How does neural transmission occur

But nothing below the level of neurons does. We shall ignore that this view, called the neuron doctrine, is somewhat controversial. Synapses are connections between neurons through which "information" flows from one neuron to another. Hence, neurons process all of the "information" that flows within, to, or out of the CNS. All of it! All of the motor information through which we are able to move; all of the sensory information through which we are able to see, to hear, to smell, to taste, and to touch; and of course all of the cognitive information through which we are able to reason, to think, to dream, to plan, to remember, and to do everything else that we do with our minds.

Processing so many kinds of information requires many types of neurons; there may be as many as 10, types of them. Processing so much information requires a lot of neurons. How many? Well, "best estimates" indicate that there are around billion neurons in the brain alone! And as each of these neurons is connected to between 5, and , other neurons, the number of ways that information flows among neurons in the brain is so large, it is greater than the number stars in the entire universe!

While we are considering numbers, it is worth noting that there are as many as 50 times more glia than neurons in our CNS! Glia or glial cells are the cells that provide support to the neurons. In much the same way that the foundation, framework, walls, and roof of a house prove the structure through which run various electric, cable, and telephone lines, along with various pipes for water and waste, not only do glia provide the structural framework that allows networks of neurons to remain connected, they also attend to the brain's various house keeping functions such as removing debris after neuronal death.

Because our main interest lies in exploring how information processing occurs in the brain, we are going to ignore glia.

But before we see how neurons process information and what that means , you need to know a few things about the structure of neurons. While there are as many as 10, specific types of neurons in the human brain, generally speaking, there are three kinds of neurons: motor neurons for conveying motor information , sensory neurons for conveying sensory information , and interneurons which convey information between different types of neurons.

The following image identifies how neurons come in various shapes and sizes. It is based on drawings made by Cajal. A "typical" neuron has four distinct parts or regions. The first part is the cell body or soma.

This is not only the metabolic "control center" of the neuron, it is also its "manufacturing and recycling plant. The second and third parts are processes — structures that extend away from the cell body.

From the neuron, the neurotransmitter is released particularly from its axon and interacts with the dendrites of another neuron.

They are produced in the ribosomes of the presynaptic neuron. They are stored in vesicles. These vesicle's location is cytoplasm of a neuron. When an action potential arrives at the pre-synaptic terminal, there is the entry of the calcium ions in pre-synaptic neurons. Now, after calcium ions entry into the cell, synaptic vesicles merge with pre-synaptic membrane and neurotransmitter is released into the synaptic cleft. When neurotransmitter arrives at the cell membrane of a post-synaptic neuron , certain protein molecules are activated.

These protein molecules are receptors for neurotransmitters. After binding with receptors, neurotransmitters have two effects on the post-synaptic membrane. Excitation of the postsynaptic membrane or its inhibition.

During excitation, an action potential is generated. During inhibition, an action potential is inhibited. Neurotransmitters are released in small amounts and produce minimal excitatory or inhibitory effects. This process takes place regardless of the action potential generated or not. This process is amplified when an action potential arrives and the required message is sent from neuron to its target through neurotransmission.

Neurons are connected with multiple other neurons. They receive impulses from them. These impulses can sum up together to cause the desired effects. This is called summation. Spatial summation It happens when multiple action potentials arrive at the presynaptic terminal and cause the release of the amount of neurotransmitter enough to exceed the trigger point of the postsynaptic neuron. Temporal summation occurs when multiple action potentials are generated in a short period to reach the desired threshold of the postsynaptic neuron.

Both convergence and divergence are important aspects of neurotransmission. By taking input from multiple neurons, neurons converge the information. By sending signals to different neurons, they diverge information. Sometimes many neurotransmitters are released from a single neuron presynaptic terminal. This phenomenon is called co-transmission.

The same is true for dopamine and glutamate. There are several types of neurotransmitters. Most common that are in abundance and have a great impact on the body are Acetylcholine, Dopamine, Norepinephrine, Serotonin, GABA, endorphins, glycine, and glutamate.

Acetylcholine is the most abundant neurotransmitter in the brain. It is responsible for producing the effects of the parasympathetic nervous system. Acetylcholine causes contraction of muscles. It causes activates of receptors for pain. Acetylcholine is involved in the normal functioning of many glands. It controls many stages of sleep especially the REM sleep stage. Acetylcholine acts as a vasodilator.

It increases sweating, lacrimation, and all body secretions. It can be a culprit for causing a decrease in heart rate. Norepinephrine is an important neurotransmitter. Now why you remain attentive has something to do with norepinephrine levels.

Our emotional IQ is dependent on nor-epinephrine levels. It regulates sleeping, dreaming, and learning. Many neuromodulators, such as dopamine , are monoamines. There are several dopamine pathways in the brain, and this neurotransmitter is involved in many functions, including motor control, reward and reinforcement, and motivation.

Noradrenaline or norepinephrine is another monoamine, and is the primary neurotransmitter in the sympathetic nervous system where it works on the activity of various organs in the body to control blood pressure, heart rate, liver function and many other functions.

Neurons that use serotonin another monoamine project to various parts of the nervous system. As a result, serotonin is involved in functions such as sleep, memory , appetite, mood and others. It is also produced in the gastrointestinal tract in response to food. Histamine , the last of the major monoamines, plays a role in metabolism, temperature control, regulating various hormones, and controlling the sleep-wake cycle, amongst other functions.

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