Central Nervous System

In the previous post we talked about all types of Cells in the Nervous System (NS).

That’s why in this post we start describing the essential parts (organs) that make up the CNS (Central Nervous System) and explain their function.

Central Nervous System consists of 1-Brain and 2-Spinal Cord. 

1-Brain includes the  following: Cerebrum, Cerebellum and the Brain Stem.

Fig2: The Cerebrum includes all the lobes shown
(Frontal, Parietal, Occipital, Temporal)

The Cerebrum (or Telencephalon) is the most developped and complicated part of the brain. It makes about 2/3 of the brain mass, and is covered with thin layer of Gray Matter called the Cerebral Cortex. The cerebrum is also divided into right and left Hemispheres that stay connected through the Corpus Callosum. The Corpus Callosum made of White Matter is essentially a thick band of nerve fibers. Each Hemisphere contains 4 lobes, the Sylvian Fissure defines the Temporal Lobe (whether its right or left) the Central Sulcus defines the Frontal lobe from the Parietal and Occipital Lobes. Each lobe has some caracteristic tasks like the Temporal Lobe for instance is involves in comprehending language, deriving meaning and keeping visual memories. As for the Parietal Lobe it is known to integrate sensory info which is why it contains the proprioceptive and somatosensory cortex.

The Cerebellum is connected to the three parts that constitute the Brain Stem (midbrain, pons, medulla oblongata) and can be divided into two Cerebellar Hemispheres (right and left) connected with the Vermis. Each hemisphere can be divided into Anterior and Posterior Lobes, separated by the Primary Fissure (See Figure 1 for better understanding). Also between each Hemisphere and the Vermis exists a zone called Intermediate or Paravermal Area (para meaning alongside). The cerebellum controls voluntary motor movement coordination and muscle tone resulting in smooth movements, including posture, speech and balance.

Fig3: An image showing the cerebellar hemispheres and the vermis from the posterior view.

The Brain Stem just anterior to the cerebellum, it is the portion of the brain that connects cerebrum to spinal cord, consisting of three following parts: midbrain, pons and medulla oblongata. The midbrain being closer to the cerebrum and the medulla closer to the spinal cord. The brain stem is not limited to just transmitting motor signal but also controls mostly autonomic functions of the PNS (Peripheral Nervous Sytem) those are mostly life supporting and vital functions like heart rate, blood pressure, breathing, digestion and sleep cycles.