noadswood science, 2011. the nervous system to know how the body responds to the outside...
TRANSCRIPT
Noadswood Science, 2011
The Nervous System
To know how the body responds to the outside environment
Tuesday, April 18, 2023
The Nervous System
The nervous system allows us to react to the surroundings and respond to the changes – it carries electrical impulses up to 120m/sec
Receptors are groups of specialised cells which detect stimuli (changes in the environment)
These stimuli detections are then converted into electrical impulses
Receptors are often located in the sense organs, with each sense organ having receptors sensitive to particular kinds of stimuli – what sense organs does the human body have?
Sense Organs
Each organ has receptors sensitive to particular kinds of stimulus…
Skin Tongue Nose Eyes Ears
What stimuli do these sense organs detect?
Sense Organs
Each organ has receptors sensitive to particular kinds of stimulus…
Sense Organ Receptor Sensitive To…
Skin Touch, pain, pressure, temperature
Tongue Chemicals in food (taste)
Nose Chemicals in air (smell)
Eyes Light
Ears Sound (and position of head)
Receptors
In groups test your senses on one another – have someone blindfolded within the group and investigate their different senses (taking this in turns)
Try and keep the equipment secret so those being tested cannot just guess from what they have already seen!
Coordinator
The central nervous system (CNS) in humans consists of the brain and spinal cord
When a receptor is stimulated, it sends a signal along the nerve cells (neurones) to the brain
The brain then co-ordinates the response
Effectors
An effector is any part of the body that produces the response
Some examples of effectors in the human body include: - A muscle contracting to move the arm A muscle squeezing saliva from the salivary gland A gland releasing a hormone into the blood
Conscious Responses
The nervous system enables us to react to our surroundings
It consists mainly of the brain, the spinal chord, nerve cells (neurones) and receptors…
When we react to a stimulus our bodies use the following pattern: -
Stimulus Receptor Coordinator Effector Response
Conscious Responses
Stimulus Receptor Coordinator Effector Response
Stimulus – a change in the environment Receptor – a specialised cell which detects the stimulus Coordinator – part of the body which coordinates a
response Effector – part of the body which produces a response Response – the change in the body
Conscious Response ExampleStimulus Receptor Coordinator Effector Response
What are the stimulus, receptor, coordinator, effector and response in the following example?
Oh No!
Conscious Response Example
Stimulus – shark swims close; receptor – eyes detect shark; coordinator – brain determines what to do; effector – muscles respond; response – individual swims quickly!
Neurones
Neurones are nerve cells – they carry information as tiny electrical signals
There are three different types of neurones, each with a slightly different function: - Motor neurones carry signals from the central
nervous system to effectors Sensory neurones carry signals from receptors to the
spinal cord and brain Relay neurones carry messages from one part of the
central nervous system to the another
Motor neurone Sensory neurone Relay neurone
Neurone
A typical neurone consists of the: - Cell body – containing the nucleus, cell membrane,
cytoplasm and many dendrites (highly branched to convey nerve impulses towards the cell body)
Axon – long extension from the neurone to carry the impulse)
Nerve endings – where the synapses are located (connection between two neurones)
Synapses
Where two neurones meet, there is a tiny gap called a synapse
Signals cross this gap using chemicals – one neurone releases the chemical into the gap and the chemical diffuses across resulting in the next neurone transmitting an electrical signal
Conscious Response
1. Receptors in your skin detect a stimulus
2. The impulse is carried by sensory neurones to the spinal chord
3. Here relay neurones carry signals to and from the brain
4. The brain ‘decides’ to move away the hand
5. This impulse is sent by motor neurones to the hand muscles (the effectors) via the spinal chord…
6. Which then moves the hand away
Conscious Responses
Stimulus Receptor Sensory neurone Relay neurone
Coordinator Motor neurone Effector Response
Sensory neurone
Relay neurone
Motor neurone
Stimulus & receptor
Co-ordinator
(CNS)
Effector & response
Reflex Responses
When a receptor is stimulated, it sends a signal to the central nervous system, where the brain co-ordinates the response
Sometimes a very quick response is needed, one that does not need the involvement of the brain – this is a reflex action
Reflex actions are rapid and happen without us thinking, e.g. you would pull your hand away from a hot flame without thinking about it
Reflex Responses
Reflex Responses
Stimulus Receptor Sensory neurone Relay neurone
Motor neurone Effector Response
Reflex Arcs
1. Receptor detects a stimulus - change in the environment
2. Sensory neurone sends signal to relay neurone
3. Motor neurone sends signal to effector
4. Effector produces a response
Reflex Arcs
The way the iris in our eye adjusts the size of the pupil in response to bright or dim light is also a reflex action
In bright light – radial muscles of the iris relax and circular muscles of the iris contract resulting in less light entering through the eye via the contracted pupil
In dim light – radial muscles of the iris contract and circular muscles of the iris relax resulting in more light entering through the eye via the dilated pupil
Conflict
Look at the following and say the COLOUR, not the word!
Left / right side brain conflict – the right side of your brain is trying to say the colour, whilst the left side is trying to read the word!
YELLOW
BLACKINDIGO
WHITE
BLUE
PURPLEORANGE
REDGREEN
LILAC