As is well known, stroke is due injury to brain due various reasons. The human brain – as can be expected – is a complex organ indeed. Each zone of it controls specific abilities and functions, including mental functions. Following is a basic discussion of the brains’ anatomy and how it works.
The nervous system : It comprises nerves and cells that enable communication between the brain and the rest of the body. It has two main parts – the Central Nervous System ( CNS) , made up of spinal cord and the brain; and the peripheral nervous system (PNS) which are the nerves and other supporting cells etc. branching throughout the body and enabling communication of the various body parts with the CNS. Some further break down the CNS into the hindbrain, the lower part of the brain stem; the midbrain, the central part of the brain stem; and the forebrain, which includes the cerebral hemispheres. The brain stem handles automatic processes for survival – such as heart rate, breathing, and carries information from the brain to the PNS. The “little brain” ( cerebellum) handles balance and movement coordination. Above the brain stem and the cerebellum is the cerebral cortex – for “higher mental functions” such as sensory perception, information processing, and memory, learning, and decision-making. The parts of the CNS work together seamlessly in healthy individuals, allowing the brain to govern functions and behaviors ranging from breathing to reading.
The hemispheres : The cerebral cortex is divided into two hemispheres, connected via “corpous callosum” , a bridge of neural fibres conveying signals between them. The right cerebral hemisphere receives sensory input from and directs movement on the left side of the body, while the left hemisphere governs corresponding functions for the right side. Two key areas involved in language—Broca’s Area, responsible for language grammar and syntax, and Wernicke’s Area, implicated in language content and meaning processing—reside on the left side of the brain for most. (Those areas may be on the right side in some left-handed individuals). Besides, activity for most cognitive tasks is seen in both hemispheres although it is usually understood that these two sides of the brain are important to specific functions—that is, the right side of the brain is responsible for creativity while the left side handles your more analytical-type processing.
The lobes. : Each cerebral hemisphere has four major lobes – the occipital, towards the back of the brain; the parietal, just above the ear; the temporal, just behind the forehead temples; and the frontal, resting above the eyes at the very front of the cortex. The occipital lobe is mainly responsible for processing and interpreting visual information. It’s the seat of the primary visual cortex. The temporal lobe is the major processing center of sound (including language) and some forms of memory. The parietal lobe is the home of the somatosensory cortex, the area of the brain responsible for processing sensation and touch information, as well as some aspects of spatial processing. The frontal lobe is the most complex part of the human brain. Indeed, it separates humans from apes. It is teh largest lobe, and handles all executive functions such as reasoning, decision-making, sensory integration, planning, and execution of movement.
Folds and grooves : The cortex has pleats. The outer bump in each pleat is called the gyrus, while the groove inside each fold is called the sulcus. These pleats are different in each human, except form some broad structural similarities.The lateral suclus seperates the temporal lobe from the frontal lobe, and along with its neghbor the temporal gyrus house the primary auditory cortex, the area of the brain that processes sound information. Wernicke’s Area, that important language region, also can be found on the temporal gyrus. References to gyri and sulci can help pinpoint more specific locations on a particular lobe of the cortex.
Gray and white matter : The brain’s most basic working unit is called a neuron, which , unlike other cells have specialized branching extensions called dendrites and axons. These allow the neurons to communicate with one another through small gaps among them called synapses where messages are exchanged using chemical processes. Different sections of neurons make the two types of brain matter – gray and white. Gray matter consists of the cell bodies and dendrites of neurons as well as other support cells called glia, or glial cells. White matter, on the other hand, is made up of the neuron’s axons, sheathed in myelin which is a fatty insulation that helps brain cells communicate more efficiently, and gives the white matter its color.
The connectome : Various parts of the brain work together to govern perception, processing, and behavior and help one make sense of the world around us. Important regions of the brain are strongly connected to one another through circuits, or tracts of networked neurons that help those regions communicate with one another with ease. Increasingly, beyond functional segregation as per different areas of the brain, researchers are using new techniques to follow these critical circuits to understand how groups of different brain areas work together to determine human behavior. This intricate pattern of connections is called “the connectome.”
( The description above is understood and summarized from article here. )