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Body Works in Balance:
Messages from the Control Center
Jennifer Kitchen
June 20, 2011
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The human body is an amazing structure that performs many wondrous
functions. Each structure of the body has its own special functions, which maintain the
body in homeostasis. The word homeostasis can be understood by understanding the
parts of the word. Homeo means “the same” and stasis means “staying”, so
homeostasis means “staying the same”. Although, the meaning of homeostasis is “to
stay the same” the body really only maintains a relative uniformity due to the many
factors that keep the body constantly changing because of internal and external factors
(Thibodeau, & Patton, 2008). There are eleven organ systems within the body
constantly working to keep the body relatively stable and in balance. These systems
work together and when one system is not in balance it can affect the other systems.
Functional Relationships: Balance and Control in the Body
The body is complex and can be compared to a factory, which produces many
products and bi-products, and has an extensive computer control center. The nervous
system made up of the brain, spinal cord, and nerves. It is the control center of the
human body, receiving and interpreting stimuli, then transmitting impulses to organs
(Thibodeau, & Patton, 2008). The brain uses the information it receives to coordinate all
of the actions and reactions which occur in the body. By using action potentials
(through neurons), the nervous system organizes rapid and precise responses to
stimuli, making musculoskeletal system move the body and to pick up what is going
around us by way of the senses. Neurons have three parts; dendrites receive
information and transmit the message to the cell body and the axon conducts messages
away from the cell body (Farabee, 2006). This is like a two way receiver or telephone, a
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message is given and received and then a new message is transmitted as to what to do
accordingly with the first message. The junction between a nerve cell and another cell
is called a synapse; this is where the message travels through. There is a space
between the transmitting and receiving cells which is called the synaptic cleft. To cross
this gap requires the actions of neurotransmitters, the chemicals and hormones that are
the messages being sent and received (Farabee, 2006). This being so, many units in
the whole body must work together to get a job done; maintaining homeostasis.
The integumentary system consists of the skin, hair, nails, and sweat glands. It
functions as a barrier to protect the body from the outside world and to retain body
fluids, protect against disease, eliminate waste products, and regulate body temperature
(Thibodeau, & Patton, 2008). The skin is like a full body, water-proof suit that breathes.
The skin is the largest organ in the body, making up 12-15% of body weight and a
surface area of 1-2 meters (that’s about 3 and a quarter to 6 and half feet) (Farabee,
2006). It protects the internal organs and keeps helps maintain the body’s internal
balance by sweating to keep us cool and constricting sweat glands to help us stay
warm. This happens when nerve impulses send signals to the skin and sweat glands,
maintaining homeostasis.
The skeletal system consists of the bones, cartilage, and joints. It provides the
shape and form for our bodies as well as supporting and protecting our bodies, allowing
bodily movement, producing blood cells, and storing minerals (Thibodeau, & Patton,
2008). The skeletal system is complex and has been divided into sections for easier
understanding. This system is like an inner armor, the axial skeleton, with gears that
helps a body move, the appendicular skeleton. The skull, vertebral column, and rib
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cage are part of the axial skeleton consists and the appendicular skeleton consists of
the bones of the appendages (arms and legs) and the pectoral and pelvic girdles
(Farabee, 2006). The axial skeleton protects the inner organs of the body, keeping
them from becoming crushed by each other. The appendicular skeleton, in cooperation
with the muscular system, moves the body. These bones include the moveable joints
which are connected (bones to joints and joints to bones) by ligaments. The
movements of the body are made when an impulse is sent via motor units to the
muscles that move the bones and joints.
The muscular system made up of muscle tissue and is the power behind
movement with the help of the motor units of the nervous system. These muscle tissues
work to move the body and move materials through the body. Muscles are bundles of
cells and fibers that work by contractions (Thibodeau, & Patton, 2008). Quite simply,
muscles make us move by tightening and relaxing. There are 3 different types of
muscle tissue, each with a specific purpose. Skeletal muscles run the full length of a
muscle and are striated (they got stripes, these are the fibers). These muscles cells are
multicellular. The skeletal muscles are voluntary and are connected to bones by
tendons. Smooth muscle cells are spindle shaped and uninucleate (having a single
nucleus) and are located in the walls of hollow organs, (stomach, intestine, uterus, and
ureter). Smooth muscles are involuntary and do such things as churn the food in the
stomach and move the urine from the kidney to the bladder. Cardiac muscle cells are
striated and uninucleate. They are the heart muscles that make the blood flow by
involuntary, rhythmic contraction (Wick, 1997). All the movements of the muscular
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system are dependent on the nervous system which sends impulses to cause the
contractions that make the muscular tissues contract or relax.
The endocrine system works in a corresponding manner with the nervous
system. It is like the center of operations, as the nervous center is the control center.
The endocrine system consists of a collection of glands; the pituitary, the hypothalamus,
adrenal, and thyroid glands, the pancreas, the ovaries and testes. This system
regulates, coordinates, and controls a number of body functions by secreting chemicals,
known as hormones. These secretions help control moods, growth and development,
and metabolism, maintaining homeostasis (Thibodeau, & Patton, 2008). The endocrine
system secretes chemical known as hormones to accomplish its duties. Homeostatic
feedback controls these secretions. In this center of operations the pituitary gland is the
master gland, signaling for hormones to be produced by other the other glands
(Farabee, 2006). Both the nervous system and the endocrine system are
communication centers of the body and aid the body’s organ systems to function
correctly and in relation to each other. Unlike the quick impulses of the nervous system,
the endocrine system has a slower but longer lasting effect.
Concept of Homeostasis: The Senses and Nervous System Work Together
The senses allow humans to perceive the World around them. Without the
senses people would run into walls, not recognize other people and objects, and would
not be able to feel pain or smell when foods were spoiled. The senses are comprised of
the general sense organs (microscopic receptors) widely distributed throughout the
body which give us the ability to feel what we touch and the localized special sense
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organs of the eyes, ears, nose, and taste buds which vary according to the sense they
are responsible for (Thibodeau, & Patton, 2008). The sense organs (and the senses
related to them) send to the brain important information about the environment and help
keep humans stay away from danger, find food, and relate to each other.
The eyes are very complex structures, with photoreceptors that capture light and
transmit to the brain what the brain changes into picture, and probably the most useful.
The ears, the organs for hearing, are very complex and constantly working. Hearing is
accomplished by vibration of tiny drum (tympanic membrane), tiny bones, and a tube
(cochlear duct) within the ear. The vibrations cause fine “hairs” within the ear to
transmit to the brain what one hears. The sense of smell is extremely useful. The nose
contains smell receptors, olfactory receptors, which have links to the memory part of the
brain and tells humans what is good or bad, by smell, in the environment. Taste is
connected to smell through the throat/nose area at the back of the mouth, which is why
if a food smells bad a person will not want to eat it. Taste is accomplished by the taste
buds sending nervous impulses to the brain via the gustatory cells, where taste is
registered. Touch, the sense that comes from the sensory receptors that are distributed
throughout the skin, react to stimulation from the environment (Thibodeau, & Patton,
2008). When a person feels heat from a flame the reaction is to pull away. When a
child touches their mother’s soft skin the sensation travels to the brain and the child will
feel comforted. These sensory receptors also tell a person about movement and
position of the body.
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The 5 senses consist of organs with specialized cells that have receptors for
specific stimuli. These cells contact the nervous system, through cranial nerves, and
therefore the central nervous system, to tell a person what is going on in their
environment. This is very important in keeping a person alive and maintaining
homeostasis. What a person sees, hears, smells, tastes, and feels can mean a lot in
any environment but in today’s world where so many things are happening at once
there could be such a thing as sensory overload, but somehow the brain works out what
is going on and helps maintain a balance.
The systems of the body work together and when one system is not in balance it
can affect the other systems. The human body is an awesome and complex structure
that performs many amazing functions without a person every really noticing. Each
structure of the body has its special functions, which maintain homeostasis, internally
and externally. The body may not have a solid balance but it is relatively stable.
Maintaining this relative balance is no small feat for such a compact unit, the body, but
with these systems all doing their part it is possible.
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References
Farabee, M. J., (2006). On-Line Biology Book. Arizona; Estrella Mountain Community
College. Retrieved from
http://www2.estrellamountain.edu/faculty/farabee/biobk/biobooktoc.html .
Thibodeau, G. and Patton, K., (2008), Structure & Function of the Body. Mosby
Elsevier; St. Louis, MO.
Wick, S., (1997). Human Anatomy and Physiology: biology 2740- biology 2840.
Retrieved from http://www.unomaha.edu/hpa/index.html .