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B5 - Homeostasis and Response Cheat Sheet (DRAFT) by

5.1 - Homeostasis 5.2 - The Human Nervous System

This is a draft cheat sheet. It is a work in progress and is not finished yet.

5.1 Homeos­tasis

homeos­tasis
the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
In the human body, homeos­tasis controls :
· blood glucose concen­tration
· body temper­ature
· water levels
These automatic control systems, involving nervous responses & hormonal (chemical) responses, detect changes and respond to them.
All control systems include :
· receptors - cells that detect stimuli (changes in the enviro­nment)
· coordi­nation centres - receive and process inform­ation from receptors, e.g. brain, spinal cord, pancreas
· effectors - muscles or glands that bring about responses to restore optimum levels

5.2.1 Structure and Function

The nervous system enables humans to react to their surrou­ndings and to coordinate their behaviour.
neurone
adapta­tions
· long axon - can travel long distances in the body
· myelin sheath - insulates axon -> increases speed of nerve impulses
· dendrites - branch from dendrons ; receive incoming nerve impulses from other neurones
stimulus > receptor > coordi­nator > effector > response
· Inform­ation from receptors passes along cells (neurones) as electrical impulses to the central nervous system (CNS)
· The CNS (brain & spinal cord) coordi­nates the response of effectors which may be muscles contra­cting or glands secreting hormones
reflexes
automatic responses which occurs uncons­ciously
The inform­ation travels down a reflex arc, allowing vital responses to take place quickly.
These impulses do not pass through the conscious part of the brain.
· When a stimulus is detected by receptors, impulses are sent along a sensory neurone to the CNS
· In the CNS the impulse passes to a relay neurone from a sensory neurone via a synapse*
· Impulses are passed onto a motor neurone from a motor neurone via another synapse*
· The impulse reach an effector resulting in an approp­riate response (quicker than normal)
synapse
the connec­tio­n/gap between two neurones
*
· The electrical impulse is transf­erred by chemicals which diffuse across the gap
· These chemicals then set off a new electrical impulse in the next neurone.
stimulus > receptor > sensory neurone > CNS > motor neurone > effector > response
reaction
time
- how long it takes you to respond to a stimulus
- can be measured with the ruler drop test
·

5.2.2 The Brain

 

5.2.3 The Eye