Homeostasis is the process that controls certain
things in the body such as body temperature (37oC) and water
levels in order to ensure they say the same. It can also be described as
maintenance of a constant internal environment. (GCSE Bitesize, OCR 21C
Additional Science (Pre-2011), Homeostasis)
As well as temperature, homeostasis helps to
keep the concentration of ions in the bloodstream stable, alongside the pH
balance and the concentration of glucose in the bloodstream.
Homeostasis is maintained in different ways. For
example, body temperature is maintained through the whole body whereas the stomach
will maintain a pH level that is different to a surrounding organ. Furthermore,
every cell will have a different concentration of ions to each other. In order
to maintain the body’s overall function then, homeostasis needs to be
maintained at every level within the body.
Organs and other biological systems are
constantly being pushed away from their stable levels. An example of this would
be that during physical activity: your body temperature would increase due to
heat being produced.
Negative and positive feedback loops are
involved in the process of maintaining homeostasis. Negative feedback loops are
a trigger that starts the process of adjusting something back to a stable
level. For example, if you drink a glass of orange juice, your blood glucose
levels will rise and the pancreas will act to produce insulin to bring the
blood glucose level back to stable. Another example would be if your body
temperature rises, a negative feedback loop would bring it back to the stable
range. It works through sensors detecting the increase in body temperature and
relaying the information to the part of the brain that controls body
temperature, the hypothalamus. Once the hypothalamus receives this information
it will activate the relevant effector, which will oppose what is happening in
the body, and stabilise the body temperature.
The set target value is not always a fixed
value. For example, body temperature will change over a 24-hour period. Having
a fever will also have a temporary increase in the temperature set value so
that the heat generating response is activated when it needs to be with
temperatures higher than the normal set value.
Most homeostatic circuits have two negative
feedback loops, one for when something in the body is above the set target
value and one for when it’s under. Due to the fact that homeostasis is
dependant on negative feedback loops, anything that interferes with them,
usually causes disruption within homeostasis, which can lead to diseases. (“Homeostasis”
by OpenStax College, Anatomy & Physiology)
An example of this is diabetes. Diabetes is
caused by a broken feedback loop involving insulin. The broken feedback loop
means that the body cannot bring high blood sugar levels down to the healthy
level, which is generally between 70mg/dl (milligrams per decilitre) and
Normally within the human body, blood sugar
levels are controlled by two hormones, which are insulin and glucagon. The
purpose of insulin is to decrease the concentration of glucose in the blood.
After eating, your blood sugar levels rise, which cause the pancreas to secrete
insulin to bring the level back down. Insulin is also used as a signal that
triggers cells like fat and muscle to use the glucose in the body for energy
and it allows glucose to convert into glycogen, which is a storage molecule
usually found in the liver. Both of these processes take sugar out of the
blood, which brings blood sugar levels back down to the normal range.
If you haven’t eaten for a while it will cause
your blood glucose levels to fall, which will cause glucagon to be secreted
from a different group of pancreatic cells. Once glucagon is broken down into
glucose, it is released into the bloodstream and therefore causes the blood
sugar levels to go back up to the normal range.
Diabetes occurs when the pancreas can’t make
enough or any insulin, or when the body stops responding to insulin. This means
that blood sugar levels will stay high and continue rising after a meal. This
is because muscle and fat cells do not get enough energy from glucose, which
can cause fatigue and causing muscle and fat tissues to degrade. Also, high
blood sugar can cause things such as urination, thirst, and dehydration and
eventually can lead to more serious complications. (“Homeostasis”
by OpenStax College, Biology) The pancreas is also part of the
endocrine system, and the involvement it has within homeostasis is very
Another example of homeostasis within the body
is based around bacteria and viruses. When the human body gets ill due to
bacteria and viruses, the lymphatic systems helps to maintain homeostasis. The
lymphatic system has a number of functions: It removes fluid from tissues,
absorbs and transports fatty acids from the digestive system and transports
white blood cells from the lymph nodes into the bones. Therefore, the lymphatic
system will try to fight illnesses before you become sick, trying to make sure
you remain healthy. (Homeostasis
Example. YourDictionary, n.d. Web. 19 January 2018.)
The endocrine system is a system of glands that
assist the body in carrying out bodily function. The endocrine system secretes
and produces hormones, which affects all the organs within the body and is
important for things such as the regulation of temperature, therefore making it
important for homeostasis.
The function of the hypothalamus in the
endocrine system is to assist the pituitary gland. Hormones that are produced
within the hypothalamus travel to the pituitary gland to help control and
stimulate it. The pituitary gland is also known as the master gland due to the
fact that it is able to regulate other glands in the human body. It does this
by deciding how much of the hormone is needed to be secreted into the
The pituitary gland consists of two parts. These
are the anterior lobe and the posterior lobe. The posterior lobe is smaller
than the anterior lobe. It secretes and stores two hormones: oxytocin and
antidiuretic hormone, otherwise known as ADH. Oxytocin is responsible for the
contractions in the uterus during childbirth. ADH is made in the hypothalamus,
secreted by the pituitary gland and gets stored in the posterior lobe. ADH
helps to control blood pressure through acting on the kidneys and blood vessels.
Alongside this, it has another, more important role in the human body, which is
to conserve the fluid volume of the human body. It does this by reducing the
amount of water that is passed out in the urine; it allows water in the urine
to be taken into the body in a specific area of the kidney. Thus, more water
returning to the bloodstream, urine concentration rises and water loss
There are four glands that are located behind
the thyroid called the parathyroid glands. The hormone that is produced by this
gland is called PTH, also known as parathyroid hormones. This hormone regulates
calcium levels through stimulating the bones so more of it is released when the
levels in the bloodstream are too low.
The adrenal gland is just above the kidney and
is involved in releasing epinephrine and norepinephrine in stressful situations.
Furthermore, the pineal gland, which is found in
the centre of the brain, produces melatonin, which is what causes people to
become tired and sleepy. Melatonin levels are higher at night than during the
The ovaries and testes are also involved in the
endocrine system. The hormones produced in female ovaries are oestrogen and
progesterone, which help to regulate the menstrual cycle and assists with the
production of eggs. Testosterone is produced in the testes, which is important
for male sperm production. (L. Samuel, The Endocrine System)
Similarly to the endocrine system working with
homeostasis to regulate control within the human body, all the organ systems
within the body are required to work together in order to allow for a good
overall functioning of the body.
Tasks within the body, such as cellular
respiration, need the support of multiple organ systems working together.
Cellular respiration requires glucose from food and oxygen, where the
respiratory system brings oxygen into the lungs when you breathe and the
digestive system breaks down food into glucose. The circulatory system moves
glucose and other nutrients to the cells as well as moving oxygen from the
lungs to the cells. The circulatory system also moves carbon dioxide waste from
the cells to the lungs and through gas exchange; carbon dioxide waste is
removed from the body when you breathe out. Therefore, this demonstrates how
multiple organ systems will work together in order to provide normal and
healthy bodily function.
Both the endocrine and nervous system help to
control functions in the human body, however they both do so in different ways.
Within the endocrine system, chemical messages travel to all parts of the body,
whereas in the nervous system the messages travel to specific target cells or
group of cells.
The conduction of messages in the endocrine
system is chemical, yet is both chemical and electrical in the nervous system.
The effectors of the endocrine system are organs
and glands, which are to do with the internal environment and development, yet
within the nervous system the effects, are muscles and glands.
Within both the endocrine and nervous systems,
the hypothalamus is involved in controlling the internal environment within
The speed of movement of information in the
endocrine system is slower than the nervous system, where the information moves
a lot faster.
The endocrine system provides a long-term effect
yet the nervous system has a short-term effect.