Neuronal Communication 1 Flashcards
What does the CNS consist of ?
Brain and spinal chord
What does the peripheral nervous system consist of ?
- Somatic nervous system- motor neurons to skeletal muscle
- Autonomic nervous system
What do afferent neurons do ?
Sensory neurons
Carry sensory info from the body to the CNS
What do efferent neurons do ?
Motor neurons
Carry motor commands from the CNS to effectors
What is a synapse ?
The small gap that exists between a pre and post synaptic membrane
What are chemical synapses ?
They prevent direct electrical propagation of APs from pre to post synaptic neurons
What are electrical synapses ?
They exist but they are rare in the CNS
Describe chemical synaptic transmission
- AP reaches terminal
- Voltage gates Calcium channels open
- Calcium enters axon terminal
- NT released into synaptic cleft
- NT bind to post synaptic receptors
How wide is a synapse ?
20-30nm
How are NTs removed from the synaptic cleft?
- Enzymatic breakdown
- Active repuptake- pumped back into pre-synaptic terminal
- Active uptake- pumped into glial cells
What are EPSP and IPSP ?
Excitatory and inhibitory post-synaptic potentials
They are like “mini action potentials” which cause a small transient change in membrane potential of a cell, but the membrane potentials aren’t high enough to reach the threshold to cause action potential
What do EPSPs and IPSPs look like on a graph ?
EPSPs are a bump in membrane potential
IPSPs are a drop in membrane potential
What is temporal summation ?
The summation of multiple signals from a single presynaptic neuron firing repeatedly over time
What is spatial summation ?
The summation of signals from multiple pre synaptic neurons firing at the same time
What is convergence ?
Multiple pre synaptic neurons onto a single postsynaptic neuron
What is divergence ?
A single presynaptic neuron synapses with multiple post synaptic neurons
What is pre-synaptic inhibition?
An inhibitory neuron releases an inhibitory NT into synapse of another neuron.
This causes inhibition of calcium and so a reduction in NT release, so the AP is weakened or does not occur at all.
Eg. Can help modulate pain signals in the spinal chord.
Describe an EPSP
A small depolarisation of the membrane.
Increases likelihood of neuron reaching threshold and firing an AP
Describe an IPSP
A small hyperpolarisation of the membrane
Decreases likelihood of firing an AP
Describe the fusion of vesicle with pre-synaptic membrane
- Opening of Ca channels
- Fusion protein macromolecules (FPM) separate
- Vesicle membrane incorporated into presynaptic membrane
- Cathrin molecules assist inward movement of the vesicle membrane.
Dynamin assists in FPM pairs and pinching the neck of the emerging vesicle - Vesicle is now free for recycling
