calcium ions in
response to action potential.
Calcium ions trigger sliding of myosin and
actin filaments, resulting in a contraction.
Myofiber Type
The myofiber type (red or white) depends
on innervation.
 All myofibers in a motor unit are of the
same type.

Dark (red) Fibers
Fatigue resistant
 Contract slowly (slow twitch)
 Rely on oxidative phosphorylation
 Have a large number of mitochondria
 Have a high concentration of myoglobin
 Have a low concentration of ATPase

Light (white) Fibers
Fatigue easily
 Contract rapidly (fast twitch)
 Rely on glycolysis
 Have a small number of mitochondria
 Have a low concentration of myoglobin
 Have a high concentration of ATPase

Neuromuscular Junctions

Components:
Presynaptic membrane:
Terminal end of motor neuron.
Synaptic cleft
Postsynaptic membrane:
Sarcolemma (cell membrane of myofiber)
Motor Unit

Consists of a motor neuron and all the
myofibers it innervates
Units for fine control have fewer fibers
Units for gross control have many fibers
Muscle Classification
Fiber arrangement
 Shape
 Origin and insertion
 Function

Fiber Arrangement

Straight:
Example: rectus abdominis

Fusiform:
Example: biceps brachii

Unipennate:
Example: palmar interosseous muscles

Bipennate:
Example: dorsal interosseous muscles

Multipennate:
Example: deltoid muscle
Muscle Shape

Deltoid

Trapezius
Muscle Origin/Insertion

Coracobrachialis

Sternocleidomastoid
Muscle Function

Pronater teres

Extensor digitorum
Contraction

Definition:
A contraction is a muscle’s response to a
stimulus.

Types of contraction:
Isotonic (the length of the muscle changes)
Concentric (length decreases)
Eccentric (length increases)
Isometric (the length of the muscle stays the
same)
Types of Action

Agonist (prime mover):
A muscle that primarily carries out the
desired action.

Antagonist:
A muscle that opposes the agonist.

Synergist:
A muscle that eliminates the unwanted
action of the agonist.
Types of Action

Fixator:
A muscle that stabilizes the origin of another
muscle.

Note: a single muscle can be all the above
at one time or another.
Insufficiency

Refers to the inability of a multijoint muscle
to maximally contract simultaneously over
all joints crossed.
Active:
Refers to the agonist
Passive:
Refers to the antagonist
Smooth Muscle

Synonyms:
Visceral
Involuntary

Found in:
Walls of visceral tubes (intestines, etc.)
Associated with hair follicles
Around glandular structures
In walls of blood vessels
Smooth Muscle Characteristics
Bundles of sheets of individual cells.
 Not striated (smooth).
 Cells are primarily elongated and tapered.
 Mononucleated.

Smooth Muscle Characteristics
Nuclei are centrally located in each cell.
 Does not conduct action potential.
 Cells connected by gap junctions.
 Not under voluntary control.

Cardiac Muscle Tissue
Found only in walls of heart.
 Characteristics:

Striated (sarcomeres)
Mononucleated cells:
May branch
Intercalated discs:
Sites of transfer of stimulus between adjacent
cells.