Neurons and synaptic transmission Flashcards
neuron
definition
basic building blocks on the nervous system
└nerve cells that process and transmit messages through electrical and chemical signals
Types of neuron
sensory neurons: PNS → CNS
└long dendrites, short axons
relay neurons: sensory neuron → motor/relay neurons
└short dendrites, short axons
motor neurons
└CNS → effectors (muscles/glands)
└short dendrites, long axons
sensory neurons
PNS → CNS
└long dendrites, short axons
relay neurons
sensory neuron → motor/relay neurons
└short dendrites, short axons
motor neurons
CNS → effectors (muscles/glands)
└short dendrites, long axons
Structure of a neuron
└cell body includes a nucleus
└dendrites protrude from the cell body
└carry nerve impulses from neighbouring neurons →cell body
└axon: carries impulses from cell body →down neuron
└covered in fatty layers of myelin sheath
└protects axon, speeds electrical transmission of impulse (nodes of Ranvier force it to jump)
└terminal buttons at the end of the axon
└communicate with the next neuron across a synapse
Electric transmission- firing of a neuron
└neuron at resting state
└inside of cell is negatively charged compared to the outside
└neuron is activated by stimulus
└inside of cell becomes positively charged for a split second → causes action potential to occur
└creates an electrical impulse that travels down the axon towards the end of the neuron
synaptic transmission
definition
the process by which neighbouring neurons communicate with each other by sending chemical messages across the gap (synaptic cleft) that separates them
└neurons communicate with each other in neural networks
how different types of signals are transmitted
└signals within neurons are transmitted electrically
└signals between neurons are transmitted chemically- by synaptic transmission
synaptic transmission
process
└when the electrical impulse reaches the end of the neuron (presynaptic terminal) it triggers the release of neurotransmitter from tiny sacs called synaptic vesicles
└once the neurotransmitter crosses the gap, it is taken up by the postsynaptic receptor sites (dendrites of next neuron)
└chemical message → electrical impulse
└process of transmission begins again with next neuron
Neurotransmitter
definition
brain chemicals released from synaptic vessels that relay signals across the synapse from one neurone to another
acetylcholine (ACh)
causes muscles to contract
excitation
when a neurotransmitter (e.g. adrenaline) increases the positive charge of the postsynaptic neuron
└increases the likelihood that the neuron will fire and pass on the electrical impulse
inhibition
when a neurotransmitter (e.g. serotonin) makes the charge of the postsynaptic neuron more negative
└decreases the likelihood that the neuron will fire and pass on the electrical impulse
Neurotransmitter
functions
└excitatory function
└inhibitory function
