Synapse: Definition, Meaning, Anatomy, Function, Types, Diagram

What Is a Synapse?

A synapse is a small junction located at the end of a neuron, communicating and connecting with another neuron. The neuron is set into action in propagating electrical or chemical signals that lead it to release neurotransmitters into the synapse. These released messengers in turn excite the receptors inside the receiving neuron.

Synapses form the core centre for the processing and transmission of information in the nervous system and thereby are a driving force for enabling complex functions corresponding to movement, perception, and thought processes.

Structure of A Synapse

The synapse includes several components involved in the same, to pass the signals between the neurons.

Pre-Synaptic Neuron

• Contains the synaptic vesicles full of neurotransmitters.

• Dumps the neurotransmitters into the synaptic cleft.

Synaptic Cleft

• The minute gap or junction between neurons where neurotransmitters are dumped.

Post-Synaptic Neuron

• Receptors and Signal Reception: Contains the receptors which are attached to the neurotransmitters leading to the propagation of response in the neuron.

Types of Synapses

Depending on the mode of transmission of the signal, synapses may be either chemical or electrical.

Chemical Synapses

• Neurotransmitters released into the synaptic cleft convey the signal.

• Examples and Importance: More commonly found in the central nervous system. The principle behind complex signalling processes.

Electrical Synapses

• Ions are transmitted directly from the presynaptic to the postsynaptic neuron through gap junctions.

• Examples and Significance: Present in some neural circuits; enable fast transmission of signals.

Synaptic Transmission

The synaptic transmission is a process by which a signal is being forwarded from one neuron to another.

• Arrival of Action Potential: This subsequently leads to the stimulation of the extrusion of neurotransmitters.

• Neurotransmitter release: neurotransmitters are released into the synaptic cleft by synaptic vesicles.

• Neurotransmitter Binding: Transmitters are chemicals that bind to a certain receptor in the post-syn.

• Generation of Post-synaptic Potential: The post-synaptic neuron generates a response in it.

Neurotransmitters – Types & Functions

Neurotransmitters are chemicals that diffuse an impulse conduction at the synapse. They act as communicator between the neurons.

Types Of Neurotransmitters:

• Excitatory Neurotransmitters: Generates action potentials (e.g. Glutamate)

• Inhibitory Neurotransmitters: Inhibit the action potentials (e.g. GABA)

• Modulatory Neurotransmitters: Modulate multiple neural processes (e.g. Dopamine, Serotonin)

Synapse Dysfunction & Associated Disorders

Disorders in synapse dysfunction are associated with both neurological and psychiatric illnesses.

Neurological Disorders

• Alzheimer's Disease: Pathological in synaptic loss and dysfunction.

• Parkinson's Disease: Entails deficient synaptic transmission in motor pathways.

Psychiatric disorders

• Depression: Correlated with imbalances in neurotransmitter concentrations.

• Schizophrenia: Correlated with defective synaptic connectivity and mechanisms.

Research and Study of Synapses

There are various methods used in the studies that explore the status of synapses.

Microscopic Techniques

• Electron Microscopy provides very detailed images of the structures of synapses.

• Live imaging can be done of the synapses through confocal microscopy.

Electrophysiological Techniques

• Through the Patch Clamp Technique recording of ion channel activities of neurons

Synapse NEET MCQs (With Answers & Explanations)

Important questions asked in NEET from this topic are:

• Phases of action potential

• Factors affecting action potential

Practice Questions for NEET

Q1. The junction b/w the axon of one neuron and the dendrite of the next is called

1. Constant bridge

2. Junction point

3. Joint

4. Synapse

Correct answer: 2) The interior of the axon is filled with extracellular fluid

Explanation:

A synapse is a functional junction between two neurons, where communication in the nervous system occurs. In other words, it's part of the presynaptic membrane of the first neuron that releases neurotransmitters and the postsynaptic membrane of the second neuron, on which the receptors for these neurotransmitters are located. The tiny gap between them is called the synaptic cleft. The structural feature allows signal transmission without any direct anatomical continuity; it plays the crucial role of neural signalling and processing.

Hence the correct answer is option 4) synapse.

Q2. What is a synapse?

1. A type of neurotransmitter

2. A gap between two neurons

3. A type of receptor

4. A part of the cell membrane

Correct answer: 2) A gap between two neurons

Explanation:

The connection or space between two neurons where they make contact and exchange information is known as a synapse. It is the location where the axon terminal of one neuron connects with the dendrites or cell body of another neuron. A chemical signal is conveyed between the two neurons when neurotransmitters are released from the presynaptic neuron's axon terminal and bind to receptors on the postsynaptic neuron's dendrites or cell body. The nervous system's ability to function and the brain's ability to transmit information depend on this connection.

Hence, the correct answer is option 2) A gap between two neurons.

Q3. What is the role of the presynaptic neuron in a synapse?

1. To receive signals from other neurons

2. To send signals to other neurons

3. To release neurotransmitters

4. To receive neurotransmitters

Correct answer: 3) To release neurotransmitters

Explanation:

The role of the presynaptic neuron in a synapse is to release neurotransmitters. The presynaptic neuron is the neuron that is sending the signal across the synapse. When an action potential reaches the end of the presynaptic neuron's axon, it triggers the release of neurotransmitters into the synapse. These neurotransmitters then bind to receptors on the postsynaptic neuron, causing a response in that neuron. In other words, the presynaptic neuron is responsible for transmitting signals to the postsynaptic neuron by releasing neurotransmitters into the synapse.

Hence, the correct answer is option 3) To release neurotransmitters.

Also Read:

• MCQs on Synapse

• Lobes of Cerebrum

• Cerebrospinal Fluid

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