Discuss human
biological levels of organization from atom to organism. Discuss each level in detail and describe how
each contributes to homeostasis by giving specific examples.
Biology is a life study that defines
the difference between living versus nonliving organisms. The world of living matter consists of levels
of organization. Each level is important
in the function of human beings. The
levels are atom/molecule, cell, tissue, organ, organ systems and organism
(Miller & Levine 13).
All living organisms begin with an
atom defined as a unit of matter. To be
considered matter it must contain the 4 characteristics of weight, volume, mass
and density. An atom is microscopic in size, consisting of protons that have
positive charges and neutrons with no charge which form the nucleus or center
of the atom. Outside the atom circulate
a variety of electrons which help define the abilities of that atom. Each atom, based on its structure, makes up
different elements of matter. A single atom
or element can combine with other atoms to form a molecule. Humans are made up of billions of atoms
(Miller and Levine 28).
Even though each element begins in a pure
state cooperative binding must occur for the building of a new structured
matter. Any disruption in the binding process
or introduction of other elements, or an unstable environment can change the
outcome. For instance there is a
presence of an atom of pure oxygen (an element required to be present for all
living organisms that are aerobic in nature) in the environment. Inject the pure element of carbon and the
atoms will bind forming a strong triple co-valent bond and create a new
compound called carbon monoxide, a totally different form of matter (Miller and
Levine 31). Carbon monoxide biologically
can be the by-product of hemoglobin breakdown within the human body, but if
found in large quantities can be a dangerous, toxic gas (Miller and Levine 800). Take the same two atoms of carbon and oxygen
and add one more oxygen atom to the compound and a new compound is formed called
carbon dioxide. Large quantities of
carbon dioxide can drastically affect the homeostasis within a living body. When the organism is balancing carbon
dioxide correctly it is a natural by-product of respiration (Miller and Levine
799).
Some molecules are more stable than
others but can join together to eventually form a single cell. All living
organisms consist of the basic unit of life known as a cell. Cells are complete
in nature but some living things remain in a unicellular state all of their
life cycle while other organisms have more and more cells that become when
combined as complex as the human body. The human body is the most complex form
of life (Miller and Levine 160).
Living organisms have several
characteristics that make them common in nature and they must have these to be
considered living. These characteristics
and functions are beginning with a basic unit cell, universal genetic code
(heredity) ability, obtaining and using materials and energy, able to grow,
develop and reproduce, respond to their environment, maintain a stable internal
environment (homeostasis), and change overtime (evolution). Cells are generated
from other pre-existing cell matter so the ability of reproduction is essential
(Miller and Levine 160).
When considering the living species of
human cells scientists classify these cells as eukaryotes. To be able to have this classification the
cell must have the three basic structures present; a plasma membrane, nucleus
and cytoplasm. These structures
contained within a single cell maintain its existence and survival. The plasma membrane is the outside wall of
the cell, the nucleus contains the genetic matter and communication, and the
cytoplasm contains other structures that help the cell change food into energy.
The human cell works much like a sport
team and each part has their own vital function, must communicate within, must
send and contain receptors to receive messages through the effective use of
chemicals. There are several stages that a cell goes through to multiple. Each phase is critical, but DNA damage during
division is the reason the cell cycle and cell death will occur because a
homeostatic state has not been maintained to assure survival (Mader 164).
When the cell does complete its phases
and survives risk continues. For example
within the human body viruses can invade the body that contain proteins
surrounding the cell wall that has the ability to bind to the protein receptors
of the human cell allowing entry through the human cell wall. In the HIV retroviruses the virus robs the
human cell of its own genetic information by copying RNA to DNA and then
replicates causing the virus to spread into the cells that specifically fight
infection. When this occurs homeostasis
is disrupted within the human body and can lead to the drastic life threatening
HIV (Miller and Levine 484).
The grouping together of cells forms
human tissue and works in harmony to maintain homeostasis (Mader 607). There are 4 primary tissue types in the human
body; epithelial, connective, muscle and nerve (Mader 598). Epithelial tissue lines organs and provides
protection from abrasion and dehydration (Carpi). Muscle tissue accomplishes hematopoietic
tissue that manufactures blood cells helping the body maintain homeostasis with
assistance in blood production. Nerve tissue
transmits impulses and provides physical support for the neural tissue,
controls tissue fluids around the neurons, and helps defend the neurons from
invading organisms (Carpi).
Organs are the next level of
organization in the body. An organ is a
structure that contains at least two different types of tissue working together
for a common purpose (Carpi). There are many organs that perform as a system such
as the heart, liver, kidneys, gastrointestinal, respiratory and even the skin,
with the skin being the largest (Carpi).
There are three layers of the skin; the epidermis, dermis and
subcutaneous. The epidermis is the
outermost layer of skin and works as a barrier between the outside environment
and the inside of the body. The dermis
contains blood vessels that nourish skin cells and contains nerve tissue that
provides blood supply, temperature, and sensations (Carpi). The subcutaneous layer contains mostly
connective and adipose tissue. Adipose
tissue known as fat helps cushion the skin and provides protection from the
cold (Carpi). Homeostasis for the body
is maintained by protection, nerve impulses and circulation. Homeostasis is disrupted anytime there is a
break in the skin allowing potential for viral or bacterial invasion and body
infection.
Each organ and organ system must
work together to maintain homeostasis. The
perfect balance of homeostasis does not permit the body to under work or
overwork and each organ facilitates each other (Beers). The nervous system is very complex and has
the ability for the human body to survive, but it is dependent upon the ability
to monitor internal and external conditions and making appropriate changes as
needed. A loss of homeostasis becomes
evident in nervous system diseases such as Lou Gehrig Disease (Beers). The heart and circulatory system move
materials to and from body tissue very efficiently and loss of homeostasis
occurs with coronary artery disease and disruption of blood supply (Beers). The
digestive system takes in and digests food, and provides nutrient molecules
that enter the blood and replace the nutrients that are being used by the body
with the inability to eat causes death in the organism (Beers). The respiratory system adds oxygen and removes
carbon dioxide from the body and loss of homeostasis occurs anytime when ph
imbalance occurs (Miller & Levine 799). The liver and kidneys
work together to maintain homeostasis by regulating blood glucose levels. When the glucose enters the blood stream it
is filtered out by the liver and stored as glycogen and then broken down at a
later time as needed by the secretion of
insulin from the pancreas (Miller
& Levine 39). The kidneys regulate the balance of water in the blood
maintaining blood volume and blood pressure while excreting waste, salts and
substances that regulate the PH of the blood to maintain homeostasis (Mader 695).
Homeostasis is controlled somewhat by
body hormones but it is ultimately controlled by the nervous system with the
assistance from the brain by using negative feedback (Mader 608). Negative feedback is a mechanism that
maintains homeostasis and is regulated by a sensor and control center (Mader 608). The sensor detects imbalance in the internal body and the control
center brings about change and when homeostasis has been restored the organ
involved stops its’ action (Mader
608). Negative feedback works well
for example with regulation of blood glucose and body temperature.
Homeostasis is controlled as well with a
positive feedback system. This system is
useful to maintain homeostasis in situations such as childbirth, blood clotting,
and gastro intestinal breakdown of protein (Mader 609). A situation such as childbirth is a temporary change in the
body’s environment. Positive feedback is
stimulated by the nerves, the brain, and pituitary gland to assist in the
delivery process and eventual return to a pre-pregnant homeostatic state.
The body can tolerate slight fluctuations
within certain limits, but when homeostasis is outside the limits organ systems
begin to work to re-regulate the situation.
Any lack of response by organs in a timely manner can cause long lasting
effects on the body as a whole. For
example, when nutrients enter the body and glucose enters the blood stream, if
the stimulation of insulin in the correct amounts does not occur it can give
rise to a long lasting disease such as diabetes mellitus that can have very
harmful effects on the body. This
disease is an example of the body’s struggle with maintaining homeostasis that will
eventually affects every body system.
“If life is to continue, temperature, moisture
level, acidity and other physiological factors must remain within the tolerance
range of the organism” (Mader 4). The miracle of survival of the
organism is possible when homeostasis is maintained by body systems working
together to routinely monitor internal conditions and make indicated adjustments
without the conscious awareness of the organism.
