This presentation is done by Orji Jonathan Orji with the guidance of Tamriko valishvili, Associate Prof. Doctor of medicine. Is very educative, well organized and a good learning material, enjoy it to the fullness. Comment, like and share if you fine it useful.

1. ORJI JONATHAN ORJI
DE GENIUS
PRESENTED BY:

2. walls of hollow
organs
•Lack striations
•Contractions
are involuntary
(not voluntary)
Smooth muscle
Muscle tissue found in hollow
internal organs is called
SMOOTH MUSCLE

3. • Spindle Shaped
• Central nuclei
• Lack Striations, transverse tubules, and lack well
developed sacroplasmic reticulum
• Actin and myosin thin and randomly distributed
TYPES OF SMOOTH MUSCLE
•Multi-unit smooth muscle-Separate units e.g
ciliary muscle of the eye, the iris muscle of the eye, and the
piloerector muscles that cause erection of the hairs when
stimulated by the sympathetic nervous system.
•Unitary smooth muscle-
It is also called visceral smooth muscle because it is found in the
walls of most viscera of the body, including the gastrointestinal
tract,
bile ducts, ureters, uterus, and many blood vessels.
Smooth muscle Contraction

4. Gap junctions assure contraction as “single unit.”
It has a mass of hundreds to thousands of smooth muscle
fibers that contract together as a single unit.
The fibers usually are arranged in sheets or bundles, and their
cell membranes are adherent to one another at multiple
points so that force generated in one muscle fiber can be
transmitted to the next.

5. Fewer or no gap junctions assure independent
contraction and more precise control.
This type of smooth muscle is composed of
discrete, separate smooth muscle fibers.
Each fiber works independently of the
others and often is innervated by a single
nerve ending, as occurs for skeletal muscle
fibers.

6. Physical Basis for Smooth Muscle
Contraction
 Smooth muscle does not have the
same striated arrangement as is
found in skeletal muscle.
 There are large numbers of actin
filaments attached to so-called
dense bodies.
 Some of these bodies are attached to
the cell membrane.
 Others are dispersed inside the cell.
 Some of the dense bodies of
adjacent cells are bonded together
by intercellular protein bridges.
through these bonds that the force
of contraction is transmitted from
one cell to the next.

7. •Attach to and move
skeleton
•40% of body weight
•Fibers = multinucleate
cells (embryonic cells
fuse)
•Cells with obvious
striations
•Contractions are
voluntary
Skeletal muscle
Muscle tissue that attaches to
and move bones is called
SKELETAL MUSCLE

8. • Fast, slow and intermediate
• Whether or not they predominantly use oxygen to produce
ATP (the energy molecule used in muscle contraction)
– Oxidative – aerobic (use oxygen)
– Glycolytic – make ATP by glycolysis (break down of
sugars without oxygen=anaerobic)
• Fast fibers: “white fibers” – large, predominantly
anaerobic, fatigue rapidly (rely on glycogen reserves); most
of the skeletal muscle fibers are fast
• Slow fibers: “red fibers” – half the diameter, 3X slower, but
can continue contracting; aerobic, more mitochondria,
myoglobin
• Intermediate: in between
Types of skeletal muscle fibers

9. Low Energy Requirement to Sustain Smooth Muscle Contraction
 The smooth muscle is required far less E to
sustain the same tension of contraction than
in skeletal muscle.
 This sparsity of E utilization by smooth
muscle is important to the overall E economy
of the body because organs such as the
intestines, urinary bladder, gallbladder, and
other viscera often maintain tonic muscle
contraction almost indefinitely.

10. • A skeletal muscle contracts when its motor units
are stimulated
• Amount of tension depends on
1. the frequency of stimulation
2. the number of motor units involved
• Single, momentary contraction is called a muscle
twitch
• All or none principle: each muscle fiber either
contracts completely or not at all
• Amount of force: depends on how many motor
units are activated
• Muscle tone
– Even at rest, some motor units are active: tense the
muscle even though not causing movement: “resting
tone”

11. the ends of the
actin filaments are
attached to a so-
called Z disc.
From this disc,
these filaments
extend in both
directions to
interdigitate with
the myosin
filaments.