Synaptic Cleft- Anatomy, Structure, Disease & Function

Synaptic Cleft: The neurons are the functional units of the nervous system which transmit electrical impulses from one neuron to the other. The space between the two neurons across the impulse which is transmitted by a neurotransmitter is called the synaptic cleft. The synaptic cleft is also known as the synaptic gap. It is important for the cells to communicate using chemical transmission.

What is Synaptic Cleft?

A synaptic cleft is a space that separates the two neurons and forms a junction between two or more neurons and it also helps nerve impulses to pass from one neuron to the other one. Synaptic cleft has connections with neurology and the brain. It is also known as the synaptic gap.

Anatomy of Synaptic Cleft

A synaptic cleft acts like a junction that connects two or more neurons with one another. It is present between two neurons – pre-junction or pre-synaptic or post-junction neuron. It depends on the type of nerve fiber which involves in the formation of a synapse. Below mentioned are the types of synaptic clefts:

Axo-axonic synapse

In this, the synaptic cleft is present between two axons. The axon of one neuron creates a synapse with the axon of another neuron.

Axo-dendritic synapse

In this, the synaptic cleft is present between the dendrite and axon. The axon of one neuron creates a synapse with the dendrites of the other neurons.

Axo-somatic synapse

The synaptic cleft is present between the cell body or soma and the axon. The axon of one neuron creates a synapse with the cell body of other neurons. Therefore on one end synaptic cleft has an axon on the other end, it is bounded by either the cell body, axon, or dendrite of the other neuron.

Diseases of Synaptic Cleft

Synaptic Cleft has an important role in psychiatric and neurologic conditions. Some of the important diseases are mentioned below:

Autism Spectrum Disorder

This type of disease has spectrum disorders including Asperger Syndrome, autism, and pervasive developmental disorder. Some of the common symptoms are the affected individual lack of social communication and delay in stereotypy and language. The synaptic level plays an important role in the pathogenesis of the disease. Mutations affect the adhesion molecules in the synaptic cells which are seen to be connected with Autism Spectrum Disorder.

Fragile X Syndrome: Mental Retardation

This is the most common disorder inherited form of mental retardation. Common symptoms are reduced intellectual ability, hyperactivity, anxiety, developmental delay, and hypersensitivity to stimuli.

Alzheimer’s Disease

This is a neurodegenerative disorder that affects older age people. A-beta amyloid formed in Alzheimer’s disease causes a significant decrease in synaptic plasticity. It is also characterized by a decreased number of synapses in the hippocampus, subcortical regions of the brain, and cerebral cortex.

Addiction

Synaptic alteration is seen in different types of addictions. Chronic administration of drugs changes in synaptic proteins and dendritic spines. It affects the synaptic plasticity.

Functions of Synaptic Cleft

The following functions of the synaptic cleft are:

Degradation of Neurotransmitters

Synaptic cleft has different enzymes which are involved in the degradation of released neurotransmitters. They can degrade the neurotransmitters which decreases their concentration. The depletion of neurotransmitters impedes nerve impulse transmission.

Fusion of Neurotransmitters

The neurotransmitters are released by the pre-synaptic neurons. Synaptic cleft allows the neurotransmitters to pile up and diffuse to act on postjunctional neurons. It also provides the space for the neurotransmitters to diffuse through and act on post-synaptic neurons.

Drug Action

Synaptic cleft acts as a site of action for many drugs. Some are agonists or antagonists of neurotransmitters that are used in the treatment of neurologic conditions.

Regulation of Nerve Impulse Transmission

The neurotransmitters which are released into the synaptic cleft are greater than the next neuron. Synaptic cleft harbors enzymes which degrade neurotransmitters. This degradation regulates nerve impulse transmission.

FAQs on Synaptic Cleft

Q1: Define Synaptic cleft.

Answer:

A synaptic cleft is defined as a space after the axon terminal of a neuron between the next target cells.

Q2: Define the Axo-dendritic synapse.

Answer:

The synaptic cleft is present between the axon and the dendrite. The axon of one neuron creates synapse with dendrites of the other neurons.

Q3: Name the types of Synaptic cleft.

Answer:

The types of synaptic cleft are:

• Axo-axonic synapse
• Axo-dendritic synapse
• Axo-somatic synapse

Q4: Write the functions of the Synaptic cleft.

Answer:

The functions of synaptic cleft are as follows:

• The Degradation of Neurotransmitters
• The Fusion of Neurotransmitters
• It regulates the Nerve Impulse Transmission
• Drug Action