neurons Flashcards
what are neurons?
nerve cells that process and transmit messages through electrical and chemical signals
what are the 3 types of neurons?
- sensory neurons
- relay neurons
- motor neurons
what is the role of sensory neurons?
carry messages from PNS to CNS
what is the role of relay neurons?
connect sensory neuron to motor or other relay neurons
what is the role of motor neurons?
connect CNS to effectors (eg. muscles, glands)
what is the length of the dendrites and axons of the 3 neurons?
- sensory - long dendrites, short axons
- relay - short dendrites, short axons
- motor - short dendrites, long axons
what is the soma in a neuron?
- cell body
- includes a nucleus which contains genetic material of cell
what do dendrites do?
carry nerve impulses from neighbouring neurons towards the cell body
what does the axon do?
carries impulses away from cell body down the length of the neuron
what is the myelin sheath
fatty later that covers and protects the axon
what is the purpose of the myelin sheath?
speeds up electrical transmission of the impulse
what are the nodes of ranvier?
gaps in the myelin sheath
what is the purpose of the nodes of ranvier?
speed up the transmission of the impulse by forcing it to ‘jump’ across the gaps along the axon
what are terminal buttons?
- at the end of the axon
- communicate with the next neuron in the chain across a synapse
where are motor neurons found?
- cell bodies in the CNS
- have long axons so form part of PNS
where are sensory neurons found?
- outside of CNS
- in PNS in clusters known as ganglia
where are relay neurons found?
- make up 97% of all neurons
- most are found in brain and visual system
how is an electrical impulse that travels down the axon towards the end of the neuron created?
- when a neuron is in a resting state, the inside of the cell is negatively charged compared to the outside
- when a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second
- this causes action potential to occur
