Negative feedback

Negative feedback loop

Where a change in something brings about a process that causes the opposite effect, keeping levels constant

Positive feedback loop

A process in which the end products of an action cause more of that action to occur in a feedback loop, for example adrenaline promotion

Thyroxine or thyroid hormone

A hormone which stimulates the basal metabolic rate and plays an important role in growth and development

Thyroid gland

Releases thyroxine in response to stimulation by TSH

Thyroid-stimulating hormone (TSH)

A hormone released by the pituitary gland which stimulates the thyroid gland to release thyroxine

Thyroxine negative feedback

When thyroxine levels are high, thyroxine inhibits itself by signalling the pituitary gland to stop releasing TSH

Basal metabolic rate

The rate of activity from basic life-sustaining metabolic processes that occur in the body, even when at rest

Adrenaline

A hormone secreted by the adrenal glands that regulates internal conditions required for a fight or flight response

Effects of adrenaline on the body

Increased heart and ventilation rate, increased blood supply to key organs, promotion of glucagon and inhibition of insulin

Adrenal glands

Glands situated above the kidneys that are responsible for the release of adrenaline during a fight or flight response

Fight or flight response

A physiological reaction that occurs in response to a stimulus that is perceived as being stressful

Stress

Exposure to a negatively perceived stimulus that can be physical or emotional

Increased heart rate

Blood is pumped quicker during fight or flight and can reach key structures quickly to provide them with glucose and oxygen

Increased ventilation rate

Gas exchange can occur quicker during fight or flight so that more oxygen is available for aerobic respiration

Reduced blood supply to the gut

Reduces the supply of glucose and oxygen to digestive organs, which are not a priority during fight or flight

Increased blood supply to the brain and muscles

Provides the brain and muscles with more glucose and oxygen during fight or flight, allowing quicker responses to stressful stimuli

Glucose and oxygen

Reactants required for aerobic respiration, so that energy can be released and supplied to key organs during fight or flight

Pancreas during fight or flight

Inhibits insulin and promotes glucagon so that increased levels of glucose are available for respiration

Negative feedback of reproductive hormones

If the levels of one reproductive hormone are too high, another reproductive hormone such as progesterone will inhibit it

Negative feedback of insulin and glucagon

High levels of blood glucose leads to insulin production and low levels of blood glucose leads to glucagon production

Negative feedback loop

Where a change in something brings about a process that causes the opposite effect, keeping levels constant

Positive feedback loop

A process in which the end products of an action cause more of that action to occur in a feedback loop, for example adrenaline promotion

Thyroxine or thyroid hormone

A hormone which stimulates the basal metabolic rate and plays an important role in growth and development

Thyroid gland

Releases thyroxine in response to stimulation by TSH

Thyroid-stimulating hormone (TSH)

A hormone released by the pituitary gland which stimulates the thyroid gland to release thyroxine

Thyroxine negative feedback

When thyroxine levels are high, thyroxine inhibits itself by signalling the pituitary gland to stop releasing TSH

Basal metabolic rate

The rate of activity from basic life-sustaining metabolic processes that occur in the body, even when at rest

Adrenaline

A hormone secreted by the adrenal glands that regulates internal conditions required for a fight or flight response

Effects of adrenaline on the body

Increased heart and ventilation rate, increased blood supply to key organs, promotion of glucagon and inhibition of insulin

Adrenal glands

Glands situated above the kidneys that are responsible for the release of adrenaline during a fight or flight response

Fight or flight response

A physiological reaction that occurs in response to a stimulus that is perceived as being stressful

Stress

Exposure to a negatively perceived stimulus that can be physical or emotional

Increased heart rate

Blood is pumped quicker during fight or flight and can reach key structures quickly to provide them with glucose and oxygen

Increased ventilation rate

Gas exchange can occur quicker during fight or flight so that more oxygen is available for aerobic respiration

Reduced blood supply to the gut

Reduces the supply of glucose and oxygen to digestive organs, which are not a priority during fight or flight

Increased blood supply to the brain and muscles

Provides the brain and muscles with more glucose and oxygen during fight or flight, allowing quicker responses to stressful stimuli

Glucose and oxygen

Reactants required for aerobic respiration, so that energy can be released and supplied to key organs during fight or flight

Pancreas during fight or flight

Inhibits insulin and promotes glucagon so that increased levels of glucose are available for respiration

Negative feedback of reproductive hormones

If the levels of one reproductive hormone are too high, another reproductive hormone such as progesterone will inhibit it

Negative feedback of insulin and glucagon

High levels of blood glucose leads to insulin production and low levels of blood glucose leads to glucagon production