Cheatography
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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 |
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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 |
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