Structure and functiom of neurons Flashcards
Describe neurons
Fundamental units of the brain and the nervous system, responsible for receiving sensory input and sending electrical impulse between the brain and body to transfer messages
What is the role of neurons
Pass messages via electrical impulses
- receive and transmit between brain cells in response to info received from the rest of the body
Describe dendrites
Collects chemical signal from another neuron
Receives message to send to soma
Branched and short extension
Describe the soma (cell body)
Life support
Receives chemical signal from dendrite and changes it to electrical signals
Contains nucleus, DNA, ribosomes and mitochondria
Describe the axon
Long cable like extension
Sends a nerve impulse ( action potential ) through the neuron to transmit a message to the next neuron
Describe the myelin sheath
Protect the axon
Speed up transmission of the message by providing insulation
Describe the axon terminal (terminal button)
End of the neuron
Contains vesicles that store neurotransmitter
Sends the information through the neuron to the next neuron through the release of neurotransmitters
Pass nerve impulse from cell body to part of the body they control or activate
When do neurones transmit signals.
When stimulated by the sensory input or triggered by neighbouring neurones
What are the contact points between neurons
Synapses
What is sent across the synaptic cleft
Neurotransmitters- Chemical messages
What happens if the neurotransmitter isn’t accepted into the next neurone
It is reabsorbed by the pre synaptic neurone
Describe the sensory neuron
Send info from the sense (PNS) towards the brain (CNS)
Receptors found in eyes,ears, tongue, skin
Long dendrites and short axon
Describe the relay neuron
Connect sensory neuron to motor neuron or other relay neurons
Involved in analysing the sensations from these neurons and deciding how to respond
Short dendrites and short axon
Describe the motor neuron
Send info via long axons from the brain ( CNS) through to the effector eg muscle or glands
Long axon and short dendrites
Explain neurotransmitter and there functions
Chemical messages within the brain
Stored in vesicles
Only located in the presynaptic neuron
Transmit info from one neurone to another so a person performers an action
What is the synaptic cleft
The gap between each neuron
Where are receptors site found
Only on postsynaptic neuron
Describe excitatory neurotransmitter
Makes it more likely that the post synaptic neuron will fire so a impulse will travel down the axon
Increase the brain activity in the CNS
example-noradrenaline
Involved in maintaining alertness and arousal
Low levels casue- low energy, poor concentration
High levels cause - nervousness, high blood pressure
Describe inhibitory neurotransmitter
Prevents or reduces the likelihood that the next neuron will fire
Decrease the brains actively in the CNS
example - serotonin
Helps maintain a stable mood and plays a role in sleep,appetite and the pain response
Low levels cause - low mood, depression, aggression, sleep problems
High levels cause - happiness , risk taking behaviour
What is summation
When the excitatory and inhibitory influence are added together
If overall effect is mainly inhibitory- decrease likelihood of next neurone firing
If overall effect is mainly excitatory - increase likelihood of next neuron firing
Explain the role of serotonin
Helps maintain a stable mood and plays a role in sleep,appetite and the pain response
Low levels cause - low mood, depression, aggression, sleep problems
High levels cause - happiness , risk taking behaviour
Explain the role of noradrenaline
Involved in maintaining alertness and arousal
Low levels casue- low energy, poor concentration
High levels cause - nervousness, high blood pressure
Jeremy is digging in the garden. He feels the spade hit a rock and stops digging immediately.
Explain how sensory, relay and motor neurons would function in this situation.(6 marks)
The sensory neuron sends the information from the sense to the brain(CNS). The receptors in Jeremy’s hand would sense the jolt of the spade hitting the rock and send that information via the peripheral nervous system to his brain/CNS.Relay neurons connect with other neurons, mostly found in the brain/CNS - here they would be involved in analysis of the sensation, what it means, deciding about how to respond to it, thus acting between the sensory and motor neurons.Motor neurons send messages via long axons from the brain to the muscles or effectors – here the message from the brain instructs Jeremy’s arm muscles to stop working and stop the digging action.
Briefly outline how excitation and inhibition are involved in synaptic transmission.(4 marks)
Excitation and inhibition is the effect the neurotransmitter has on the likelihood of the next neuron being ready to fire. If the neurotransmitter is excitatory it increases the likelihood of the postsynaptic neuron firing an impulse which increases brain activity in the central nervous system for example noradrenaline. Whereas,if the neurotransmitter is inhibitory it decreases the likelihood of postsynaptic neuron firing an impulse which decreases brain activity in the central nervous system for example serotonin. The excitatory and inhibitory influences are summed, if the net effect on the postsynaptic neuron is inhibitory, the neuron will be less likely to ‘fire’ and if the net effect is excitatory, the neuron will be more likely to fire
