Synaptic function is to transmit nerve impulses between two nerve cells (neurons) or between a neuron and muscle cell. Synapses connect one neuron to another and are thus responsible for the transmission of messages from the nerves to the brain and vice versa.
- Neurons communicate with one another at junctions called synapses. At a synapse, one neuron sends a message to a target brain cell or muscle cell.
- The synapse, rather, is a small pocket of space between two cells where they can pass messages to communicate. A single neuron may contain thousands of synapses. In fact, one type of neuron called the Purkinje cell, found in the brain’s cerebellum, may have as many as 100,000 synapses.
- Synapses are part of the circuit that connects sensory organs such as those that detect pain or touch.
- They connect neurons in the brain to neurons in the rest of the body and from those neurons to the muscles. This is how the intention to move our arm, for example, translates into the muscles of the arm actually moving.
- Synapses are also important within the brain and play a vital role in the process of memory formation.
- The transmission of information within the nervous system operates in circuits, which can take up information; each of these circuits has several synapses that connect the neurons that carry sensory information to the brain and neurons that execute the motor commands from the brain.
- At the same time, all these transmissions happen very quickly (in milliseconds), so it seems to all happen simultaneously.
- At the synapse, the firing of an action potential in one neuron is called presynaptic. The neuron that causes the transmission of a signal to another neuron is called postsynaptic.
There are two types of synapses:
- Electrical synapse: There are essentially no gaps between the cells. Instead, ions travel through the leaky parts called gap junctions and transfer an electrical charge to the next neuron. Electrical synapses have been understudied. They are present in the heart cells along with the gap junctions that transmit electrical signals.
- Chemical synapse: The electrical signal within the neurons, called an action potential, is translated into a chemical signal that can travel across the synapse to the next neuron in the circuit. This is done through the release of chemicals called neurotransmitters, which are released in packets upon the arrival of an action potential at the synapse. When the neurotransmitter reaches the next neuron in the chain, the chemical signal is transformed back into an action potential that travels down that neuron to the next synapse and so on. The neurotransmitter is destroyed once the action potential crosses over.
Synaptic transmission can be either electrical or chemical and, in some cases, both at the same synapse. Chemical transmission is more common and more complicated than electrical transmission.
- Loss of synapses in the brain due to degenerative diseases such as Alzheimer’s or Parkinson’s will cause a corresponding loss of function related to whatever those synapses did.
- In fact, recent research indicates that synapses, rather than the neurons themselves, may be the first to show the effects of these conditions.
- The fact that problems with synapses can cause someone to stop breathing just goes to show how vitally important synaptic functions are to our very survival.
- People often focus on the neurons or muscle cells, but the connections between them are just as essential.