A neuron is a cell that is specialized in conducting electrochemical impulses known as nerve impulses or action potentials. They conduct impulses along hair-like cytoplasmic extensions known as the nerve fiber or axons. These axons connect the spinal cord to the feet and can be as much as one meter long though only some few micrometers in diameter. There three major classes of neurons and this include the sensory neurons, interneurons and motor neurons. Sensory neurons run from the various types of stimulus receptors such as touching, taste and sound to the central nerves system the brain and the spinal cord. Interneuron’s are found exclusively within the spinal cord and the brain and are stimulated by signals reaching them from the sensory neurons and other interneurons. The human brain contains billions of these interneurons. Motor neurons transmit impulses from the central nerves system to the muscles and the glands that carry out the response. These neurons are stimulated by the interneurons though some of them are stimulated directly by sensory neurons (Leonard, 2001, 34).
Depolarization in respect to neurons is the decrease in the absolute value of a cell’s membrane potential. Consequently, the membrane potential becomes less positive or less negative. In neurons, a depolarization large enough may result into action potential whose rising and falling phases are often imprecisely also called depolarization and hyper-polarization respectively.
The brain is a vital human organ and it is the one charged by controlling almost all other organs. Human brain as stated earlier contains billions of neurons that facilitate the proper functioning of the brain. It is the brain that is responsible for the proper functioning of the memory. In psychology, memory inhibition is the ability of the brain not to remember irrelevant information and it is a critical component of an effective memory system. Neurons in the brain are of two kinds. There are those that transmit and amplify signals known as the excitatory neurons and there are those that inhibit and refine these signals and these are known as the inhibitory neurons. The latter is also the one responsible for memory inhibition (Leonard, 2001, 38).
In some ways the action of the neurons resemble an act of a computer so to say. They receive messages, process them and then send back a feedback to other cells in the body. These messages are in chemical form, which interact with the other surface of a cell membrane. The interaction the causes chemical changes within the receiving neuron. This process is termed as neurotransmission and it involves three basic steps. The first step is that of neurons releasing neurotransmitters.
When a neuron is excited, some events take place to create an electric impulse. The consequence of this events leads to depolarization of the axon. The aftermath of this is that the vesicles swarm to the very edge of the axon and release neurotransmitters. The next step involves binding of the neurotransmitters to receptors. The latter only accept certain neurotransmitters which they let go after binding has taken place. The third and final step involves the binding passing on the neurotransmitter’s message. In summary the release of a neurotransmitter is triggered by the arrival of a nerve impulse and it occurs through a usually rapid process of cellular secretion. The re-absorption of a neurotransmitter by a neurotransmitter transporter of a presynaptic neuron and after it has perfumed its function of transmitting an impulse is generally known as reuptake (re-uptake) (Leonard, 2001, 43).
Leonard Austin. Neurons: Building Blocks of the Brain. New York Blackwell Publishers, 2001, 34, 38, 43