Bionic Bodies Focus 3 + 4

Endocrine System

The endocrine system also works to maintain homeostasis in humans. It is made up of glands and tissues that produce hormones.

Key word hormone: A hormone is a chemical substance, carried via the bloodstream, which alters the activity of specific target organs.

An example of this is the release of the hormone adrenaline, which is released by the adrenal gland. One of its target organs is the heart, where it increases the heart rate. Once a hormone has been used, it is destroyed by the liver.

Hormones can control the body, and the affects are much slower than the nervous system, but they last for longer.

Endocrine system vs nervous system

·        endocrine system communicates through the use of chemical molecules as opposed to electrical impulses – transported through the bloodstream à this means a slow but longer-lasting response.

·        The endocrine system has slower responses because it takes time to produce hormones and for those hormones to travel where they need to go.

·        The response is long-lasting as it will continue as long as hormones are in the area, and it takes time to destroy or remove them.

·        Both respond to stimuli and both use specialised communicational signals, transmitting messages around the body, both detect changes.

Homeostasis

The process by which organisms maintain a relatively stable internal environment. > variability kept within normal ranges.

Greek – ‘homeo’ – the same, ‘stasis’ – to stay.

Receptors, command centres and effectors work together to regulate processes and maintain homeostasis.

Stimulus response model:

Stimulus > receptor > command centre > effector > response

·        Negative and Positive Feedback Loops

-        Your body uses feedback loops to monitor and adjust internal conditions, keeping everything in balance.

-        Feedback loops are sometimes used to visualise the stimulus response pathway, and an important part of these models is the command centre (control centre).

-        Feedbacks loops are a variation of the stimulus-response model that represent how the body maintains homeostasis, but they have similar features to the flow diagrams you are already familiar with.

-        Negative feedback loops reverse a change brought on by a stimulus and brings internal conditions back to within normal ranges.

Ø  When a variable move too far from a set point, it triggers a negative feedback response that brings conditions back toward normal, like an in-built safety harness.

Ø  Most of your body’s systems use negative feedback. They are how your body maintains homeostasis.

Ø  E.g. when you are too hot (stimulus) you sweat, which cools you down (response). Eventually the original stimulus decreases until you are back at a normal temperature and you stop sweating.

-        Positive feedback loops amplify the change and increase the stimulus until the job is done.

Ø  E.g. during childbirth a woman as contractions (stimulus) which trigger the release of hormones that cause more contractions that are stronger and faster. Every time the body responds it causes the stimulus to increase until the job is done – the baby is born.

Ø  As positive feedback loops increase the change (stimulus), they move the body further away from homeostasis.

Glossary

·        Negative feedback loops – reverse a change brought on by a stimulus and bring internal conditions back within normal range.

·        Positive feedback loops – amplify the change and increase the stimulus until the job is done.

·        Homeostasis – the process by which organisms maintain a relatively stable internal environment.

·        Hormone - a chemical substance, carried via the bloodstream, which alters the activity of specific target organs.

·        Stimulus response model: Stimulus > receptor > command centre > effector > response