B7.3 Peak performance – energy balance

B7.3 Peak performance – energy balance

Homeostasis is the maintenance of a constant internal environment – it is achieved by balancing bodily inputs and outputs, while removing waste products.

In order to maintain a constant body temperature, the heat produced within the body (e.g. from respiration) or absorbed from the environment must be balanced by the heat lost from the body.

Sensors in the body are called receptors – they are often located in the sense organs such as the ear, eye and skin. Receptors are groups of specialised cells that can detect changes in the environment – these changes are called stimuli.

Temperature receptors in the skin detect external temperature and send nerve impulses to the brain.

There are also temperature receptors in the brain (in the hypothalamus) which monitors the temperature of the blood flowing through it. The brain processes this information and send impulses to the effectors – parts of the body (e.g. sweat glands and hair muscles) which produce a response to a stimulus.

The hypothalamus acts as a processing centre


If the temperature of the body is TOO HIGH then heat needs to be transferred to the environment – this is achieved through sweat being produced by sweat glands which cools the body when it evaporates.

Vasodilation is the widening of the blood vessels (capillaries) that run very close to the surface of the skin.

When the hypothalamus senses hot conditions, it sends impulses which cause blood vessels supplying the capillaries in the skin to dilate (vasodilation) – the increased blood flow to the surface tissues under the skin means that more heat is lost

Dehydration can be caused by increased sweating – dehydration stops sweating from taking place which leads to the core temperature (37˚C) increasing even further.

If the temperature of the body is TOO LOW then the body starts to shiver – shivering is the rapid contraction and relaxation of muscles – these contractions require energy from increased respiration and heat is released as a by-product, warming surrounding tissue.

Vasoconstriction is the narrowing of the blood vessels (capillaries) that run very close to the surface of the skin

When the hypothalamus senses the body is in cold conditions – it sends impulses which cause blood vessels supplying the capillaries in the skin to contract (vasoconstriction) and it reduces the blood flow to the surface tissues under the skin – as a result less heat is lost.

This an example of  effectors working antagonistacally – which means that they do opposite things – this allows a more sensitive and controlled response.

Glucose is needed for respiration – when we eat foods containing carbohydrates, enzymes are needed to break them down into monomers.

Processed foods, compared to fresh foods are foods that have been changed from their naturally occurring state to make them healthier and/or for convenience.

After a meal, the digestion of carbohydrates in the intestines release sugars – these sugars are absorbed into the blood.

High levels of sugar, common in some processed foods are quickly absorbed into the blood stream causing a rapid rise in the blood sugar level

The brain, the pancreas and the liver are all involved in regulating blood glucose.

Insulin is a hormone which is released by the pancreas in the response to rising blood sugar levels – insulin causes sugars to be stored in the liver in the form of glycogen and this in turn lowers your blood sugar level.

If the body does not produce insulin, or the insulin does not work properly, then this is called diabetes

A balanced diet which includes complex carbohydrates and fibre can help to maintain a steady blood sugar level

This is because complex carbohydrates take longer to digest, so the release of sugar happens over a long period of time – fibre meanwhile cannot be digest and therefore does not affect the concentration of sugar in the blood.