Muscle physiology

sustained contraction or alternating contraction
and relaxation, muscular tissue has four key
functions:
 Produces body movements.
 Stabilizes body positions.
 Stores and moves substances within the
body.
 Generates heat.
By Gladys Stephen

Muscular tissue has four special properties that
enable it to function and contribute to
homeostasis:
 Electrical excitability
 Contractility
 Extensibility
 Elasticity
By Gladys Stephen

 Electrical excitability:
› a property of both muscle and nerve cells
to respond to certain stimuli by producing
electrical signals called action potentials
 Contractility
› ability of muscular tissue to contract
forcefully when stimulated by an action
potential. When a muscle contracts, it
generates tension (force of contraction)
while pulling on its attachment points.
By Gladys Stephen

 Extensibility
› ability of muscular tissue to stretch without
being damaged. Extensibility allows a
muscle to contract forcefully even if it is
already stretched.
 Elasticity
› ability of muscular tissue to return to its
original length and shape after contraction
or extension
By Gladys Stephen

 Muscles are classified by three different
methods, based on different factors:
› I. Depending upon the presence or absence of
striations
› II. Depending upon the control
› III. Depending upon the situation.
By Gladys Stephen

 Depending upon the presence or absence of
cross striations, the muscles are divided into
two groups:
› 1. Striated muscle
› 2. Non-striated muscle.
By Gladys Stephen

Striated Muscle
Striated muscle is the muscle
which has a large number of
cross-striations (transverse
lines).
› Examples are skeletal muscle and
cardiac muscles.
By Gladys Stephen

Non-striated Muscle
 Muscle which does not have cross-
striations is called non-striated
muscle.
 It is also called plain muscle or
smooth muscle.
 It is found in the wall of the visceral
organs.
By Gladys Stephen

 Depending upon control, the muscles are
classified into two types:
› 1. Voluntary muscle
› 2. Involuntary muscle.
By Gladys Stephen

 1. Voluntary Muscle
› Voluntary muscle is the muscle that is controlled
by our own will. Skeletal muscles are the
voluntary muscles.
› These muscles are innervated by somatic
nerves.
 2. Involuntary Muscle
› Muscle that cannot be controlled by the will is
called involuntary muscle.
› Cardiac muscle and smooth muscle are
involuntary muscles
By Gladys Stephen

 Depending upon situation, the
muscles are classified into three
types:
› 1. Skeletal muscle
› 2. Cardiac muscle
› 3. Smooth muscle.
By Gladys Stephen

1. Skeletal Muscle
 Skeletal muscle is situated in association
with bones forming the skeletal system.
 form 40% to 50% of body mass and are
voluntary and striated.
 Supplied by somatic nerves.
 Fibers of the skeletal muscles are arranged
in parallel.
 Muscle fibers are attached to tendons on
either end.
 Skeletal muscles are anchored to the bones
by the tendons.
By Gladys Stephen

 Description:
› Long, cylindrical, striated fibers with
many peripherally located nuclei;
voluntary control.
 Location:
› Usually attached to bones by tendons.
 Function:
› Motion, posture, heat production, and
protection.
By Gladys Stephen

Skeletal muscle
Longitudinal section of skeletal muscle tissue
Skeletal muscle fiber
nucleus
striations
Skeletal muscle fiber
By Gladys Stephen

 MUSCLE MASS OR TISSUE
 Muscle mass or muscle tissue is made up of
a large number of individual muscle cells or
myocytes.
 The muscle cells are commonly called
muscle fibers because these cells are long
and slender in appearance.
 Skeletal muscle fibers are multinucleated
and are arranged parallel to one another with
some connective tissue in between.
By Gladys Stephen

 Muscle mass is separated from the
neighboring tissues by a thick fibrous tissue
layer known as fascia.
 Beneath the fascia, muscle is covered by a
connective
 tissue sheath called epimysium.
 In the muscle, the muscle fibers are arranged
in various groups called bundles or fasciculi.
 Connective tissue sheath that covers each
fasciculus is called perimysium.
 Each muscle fiber is covered by a connective
tissue layer called the endomysium
By Gladys Stephen

 Each muscle cell or muscle fiber is cylindrical in shape.
 Average length of the fiber is 3 cm (1-4 cm, depending upon
the length of the muscle).
 The diameter of the muscle fiber varies from 10 μ to 100 μ
and it varies in a single muscle.
 Muscle fibers are attached to a tough cord of connective
tissue called tendon.
 Tendon is in turn attached to the bone.
 Tendon of some muscles is thin, flat and stretched but tough.
 Such type of tendon is called aponeurosis.
 Each muscle fiber is enclosed by a cell membrane called
plasma membrane, that lies beneath the endomysium.
 It is also called sarcolemma .
 Cytoplasm of the muscle is known as sarcoplasm.
By Gladys Stephen

 Structures embedded within the sarcoplasm
are:
› 1. Nuclei
› 2. Myofibril
› 3. Golgi apparatus
› 4. Mitochondria
› 5. Sarcoplasmic reticulum
› 6. Ribosomes
› 7. Glycogen droplets
› 8. Occasional lipid droplets.
By Gladys Stephen

 It is the cell membrane of the muscle fiber.
 The sarcolemma consists of a true cell
membrane, called the plasma membrane, and
an outer coat made up of a thin layer of
polysaccharide material that contains numerous
thin collagen fibrils. At each end of the muscle
fiber, this surface layer of the sarcolemma fuses
with a tendon fiber.
 Tendon fibers in turn collect into bundles to form
the muscle tendons that then insert into the
bones. By Gladys Stephen

MYOFIBRIL
› Each muscle fiber contains several hundred to
several thousand myofibrils.
› Myofibrils or myofibrillae are the fine parallel
filaments present in sarcoplasm of the muscle
cell.
› some of the myofibrils are arranged in groups
called Cohnheim’s areas or fields.
› Each myofibril is composed of about 1500
adjacent myosin filaments and 3000 actin
filaments, which are large polymerized protein
molecules responsible for the actual muscle
contraction.
By Gladys Stephen

 The myofibrils contain 2 kinds of protein
filaments .
› Thick filaments – composed of myosin .
› Thin filaments – composed of Actin , troponin
and tropomyosin .
› c. striations are produced by alternating light and
dark filaments .
By Gladys Stephen

2. Cardiac Muscle
 Cardiac muscle forms the
musculature of the heart.
 These muscles are striated and
involuntary.
 Cardiac muscles are supplied by
autonomic nerve fibers.
By Gladys Stephen

Heart
Longitudinal section of cardiac muscle tissue
Cardiac muscle fibers
Nucleus
Cardiac
muscle fiber
(cell)
Striations
By Gladys Stephen

 Description:
› Branched striated fibers with one or two centrally
located nuclei; contains intercalated discs;
involuntary control.
 Location:
› Heart wall.
 Function:
› Pumps blood to all parts of the body.
By Gladys Stephen

 Description:
› Spindle-shaped (thickest in middle and tapering
at both ends), nonstriated fibers with one
centrally located nucleus; involuntary control.
 Location:
› Iris of the eyes, walls of hollow internal structures
such as blood vessels, airways to the lungs,
stomach, intestines, gallbladder, urinary bladder,
and uterus.
 Function:
› Motion (constriction of blood vessels and
airways, propulsion of foods through
gastrointestinal tract, contraction of urinaryBy Gladys Stephen

3. Smooth Muscle
 Smooth muscle is situated in association
with viscera.
 It is also called visceral muscle.
 It is different from skeletal and cardiac
muscles because of the absence of cross
striations.
 Smooth muscle is supplied by autonomic
nerve fibers.
 Smooth muscles form the main contractile
units of wall of the various visceral organs
E.g. stomach.
By Gladys Stephen

Artery
Smooth
muscle
Longitudinal section of smooth muscle tissue
Nucleus of
smooth
muscle
fiber
Smooth muscle
fiber (cell)
SMOOTH MUSCLE
By Gladys Stephen

Muscle physiology

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