Neurotransmission occurs when signals are transmitted between neurons through chemical synapses or neuromuscular junctions. The document discusses the historical discoveries of neurons, dendrites, axons and synapses. It describes how neurotransmitters are released by the axon terminal of the presynaptic neuron, binding to receptors on the postsynaptic neuron or muscle cell. The types of synapses and neurotransmitters are also outlined, as well as the roles and components of the neuromuscular junction in facilitating muscle contraction.

1. Neurotransmission and
Neuromuscular junction
Prepared by,
Inbaraj Anandan
20BIOB09
I M.sc Biotechnology
Bharathiyar university, Coimbatore

2. Neurotransmission
• Neurotransmission, also called synaptic transmission, is a process by which
the nervous system transmits signals throughout the
body(Latin: transmissio "passage, crossing" from transmittere "send, let
through")
• It is essential for the communication that occurs between two neurons.
• In a neuron, neurotransmitters are released by the axon terminal of a neuron.
• The neurotransmitters then bind to the receptors located on the on
the dendrites of another neuron, activating the receptors.

3. The nervous system and its components

4. Historical perspective
• Lets see about some historical perspective of neurotransmission
Until 1838-globules in the tissue; in retrospect it can be said in three steps
Discovery of neurons dendrites and axons
Discovery of neuron doctrine
Discovery of synapses and chemical transmission

5. Now lets see about each and every discovery's related to neurons and
synapses:
 Neurons, dendrites and axons- antonvan leewenhoek(1632-1723),
Robert hook(1635-1703)
 Nucleus and nucleolus of neurons-Gabriel gustan valentin(1810-1863)

6.  Neuron cerebellum- Jan evangelista purinjie(1787-1869)
 Nervous tissue and its filamentous process-Robert remak(1815-1865)
 Mylein sheath- Theodar Schwan(1810-1882)
 First to observe neural cells clear images- Joseph van Gerlach(1820-1886)
 Axis cylinder- Rudolph A van kolliker(1896)
 After a twenty years later willhelm von waldeyr projected a
clear structure of neuron

7. Types of neurons
Lets see about the types of neurons:
 The neurons can be classified into three as
1. Efferent (Motor)
2. Afferent (sensory)
3. Interneuron

8. Synapses and neurotransmitters
The term synapse was first introduced in 1897 by physiologist Michael Foster
in his "Textbook of Physiology" and is derived from the Greek synapsis,
meaning "conjunction.“
What do synapses do?
oWhen a nerve signal reaches the end of the neuron, it cannot simply continue to
the next cell. Instead, it must trigger the release of neurotransmitters which can
then carry the impulse across the synapse to the next neuron.

9. o Once a nerve impulse has triggered the release of neurotransmitters, these
chemical messengers cross the tiny synaptic gap and are taken up by
receptors on the surface of the next cell.
o These receptors act much like a lock, while the neurotransmitters function
much like keys. Neurotransmitters may excite the neuron they bind to or
inhibit it.

10. Types of synapses:
And coming about the types of synapses are listed as follows:
1. Axo- dendric
2. Axo- axonic
3. Axo- somatic
4. Dendro- dendric

11. Information exchange by synaptic transmission
Neurons constantly rely information between each other and in environments
Information on cells is transmitted using following forms:
oAxon to dendrite-axodendritic exchange
oAxon to cell body-axosomatic exchange
oAxon to axon-axoaxonic exchange
o Dendron to dendron- dendrodendritic exchange
A synapse consists of A synaptic terminal, pre synaptic ending, A post
synaptic ending, A synaptic cleft, communications are crossed across using a
neurotransmitter

12. Neurotransmitters and their types
Neurotransmitters are chemical signals that transmits signals from
neurons to target cell across the synapse
Target cell may be neuron or some other cell like gland or muscle cell
Necessary for rapid communication in synapse
Neurotransmitters are packaged into synaptic vesicles

13. Types of Neurotransmitters
• In some instances, they are simply divided into monoamines, amino acids, and
peptides.
• To get a explained detail one its classification can be as followed:
1. Amino acid- Gamma-aminobutyric acid (GABA), Glutamate
2. Peptides- Oxytocin, Endorphins.
3. Monoamines- Epinephrine, Norepinephrine, Histamine, Dopamine, Seratonin.
4. Purines- Adenosine, Adenosine triphosphate.
5. Gasotransmitters- Nitric oxide, Carbonmonoxide.
And finally, Acetylcholine

14. Properties of
neurotransmission
• Synthesized in the
presynaptic neuron
• Localised to vesicles in
presynaptic neuron
• Released from
presynaptic neuron
under a physiological
condition
• Rapidly removed from
synaptic by uptake or
degradation

16. Neuromuscular junction
It’s a junction between terminal branch of nerve fibre and muscle fibre
It allows motor neurons to transmit signal to muscle fibre and to make
muscle contraction
Lets look about some parts of neuromuscular junction that helps in
neurotransmission

17.  Here are some basic factorial parts that helps in neurotransmission
1. Axon terminal : terminal branch of nerve fibre
2. Motor end plate : bulb like expansion on axon terminal
3. Synaptic trough/gutter : depression on the muscle fibre due to the
invagination on the muscle fibre
4. Subneural cleft : numerous folds of post synaptic membrane
5. Pre synaptic membrane : membrane of nerve ending
6. Post synaptic membrane : membrane of muscle fibre

18. 7. Synaptic cleft : space between post and presynaptic membrane
8. Basal lamina : thin spongy layer of reticular matrix in synaptic cleft
Neuromuscular transmission
 Transfer of information from the motor nerve ending to the muscle
fibre through neuro muscular junction to initiate muscle contraction

19. Neuromuscular junction function
The essential role of the NMJ is to convert a temporal sequence of action
potentials (APs) in motor neurons into muscle contractions.
The molecular events that cause muscle contraction are triggered by increases
in the intracellular calcium concentration.

20. The Human NMJ
Even though human muscle fibers have quite large diameters (50 vs. 30
μm in mice), human NMJs are among the smallest vertebrate NMJs that
have been described.
Consistent with the relatively constant relationship of QC and synaptic
area, the QC at human NMJs is only about 20–30, while that at mouse
NMJs is typically 50–100.

21. Human NMJ and it’s response to diseases
myasthenia gravis, has a prevalence of only 15/1,00,000 probably reflecting
the vital role played by the NMJ in survival.
There are two main classes of NMJ disease; sporadic, mediated by
autoantibodies which attack NMJ components.
Inherited, mediated by mutation of genes encoding proteins which play
functionally significant roles at the NMJ.

22. References
Dynamic and modulation of synaptic transmission in mammalian CNS
-Maria elisa calcagnotto and idan segev(apr-2019)
Article: Extrasynaptic Neurotransmission Mediated by Exocytosis and
Diffusive Release of Transmitter Substances
-Eline-del-bel and Francisco el-fidel
Adventures in physiology
-sir henry hallet dale and pergamon press(1953)
NCBI resources: The Structure of Human Neuromuscular Junctions: Some
Unanswered Molecular Questions
-clareRslater(oct 2017)