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Biology (Human Biology (The Nervous System (Sense Organs Detect Stimuli…
Biology
Human Biology
The Nervous System
Sense Organs Detect Stimuli
Stimulus
a change in your environment which you may need to react to
You need to be constantly monitoring what's going on so you can respond if you need to
You have 5 sense organs
Ears
Sound Receptor
Balance Receptor
Nose
Smell Receptors
Sensitive to chemical stimuli
Tongue
Taste Receptor
Sensitive to...
Sweet
Sour
Salt
Bitter
Taste of savoury things
Monosodium glutamate
1 more item...
Skin
Sensitive to...
Touch
Pressure
Temperature change
Eyes
Light Recepetor
All your sense organs contain different receptors.
Receptors are groups of cells which are sensitive to a stimulus
They change stimulus energy into electrical impulses
Examples of a stimulus...
Light
Sound
Touch
Pressure
Chemical
Change in position
Change in temperature
Sense organs and Receptors
Don't get them mixed up
The Eye
Sense Organ
Contains light receptors
The Ear
Sense Organ
Contains sound receptors
Sensory Neurones
Nerve Cell
Carries signals as electrical impulses
from the receptors in the sense organs to the central nervous system
Motor Neurones
Nerve Cell
Carries signals to the effector muscles or glands
Effectors
Muscles and glands are known as effectors
They respond in different ways
Muscles contract
in response to a nervous impulse
Glands secrete hormones
The Central Nervous System
Coordinates a resonse
The CNS is where all information from the sense organs is sent
and where reflexes and actions are coordinated
The CNS consists of the brain and spinal cord
Neurones transmit the information very quickly to and from the CNS
Instructions from the CNS are sent to effectors which respond accordingly
Reflexes
Reflexes help prevent injury
If someone shines a bright light in your eyes
Pupils automatically get smaller
So less light gets into the eye
Stops it getting damaged
When you get a shock!
body releases the hormone adrenaline automatically
It doesn't wait for you to decide that you're shocked
Automatic responses to certain stimuli
They can reduce the changes of being injured
The passage of information in a reflex
from receptor to effector
Called a reflex arc
The reflex Arc goes through the CNS
The neurones in reflex arcs go through the spinal cord (or an unconscious part of the brain)
When a stimulus is detected by receptors, an impulse is sent along a sensory neurone to the spinal cord
In the spinal cord the sensory neurone passes on the message to another type of neurone
The impulse then travels along the motor neurone to the effector
The muscle then contracts and moves your hand away from the bee
Becuase you don't have to think about the response it's quicker than normal responses
Bee stings finger
Stimulation of the pain receptor
Messages travels along the sensory neurone
Message is passed along a relay neurone
Message travels along a motor neurone
When message reaches muscle, it contracts
Synapses connect neurones
The connection between two neurones is called a synapse
The nerve signal is transferred by chemicals which move across the gap
These chemicals then set off a new electrical signal in the next neurone
Hormones
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Evolution and Environment
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Enzymes and Homeostasis
Genetics
Microorganisms