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Organization of Nervous System

Central nervous system (CNS), Meninges, Brain, Cerebrum, Diencephalon, Brain stem, Cerebellum, Ventricles and cerebrospinal fluids, Spinal cord.
It's important to remember that the body has only one nervous system, despite terminology that suggests otherwise. In addition to being called "nervous systems" by each subdivision, all of these smaller systems are highly integrated into a single system. Each subdivision is distinct in terms of its structure and function.

Central nervous system (CNS)

The brain and spinal cord are both important organs of the central nervous system, located within the dorsal cavity of the body and surrounded by bone as a protective unit In the cranial vault of the spine is the brain, which is found in a network of canals and spinal cords. At the foramen magnum, the brain and spinal cord are joined despite initially being considered separate organs.

The spinal cord is shielded by vertebrae, which are held together by the cranium. When the spinal cord connects with the brain, a foramen magnum is created. Meninges, which are connective tissue membranes that surround the CNS, are also contained in cerebrospinal fluid.


Meninges surround the spinal cord and brain in three layers. Connective tissue calleddura mater, which acts as the outermost layer of the brain, is tough and white. It is a thin layer with threadlike strands that attaches to the innermost layer and resembles a cobweb when viewed from the top down. In the subarachnoid space, which is below the arachnoid, cerebrospinal fluid and blood vessels are contained. Layers of meninges exist, with pia mater forming the innermost layer. It cannot be dissected away without damaging the brain and spinal cord surface because this thin, delicate membrane is tightly attached to them.

A meningioma is a tumor that affects the nerve tissue that covers the spinal cord and brain. Even though meningiomas do not spread, doctors often treat them as though they were malignant to treat symptoms that may develop when a tumor presses on the brain.



A deep longitudinal fissure divides the cerebrum into the cerebrum and the cerebral hemispheres. A connection between the left and right hemispheres is provided by the corpus callosum, a band of white fibers that lies in the middle of the two halves that facilitates communication between them.

Each brain hemisphere is divided into five lobes, which all have the same names as their surrounding bony structure: the frontal lobe, parietal lobe, occipital lobe, and temporal lobe. Within the lateral sulcus is the insula, or the Island of Reil, the fifth lobe of the brain.


Located almost in the center of the cerebral hemispheres, the diencephalon is located centrally. There are three parts to the thalamus: thalamus, hypothalamus, and epithalamus. In the diencephalon, the thalamus accounts for approximately 80 percent of space. As a sensory relay system, it consists of two oval masses of gray matter, except that the sense of smell is associated with the cerebral cortex. The hypothalamus is a small, midbrain region below the thalamus that controls many visceral functions, thereby contributing to homeostasis. There are two diencephalon regions: a dorsal region and a central region. Associated with puberty and rhythmic cycles of the body, this small gland lets hormones out when the body needs them. Biological clocks are produced by the glands in the body.

Brain stem

There is a region of the brain between the diencephalon and the spinal cord called the brain stem. Midbrain, pons, and medulla oblongata are the three parts of the medulla. There is midbrain at the top of the brain stem that is different from the pons and medulla. The pons is a bulging portion located in the middle of the body. Conduction tracts, which link the higher brain centers to the spinal cord, make up the bulk of this region. An inferior extension of the pons is the medulla oblongata, or medulla also called the medulla. There is a foramen magnum where it connects to the spinal cord. During the ascending (sensory) and descending (motor) neural connections between the brain and spinal cord, the medulla conducts those signals.


There is a second largest part of the brain named the cerebellum under the occipital lobes of the cerebrum. As part of the central nervous system, the cerebellum communicates with other parts of the body via three paired bundles of myelinated fibers called cerebellar peduncles.

Ventricles and cerebrospinal fluids
Brains contain a series of fluid-filled cavities that are interconnected. In these chambers is cerebrospinal fluid (CSF), which is fluid that surrounds the ventricles of the brain.

Spinal cord
Foramen magnum, which is near the base of the skull, is the origin of some spinal cord and reaches the first lumbar vertebra. A cord connects the foramen magnum to the medulla oblongata. Bone, meninges, and cerebrospinal fluid surround the spinal cord, as do the meninges and meninges of the brain.

Several spinal nerves extend past the conusmedullaris at the distal end of a horse's cord, forming a tail-shaped collection.

There are two main functions of the spinal cord:
  • Input and output pathways for nerve impulses in and out of the brain. A pair of ascending tracts carry sensory impulses to the brain from the spinal cord. Motor impulses travel downstream.
  • The spinal cord serves as a reflex center. Reflex arcs serve as an essential unit in the nervous system. As a result, reflexes occur faster than reactions requiring conscious thought. They allow us to respond to stimuli without thinking about them. As an example, the withdrawal reflex has the effect of forcing you to withdraw the affected part before you realize you are in pain. The spinal cord regulates many reflexes without direct communication with the higher brain centers.

Peripheral nervous system (PNS)

The brain and the nervous system are made up of bundles of nerve fibers, much as muscles are made up of muscle fibers. Neurons in the spinal column and cranial nerves connect the brain to peripheral organs like muscles and glands. There are ganglia outside the central nervous system, which are small collections of nerve cell bodies. There are two branches to the peripheral nervous system: an afferent (sensory) branch and an efferent (motor) branch. Signals from peripheral organs to the central nervous system are transmitted by the afferent or sensory division. Efferent impulses are transmitted from the central nervous system to the peripheral organs to create effects or actions.

Further, the efferent or motor division can again be divided into the autonomic as well as the somatic nervous system. Somato-motor neurons (also called somatic efferent neurons) transmit motor impulses to skeletal muscles through the somatic nervous system. In addition to enabling conscious control over skeletal muscles, these nerves are called the voluntary nervous system. Afferent motor impulses are emitted by the autonomic nervous system, which is also known as the visceral efferent nervous system, to cardiac muscle, smooth muscle, and glandular epithelium. Furthermore, it can be divided into sympathetic and parasympathetic components. Because it regulates involuntary and automatic functions, the autonomic nervous system is also known as the involuntary nervous system.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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