Neurons Flashcards
What are neurons?
The basic building blocks of the nervous system, neurons are nerve cells that process and transmit messages through electrical and chemical signals
What does the cell body of a neuron do?
Hold the nucleus
What does the nucleus of a neuron do?
Contains genetic material for each neuron (the DNA)
What does the dendrites of a neuron do?
Carry electrical signals from other neurons
What does the axon of a neuron do?
Carries the electrical signal away from the cell body and down the length of the neuron
What does the myelin sheath of a neuron do?
It is a fatty layer that covers the axon. It is a ‘specialised’ feature of the neuron that speeds up the electrical signal
What does the nodes of ranvier of a neuron do?
they are gaps in the myelin sheath that make the signal go even faster - the signal ‘jumps’ across each gap
What does the axon terminal of a neuron do?
They are found at the end of the axon and are where synaptic transmission takes place
What are the three types of neurons?
Sensory neurons, relay neurons and motor neurons
What is the function of a sensory neuron?
Brings message from the peripheral nervous system to the central nervous system
What is the function of a relay neuron?
Carry messages from one part of the CNS to another. They connect motor and sensory neurons. They also connect other relay neurons
What is the function of a motor neuron?
Carry signals from the CNS to effectors in our body to execute a response, or to allow organs, glands and muscles to function
What are the characteristics of a sensory neuron?
Long dendrites, short axons, a cell body within the axon
What are the characteristics of a relay neuron?
Short dendrites, short axons, no myelin sheath
What are the characteristics of a motor neuron?
Short dendrites, long axons, cell body at the end of the axon
What are action potentials caused by?
Changes in the electrical charge in the neuron
What happens when the action potential reaches the axon terminal?
It can’t go any further so it instructs chemical transmission of the message at the synapse
Do neurons physically connect with other neurons?
No, there is a microscopic gap between each neuron - called the synaptic cleft
Where does chemical transmission of a message take place?
At the synapse
What is the process of chemical transmission?
→ When an action potential reaches the axon terminal the vesicles move and then fuse with the pre-synaptic membrane
→ This causes the neurotransmitters to be released into the synaptic cleft
→ The neurotransmitters diffuse across the synaptic cleft and attach to the receptors on the membrane of the post synaptic neuron
→ This binding then sets off an action potential in this neuron
What are the two effects that neurotransmitters can have on the next neuron?
Excitatory or inhibitory
What do excitatory neurotransmitters do?
Increase the neuron’s positive charge and make it more likely to fire
What do inhibitory neurotransmitters do?
Increase the neuron’s negative charge and make it less likely to fire
Give an example of an excitatory neurotransmitter
Adrenaline
Give an example of an inhibitory neurotransmitter
Serotonin
What happens if there are enough excitatory signals received by a neuron?
Summation occurs
