The document provides an overview of muscle physiology, detailing the three types of muscular tissue: skeletal, cardiac, and smooth. It outlines the functions of muscular tissue, including movement, stabilization, substance storage, and heat generation, as well as its key properties such as electrical excitability and contractility. Additionally, it describes the organization of skeletal muscle tissue, including connective tissue layers and the structure of muscle fibers and myofibrils.

1. MUSCLE
PHYSIOLOGY Marilyn E. Soriano, PTRP, LPT
License No.: 0015216

2. OVERVIEW OF MUSCULAR
TISSUE
The three types of muscular tissue—
1. skeletal,
2. cardiac,
3. smooth

3. SKELETAL MUSCLE TISSUE

4. DESCRIPTION:
• Skeletal muscle tissue: consists of
long, cylindrical, striated fibers
(striations are alternating light and
dark bands within fibers)
• Skeletal muscle fiber: roughly
cylindrical, multinucleated cell with
nuclei at the periphery
• Skeletal muscle: voluntary ( it can
be made to contract or relax by
conscious control)
LOCATION: attached to bones and
tendons
FUNCTION: Motion, Posture, Heat
production, Protection

5. Functions of Muscular Tissue
1. Producing body movements.
 Movements of the whole body such as
walking and running, and localized
movements such as grasping a pencil,
keyboarding, or nodding the head as a
result of muscular contractions, rely on the
integrated functioning of skeletal muscles,
bones, and joints.
2. Stabilizing body positions.
 Skeletal muscle contractions stabilize joints
and help maintain body positions, such as
standing or sitting. Postural muscles
contract continuously when you are awake;
for example, sustained contractions of your
neck muscles hold your head upright when
you are listening intently to your anatomy
and physiology lecture.
3. Storing and moving substances within the
body.
 Storage is accomplished by sustained
contractions
o Cardiac muscle contractions
o Smooth muscle contractions also
move food and substances
4. Generating heat.
 As muscular tissue contracts, it
produces heat, a process known as
thermogenesis.
 heat generated by muscle is used to
maintain normal body temperature.
 Involuntary contractions of skeletal
muscles, known as shivering, can
increase the rate of heat production.

6. Properties of Muscular Tissue
1. Electrical excitability
 is the ability to respond to certain stimuli
by producing electrical signals called
action potentials (impulses).
 Action potentials in muscles are referred
to as muscle action potentials; those in
nerve cells are called nerve action
potentials.
 two main types of stimuli trigger action
potentials:
i. Auto-rhythmic electrical signals
arising in the muscular tissue itself,
as in the heart’s pacemaker.
ii. Chemical stimuli, such as
neurotransmitters released by
neurons, hormones distributed by
the blood, or even local changes in
pH.
2. Contractility
 is the ability of muscular tissue to contract
forcefully when stimulated by an action
potential.
 When a skeletal muscle contracts, it
generates tension (force of contraction) while
pulling on its attachment points.
3. Extensibility
 is the ability of muscular tissue to stretch,
within limits, without being damaged.
 The connective tissue within the muscle
limits the range of extensibility and keeps it
within the contractile range of the muscle
cells.
4. Elasticity
 is the ability of muscular tissue to return to
its original length and shape after
contraction or extension.

7. Layers of connective tissue:
• extend from the fascia to protect and
strengthen skeletal muscle
1. Epimysium (Muscle)
• dense irregular connective tissue.
2. Perimysium (Muscle fascicle/ bundle)
• dense irregular connective tissue
• surrounds groups of 10 to 100 or more
muscle fibers, separating them into
bundles called fascicles.
3. Endomysium (muscle fiber)
• penetrates the interior of each fascicle and
separates individual muscle fibers from one
another
• mostly reticular fibers.
Epimysium
.
Perimysium
.
Endomysium
.

8. Gross Organization
Epimysium
.
Perimysium
.
Endomysium
.

9. 1. SKELETAL MUSCLE
o Organ made up of fascicles
that contain muscle fibers
(cells), BV, and nerves
o Wrapped in epimysium
2. FASCICLE
o Bundles of muscle fibers
o Wrapped in perimysium

10. 3. MUSCLE FIBER (CELL)
o Long cylindrical cell
o Wrapped in endomysium and
sarcolemma
o Straited appearance
o each fiber extends the entire
length of the muscle except for
about 2 per cent of the fibers
o each fiber is usually innervated
by only one nerve ending,
located near the middle of the
fiber.4. MYOFIBRIL
o Threadlike contractile elements
within a sarcoplasm of muscle fiber
that extend entire length of fiber
o Composed of filaments

11. 5. FILAMENTS
o Contractile proteins within
myofibrils that are two types:
thick and thin
o Sliding of thin filaments
produces muscle shortening

12. Sarcolemma
Sarcoplasmic Reticulum
Transverse Tubules
SARCOLEMMA:
- the cell membrane of the muscle fiber
-where muscle action potentials travel along
SARCOPLASMIC RETICULUM
-wraps around each myofibril
-where muscle action potentials quickly
spread throughout the muscle fiber
TRANSVERSE TUBULES
- Filled with extracellular fluid
-invaginate from the sarcolemma toward the
of the muscle fiber
MUSCLE FIBER (CELL)
 This arrangement ensures
that an action potential
excites all parts of the muscle
fiber at essentially the same
instant.
• single cell
• multinucleated
• surrounded by the sarcolemma

13.  Intracellular fluid containing large quantities of
potassium, magnesium, and phosphate, plus multiple
protein enzymes.
 Presence of tremendous numbers of mitochondria that
lie parallel to the myofibrils which supply the
contracting myofibrils with large amounts of energy in
the form of adenosine triphosphate (ATP)
 includes a substantial amount of glycogen which can be
used for synthesis of ATP
 contains a red-colored protein called myoglobin
• which binds oxygen molecules that diffuse into
muscle fibers from interstitial fluid
• releases oxygen when it is needed by the
mitochondria for ATP production
SARCOPLASM

14. Invaginations of the sarcolemma
filled with extracellular fluid
• Penetrate the muscle fiber,
branch and form networks
• Transmit AP’s deep into the
muscle fiber
TRANSVERSE TUBULE
(T- TUBULES)

15.  Terminal cisterns are
dilated end sacs of the
sarcoplasmic reticulum
butt against the T tubule
from both sides.
 TRIAD: Transverse tubule
and the two terminal
cisterns on either side of it
form.
 Stores calcium ions
 Release of Ca ions from the
terminal cisterns of the
sarcoplasmic reticulum
triggers muscle contraction.
Sarcolemma
Sarcoplasmic Reticulum
Transverse Tubules
 fluid-filled system of membranous sacs encircles
each myofibril
SARCOPLASMIC
RETICULUM

16. Embryonic development of skeletal muscle
MYOBRILS- The contractile elements of muscle fibers which
contain overlapping thick and thin filaments
embryonic development
myoblasts fuse to form one
skeletal muscle fiber
fusion has occurred
skeletal muscle fiber loses the
ability to undergo cell