Central Nervous System
The Nervous System has several divisions. Anatomically, it is divided into:
- Central Nervous System (CNS): brain and spinal cord;
- Peripheral Nervous System (PNS): nerves and nerve ganglia that connect the CNS to the organs of the body.
Anatomy of the Central Nervous System
The Central Nervous System is made up of the brain and spinal cord . We can say that it is located within the axial skeleton, even though some nerves penetrate the skull or the spinal column.
The Central Nervous System is protected by bony parts. The brain is protected by the skull and the spinal cord by the spinal column.
Brain
The brain is made up of the cerebrum, cerebellum and brain stem. It has around 35 billion neurons and weighs approximately 1.4 kg.
Brain
The brain is the most massive part and the main organ of the Nervous System. It is responsible for controlling motor actions, sensory stimuli and neurological activities such as memory, learning, thinking and speech.
It is formed by two halves, the right and left hemispheres, separated by a longitudinal fissure. The two hemispheres comprise the telencephalon.
They work together, however, there are some specific functions for each of the hemispheres. The right hemisphere controls the left side of the body and the left hemisphere controls the right side.
Blood flow to the brain is quite high, surpassed only by the kidneys and heart.
Cerebellum
The cerebellum or metencephalon represents 10% of the brain volume. It is related to maintaining body balance, controlling muscle tone and motor learning.
Thus, as occurs in the brain, the cerebellum has two hemispheres separated by a narrow strip, the vermis.
Brainstem
The brain stem is made up of the midbrain, pons and medulla.
The midbrain is the smallest part of the brain stem, located between the pons and the cerebrum. The pons is located between the midbrain and the medulla. In the medulla, the lower part connects to the spinal cord and the upper part connects to the pons.
Spinal Cord
The spinal cord is the most elongated part of the central nervous system. It is characterized by a cylindrical cord, composed of nerve cells, located in the internal canal of the vertebrae of the spinal column.
The function of the spinal cord is to establish communication between the body and the nervous system. It also coordinates reflexes, occasions when the body needs a quick response.
The 31 pairs of spinal nerves originate from the spinal cord. They connect the spinal cord to sensory cells and various muscles throughout the body.
Meninges
The entire Central Nervous System is covered by three membranes that isolate and protect it, the meninges.
The meninges are:
- Dura mater : It is the outermost layer, being thick and resistant. It is formed by connective tissue rich in collagen fibers. Its outermost portion is in contact with the bones.
- Arachnoid : It is the intermediate membrane between the dura mater and the pia mater. Its structure looks like a spider’s web, hence its name.
- Pia mater : It is the most internal and delicate, in direct contact with the CNS.
The arachnoid and pia mater are separated by cerebrospinal fluid or liquor . It provides mechanical protection and shock absorption to the organs of the Central Nervous System. It also provides nutrients to the brain.