What Happens in a Synapse?
A synapse is the point of communication between brain cells. When a signal is transmitted across a synapse, neurotransmitters are released from special pouches called synaptic vesicles into the gap between neurons called the synaptic cleft. The neurotransmitters then bind to receptors on the postsynaptic cell.
If multiple excitatory signals arrive at the same time from different dendrites, they can add together to reach the threshold for firing an action potential (spatial summation). They can also be counteracted by inhibitory signals.
What is a synapse?
The synapses that link your neurons together are the reason your brain can think, remember, and do the things that make you who you are. Neurons in your brain and spinal cord have anywhere from a few to thousands of synapses. Each synapse is a tiny gap across which an impulse can jump from one neuron to another, or from one nerve cell to a muscle fiber.
The presynaptic neuron secretes chemicals called neurotransmitters into the synapse to transmit the electrical signal to the postsynaptic cell. The neurotransmitters bind to receptors on the post-synaptic cell and activate it, or inhibit it, depending on whether the signal is positive or negative.
There are 2 kinds of synapses: chemical and electrical. At chemical synapses, signals travel faster than at electrical ones because the terminal buttons are closer to each other. They also use different neurotransmitters, which have a variety of effects on the post-synaptic cells. There is also a special type of electrical synapse known as a gap junction, which uses channels formed by proteins called connexins that allow current (ions) to flow directly from one neuron to the next.
How does a synapse work?
The synapse is where one neuron passes a message to another. In chemical synapses, an electrical signal travelling down the axon of a presynaptic neuron triggers the release of tiny vesicles that contain neurotransmitters. These molecules rapidly diffuse across the synapse and bind to specialized receptors on the membrane of the postsynaptic cell. This binding initiates a second messenger pathway that either excites or inhibits the next neuron.
At this point the postsynaptic cell is ready to receive a new signal. This is because its voltage has dropped to about -70 millivolts, which is below its resting potential. A few microseconds later, the other synapse will fire and cause an additional depolarization of about -60 mV. The second depolarization adds on to the first, triggering an action potential and an increase in the voltage of the postsynaptic cell to about +40 mV. Once this happens, the cell’s membrane can no longer contain ions and is reversibly depolarized.
What happens at a synapse?
A brain cell, or neuron, has a long main body and thin strands that branch out like branches on a tree, called dendrites. The tip of one neuron’s axon can connect to the dendrites of another neuron through a thin bridge, or synapse.
An electrical impulse traveling down the axon of a neuron triggers the release of tiny pouches in the cell membrane, called synaptic vesicles, that contain chemical messengers called neurotransmitters. These chemical signals travel across the tiny gap between cells, and bind to receptors on the membrane of the next neuron. The neurotransmitters can excite or inhibit the neuron they bind to.
After the neurotransmitter leaves the synapse, it may be broken down by enzymes or sucked back up into the presynaptic neuron. This process is known as reuptake. It allows the postsynaptic neuron to return to its normal resting potential, and prevents the accumulation of too many excitatory postsynaptic potentials (EPSP). There is also a special kind of synapse, called a gap junction, that bypasses the need for neurotransmitters. Gap junctions allow direct current to flow between neurons, and can be very fast.
What happens at the end of a synapse?
The synapse is where neurons send signals to other cells. To communicate, one neuron secretes chemicals called neurotransmitters from special pouches clustered near its membrane known as synaptic vesicles. These vesicles are then released into the tiny gap between neurones, the synaptic cleft, and are taken up by receptors on the dendrites of the other cell.
When an action potential triggers release of neurotransmitters, the chemical messengers travel across the synapse and bind to receptors on the dendrites of another cell. This causes the next cell to change its behavior, either stimulating or inhibiting it.
This type of neurotransmission is only possible at chemical synapses, and it is primarily responsible for the ability of neurons to show plasticity, which in turn forms the basis of memory and learning, as well as higher intellectual functions. However, there is also a special type of synapse called a gap junction that can conduct electrical impulses in a bidirectional manner.