Main Difference – Synapse vs Synaptic Cleft
The nervous system of animals is made up of millions of neurons. Neurons transmit nerve impulses in the form of electrical signals, coordinating the functions of the whole body through the central nervous system. These nerve impulses are transmitted in the form of chemical signals between neurons with the help of neurotransmitters. The transmission of nerve impulses between neurons is known as the synaptic transmission, which occurs in the synapses and synaptic clefts. Hence, synapse and synaptic cleft are two structures found in between neurons. The main difference between synapse and synaptic cleft is that synapse is the junction between two neurons whereas synaptic cleft is the gap that separates the pre-synaptic and post-synaptic neuron.
Key Areas Covered
1. What is Synapse
– Definition, Components, Electrical and Chemical Synapse
2. What is Synaptic Cleft
– Definition, Facts, Synaptic Transmission
3. What are the Similarities Between Synapse and Synaptic Cleft
– Outline of Common Features
4. What is the Difference Between Synapse and Synaptic Cleft
– Comparison of Key Differences
Key Terms: Neurotransmitters, Post-Synaptic Neuron, Pre-Synaptic Neuron, Synapse, Synaptic Cleft
What is Synapse
Synapse refers to a site of functional contact between two neurons where an electrical impulse is transmitted from one to another neuron. A synapse is composed of the pre-synaptic membrane, synaptic cleft, and post-synaptic membrane. Pre-synaptic and post-synaptic membranes are the two ends of membranes of the pre-synaptic and post-synaptic neurons, respectively. Synapses may occur between two dendrites, dendrite/axon or dendrite/cell body of another neuron. Synapses in different destinations of the nervous system are shown in figure 1.
Figure 1: Synapses
Two types of synapses can be identified in animals based on the type of synaptic transmission of nerve impulses. They are electrical synapses and chemical synapses.
Electrical Synapse
Electrical synapses are mainly found in the brain and retina. It is made up of tight junctions. A tight junction is a kind of cell junction between two neurons that rapidly transmits nerve impulses in the form of electrical signals.
Chemical Synapse
Chemical signals are found in most neuron junctions. They are mainly found in higher animals. Chemical synapses are larger than electrical synapses, and chemical signals are transmitted through the synaptic cleft. Neurotransmitters are involved in the chemical transmission. In addition, the transmission of signals occurs only in one direction.
What is Synaptic Cleft
Synaptic cleft refers to the space between neurons at the nerve synapse across which a nerve impulse is transmitted by neurotransmitters. Thus, only chemical signals are transmitted through the synaptic cleft. The width of the synaptic cleft is around 0.02 microns. Various types of vesicles, receptors as well as neurotransmitters are involved in synaptic transmission. The transmission of the nerve impulse through the synaptic cleft is shown in figure 2.
Figure 2: Synaptic Transmission
Synaptic Transmission
When a nerve impulse arrives through the pre-synaptic neuron to its end, the synaptic vesicles at the pre-synaptic membrane fuse with the membrane to release neurotransmitters into the synaptic cleft. These neurotransmitters diffuse through the synaptic cleft and bind to the receptors on the post-synaptic membrane. The binding of the neurotransmitters with the receptors generates a nerve impulse on the post-synaptic neuron. Epinephrine, norepinephrine, GABA, etc. are the types of neurotransmitters involved in synaptic transmission.
Similarities Between Synapse and Synaptic Cleft
- Synapse and synaptic cleft are two structures found between two neurons.
- Both synapse and synaptic cleft are involved in the synaptic transmission of nerve impulses in the form of chemical signals.
Difference Between Synapse and Synaptic Cleft
Definition
Synapse: Synapse refers to a site of functional contact between two neurons where an electrical impulse is transmitted from one to another neuron.
Synaptic Cleft: Synaptic cleft refers to the space between neurons at the nerve synapse across which a nerve impulse is transmitted by neurotransmitters.
Significance
Synapse: Synapse is the junction between two neurons.
Synaptic Cleft: Synaptic cleft is the gap between the pre-synaptic and post-synaptic neurons.
Correspondence
Synapse: A synapse is composed of a pre-synaptic membrane, synaptic cleft, and a post-synaptic membrane.
Synaptic Cleft: Synaptic cleft is a component of the synapse.
Type of Transmission
Synapse: Synapses transmit nerve impulses in the form of electrical or chemical signals.
Synaptic Cleft: Nerve impulses are transmitted in the form of chemical signals across a synaptic cleft.
Role
Synapse: Synapse is involved in the conversion of electrical signals into chemical signals and transmission of the nerve impulses into an adjacent neuron.
Synaptic Cleft: Synaptic cleft is involved in the transmission of nerve impulses between the membranes of two neurons.
Conclusion
Synapse and synaptic cleft are two structures found between the neurons. Both synapse and synaptic cleft are involved in the transmission of nerve impulses between neurons in the form of a chemical signal. Synapse refers to the junction between two neurons that consists of the pre and post-synaptic membranes and the synaptic cleft. Synaptic cleft is the gap between pre and the post-synaptic membranes. Therefore, the main difference between synapse and synaptic cleft is the structure of each between the neurons.
Reference:
1. “Synapse.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 18 Feb. 2011, Available here.
Image Courtesy:
1. “Blausen 0843 SynapseTypes” By Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia
2. “Synapse Presynaptic Neuron” By BruceBlaus – Own work (CC BY-SA 4.0) via Commons Wikimedia
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