The Four Systems

The human body has various systems that work together for the execution of various
functions. The skeletal system comprises of various bones that form the rigid framework of
the human body. The skeletal system also shields various organs, including the brain and the
spinal cord. The bones join together through joints that form the articular system. The skeletal
system and the articular system work closely with the muscular system to produce the much–
needed movement. Muscles are connected to bones through tendons. The nervous system
helps the brain to communicate with the different organs in the body. The nervous system helps
in the coordination of movement. All four systems play a vital role in the
functioning of the body.
Skeletal System
There are four different types of bones. They include long bones, short bones,
irregular bones, and sesamoid bones. Long bones are bones that are long in length. Long
bones are the largest type of bones in the human body. The appendicular skeleton is mainly
comprised of long bones (Lippert, 2017). Examples of long bones include the femur and
tibia. The two are found in the leg. The femur is the bone that forms the thigh. It is also the
strongest bone in the human body. The tibia is the bone that is located in the lower leg. It
forms the shin and expands both at the proximal and distal ends.
Short bones are bones that have an equal length and width. Short bones have a cube
shape, and this means they tend to take a cube shape. They have a composition that resembles
that of long bones with a thin layer of compact bone covering the cancellous tissue. Examples
of short bones are tarsals and carpals (Lippert, 2017). Tarsals are bones that are located in the
foot in the ankle area. Carpals are bones that make up the wrist. Flat bones are bones that
have a broad surface. The bones have a broad surface but are not thick. Examples of flat

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bones are ilium and scapula. The ilium is a bone that forms part of the pelvis. On the other
hand, the scapula is located in the shoulder. Irregular bones are bones that have varying
shapes making them not to fit in other categories (Lippert, 2017). They have unique shapes
that help them fulfil various functions. Examples include the vertebrae and sacrum. The
vertebrae are located at the bottom of the neck, running to the top of the pelvis. The sacrum
forms the back of the pelvis (Lippert, 2017). Sesamoid bones have the shape of sesame seeds.
They are located where tendons cross the end of long bones. An example is patella located in
the knee.
Articular System
A synovial joint is a joint that is characterized by the lack of a direct union between
the bone ends. A cavity exists and is filled with synovial fluid. The synovial fluid facilitates
the movement of the bones freely (Lippert, 2017). Cartilage surrounds the synovial fluid
cavity, and the cartilage plays a role of protecting the synovial fluid. The cartilage helps in
preventing the breakage of the synovial joint. Additionally, the cartilage prevents the rubbing
of the bones (Lippert, 2017). The outer layer of the capsule is made up of robust fibrous
tissues that help in holding the joint together. The synovial membrane makes up the inner
layer and secretes the synovial fluid. Synovial joints are also referred to as diarthrodial joints.
Muscular System
There are three types of muscle contractions, namely isometric, isotonic, and
isokinetic. Isometric contraction involves the contraction of the muscle without changes in
the length of the muscle (Lippert, 2017). Concentric contraction is accompanied by a joint
movement and the shortening of the length of the muscle. Concentric contractions can further
be split into two, namely concentric and eccentric (Lippert, 2017). Concentric contractions
are characterized by the shortening of the muscles and an increase in the tension. Eccentric

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contractions are characterized by the increase in the length of the muscle. When lifting
weight and working the bicep muscles, as one lifts the weight, the biceps undergo concentric
contraction (Lippert, 2017). As one puts the weight down, the biceps undergo eccentric
contraction. Isokinetic is a muscle contraction that is associated with speed. It is a muscle
contraction where the speed of the motion remains constant throughout the contraction.
Nervous System
The central nervous system is tasked with the transportation of messages across the
body. The central nervous system helps in controlling both the voluntary and involuntary
muscles (Lippert, 2017). The major components of the central nervous system are the brain
and the spinal cord. The peripheral nervous system comprises of the nervous tissue that falls
outside the vertebral canal and brainstem (Lippert, 2017). The peripheral nervous system
delivers messages from the central nervous system to other areas in the body.
Pathology Affecting All Four Systems
One of the diseases that affect the four systems is multiple sclerosis. Multiple
sclerosis affects the brain and the spinal cord. It is a lifelong condition that could result in
disability. The disease causes a reduction in average life expectancy. The disease is common
in young people in their 20s or 30s, although it can affect people of all age groups (Palmer,
2013). It is more common in women more than men. It results in a reduced quality of life as
well as impaired functional capacity. Multiple sclerosis predominantly affects the nervous
system. The disease is an autoimmune disorder that is characterized by the immune system
attacking the protective sheath, and this result in communication problems between the brain
and the rest of the body (Wens et al., 2014). The attack on myelin leaves the nerves damaged,
and this interferes with the normal communication pattern in the body.

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Multiple sclerosis results in reduced muscle strength. Muscles of the lower limbs are
affected by the disease. Loss of muscle mass, as well as decreased muscle strength, is one of
the results of multiple sclerosis (Palmer, 2013). As the signal between the muscles and the
nerves dissipates, the result is the muscles weakening (Wens et al., 2014). Multiple sclerosis
increases the risk of osteoporosis. Osteoporosis is associated with a decline in the bone mass,
and this affects the skeletal system as a whole. Osteoporosis also results in bone fragility, and
this leaves one vulnerable to fractures (Wens et al., 2014). While multiple sclerosis does not
affect the articular system directly, it can create problems that cause joint pains. When
muscles lack the necessary strength for movement, one may lose balance. The result is that
there will be uneven gait, and this may affect joints result in pain.
Conclusion
The human body has distinct systems that work closely together. The coordination
between the muscular system, the skeletal system, the articular system, and the nervous
system ensures that the body executes several key functions. Any disorder that attacks any of
the four systems is likely to create problems in all other systems. The skeletal system plays
the role of creating a rigid framework for the body. The articular system ensures that that
bones can move freely. On the other hand, the muscular system provides the much-needed
energy for the movement of the bones. The central nervous system helps coordinate both
voluntary and involuntary movements. Diseases like multiple sclerosis can have an impact on
the functioning of the four systems. It is, therefore, important to ensure that these diseases are
treated or addressed appropriately.

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References

Wens, I., Dalgas, U., Vandenabeele, F., Krekels, M., Grevendonk, L., & Eijnde, B. O. (2014).
Multiple sclerosis affects skeletal muscle characteristics. PloS one, 9(9), e108158.
Palmer, A. M. (2013). Multiple sclerosis and the blood-central nervous system
barrier. Cardiovascular Psychiatry and neurology, 2013.
Lippert, L. (2017). Clinical kinesiology