Skip to main content

The Synapse

By
Let's zoom into the synapse that makes neurotransmission possible.

Action potentials travel in the direction from the dendrite to the axon. Therefore, in order to transmit signals from one neuron to another, the signal must leave the axon of one neuron and cross the synaptic cleft to reach the receiving dendrite of another neuron. The neuron that delivers the signal is known as the presynaptic neuron, as shown in the image below. The neuron receiving the signal is known as the postsynaptic neuron. The gap between both neurons is the synaptic cleft. Now, don't confuse the terms "synapse" and "synaptic cleft". The synapse includes the presynaptic neuron, the postsynaptic neuron, and the gap in between. The gap is known as the synaptic cleft.

Image result for postsynaptic and presynaptic neuron


Electrical signals travel as action potentials through the axon. When they reach the axon terminal, which is the very end of the axon, neurotransmitters are released into the synaptic cleft. The neurotransmitters are stored in synaptic vesicles in the axon terminal, as shown in the image below. The vesicle fuses with the membrane of the axon terminal and the neurotransmitters are released into the synaptic cleft. There, they diffuse through the synaptic cleft and bind to receptors on the postsynaptic dendrite.


Image result for neurotransmitter vesicles

                                                                                                                    ________

 Image Credit:
(1) “Depiction of Neuronal Synapse.” Wikimedia Commons, 26 Nov. 2011, upload.wikimedia.org/wikipedia/commons/0/08/Neuronal_Synapse.jpg.

 (2) Splettstoesser, Thomas. “Synaptic Vesicles and Neurotransmission.” Wikimedia Commons, 3 July 2015, upload.wikimedia.org/wikipedia/commons/3/30/SynapseSchematic_en.svg.


Labels:

Comments

Post a Comment

Popular Posts

The Plasma Membrane and the Fluid Mosaic Model

By
Let's take a look at a cell. One thing that you will find common among all cells is the cell membrane - whether it's an animal cell, a plant cell or a bacterial cell. While this layer may only be ten nanometers thick, it has an intricate molecular structure designed for efficient transport of material into and out of the cell. This property is known as selective permeability , the control of the passage of materials across the cell membrane. The cell membrane is designed in a way that substances having certain properties are unable to enter or leave the cell (this movement across the cell boundary is known as transport ). The fluid mosaic model  describes how substances, mainly cholesterol, phospholipids and proteins, slide freely in the membrane. First, let's start with the phospholipid bilayer . A phospholipid a complex lipid with a "head" and a "tail". The head is made of one polar/hydrophilic phosphate group and a glycerol molecule. The ta
Post a Comment
Read more

Paul Broca and "Tan"

By
Paul Broca is one of the most influential neuroscientists best known for his patient, Tan. Well, his name wasn't really Tan. His name was Louis Victor Leborgne, and his incredibly unusual neurological disorder settled a debate about the location of language capabilities in the brain. In 1861, Leborgne approached Broca at the Bicetre Hospital to receive surgery for a leg infection. Leborgne had suffered from several medical conditions prior to his surgery; he had epilepsy at a young age and subsequently lost his ability to produce fluent speech. It was Leborgne's language disorder that really caught Broca's attention. Leborgne could think properly, but whenever he tried to communicate with Broca and verbalize his thoughts, all that came out of his mouth was the meaningless word "tan." For this reason, many scholars of neuroscience simply refer to Leborgne as "Tan". Broca realized that he could learn about our language capabilities by studying Leborg
Post a Comment
Read more

Myelination

By
Neurons can transmit signals at astonishing speeds - some signals can travel as fast at 268 miles per hour! How are neurons capable of such speeds? Well, their axons, which transmit signals to other neurons, have a special covering known as the myelin sheath. Myelin, a lipid-rich substance, insulates the axon and increases the speed of signal transmission. As an action potential travels down the axon, some ions may cross the membrane and exit the cell. However, the presence of myelin prevents this escape. In the peripheral nervous system, myelin is found in the membranes of Schwann cells, a type of glial cell. Each Schwann cell forms one unit of myelin. In the central nervous system, oligodendrocytes, another type of glial cell, tightly wrap around the axon to form several layers of insulation. Each process of an oligodendrocyte can form one segment of myelin for several different cells. Myelin is not the only special feature of neurons that accelerates signal speeds. There are
Post a Comment
Read more