Biopsychology: Neurons And Synaptic Transmission Flashcards
What are neurons
- 80% neurons are located in the brain
- they transmit signals chemically and electrically
- provide the nervous system with its primary means of communication
What are the three types of neurons
- motor neurons
- sensory neurons
- relay neurons
Outline ‘sensory neurons’
- carry messages from the PNS (peripheral nervous system) to the CNS
- long dendrites + short axons
Outline ‘relay neurons’
- connect sensory neurons to the motor and other relay neurons
- short dendrites and short axons
Outline ‘motor neurons’
- connect the CNS to effectors such as muscles and glands
- short dendrites and long axons
What is the role of a ‘cell body’ in a neuron
- includes a nucleus - which contains the genetic material of the cell
What is the role of a ‘dendrite’ in a neuron
- carry nerve impulses from neighbouring neurons towards the cell body
What is the role of an ‘axon’ in a neuron
- carries the impulses away from the cell body down the length of the neuron
- covered in a fatty layer of myelin sheath that protect the axon + speeds up electrical transmission of the impulse
What is the role of the ‘nodes of ranvier’ in a neuron
- segments the myelin sheath
- speeds up transmission of the impulse by forcing it to ‘jump’ across the gaps along the axon
What is the role of ‘terminal buttons’ on a neuron
- located at the end of the axon
- communicate with the next neuron in the chain across a synapse
How does electrical transmission (the firing of a neuron) occur
- when a neuron is activated by a stimulus, the inside becomes positively charged for a second, causing action potential to occur
- this creates an electrical impulse that travels down the axon towards the end of a neuron
What is synaptic transmission
The process by which neighbouring neurons communicate with each other by sending chemical messages across the gap (synaptic cleft) that separates them
How does chemical transmission occur (across a synapse)
- signals between neurons are transmitted chemically by synaptic transmission
- when the electrical impulse reaches the end of the neuron (presynaptic terminal) it triggers the release of neurotransmitter from sacs called synaptic vesicles
What is a neurotransmitter and what role do they play
- chemicals that diffuse across the synapse to the next neuron in the chain
- when the neurotransmitter crosses the gap it is taken up by the post synaptic receptor sites
- then, the chemical message is converted back into an electrical impulse
- there are different types of neurotransmitters each with their own structure that fits into a post synaptic receptor site
What is ‘excitation’
- neurotransmitters have either an excitatory or inhibitory effect on the neighbouring neuron
- excitation is when a neurotransmitter such as adrenaline, increases the positive charge of the post synaptic neuron
- this increases the likelihood that the neuron will fire and pass on the electrical impulse
What is inhibition
- when a neurotransmitter (such as serotonin) makes the charge of the post synaptic neuron more negative
- this DECREASES the likelihood that the neuron will fire and pass on the electrical impulse
What is ‘summation’
- the question of whether a postsynaptic Neuron does fire is decided by the process of summation
- if the net effect on the post synaptic neuron is inhibitory then the post synaptic neuron is less likely to fire
