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Synapses are essential for the transmission of neuronal impulses from one neuron to the next, [10] playing a key role in enabling rapid and direct communication by creating circuits. In addition, a synapse serves as a junction where both the transmission and processing of information occur, making it a vital means of communication between ...
Once at the synapse, synaptic vesicles are loaded with a neurotransmitter. Loading of transmitter is an active process requiring a neurotransmitter transporter and a proton pump ATPase that provides an electrochemical gradient. These transporters are selective for different classes of transmitters.
A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory. [11]
An autapse is a synapse in which a neuron's axon connects to its dendrites. The human brain has some 8.6 x 10 10 (eighty six billion) neurons. [31] [32] Each neuron has on average 7,000 synaptic connections to other neurons. It has been estimated that the brain of a three-year-old child has about 10 15 synapses (1 quadrillion).
Axon terminals are specialized to release neurotransmitters very rapidly by exocytosis. [1] Neurotransmitter molecules are packaged into synaptic vesicles called quanta that cluster beneath the axon terminal membrane on the presynaptic side (A) of a synapse.
When a reflex arc in an animal consists of only one sensory neuron and one motor neuron, it is defined as monosynaptic, referring to the presence of a single chemical synapse. In the case of peripheral muscle reflexes (patellar reflex, achilles reflex), brief stimulation to the muscle spindle results in contraction of the agonist or effector muscle
The number of synapses in the human cerebral cortex has separately been estimated at 0.15 quadrillion (150 trillion) [3] The word "synapse" was introduced by Sir Charles Scott Sherrington in 1897. [4] Chemical synapses are not the only type of biological synapse: electrical and immunological synapses also exist. Without a qualifier, however ...
Calyx of Held microstructure. The calyx of Held is a particularly large excitatory synapse in the mammalian auditory nervous system, so named after Hans Held who first described it in his 1893 article Die centrale Gehörleitung [1] [2] because of its resemblance to the calyx of a flower. [3]