Neurons

From the level of cnidarians (e.g., corals and jellyfish) upward, the neuron, also known as nerve cell, is the fundamental cell of the nervous system in vertebrates and most invertebrates, including humans. In a normal neuron, there is a cell body with a nucleus and two or more lengthy fibres that extend from it. Impulses are delivered to the cell body by one or more of these fibres, which are referred to as dendrites; in higher neurological systems, only one fibre, the axon, is responsible for transporting the impulse away from the cell body. Bundles of fibres from neurons are held together by connective tissue, which is what gives rise to nerve fibre bundles. Nerves in large animals can be several feet in length in some cases. A sensory neuron is a nerve cell that conducts impulses from a receptor, such as those in the eye or ear, to a more central place in the nervous system, such as the spinal cord or brain, through the nervous system. When an impulse is transmitted from a central part of the nervous system to an effector, such as a muscle, it is known as a motor neuron.

Types of neurons

Brain and nervous system cells, or neurons, are the basic building blocks of these structures. They are the essential units that send and receive impulses that let us to move our muscles, feel the external world, think, make memories, and much more.

A microscope’s magnification makes it evident that not all neurons are alike. So, how many different kinds of neurons are there? What criteria do scientists use to classify things? The answer to this issue isn’t straightforward for neurons in the brain. However, we can categorise the neurons of the spinal cord into three categories: sensory, motor, and interneurons.

Sensory neurons

Neurons activated by sensory input from the environment are known as sensory neurons. When you touch a hot surface with your fingertips, sensory neurons will fire and transmit messages to other parts of your nervous system about what you’ve just experienced.

Sensory neurons are activated by a variety of stimuli, including both physical and chemical ones. Physical inputs can include elements like sound, touch, heat, and light as well as other types of sensory information. Senses of taste and smell provide chemical input to neurons, which subsequently communicate with the brain.

The majority of sensory neurons are pseudounipolar, which implies that they only have one axon that is divided into two branches.

Motor neurons

As a part of the central nervous system (CNS), spinal cord motor neurons communicate with muscles, glands and organs all over the body. All of our muscular movements are directly controlled by these neurons, which transfer impulses from the spinal cord to skeletal and smooth muscles (including those in the stomach). To differentiate between the two types of motor neurons: those that flow from the spinal cord to muscles and those that transit between the brain and spinal cord: lower motor neurons.

Most nerve cells, including motor neurons, have multipolar ‘body plans,’ which have one axon and many dendrites as their primary structure.

Interneurons

Interneurons, as the name implies, are the neurons that sit in the middle of the nervous system, connecting spinal motor and sensory neurons. Besides conveying messages between sensory and motor neurons, interneurons can also communicate with one another, resulting in the formation of circuits of varying levels of sophistication. They behave similarly to motor neurons in that they are multipolar.

Functions

What is the mechanism through which neurons function?

Action potentials are used by neurons to transmit signals. In neurons, an action potential is a change in the potential electric energy of the neuron that is induced by the movement of charged particles into and out of the neuron’s membrane. In response to the generation of an action potential, it is conveyed along the axon to its presynaptic termination.

In addition to chemical synapses, action potentials can also activate electrical synapses. Synapses are the points at which neurons can communicate with one another electrically and chemically by passing signals between them. Essentially, synapses are made up of three parts: a presynaptic ending, a synaptic cleft, and a postsynaptic end.

Chemical synapses

A chemical synaptic connection occurs when a neuron releases chemical messengers known as neurotransmitters. These chemicals pass through the synaptic cleft and bind to receptors located at the postsynaptic end of a dendrite’s terminal segment.

In the postsynaptic neuron, neurotransmitters can elicit a reaction, prompting it to create an action potential of its own as a result. They can also inhibit activity in the postsynaptic neuron, if the situation calls for it. As a result, the postsynaptic neuron does not generate an action potential in that circumstance.

Electrical synapses

Electrical synapses are only capable of excitation. When two neurons communicate with one another through a gap junction, synapses are formed. Unlike a chemical synaptic gap, this one is made up of ion channels, which aid in the transmission of a positive electrical signal when the gap is closed.

Signals flow far more quickly across electrical synapses than they do through chemical synapses as a result of the manner these signals travel. These signals, on the other hand, can deteriorate from one neuron to the next. Consequently, they become less effective when conveying repeated messages.

Conclusion

Neurons, also known as nerve cells, are responsible for transmitting and receiving messages from the brain. While neurons share many characteristics with other types of cells, they are distinct in their structural and functional characteristics. Axons, which are specialised projections that allow neurons to transfer electrical and chemical impulses to other cells, are responsible for this function. A neuron is a specialised cell that is largely responsible for the transmission of information through electrical and chemical impulses in the nervous system. They can be found in the brain, spinal cord, and peripheral nerves, among other places. A neuron is also referred to as a nerve cell in some circles.