When the environment around us changes, what stops us from boiling, freezing or even changing our shape?!
The reason is homeostasis, which is the maintenance of a constant internal environment in the body.
Hormones (chemicals) and the nervous system detect changes outside the body and create adaptions inside the body to counteract any extreme change - and they do this automatically, so you never even know it’s happening!
Two monitoring processes that are vital are thermoregulation in our bodies and osmoregulation in our cells!
Osmoregulation maintains water levels inside and outside the cell, in the blood.
Cells work best when these water concentrations are the same, meaning that the cell is in an iostonic solution.
If there's too much water outside the cell, the cell compensates by taking in water by osmosis, swelling up and potentially bursting. We say that these cells are in a hypotonic solution (low solute level).
However, if the water concentration is too low outside the cell, the cell will expel water by osmosis, making it shrivel up when in a hypertonic solution (lots of solute so little space for water).
In our bodies, the water concentration in the blood is managed by losing sweat from skin, our lungs breathing out water vapour, and also the water balance between the blood and urine managed by the kidneys.
Thermoregulation is the control of our internal body temperature. This should ideally be 37°C for optimum enzyme function - any lower, and enzymes lack the energy to work fast, while temperatures that are too high will cause them to denature.
Body temperature is monitored by the thermoregulatory centre in the hypothalamus of the brain, and has receptors that monitor blood temperature.
It acts as a coordination centre for incoming information and outgoing responses, causing effectors, such as the sweat glands, hormone glands and muscles, to perform commands to transfer energy to or from the environment.
The skin is made of three layers called the epidermis, the dermis and a fatty tissue layer. It has its own temperature receptors, meaning that the skin sends nerve impulses with skin temperature updates to the thermoregulatory centre. This then instructs effectors to make changes in our bodies including changes to our skin capillaries.
Thermoregulation is a negative feedback mechanism making sure all changes are heavily controlled.
If our blood temperature gets too hot, our skin receptors detect the change and send signals to the thermoregulatory centre, which triggers the effectors.
It makes our blood vessels dilate their muscular walls - this is called vasodilation, making more blood pass closer to the skin, causing more heat to be lost.
Also, the sweat glands in the dermis produce sweat that evaporates off the surface of the epidermis and takes heat energy into the environment.
If we get too cold, vasoconstriction occurs as the blood vessels narrow, meaning less blood goes near the skin and so less heat is lost.
Alongside this, we stop making sweat to conserve thermal energy.
We start to shiver as our skeletal muscles (such as arms and legs) start to contract and relax rapidly to create heat, using energy from respiration.
Hair erector muscles in the dermis receive impulses to contract to make our hair stand on end, trapping a layer of air close to the skin to insulate us.
Now it's time for some questions.