neurons, synaptic transmission and neurotransmitters Flashcards
what is a neuron?
the basic building block of the nervous system. neurons are nerve cells that process and transmit messages through electrical and chemical signals
what are neurotransmitters?
brain chemicals released from synaptic vesicles. neurotransmitters relay signals from one neuron to another across a synapse. neurotransmitters can be broadly divided into those that perform an excitatory function and those that perform an inhibitory function
what is synaptic transmission?
the process by which neighbouring neurons communicate with each other by sending chemical messages across the tiny gap (synapse) that separates neurons.
what are the features of a neuron?
dendrite
cell body
nucleus
myelin sheath
node of ranvier
axon
terminal button
what is the cell body?
includes a nucleus containing the genetic material
- dendrites stick out the cell body and carry impulses from neighbouring neurons towards the cell body
what is the axon?
tube like structure that carries the impulses away from the cell body and down the length of the neuron
- the axon is covered by a fatty layer called the myelin sheath which is formed from special cells which wrap themselves around the axon
what is the myelin sheath?
protects the axon and speeds up electrical transmission of the impulse
- gaps (node of ranvier) allow this incrase in speed by forcing the impulses to JUMP across the gaps
what are the different types of neurons?
sensory neurons
motor neurons
relay neurons
what do sensory neurons do?
carry messages from sensory receptors along nerves in the peripheral nervous stem to the central nervous system
- have long dendrites and short axons
what do relay neurons do?
connect sensory and motor neurons together and also connect other relay neurons.
- short dendrites and short axon and are found in the CNS
what are the functions of the neuron?
when a neuron is in resting state it is negatively charged and when it is activated it becomes positively charged.
- this rapid switch is called depolarisation and this fires an action potential
this is generated once depolarisation reaches a certain threshold
what is synaptic transmission?
neurons communicate with each other within groups known as neural networks.
- they are separated by a synaptic cleft
although signals within neurons are transmitted electrically, signals between neurons have to be transmitted chemically across the synapse.
what is synaptic transmission?
a chemical process using biochemical substances using neurotransmitters.
what triggers the release of neurotransmitters?
when the AP reaches the end of the neuron it triggers the release of neurotransmitter from tiny sacs called synaptic vesicles
what is reuptake?
reuptake is when neurotransmitter molecules that remain in the synapse are reabsorbed into the presynaptic neuron so that they can be used again
what are the functions of neurotransmitters?
several dozen neurotransmitters have been identified in the human brain. each neurotransmitter has its own specific molecular structure and fits perfectly into specific postsynaptic neuron.
what are the categories of neurotransmitters?
- excitatory
- inhibitory
what causes inhibition?
the neurotransmitter serotonin causes inhibition in the postsynaptic neuron making the neuron more negatively charged and less likely to fire
what causes excitation?
dopamine causes excitation of the postsynaptic neuron by increasing its positive charge and making it more likely to fire
what is summation?
firing depends on summation of signals over time (temporal) or space (spatial)
- the excitatory and inhibitory influences are summed - if the net effect on the postsynaptic neuron is inhibitory then it is less likely to fire but if its excitatory the postsynaptic neuron is more likely to fire.
