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Unit-III
Muscular System
Muscular System
The muscular system is the anatomical system of a species
that allows it to move.
The muscular system makes up nearly half the weight of
the human body, this is why when we train we sometimes
put on weight instead of losing it. We put on muscle weight.
Muscular System Functions
1.
Body movement (Locomotion)
2.
Maintenance of posture
3.
Respiration
4.
Communication (Verbal and Facial)
5.
Constriction of organs and vessels
6.
Heart beat
7.
Production of body heat
Muscles
Muscles are all made of the same material, a type of
elastic tissue (sort of like the material in a rubber
band). Thousands, or even tens of thousands, of small
fibers make up each muscle.
Types of Muscle
1. Skeletal Muscle
2. Smooth Muscle
3. Cardiac Muscle
Skeletal muscles
1. Attached to bones
2. Makes up 40% of body weight
3. Responsible
for
locomotion,
facial
expressions,
posture, respiratory movements, other types of body
movement
4. Voluntary in action; controlled by somatic motor
neurons
Skeletal muscle
Structure of Skeletal muscle
Structure of Skeletal muscle
Skeletal muscle attached to bones via strong bands of
connective tissue called tendons .
Skeletal muscle is organised into bundles of muscle
cells or fibres. that are held together by a sheath of
connective tissue.
Structure of Skeletal muscle
Each muscle fibre is a single cell with many nuclei.
Around each cell is plasma membrane called the
sarcolemma which contains sarcoplasm (cytoplasm).
Each
cell/fibre
is
comprised
smaller myofibrils arranged lengthwise.
of
many
Smooth Muscle
Smooth Muscles
1. In the walls of hollow organs, blood vessels, eye,
glands, uterus, skin.
2. Some functions: propel urine, mix food in digestive
tract, dilating/constricting pupils, regulating blood
flow, in some locations, autorhythmic.
3. Controlled involuntarily by endocrine and autonomic
nervous systems.
Structure of Smooth Muscles
1. Smooth muscle fibers have a fusiform shape and,
like striated muscle, can tense and relax.
2. However, smooth muscle containing tissue tend to
demonstrate greater elasticity and function within a
larger length-tension curve than striated muscle.
Smooth Muscles
This ability to stretch and still maintain contractility is
important in organs like the intestines and urinary
bladder. In the relaxed state, each cell is spindleshaped, 20-500 micrometers in length.
Cardiac Muscles
1. Heart: major source of movement of blood
2. Autorhythmic
3. Controlled involuntarily by endocrine and
autonomic nervous systems
Structure of Cardiac Muscles
Cardiac muscle is dense and packed tightly. The
muscle fibers are striated and branched and have
intercalated discs.
Muscle Fiber
A cylindrical, multinucleate cell composed of numerous
myofibrils that contracts when stimulated.
Types of Muscle Fiber
Muscle Fiber
Fast Twitch
Muscle Fiber
Slow Twitch
Muscle Fiber
Types of Muscle Fiber
 Fast/White Twitch Muscle
Fiber
Twitch Muscle
Fiber
Fast twitch fibers, as the
name
 Slow/Red
suggests,
contract
more quickly than slow
twitch muscle fibers and,
Slow twitch fibers, as the
name
suggests,
more
slowly
contract
than
fast
twitch muscle fibers and
as a result, they produce
more power and strength.
they can contract for a
longer period of time.
Muscle Fiber
Characteristics Of Muscle Tissue
Excitability: capacity of muscle to respond to a stimulus.
Contractility: ability of a muscle to shorten and generate
pulling force.
Extensibility: muscle can be stretched back to its original
length.
Elasticity: ability of muscle to recoil to original resting
length after stretched.