Topic 7: Run for your Life
Homeostasis
Homeostasis
Homeostasis is the maintenance of a constant internal environment. Things like our temperature,
blood pH and blood glucose concentration needs to stay relatively stable in order to keep our cells
functioning effectively. If internal conditions such as temperature or pH within our bodies don’t remain
within certain limits, then enzymes will become denatured. Fluctuations in temperature result in
hydrogen bonds breaking within the enzyme’s structure whereas changes in pH cause hydrogen and
ionic bonds to break. The enzyme loses the shape of its active site and can no longer catalyse
important biological reactions, such as respiration or DNA replication.
Negative and positive feedback mechanisms
Conditions within our bodies which are subject to homeostasis (such as temperature, pH and blood
glucose concentration) are controlled by negative feedback mechanisms. These are mechanisms
which act to reverse a change in the body - i.e. if temperature increases, a negative feedback
mechanism ensures that changes to our body occurs in order to reduce our body temperature. The
change in our body is detected by receptors (e.g. thermoreceptors which detect temperature or
chemoreceptors which detect pH) and the reversal of the change is brought about by effectors
(such as sweat glands which can modify the amount of sweat produced in order to change our body
temperature). Negative feedback mechanisms therefore enable conditions within our body to remain
within certain limits, fluctuating around the normal level.
In contrast, positive feedback mechanisms will amplify a detected change, moving conditions
away from the normal level. They are used to accelerate a biological pathway, for example, the
formation of a blood clot after an injury. At the site of a wound, activated platelets release a
Homeostasis
Homeostasis
Homeostasis is the maintenance of a constant internal environment. Things like our temperature,
blood pH and blood glucose concentration needs to stay relatively stable in order to keep our cells
functioning effectively. If internal conditions such as temperature or pH within our bodies don’t remain
within certain limits, then enzymes will become denatured. Fluctuations in temperature result in
hydrogen bonds breaking within the enzyme’s structure whereas changes in pH cause hydrogen and
ionic bonds to break. The enzyme loses the shape of its active site and can no longer catalyse
important biological reactions, such as respiration or DNA replication.
Negative and positive feedback mechanisms
Conditions within our bodies which are subject to homeostasis (such as temperature, pH and blood
glucose concentration) are controlled by negative feedback mechanisms. These are mechanisms
which act to reverse a change in the body - i.e. if temperature increases, a negative feedback
mechanism ensures that changes to our body occurs in order to reduce our body temperature. The
change in our body is detected by receptors (e.g. thermoreceptors which detect temperature or
chemoreceptors which detect pH) and the reversal of the change is brought about by effectors
(such as sweat glands which can modify the amount of sweat produced in order to change our body
temperature). Negative feedback mechanisms therefore enable conditions within our body to remain
within certain limits, fluctuating around the normal level.
In contrast, positive feedback mechanisms will amplify a detected change, moving conditions
away from the normal level. They are used to accelerate a biological pathway, for example, the
formation of a blood clot after an injury. At the site of a wound, activated platelets release a
