Synapse: Components, Types and Function

A synapse is a microscopic opening at the terminal of a neuron that facilitates the exchange of signals among neurons. Neurons in your brain provide information to different parts of the central nervous system. Neurons join together to create synapses with one another.

The functioning of the brain depends on its synapses, especially when it comes to memory.

What Are Synapses?

Synapses are the places where neurons communicate with one another. Synaptic connections can be made by a neuron with hundreds of thousands or even more other neurons, neurons in the same brain area, or neurons that are nearby. All neurons are equipped with these connections. Two terminals, one postsynaptic and the other presynaptic, come together to create a synapse.

The location where the action potential, an electrical signal, is changed into a chemical signal, neurotransmitter release is known as the presynaptic terminal, and it is located at the end of an axon. Specialized receptors and the postsynaptic terminal membrane are separated by fewer than 50 nanometers. The neurotransmitter attaches to specific receptors after diffusing across the synaptic cleft in microseconds.

The specific receptors found on the corresponding postsynaptic terminal and the type of neurotransmitter released from the presynaptic terminal determine what kind of information neurons communicate. For example, the postsynaptic neuron integrates all of the signals it gets before determining whether to fire an action potential on its own.

What Are The Components Of Synapse?

A synapse is made up of three parts:

• The presynaptic terminal that contains neurotransmitters
• The space between the two nerve cells' synapses
• The postsynaptic terminal segment that contains receptor sites

Microscopic vesicles containing neurotransmitters are released when an electrical signal is received by the axon of a neuron. Once these vesicles cling to the presynaptic cell membrane, the neurotransmitters will be released into the synapse.

After crossing the synaptic cleft, these chemical messengers bind to receptor sites in the next nerve cell to trigger an action potential, which is an electrical impulse.

Also Read: Membrane Potentials & Resting Membrane Potential

What Are The Types Of Synapse?

There are two main types of synapses:

• Electrical synapses 
• Chemical Synapse

Chemical Synapse

• When a presynaptic neuron experiences electrical activity, chemical messengers, also known as neurotransmitters, are released in a chemical synapse. Most synapses are chemical.
• After diffusing across the synapse, the neurotransmitters bind to the particular receptors on the postsynaptic cell.
• The neurotransmitter then either stimulates or inhibits the postsynaptic neuron. Excitation initiates an action potential, whereas inhibition prevents a signal from propagating.

Electrical Synapses

• Gap junctions are specialized channels that connect two neurons in an electrical synapse.
• Electrical synapses allow electrical impulses from the presynaptic cell to the postsynaptic cell, hence expediting signal transfer.
• Because of special protein channels connecting the two cells, the postsynaptic cell may directly receive the positive current from the presynaptic neuron.
• Electrical synapses are separated by a significantly smaller distance (about 3.5 nanometers as compared to 20 nanometers) than chemical synapses.
• Electrical synapses convey signals significantly faster than chemical synapses. Information is sent nearly instantaneously in electrical synapses, while it may take several milliseconds in chemical synapses.
• Electrical synapses happen quickly, which is useful, but signals weaken as they pass from one cell to the next. This reduction of signal intensity means that considerably smaller postsynaptic neurons are impacted by much larger presynaptic neurons.
• Chemical synapses transmit signals with full signal strength despite their reduced speed. Relatively few presynaptic neurons can have an impact on even very large postsynaptic cells. Chemical synapses can be both excitatory and inhibitory, whereas electrical synapses are just excitatory.

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What Is The Function Of Synapse? 

By connecting neurons, synapses help in the transfer of information between them. When a nerve signal hits the end of a neuron, it cannot simply continue to the next cell. Instead, it must trigger the release of neurotransmitters, allowing the impulse to cross the synapse and reach the next cell.

Chemical messengers known as neurotransmitters are released in reaction to nerve impulses. Once they cross the tiny synaptic gap, they are taken up by receptors on the surface of the next cell.

These receptors function as locks, and the neurotransmitters are the keys. A neurotransmitter may stimulate or inhibit the neuron to which it binds.

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