synaptic cleft

Examples of synaptic cleft in the following topics:

• Synaptic Transmission

  • In a chemical synapse, the pre and post synaptic membranes are separated by a synaptic cleft, a fluid filled space.
  • The synaptic vesicles fuse with the presynaptic axon terminal membrane and empty their contents by exocytosis into the synaptic cleft.
  • Fusion of a vesicle with the presynaptic membrane causes neurotransmitters to be released into the synaptic cleft.
  • Second, degradation by enzymes in the synaptic cleft such as acetylcholinesterase.
  • The calcium entry causes synaptic vesicles to fuse with the membrane and release neurotransmitter molecules into the synaptic cleft.

• Excitation–Contraction Coupling

  • A small space called the synaptic cleft separates the synaptic terminal from the motor-end plate.
  • Neuron action potentials cause the release of neurotransmitters from the synaptic terminal into the synaptic cleft, where they can then diffuse across the synaptic cleft and bind to a receptor molecule on the motor end plate.
  • The Ca2+ ions allow synaptic vesicles to move to and bind with the presynaptic membrane (on the neuron) and release neurotransmitter from the vesicles into the synaptic cleft.
  • Once released by the synaptic terminal, ACh diffuses across the synaptic cleft to the motor end plate, where it binds with ACh receptors.
  • AChE resides in the synaptic cleft, breaking down ACh so that it does not remain bound to ACh receptors, which would cause unwanted extended muscle contraction.

• Peripheral Motor Endings

  • This influx of Ca2+ causes neurotransmitter-containing vesicles to dock and fuse to the presynaptic neuron's cell membrane, which results in the emptying of the vesicle's contents (acetylcholine) into the synaptic cleft; this process is known as exocytosis.
  • Acetylcholine diffuses into the synaptic cleft and binds to the nicotinic acetylcholine receptors located on the motor end plate.
  • Detailed view of a neuromuscular junction: 1) Presynaptic terminal; 2) Sarcolemma; 3) Synaptic vesicle; 4) Nicotinic acetylcholine receptor; 5) Mitochondrion.

• Exocytosis

  • Some examples of cells releasing molecules via exocytosis include the secretion of proteins of the extracellular matrix and secretion of neurotransmitters into the synaptic cleft by synaptic vesicles.

• The Synapse

  • The presynaptic neuron contains a chemical called a neurotransmitter that is packaged into synaptic vesicles clustered beneath the membrane in the axon terminal.
  • The neurotransmitter is released into and diffuses across the synaptic cleft, where it binds to specific receptors in the membrane on the postsynaptic side of the synapse.
  • A: Neuron (Presynaptic) B: Neuron (Postsynaptic)MitochondriaSynaptic vesicle full of neurotransmitterAutoreceptorSynaptic cleftNeurotransmitter receptorCalcium ChannelFused vesicle releasing neurotransmitterNeurotransmitter re-uptake pump

• Neurotransmitters

  • When called upon to deliver messages, they are released from their synaptic vesicles on the presynaptic (giving) side of the synapse, diffuse across the synaptic cleft, and bind to receptors in the membrane on the postsynaptic (receiving) side.
  • A pump in the cell membrane of the presynaptic element, or sometimes a neighboring glial cell, clears the amino acid from the synaptic cleft so that it can be recycled, repackaged in vesicles, and released again.

• Neurodevelopmental Disorders: Mental Illnesses

  • For example, monoamine oxidase inhibitors (MAO inhibitors) block the enzyme that degrades many neurotransmitters (including dopamine, serotonin, norepinephrine), resulting in increased neurotransmitter in the synaptic cleft.
  • This blockage results in an increase in serotonin in the synaptic cleft.

• Mechanics of the Action Potential

  • Synaptic cleft: the small space at the synapse that receives neurotransmitters.
  • This opens the vesicles, which releases their neurotransmitter contents into the synaptic cleft, the narrow space between the membranes of the pre- and postsynaptic cells.
  • The neurotransmitter diffuses within the cleft.
  • In any case, this is the key step by which the synaptic process affects the behavior of the postsynaptic cell.
  • The synaptic delay for a chemical synapse is typically about 2 milliseconds, while the synaptic delay for an electrical synapse may be about 0.2 milliseconds.

• Types of Neurotransmitters by Function

  • Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane in the axon terminal on the presynaptic side of a synapse.
  • They are released into and diffuse across the synaptic cleft, where they bind to specific receptors in the membrane on the postsynaptic side of the synapse.
  • Once released, acetylcholine binds to post-synaptic receptors and is degraded by acetylcholinesterase.

• Cleft Palate and Lip

  • Cleft lip and cleft palate are variations of a type of clefting congenital deformity caused by abnormal facial development during gestation.
  • Approximately 1 in 700 children are born with a cleft lip and/or a cleft palate.
  • If the cleft does not affect the palate structure of the mouth, it is referred to as cleft lip .
  • Cleft lip is formed in the top of the lip as either a small gap or an indentation in the lip (partial or incomplete cleft) or it continues into the nose (complete cleft).
  • The soft palate is cleft as well.