Neurons And Synaptic Transmission Flashcards
(14 cards)
Structure and function of sensory neurons
-long dendrites (pick up lots of sensory info) and short axons
-cell body in middle and two axons branching either side
-carry messages from PNS to CNS
Structure and function of relay neuron
-short dendrites and short axons
-connect sensory to motor neuron
-only found in spinal cord and brain
Structure and function of motor neurons
-have short dendrites and long axons(so can reach from CNS to every part of body)
-send messages from CNS to effectors (muscles and glands)
Role of cell body of neuron
Contains genetic material of the neuron
Role of dendrites
Receive chemical messages from the previous neuron
Role of axon
Carries action potential (electrical message) along length of neuron
Role of myelin sheath
Protects axon and speeds up transmission of electrical messages
Role of Nodes of Ranvier
Gaps between myelin sheath to speed up transmission
Role of axon terminal
Release chemical neurotransmitters to communicate with the next neuron
What do excitatory neurotransmitters do
Make neuron more likely to fire its own action potential
What do inhibitory neurotransmitters do
Make neuron less likely to fire its own action potential
What is summation
When the post-synaptic neuron sums the amount of excitatory and inhibitory neurotransmitters to produce a net effect
Steps of synaptic transmission
-action potential arrives at the axon terminal
-this triggers the release of neurotransmitters from vesicles in pre-synaptic neuron
-neurotransmitters diffuse across the synapse
-neurotransmitters then bind to receptor sites on post-synaptic receptors
-inhibitory neurotransmitters make next neuron less likely to fire AP while excitatory neurotransmitters make next neuron more likely to fire AP, process of summation occurs
-neurotransmitters left in the synapse are reabsorbed through the reuptake ports in pre-synaptic neuron where they are reused or broken down by enzymes in synaptic cleft
Why are impulses uni-directional
the synaptic vesicles containing the neurotransmitter are only present on / released from the presynaptic membrane
• the receptors for the neurotransmitters are only present on the postsynaptic membrane
• it is the binding of the neurotransmitter to the receptor which enables the signal / information to be passed / transmitted on (to the next neuron)
• diffusion of the neurotransmitters mean they can only go from high to low concentration, so can only travel from the presynaptic to the postsynaptic membrane.
