What is the function of the nervous tissue cell?

Written by Almarie Joy B. Florida

Reviewed by Dr. Reuben J C. los Baños, Ph.D.

Nervous tissue conducts and transmits electrical signals in your body. The body calls these signals nerve impulses or an “action potential.” It enables rapid communication between your body parts. It supports sensory perception, motor coordination, and thinking. Also, it supports and regulates the activities of other cells.

Two Major Divisions of Nervous System

• Central Nervous System (CNS) – composed of cerebrum, cerebellum, spinal cord

• Peripheral Nervous System (PNS). – composed of cranial nerves, spinal nerves, ganglia

Your neurons, also called nerve cells, carry out the nervous system’s functions. They do this by responding to stimuli. They transmit chemical and electrical signals, which cause an action potential. The anatomical structure of your neurons has three main parts – cell body, dendrites, and axon.

Meanwhile, glial cells or neuroglia mean “nerve glue.” They are connective tissue in the nervous system. Your neuroglia, unlike neurons, do not conduct signals. Instead, they offer support to neurons for their structure and function.

What is the main characteristic of nervous tissue?

Nervous tissue’s main trait is its unique excitability or irritability. This property refers to the ability of some cells. They can respond to changes or stimuli. These cells include neurons, muscle cells, and some gland cells. They show their ability to react. They do this by changing the ionic gradient. They do it across their plasma membrane in response to various stimuli.

When your neurons encounter stimuli, they undergo a rapid ionic gradient reversal. This process, known as membrane depolarization, spreads across the entire membrane. This depolarization wave is often called the action potential. It can travel long distances along the neuronal processes.

As it travels, it sends signals to other neurons, muscles, and glands. These help them communicate and coordinate within your body. This allows you to respond to signals. This plays a vital role in sensing, moving, and body functions. Additionally, specialized nervous tissue is amitotic. Once something destroys it, it cannot regenerate because it does not undergo mitosis.

What is nervous tissue made of?

Nervous tissue is integral to the function of the nervous system. Two distinct cells make it, neurons and neuroglia. The neurons in your body are the primary communicators within your nervous system. Meanwhile, neuroglia provides support and maintenance for neurons. It gives insulation, nutrients, and defense from pathogens.

Figure 1. Structure of a neuron.

The structure that supports your neuron has three main parts. These parts are the cell body, dendrites, and axon. The cell body, also known as perikaryon or soma, contains a nucleus with at least one nucleolus. But unlike other cells, it lacks centrioles due to the amniotic nature of the cell.

Dendrites, also known as fibers, receive stimuli from other neurons. In some cases, the soma receives signals. They have a tree-like structure extending from the cell body to receive neurotransmitters.

Neurons can differ in the number of dendrites they have. Some lack dendrites, while others have many. They may have dendritic spines. This help increase their surface area for connecting with other neurons. Also, dendrites transmit impulses to your body’s neurons, classified as afferent processes.

Axon also transmits signals away from the cell body to other neurons, muscles, or glands. It is a tube-like structure. It carries the processed signal to endpoints called axon terminals. Your neurons can have one or two axons.

Other structures of a neuron are synapse and axon hillock. A synapse is where two neurons come close together, allowing one neuron to send a signal to the other. One side has the axon terminal of the sending neuron. The other side has a dendrite or dendritic spine of the receiving neuron. A tiny gap, the synaptic cleft, is in the middle. One neuron releases neurotransmitter across it to the next neuron.

Meanwhile, the axon hillock is where a neuron begins an action potential. It also decides whether to generate one. Not every signal received by a neuron at a synapse triggers an action potential. A single neuron can get signals from thousands to hundreds of thousands of other neurons. Some may send conflicting messages at the same time. The neuron combines these conflicting signals. It “integrates” them at the axon hillock. The hillock is between the cell body and the start of the axon. The process at the axon hillock integrates signals. It decides if the neuron will generate an action potential.

Classification of Neurons

The classification of your neurons based on their structure:

• Multipolar neurons
  • It is the most common among all neurons. It consists of one axon and two dendrites.
  • Bipolar neurons
    • Areas such as the eye, nose, and inner ear contain it. It consists of one axon and one dendrite.
  • Unipolar or pseudounipolar neurons
    • This includes all sensory neurons. They have one main branch that splits near the body. One part goes to the body’s edges, while the other goes toward the CNS.
  • Anaxonic neurons
    • It consists of many dendrites but have no true axons. It does not produce action potential. Instead, they regulate electrical changes of adjacent CNS neurons.

The classification of your neurons based on their function:

• Sensory neurons
  • It is also known as afferent neurons and are unipolar. It is the receiving stimuli from the receptors throughout the body.
  • Motor neurons
    • It is also known as efferent neurons and are multipolar. It sends impulses to effector organs such as muscle fibers and glands. Some motor neurons manage muscles you can move, like those in your arms and legs. Meanwhile, others control automatic body functions such as heart rate and digestion.
  • Interneurons
    • It creates connections between other neurons, forming complex networks in CNS. These cells make up most of the neurons in your body and can either be multipolar or anaxonic.

Neuroglia or Glial Cells

Neuroglia in the mammalian brain is more abundant, being 10 times more common. In the CNS, these cells surround both the larger neuronal cell bodies. They also surround the axons and dendrites between neurons. CNS contains little connective tissue and collagen, except around your major blood vessels. It replaces connective tissue, supporting neurons and creating ideal spaces for neuronal activity. There are six major types of neuroglia located both in your CNS and PNS.

Neuroglia in Central Nervous System

• Oligodendrocyte
  • Named from the Greek’s words oligo, small; dendron, tree; kytos, cells. It extends processes around your CNS axons, creating myelin sheath for electrical insulation. They work together to wrap axons, speeding up nerve signals. Under light microscopy, your glial cells appear as small cells with rounded nuclei.
  • Astrocyte
    • Named for their star-like appearance, from the Greek words astro-, star; kytos, cells. It has several branching processes supported by glial fibrillary acid protein (GFAP). It serves as a unique marker for this type of glial cell. This cell functions as structural and metabolic support for neurons and repair processes.
  • Ependymal cell
    • It is a columnar or cuboidal cell found lining the fluid-filled spaces in your brain and spinal cord. The ends of some cells have cilia which helps the cerebrospinal fluid (CSF) to move. The long microvilli help with absorption.

• Microglia
  • These are small cells with many long, branching processes. In some areas of CNS, they are abundant as neurons. But they are not common like oligodendrocytes and astrocytes.

Neuroglia in Peripheral Nervous System

• Schwann Cell
  • It is also known as neurolemmocytes. It does similar things to oligodendrocytes in the CNS. This includes supporting axons and making myelin sheaths. Unlike oligodendrocytes, they wrap their myelin sheath around one part of the axon.
  • Satellite Cell
    • It is a small glia that surrounds the sensory ganglia of neurons in the autonomic nervous system (ANS). These cells provide structural and metabolic support for neuronal cell bodies. Also, they are responsive to injury and can worsen pathological pain.

What are the two most important organs of the nervous system?

The brain and spinal cord are the two key organs in the nervous system.

Figure 2. Structure of a human brain.

Your brain is part of the central nervous system (CNS). It serves as the command center. It directs cognition, memory, sensation, movement, respiration, temperature regulation, and all body functions. It communicates through both chemical and electrical signals that travel throughout the body. It regulates various processes, with the brain interpreting each one. While some messages stay in the brain, others travel through the spinal cord and nerves in your body.

The average adult’s brain weighs around 3 pounds and consists of approximately 60% fat. The remaining 40% is a mixture of water, protein, carbohydrates and salt. Unlike muscles, the brain consists of blood vessels and nerves.

Main Parts of the Brain and their Functions

• Cerebrum
  • It is the largest part of the brain and located at the front. It contains two main parts: gray matter, known as the cerebral cortex, and white matter in its center. The cerebrum controls movement initiation, coordination, and regulating temperature. It is also responsible for speech, thinking, reasoning, judgment, emotions, problem- solving, and learning. Apart from that, your cerebrum carries out functions related to your five senses.
  • Brainstem
    • Found in the middle of the brain, the brainstem connects the cerebrum to the spinal cord. It consists of three main parts: the midbrain, the pons, and the medulla.
  • Cerebellum
    • Often referred to as the “little brain.” It is a first-sized region situated at the back of the head. Also, the brain divides into two hemispheres. The outer part contains neurons, while the inner communicates with the cerebral cortex. Your cerebellum functions in coordinating voluntary muscle movements and maintaining posture.

Figure 3. Structure of a spinal cord.

Your spinal cord is a lengthy, tube-like structure wherein it is about 18 inches long in most adults. This organ links your brain to your lower back. It is a pathway for nerve signals. They travel between your brain and body for you to sense feelings and control movement. Any injury can impair your mobility or function.

Main Parts of the Spinal Cord

• Sacral cord
• Lumbar cord
• Thoracic Cord
• Cervical Cord
• Coccygeal

How many nerves are in the human body?

The body consists of seven trillion nerves, transmitting various signals throughout the body.

Every part of your body has nerves. Even the bones have many nerves. Your skin, especially on your fingertips and face. is the organ that contains many nerves. These parts are full of nerve endings, so it is very sensitive to touch and change in temperature.

Your nerves arise during embryonic development. This happens through a process called neurogenesis. Stem cells become precursor cells, which then mature into neurons. Throughout your life, neurons can change. They do so in response to both internal and external signals. They change by reorganizing their structure and functions. Like other cells, neurons also undergo degeneration. This leads to cell death, which contributes to neurological disorders.

How are the nervous tissues protected?

Nervous tissues have many protective mechanisms. The central and peripheral nervous systems protect it. They do this using anatomical structures. These include the skull, vertebral column, meninges, and cerebrospinal fluid (CSF).

The skull and the vertebral column’s bone structure is important. They provide a robust protective barrier for the brain and spinal cord. The skull has a strong bone. It encases the brain, shielding it from impacts and injuries. The vertebral column consists of a series of vertebrae. It surrounds and protects the spinal cord, ensuring its safety from physical trauma.

Also, three layers of connective tissue known as meninges wrap your nervous tissues. They serve as an extra protective layer. The outermost layer is the dura mater. It forms a tough and fibrous covering around the brain and spinal cord. It provides mechanical support and protection. Below your dura mater is the arachnoid mater. It is a membrane that cushions and supports nervous tissues. Finally, the innermost layer is the pia mater. It is a thin membrane that sticks to the brain and spinal cord. It gives extra support and nourishment.

Furthermore, CSF also protects nervous tissue. Your CSF fills the spaces within the meninges. It forms a fluid cushion that absorbs shocks. This fluid also helps keep a stable environment around your brain and spinal cord.

Moreover, endothelial cells form the blood-brain barrier. They line the blood vessels in the brain. The barrier controls the passage of substances from the blood into the brain. This stops harmful substances such as toxins and pathogens that enter the brain.

Why is our nervous system important?

The nervous system is vital for your functioning and survival.

The nervous system is key for coordinating body functions. It sends signals for movement, sensation, and more. It enables responses to touch, pain, and sound. You can sense these through touch, temperature changes, and sound. They contribute to your well-being. It also controls involuntary functions like heartbeat and breathing. It also handles voluntary actions like walking and thinking. Moreover, it maintains homeostasis by regulating physiological parameters.

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