Neurons & synaptic transmission Flashcards
(20 cards)
What is a neuron?
- specialised nerve cells that transfer information throughout the body both electrically & chemically
- 100 billion neurons in the nervous system and is the primary means of communication in the nervous system
What is the function of sensory neurons?
- also known as afferent neurons
- located in the PNS in clustsers known as the ganglia
- Carry sensory information from PNS to the CNS
- long dendrites, short axons
What is the function of relay neurons?
- also know as interneurons
- located in the CNS (within brain)
- connect the sensory neuron to the motor neurons
- short axons, short dendrites
What are the functions of motor neurons?
- also known as efferent neurons
- located in the CNS
- Carry impulses from CNS towards effectors e.g. muscles/ glands to control movement
- short dendrites, long axons
What is the function of dendrites?
- branch-like structures
- carry nerve impulses from other neurons towards cell body
What is the function of axons?
- long slender structure
- carries nerve impulses (action potential) away from cell body towards axon terminal
- surrounded by myelin sheath which speeds up electrical transmission
What is the function of the axon terminal? (buttons)
- Connects neurons to other neurons via synaptic transmission
What is the function of the cell body(soma)?
- contains nucleus with ‘genetic material’ of cell
What is the function of the nodes of Ranvier?
- gaps in myelin sheath
- re-charges action potential to help impulses travel faster
What are neurotransmitters?
- chemical messengers, located in the synaptic vesicles of a neuron
What happens in the reflex arc?
- sense organs in PNS detects a stimulus e.g. change in temp
- sensory neuron sends the electrical impulse from PNS to relay neuron in brain/CNS
- Relay neurons connect sensory neurons to motor neurons (involved in analysis of sensations, what it means, how to respond etc)
- Motor neurons send electrical impulses to an effector
- effector produces a response e.g. muscle contracts
How does a firing of a neuron happen?
- neuron in resting state = inside of cell negatively charged
- activated by stimulus= inside of cell positively charged
- causing an action potential to occur
» electrical impulse travels down axon towards end of neuron
Explain the process of synaptic transmission
- signals within neurons are transmitted electrically however signals between neurons are transmitted chemically
- when the electrical impulse arrives at the end of presynaptic neuron to the terminal buttons
- it triggers release of neurotransmitters from synaptic vesicles of presynaptic neuron into the synaptic cleft
- neurotransmitters diffuse chemically across the synapse and bind to receptor sites on postsynaptic neuron
(any not picked up are broken down or reabsorbed through process of reuptake)
5 .impulse converted back into electrical impulse
Why is direction of travel in neurotransmitters only one way?
- the neurotransmitters are released from the presynaptic neuron and they are received at the post synaptic neuron
- no receptor sites on the pre synaptic neuron and no vesicles on the post synaptic neuron
What two effects can neurotransmitters have on a neighboring neuron?
excitatory or inhibitory
What is the role of inhibitory neurotransmitters?
- Serotonin, GABA
- when it binds to the post synaptic neuron it increases negative charge of postsynaptic neuron
- postsynaptic neuron is less likely to fire an impulse
What is the role of excitatory neurotransmitters?
- Adrenaline, dopamine
- when it binds to the post synaptic neuron it increases the positive charge in postsynaptic neuron
- postsynaptic neuron is more likely to fire an impulse
What is summation?
- whether a postsynaptic neuron fires is decided by the process of summation > which is the sum of excitatory and inhibitory influences
If the net effect on the postsynaptic neuron is inhibitory then it is __ likely to fire
less
If the net effect on the postsynaptic neuron is excitatory then it is__ likely to fire
more
