B5- Homeostasis and Response

Homeostasis

Homeostasis= maintaining a stable internal environment

The conditions inside your body need to be kept steady because your cells need the right conditions in order to function properly.

Homeostasis is about the regulation of the conditions inside your body and maintaining a stable internal environment in response to changes in both internal and external conditions.

Automatic control systems include nervous and hormonal communication systems. These maintain your body temperature, blood glucose levels and your water content.

Negative feedback counteracts changes;

1. Receptor detects a stimulus - level is to high

2. The coordination centre recieves and processes the information then organises a response

3. Effector produces a response which countereacts the change and restores the optimum level - the level decreases

1. Receptor detects a stimulus - level is too low

2. The coordination centre recieves and processes the information then organises a response

3. Effector produces a response which countereacts the change and restores the optimum level - the level increases.

The Nervous System

The nervous system detects adn reacts to stimuli and is made up of different parts...

Central Nervous System= Is the coordination centre- it recieves information from the receptors and then coordinates a response. The response is then carried out by effectors. In vertebrates this system consists of the brain and spinal cord only. In mammals the central nervous system is connected to the body by sensory neurones and mototr neurones.

Sensory Neurones= The neurons that carry information as electrical impulses from the receptors to the central nervous system.

Motor Neurones= The neurones that carry electrical impulses from the central nervous system to effectors.

Receptors and Effectors can form part of complex organs

Receptors= the cells that detect stimuli. Eg- taste receptors on the tounge and sound receptors in the ears. Receptors can form part of larger, complex organs, Eg- the retina of the eye is covered in light receptor cells.

Effectors= respond to the nervous impulses and bring about a change. Muscles and glands are known as effectors- they respond in different ways. Muscles contract in response to a nervous impulse, whereas glands secrete hormones.

Synapses and Reflexes

Synapses= connect neurones. The connection between two neurones is called a synapse. The nerve signal is transferred by chemicals which diffuse across the gap. These chemicals the set off a new electrical signal in the next neurone.

Reflexes= Help prevent injury. They are rapid, automatic responses to certain stimuli that don't involve the part of the brain. They reduce injury because for example if someone shines a bright light in your eye, your pupils automatically get smaller so that less light gets into the eye.

Reflec arc= The passage of information in a reflex.

The reflex arc goes throigh the central nervous system...1. The neurones in reflex arcs go through the cord or through an unconscious part of the brain.2. When a stimuli- a bee sting is detected by the receptors, impulses are sent along the sensory neurone to a relay neurone in the central nervous…