Download The muscular system

The muscular system:
The muscular system is an organ system consisting of
skeletal, smooth and cardiac muscles. It permits
movement of the body, maintains posture, and circulates
blood throughout the body. The muscular system in a
vertebrates is controlled through the nervous system,
although some muscles (such as the cardiac muscle) can
be completely autonomous.
Types of muscles:
Muscle is a contractile tissue in animals and is derived
from the mesodermal layer of embryonic germ cells.
Muscle cells contain contractile filaments that move each
other and change the size of the cell.
Muscle tissue has four main properties: Excitability
(ability to respond to stimuli), Contractibility (ability to
contract), Extensibility (ability to be stretched without
tearing) and Elasticity (ability to return to its normal
shape). Based on certain structural and functional
characteristics, muscle tissue is classified into three types:
•Cardiac muscles are involuntary and found only in the
heart. They are controlled by the lower section of the brain
called the medulla oblungata, which controls involuntary
action throughout body. Cardiac muscle cells are located
in the walls of the heart, appear striated.
•Smooth muscles: like cardiovascular muscles, are
involuntary. They make up internal organs, such as
stomach, small intestine-hyper link, and all the others,
except heart. Unlike cardiac muscles are generally
spherical, as most other human cells, and each contains
one nucleus.
•Skeletal muscles are the only voluntary muscles of body,
and make up what we call the muscular system. They are
all the muscles that move bones and show external
movement. Unlike either of the other two classes, skeletal
muscles contain multiple nuclei because of its large size,
being in strips up to a couple of feet long.
Myoglobin & Mitochondria:
Myoglobin is a protein and has oxygen bound to it,
thus providing an extra reserve of oxygen so that the
muscle can maintain a high level of activity for a longer
period of time.
Mitochondria are known as the powerhouses of the
cell. They act like a digestive system that takes in
nutrients, breaks them down, and creates energy for the
cell.
•Type I Fibres These fibres, also called slow twitch or slow
oxidative fibres, contain large amounts of myoglobin, many
mitochondria and many blood capillaries. Such fibres are
found in large numbers in the postural muscles of the neck.
•Type II Fibres These fibres contain very large amounts of
myoglobin, very many mitochondria and very many blood
capillaries. Such fibres are infrequently found in humans.
• Type II Fibres These fibres; contain a low content of
myoglobin, relatively few mitochondria, relatively few
blood capillaries. Such fibres are found in large numbers in
the muscles of the arms.