synaptic transmission. this slide contains information regarding synaptic transmission

1. BIOPSYCHOLOGY
Synaptic transmission

2. • Introduction - Synaptic transmission
• Electrical synapse
• Chemical synapse
• Structure of synapse
• Synthesis, packaging & transportation of neurotransmitter
• Release of neurotransmitter
• Activation of receptors
• Postsynaptic potentials
• Termination of Postsynaptic potentials
• Glia and gap junctions
• References
CONTENTS:

3. SYNAPTIC TRANSMISSION
• Communication between neurons
• Two key discoveries
1. Sherrington (early 1900s): Presynaptic and Postsynaptic
Neurons are separated by a gap.
2. Loewi (1920s): Synaptic transmission involves chemicals
known as neurotransmitters or neuromodulators.
• Two types based on the nature :
1. Electrical synapse
2. Chemical synapse

4. Electrical Synapse
• The membranes get closer
and gap junctions are
formed.
• These junctions form low
resistance bridges – easy
flow of ions.

5. CHEMICAL SYNAPSE
• Messages are carried by
neurotransmitters
• Released by terminal buttons
• Chemicals – diffuse across the
fluid filled gap

6. Electrical Vs Chemical Synapse

7. STRUCTURE OF
SYNAPSE

8. Types – arrangement of synapse
Axodendritic Axosomatic Axoaxonic

10. Axoaxonic synapses:
• Synapse between two terminal
buttons.
• Does not contribute directly to
neural integration.
• Selectively influence one
particular synapse
• Mediate presynaptic excitation
and inhibition.

11. Directed synapses Nondirected synapses

12. SYNTHESIS, PACKAGING AND TRANSPORT –
NEUROTRANSMITTER
• Coexistence –
one small
molecule
neurotransmitter
and one
neuropeptide

13. RELEASE OF NEUROTRANSMITTER
• Exocytosis – process of neurotransmitter release
• One action potential – release of neurotransmitter from
one vesicle
• Small molecule – released in a pulse – momentary influx
of Calcium ions.
• Neuropeptides – released gradually – increase in level of
intracellular calcium ions

15. ACTIVATION OF RECEPTORS
• Receptors – protein containing binding sites for only
particular neurotransmitter.
• Neurotransmitter - ligand of its receptor.
• Different types of receptors – particular neurotransmitter
bind – receptor subtypes.
• Receptor subtypes enable one neurotransmitter to transmit
different kinds of messages – different parts of brain
• 2 types of receptors
1. Ionotropic receptor – ligand-activated ion channels
2. Metabotropic receptor – signal proteins and G proteins.

16. Ionotropic
receptors:
• Direct method
• Open sodium
channel – ESPSs
• Open potassium
and chloride
channel - ISPSs

17. Metabotropic receptors:
• Attached to a serpentine signal proteins
– portion of signal proteins outside and
G protein inside the neuron.
• 2 process
1. Subunit of G protein - nearby ion
channel
2. Trigger – synthesis of second messenger
• Second messenger- enter the nucleus
bind to the DNA – influence genetic
expression
• Longer to begin and last longer

18. Autoreceptors:
• Many neurons – receptors respond to the neurotransmitter that
they themselves release
• Metabotropic receptor
• Located on presynaptic rather than the postsynaptic membrane ;
Located on any part of the cell
• Do not control ion channels (most cases)
• Control internal process – synthesis and release of
neurotransmitter
• Monitor the number of neurotransmitter molecules in the
Synapse

19. POSTSYNAPTIC POTENTIALS
• Opening of
chloride
channels –
Neutralize
ESPSs

20. TERMINATION OF POSTSYNAPTIC POTENTIALS
• Neurotransmitter molecule –
remain active in the synapse
• 2 mechanism can terminate
Synaptic messages
1. Reuptake
2. Enzymatic Degradation
• Terminal buttons - models of
efficiency

21. Reuptake
• Rapid removal of
neurotransmitter
• Presynaptic
membrane – special
transporter
molecules
• Postsynaptic receptor
– brief exposure to
the neurotransmitter

22. Enzymatic
Degeneration
• Postsynaptic membrane – AChE – destroys ACh – termination of
Postsynaptic potentials
• AChE – extremely energetic destroyer – one molecule breaks more
than 5000 molecules of ACh each second.
• Enzymes (proteins) destroy
molecules of the
neurotransmitter
• ACh – main mechanism of
Synaptic deactivation.

23. GLIA AND GAP JUNCTIONS
• Glial cells (astrocytes) & gap junctions play major role in brain
function.
• Cerebral gap junctions – between all classes of cerebral cells (same
kind)
• Gap junctions and glial networks – synchronize the activities of
activities of same cell in particular area.
• Astrocytes – distributed evenly – great potential to coordinate
activity of neuron.
• Astrocytes – coordinate the activity of Synapse
• Gap junctions on astrocytes – end of each process – comes in contact
with processes from adjacent astrocytes.
• Tripartite synapse

24. REFERENCES
Carlson, N. R. (2008). Foundations of Physiological Psychology
(Sixth edition). Pearson Education.
Pinel, J. P. J. (2014). Biopsychology (9th ed.). New Jersey:Pearson.
Stanford University. Synaptic Transmission. (n.d.). Retrieved from
https://web.stanford.edu/class/cs379c/archive/2010/
stanford.leture.02.pdf
Chemical and electrical synapses – CBM. (n.d.). Retrieved from
https://cbm.msoe.edu/teacherWorkshops/ddtyResources/
documents/synapseTypes.pdf