2. Introduction
The purpose of the chapter is to:
ā¢ Learn about the structure and function of the 3
types of muscular tissue
ā¢ Examine the events at the neuromuscular
junction
ā¢ Describe energy use in muscle cells
ā¢ Understand how muscle tension is controlled
3. Type and function of muscles
Types of Muscles:
1. Skeletal Muscles
2. Cardiac Muscle
3. Smooth muscles
Functions of Muscles:
1. Producing body movement
2. Stabilizing body position
3. Storing and moving substances within the body
4. Generating heat
4. Properties of Muscles
1. Electrical Excitability: ability to respond to certain
stimuli by producing electrical signal
2. Contractility: ability of muscular tissue to contract
forcefully when stimulated by an action potential
3. Extensibility: ability of muscle tissue to stretch
without being damaged
4. Elasticity: ability of muscular tissue to return to its
original length & shape after contraction or extension
5. SKELETAL MUSCLE TISSUE
(Connective tissue)
Three layers of connective tissue protect and strengthen skeletal
muscle:
1. Epimysium: the outermost layer of dense, irregular
connective tissue, encircling the entire muscle
2. Perimysium: is also a layer of dense, irregular connective
tissue, but it surrounds groups of 10 to 100 or more muscle
ļ¬bers, separating them into bundles called fascicles
3. Endomysium: penetrates the interior of each fascicle and
separates individual muscle ļ¬bers from one another. The
endomysium is mostly reticular ļ¬bers.
6.
7.
8. Nerve & blood supply
ā¢ Generally, an artery and one or two veins accompany
each nerve that penetrates a skeletal muscle.
ā¢ The neurons that stimulate skeletal muscle to
contract are somatic motor neurons.
ā¢ Each somatic motor neuron has axon that extends
from the brain or spinal cord to a group of skeletal
muscle ļ¬bers
ā¢ each muscle ļ¬ber is in close contact with one or more
capillaries.
9.
10. Microscopic Anatomy of skeletal
muscles
ā¢ The multiple nuclei of a skeletal muscle ļ¬ber are
located just beneath the sarcolemma
ā¢ Sarcolemma: the plasma membrane of a muscle cell
ā¢ Transverse (T) tubules : are tunnel in from the surface
toward the center of each muscle ļ¬ber.
ā¢ Muscle action potentials travel along the sarcolemma
and through the T tubules
11. Microscopic Anatomy of skeletal
muscles
ā¢ Sarcoplasm: the cytoplasm of a muscle ļ¬ber.
ļ¼Sarcoplasm includes a substantial amount of
glycogen
ļ¼Glycogen can be used for synthesis of ATP.
ļ¼Sarcoplasm contains a red-colored protein
called myoglobin
ļ¼Myoglobin binds oxygen molecules that
diffuse into muscle ļ¬bers from interstitial ļ¬uid.
12. Myofibril & Sarcoplasmic
Reticulum
Myofibrils:
ļ¼The contractile organelles of skeletal muscle
ļ¼Their prominent striations make the entire skeletal muscle
ļ¬ber appear striped (striated)
Sarcoplasmic reticulum (SR)
ļ¼Is represented by the endoplasmic reticulum in the
muscles
ļ¼Release of Ca2 triggers muscle contraction.
ļ¼In a relaxed muscle ļ¬ber, the sarcoplasmic reticulum stores
calcium ions (Ca2).
13.
14. Filaments & the sarcomere
ā¢ Myofibril is composed of thin & thick filament
ā¢ Filaments are arranged into Sarcomeres
ā¢ The extent of overlap of the thick and thin ļ¬laments
depends on whether the muscle is contracted, relaxed,
or stretched.
ā¢ The pattern of thick and thin ļ¬laments overlap,
consisting of a variety of zones and bands creating
the striations.
15. Filaments & the sarcomere
ā¢ A band: The darker part of the sarcomere extends the entire
length of the thick ļ¬laments.
ā¢ The I band: is a lighter part, that contains only actin
filaments
ā¢ Z disc: passes through the center of each I band.
ļ¼ Separates one sarcomere from the other
1. H zone: in the center of each A band contains thick but not
thin ļ¬laments.
ļ¼ contain overlapping actin and myosin filaments
ā¢ Supporting proteins that hold the thick ļ¬laments together at
the center of the H zone form the M line
21. The Neuromuscular Junction (NMJ)
Somatic motor neurons ļ release acetylcholine
NMJ ļ synaptic cleft ļ Motor end plate ļ
contain 30-40 million ACH receptors
ļ Activation of ACH receptors ļ channel open
ļ sodium flow across membrane ļ Production
of muscle action potential
ā¢ Termination of Ach activity:
acetylcholinesterase breaks down Ach into
acetyl and choline
22.
23.
24.
25.
26. Excitation-Contraction Coupling
Excitation ļ contraction
AP propagate along sarcolemma and into T tubules ļ
calcium release channels in SR open ļ calcium flow into
cytosol around thick & thin filament ļ calcium bind with
troponin ļ troponin change its shapeļ move tropomyosin
away from the myosin binding sites ļ sites become free ļ
myosin heads bind to the sites ļ contraction cycle begins
Relaxation
Calcium active transport pump ļ use ATP to move
calcium from cytosol to SR ļ Relaxation
37. Terms Related to movements
ā¢ Flexion
ā¢ Extension
ā¢ Hyperextension
ā¢ Abduction
ā¢ Adduction
ā¢ Circumduction
ā¢ Rotation
38. ā¢ Flexion: bending movement, that decreases the
angle of the joint and brings the articulating bones
closer together
ā¢ Extension: is the reverse of flexion and occurs at
the same joints
ā¢ Hyperextension: Continuing such movements
beyond the anatomical position
Terms Related to movements
41. ā¢ Abduction (āmoving awayā): is the movement of a limb
away from the midline or median plane of the body
ā¢ Adduction (āmoving towardā): is the opposite of
abduction, so it is the movement of a limb toward the body
midline
ā¢ Circumduction: is the movement of the limb, hand, or
fingers in a circular pattern, using the sequential
combination of flexion, adduction, extension, and
abduction motions
ā¢ Rotation: is the turning of a bone around its long axis
Terms Related to movements
43. Naming of Skeletal Muscles
Individual muscles are named according to their:
Shape:
1. Deltoid: Triangular
2. Rectus: Straight
Size:
1. Major: Large
2. Latissimus:
Broadest
Number of heads:
1. Biceps: Two heads
2. Quadriceps: Four
heads
Position:
1. Pectoralis: Of the
chest
2. Brachii: Of the arm
44. Naming of Skeletal Muscles
Individual muscles are named according to their:
Depth
1. Superficialis:
Superficial
2. Externus: External
Attachments
1. Sternocleidomastoid:
From sternum and
clavicle to mastoid
process.
Actions
1. Extensor: Extend
2. Flexor: Flex
3. Constrictor: Constrict