When the environment changes, why don’t we boil, freeze or change our shape?
This concept is HOMEOSTASIS: 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 the cell is in an ISOtonic solution.
But if there's too much water outside the cell, the cell compensates by taking in water via 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 via osmosis, making it shrivel up when in a HYPERtonic solution (lots of solute so little space for water).
In our bodies, the blood water concentration is managed by losing sweat from skin, our lungs breathing out water vapour and the water balance between the blood and urine by the kidneys.
Thermoregulation is the control of our internal body temperature, which is always aimed at an ideal 37°c for our enzyme catalysts- any lower and they lack the energy to work fast, and they will denature if we get too hot.
Body temperature is monitored by the THERMOREGULATORY CENTRE in the HYPOTHALAMUS in the brain and has receptors that monitor blood temperature.
It acts as a COORDINATION CENTRE for incoming information and outgoing responses, causing EFFECTORS like the sweat glands, hormone glands and muscles to perform commands to transfer energy to and from the environment.
The skin is made of 3 layers called the EPIDERMIS, the DERMIS and a FATTY TISSUE LAYER, and it has its own temperature receptors, meaning the skin sends nerve impulses with skin temperature updates to the thermoregulatory centre which makes effectors change our bodies including 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, send signals to the thermoregulatory centre, which triggers the effectors.
1. Here, it makes our blood vessels dilate their muscular walls- this is called VASODILATION, making more blood pass closer to the skin and so more heat is lost.
2. 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,
1. VASOCONSTRICTION occurs as the blood vessels narrow, meaning less blood goes near the skin and so less heat is lost.
2. Alongside this, we stop making sweat to conserve thermal energy
3. We start to shiver as our skeletal muscles (like arms and legs) start to contract and relax rapidly to create heat using energy from respiration.
4. Hair erector muscles in the dermis receive impulses to contract to make your hair stand on end, trapping a layer of air close to the skin to insulate you.