Investigation 5
Maddie Rita
Life: it’s a precious and fragile balance. The vitality of both single and multicellular organisms depends on its individual success in maintaining an essential
stability. This function is called homeostasis: “the ability of a system to adjust its
internal environment in order to accomplish a stable equilibrium” (Princeton.edu).
Take, for example, the human body temperature. Among many needs, we require a
consistent body heat of approximately 98.6 degrees Fahrenheit to function healthily.
Now, consider a fever. That minimal margin of only a few degrees, such as a
temperature of 101, causes great discomfort, and can even be life threatening. This
is only one instance in which homeostasis is vital. In fact, the combination and
cooperative activity of systems in a cell or larger organism is homeostasis itself.
While homeostasis is somewhat more obvious is multi-cellular organisms,
and will be discussed later, homeostasis is just as important with individual cells. In
fact, there are many parallels in the way both multi and unicellular organisms
maintain homeostasis. A single cell performs many functions that are familiar to
humans. To maintain constant chemical and physical conditions, they must respond
to the surrounding environment, grow, reproduce, and transform energy.
As explained in earlier investigations, unicellular organisms can be
prokaryotic or eukaryotic. Prokaryotes are more commonly single-celled; this
category includes bacteria, which exist in mass numbers on Earth. There are also a
fair amount of eukaryotic unicellular organisms, such as yeast. Whatever the cell
type, homeostasis requires sources of food, quick reactions to external factors, and
maintenance of water and mineral levels. Organelles allow single cells to regulate
these important factors.
Like in the human body, each organelle in a cell has a different responsibility.
Their ability to work together results in that necessary balance. For example, the cell
membrane helps maintain homeostasis by monitoring what goes in and out of a cell.
Without this, foreign bodies could enter the cell, threatening its functionality. This is
just one job of many. Another is that of lysosomes, which have enzymes that break
down things that might interfere with homeostasis. The role that each organelle
performs is not just for effective activity of the cell; it is also to maintain
homeostasis. The two goals are, in many ways, one and the same.
In a multi-cellular organism, each cell continues to maintain individual
homeostasis, but also is specialized to control homeostasis in the overall organism.
Roles vary from producing necessary substances to simply moving. These
specialized cells are organized into groups that form tissues, and the tissues then
form an organ. Groups of organs form an organ system.
Tissues are groups of alike cells that handle a specific task. To perform a
more complicated and significant task, different tissues function together as an
organ. Varying combinations of multiple organs handle jobs that relate and
intertwine, justifying the existence of organ systems. This “division of labor” allows
the consistent achievement of homeostasis. Cells in an organism also communicate,
using chemical signals to alter the activities of cells, another function that maintains
homeostasis. Junctions can be found between some cells to aid this process.
Receptors, often located in the cytoplasm or on the membrane, allow response to
chemical messages.
Eleven such systems can be found in the human body. These include
circulatory, digestive, respiratory, urinary, skeletal, muscular, integumentary,
endocrine, reproductive, immune, and nervous systems. Each system plays a role in
both the body’s functionality and homeostasis.
The circulatory system transports blood throughout the body. This is
important to homeostasis because humans require a certain blood volume and
pressure to remain functional.
The digestive system does just that – it digests, absorbing water, salt, and
nutrients from ingested substances. It also expels unneeded solid waste from the
body. Gaining nutrients and ridding the systems of waste is also important to
homeostasis because the presence of nutrients and absence of waste are necessary
to health.
The respiratory system is responsible for the transfer of carbon dioxide and
oxygen. This process is also an aspect of homeostasis maintenance because the
human body requires a specific oxygen concentration.
The urinary system excretes salts and water, expelling waste in the form of
urine from the body and therefore controlling plasma composition. Similarly to the
digestive system, the regulation of waste in the body is essential to homeostasis.
The skeletal system is the framework of the body, allowing support and
movement as well as the production of blood cells. This is helpful in maintaining
homeostasis since the body has to move in order to adjust to its surrounding
environment. The muscular system serves a similar purpose, which is why the two
systems are sometimes considered one, referred to as the musculoskeletal system.
The integumentary system is the skin, which serves the purpose of
protecting the body from foreign substances, as well as regulating temperature.
Both these tasks help to control the internal environment by blocking potential
damage.
The endocrine system produces hormones that control many aspects of the
body such as metabolism, blood pressure, reproduction, growth and electrolyte
balance. All of these are important to homeostasis.
The reproductive system produces the sex cells necessary to conceive a child.
Reproduction is important to homeostasis because animals instinctually attempt to
continue their species.
The immune system defends against foreign invaders and forms white blood
cells. This is essential to homeostasis because being sick threatens homeostasis.
Finally, the nervous system controls coordination, learning, awareness of
surrounding environments, and states of consciousness. This aids homeostasis
because it allows the body to assess and react to changes that could potentially
destabilize the internal environment.
Homeostasis is often disrupted by both internal and external stimuli, in
instances that can be mild or severe. If homeostasis is drastically affected, death can
occur. Internal threats include physical and mental distress, blood pressure,
temperature, and concentration of various substances. Externally, heat, cold, toxins,
and lack of oxygen all can interfere with effective homeostaqsis.
To counter these issues, control systems find unwanted changes and use this
information to adjust in accordance with the detected abnormality. Control systems
can be either intristic, (local to an organism), or extrinsic, (initiated outside an
organism by the nervous or endocrine systems). In a feedforward scenario, a
response occurs because of an anticipated change. A feedback scenario is a response
to a change that has already occurred and been detected. Feedback systems can be
negative or positive. Negative feedback reverses the original stimulus to frequently
adjust a condition, whereas positive feedback intensifies the original stimulus, like
the process of contractions during childbirth.
The human body has many receptors that monitor a condition and detect
when there is a change in this condition. These receptors are the five senses: smell,
taste, touch, vision, and hearing. The control center, or the brain, determines the
action to handle the change in a way that will benefit homeostasis. The effector
depends on the choice of the control center; the effector will execute whatever the
control center determines as an appropriate reaction. This type of communication is
called feed back loop.
Overall, homeostasis is essential to human life, and all life in general. In
order to survive the varying conditions of our planet, an organism must have stable
functionality. The way that a cell, or system of cells, accomplishes this stability is
fascinating and intricate. Without the many processes that monitor homeostasis, life
on Earth would not exist as we know it.