Download File - THE MUSCULAR SYSTEM!

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Comparison of 3 types of muscle:
A muscle is a tissue that performs different functions which cause some sort of movement to take
place. There are three different types of muscle cells: skeletal, smooth, and cardiac. The various
muscles of our bodies serve as the engines or powerhouses of the body and are so constructed to
provide speed and power. Each muscle cell is designed for various functions that are needed by a
certain area in the body. Muscle tissue has the ability to contract or to shorten, so producing
movement of internal and external body parts. Breathing, speaking, walking, talking, eating, and
almost every other function requires muscle tissue.
Smooth muscles are composed of spindle shaped cells and are commonly involved in involuntary
motions. Involuntary muscle contractions or motions are those movements that cannot be
consciously controlled. The nucleus is centrally located. These types of cells are located throughout
the body. Muscles made from these types of cells include those found in the walls of blood vessels,
urinary bladder, and the digestive system.
Skeletal muscles allow movement by being attached to bones in the body. Skeletal muscles control
voluntary movements which can be consciously controlled. Skeletal muscles are made up of
cylindrical fibres which are found in the locomotive system. The nucleus of each cell tends to be
toward the edge of each cell and the cells are striated.
Cardiac muscles are roughly quadrangular in shape and have a single central nucleus. The cells form
a network of branching fibres. The muscles are cross striated and are involuntary. The muscles are
found in the heart.
You would describe a muscle as the ones that are controlled as voluntary and muscles that
automatically contract are involuntary. Based on whether they appear striped or unstriped under a
microscope, muscle fibres are also referred to as striated, meaning striped or smooth. Cardiac
muscle is striated. Smooth muscle, like skeletal muscle, is found throughout the body.
In addition to their striated appearance, cardiac muscle fibres are different from smooth muscle as
they contain multiple nuclei and behave like single units. Both types of muscle contain a centrally
located nucleus. A unique feature of cardiac muscle cells or muscle fibres is that they split and link
into a chain by intercalated disks. These disks allow communication between cells, enabling the
sequential contraction of the myocardium. Therefore our brain does not have to send a signal to
every cardiac muscle cell for our heart to contract and eject blood.
The cardiac muscle forms the muscular wall of the heart. The major blood vessels arising from your
heart, such as the aorta, also contain some cardiac muscle. Smooth muscle, on the other hand, is a
major component of the walls of all blood vessels. Additionally, smooth muscle is predominant in
the ducts, tubes and cavities of your digestive, urinary, respiratory and genital systems. Smooth
muscle is also found in the skin and eyeball.
Smooth muscle and cardiac muscle are both involuntary muscles. Specialized cardiac muscle fibres
make up the pacemaker that regulates your heart rate. This pacemaker, in turn, is under the control
of the autonomic nervous system, the part of the nervous system that operates below your level of
consciousness. Smooth muscle differs in that the autonomic nervous system directly innervates it.
Other triggers that can cause smooth muscle to contract include hormonal stimulation and
stretching.
Cardiac and smooth muscles can both generate force to move or hold back the contents of the body
cavities they surround. The cardiac muscle essentially pumps blood, and the smooth muscle is
responsible for the rhythmic contractions that move contents in your digestive tract. In the eyeball,
smooth muscle helps control the size of your pupil and thickness of your lens. Compared to cardiac
muscle, it responds more slowly to signals from your autonomic nervous system. However, smooth
muscle is able to contract for longer periods of time and can stretch more than cardiac muscle
without suffering injury.
The high activity of cardiac muscle requires an important blood supply. During a heart attack, cardiac
muscle fibres lose their blood supply and become damaged. Unlike smooth muscle cells, cardiac
muscle cells cannot be replaced once they degenerate. Also, whenever our heart has to work harder
than usual, our cardiac muscle fibres increase in size. Therefore increased demand on our smooth
muscle cells causes them to increase in both size and number.
Comparison of 3 types of muscle fibres:
Type 1 muscle fibres have a higher count of mitochondria which means it can process energy
quicker, it receives a good blood supply since it has a high amount of capillaries, which means it has
a good supply of oxygen, which helps to maintain the use of the aerobic energy system for longer,
making type 1 fibres more effect for endurance events, the contraction strength and motor unit size
is small in comparison to the other fibres, meaning it itself capable of quite the same exertion of
force, its strong use of the aerobic system does however this mean it’s not quite as proficient at
using the anaerobic energy system.
Type 2a muscle fibres have a less count of mitochondria which means it can’t process energy as
quick as type 1, it receives lesser blood supply than type 1, since it has a lesser amount of capillaries,
which means it has a poor supply of oxygen in comparison, however its aerobic and anaerobic
capacity are both medium making it balanced at most activities, the contraction strength and motor
unit size is larger in comparison to type 1 fibres, meaning its capable of exerting more strength.
Type 2b muscle fibres are capable of exerting high force in their contractions, they recruit large
number of motor neurons and fibres for actions and each fibre contracts at a fast rate to make the
action promptly. However they contain low amounts of mitochondria so aren’t able to generate
energy at the same rate at which they use it, which means they are forced to use the anaerobic
energy system, so type 2b fibres have a high anaerobic capacity and a low aerobic capacity, capillary
density is also the lowest which once again means oxygen supply isn’t as good, forcing most energy
to be converted in the absence of oxygen.
Type 1 fibres are associated with a high level of endurance, opposed to type 2b fibres which are the
opposite, this is because they have low endurance and they are suited to strength and power, type
2a fibres are the compromise of endurance and power. This means that people with type 1 fibres are
best suited to events such as long distance running, power walking and long distance swimming and
cycling. Also people with type 2a fibres are best suited for medium distance running, medium short
distance swimming, hockey, basketball and football. Also people with type 2b fibres are best suited
to sprinting, boxing, rugby, American football, judo, shot-put, javelin, weight lifting, discus, long
jump and high jump.