Synapse and integration of
information at the synaptic level
Introduction
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Synapse
• Communication between
neurons
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Synapse
• Communication between
neurons
• Electrical
• Chemical
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Electrical synapse
• Evolutionary old
• Less frequent than ch.
• Ubiquitous
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Electrical synapse
• Evolutionary old
• Less frequent than ch.
• Ubiquitous
• Gap junctions
• Bidirectional transmission
• Fast
• Strength of signal may
decrease
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Chemical synapse
• Evolutionary young
• Majority type of s.
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Chemical synapse
• Evolutionary young
• Majority type of s.
• Unidirectional
• Synaptic cleft
• Neurotransmitter
• Constant signal
strength
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Neurotransmitter
• Present in presynaptic neuron
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Neurotransmitter
• Present in presynaptic neuron
• Released into the synaptic cleft due to depolarization of presynaptic
neuron (Ca2+ dependent mechanism)
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Neurotransmitter
• Present in presynaptic neuron
• Released into the synaptic cleft due to depolarization of presynaptic
neuron (Ca2+ dependent mechanism)
• Specific receptor has to be present in postsynaptic membrane
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Neurotransmitter
• Specific receptor has to be present in postsynaptic membrane:
A. Ionic channel
B. Second messenger system
Guyton&Hall. Textbook of Medical Physiology, 11th ed.
Neurotransmitter
Guyton&Hall. Textbook of Medical Physiology, 11th ed.
Neurotransmitter
• Specific receptor has to be present in postsynaptic membrane:
A. Ionic channel
B. Second messenger system
1) Excitatory transmitters
2) Inhibitory transmitters
- opening of sodium channels
- decreased conduction through chloride and/or potassium channels
- changes in internal metabolism of the postsynaptic neuron exciting
cell activity
- opening of chloride channels
- increased conduction through potassium channels
- changes in internal metabolism of the postsynaptic neuron
decreasing cell activity
Excitatory/inhibitory postsynaptic potential
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Excitatory/inhibitory postsynaptic potential
Ganong´s Review of Medical Physiology, 23rd ed.
Excitatory/inhibitory postsynaptic potential
Ganong´s Review of Medical Physiology, 23rd ed.
Signal summation
• Temporal
• Spatial
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Signal summation
http://www.geon.us/Memory/images/Summation.jpg
Synaptic convergence
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Synaptic convergence
Average number of
synapses in one
neuronal cell in
primates
✓ Primary visual cortex
(area17)
– aprox. 4 000
✓ Primary motor cortex
(area4)
– aprox. 60 000
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Synaptic divergence
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Networking
Networking
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Neuromuscular junction
https://classconnection.s3.amazonaws.com/754/flashcards/2034754/png/ch_7_pic_41349381290275.png
Neurotransmission vs. Neuromodulation
Neurotransmission vs. Neuromodulation
• Information transmission • Regulation of NS activity
Neurotransmission vs. Neuromodulation
• Information transmission
• Specific
• Regulation of NS activity
• Difuse (volume
transmission)
Neurotransmission vs. Neuromodulation
• Information transmission
• Specific
• Receptors – ion channels
• Regulation of NS activity
• Difuse (volume
transmission)
• Receptors – G-proteins
Neurotransmission vs. Neuromodulation
• Information transmission
• Specific
• Receptors – ion channels
• Short duration
– membrane potential
changes
• Regulation of NS activity
• Diffuse (volume
transmission)
• Receptors – G-proteins
• Longer duration
- changes in synaptic
properties
https://classconnection.s3.amazonaws.com/108/flashcards/956108/jpg/bookpic421333407057201.jpg
http://www.compoundchem.com/2015/07/30/neurotransmitters/
http://www.compoundchem.com/2015/07/30/neurotransmitters/
Acetylcholin
• Nucleus basalis (Meynerti)
abd other nuclei
• Nicotin receptors
• Muscarin receptors
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• Sleep/wake regulation
• Cognitive functions
• Behavior
• Emotions
Noradrenalin
• Locus coeruleus
• Nuclei raphe caudalis
• Vigilance
• Responsiveness to
unexpected stimuli
• Memory
• Learning
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Dopamin
• Nigrostriatal system
– Movement
– Sensory stimuli
• Ventrotegmentno-mesolimbicfrontal
system
– Reward
– Cognitive function
– Emotional behavior
• Tubero-infundibular system
– Hypotalamic-pituatory
regulation
• D1 receptors – excitatory
• D2 receptors - inhibitory
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Serotonin
• Nuclei raphe rostralis
• Nuclei raphe caudalis
• Anxiety
• Impulsive behavior
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Neuromodulatory systems
Neuromodulatory systems
http://ausm.org.uk/wp-content/uploads/2015/02/Dopamine_Norepinephrine_Serotonin.jpg