The CNS (central nervous system) comprises the brain and the spinal cord. The PNS (peripheral nervous system) is made of spinal nerves branching from the spinal cord; the cranial nerves branch from the brain.
The human brain is about the size of a grapefruit and weighs close to 3 pounds. There are four main regions of the adult brain –
- Cerebrum
- Cerebellum
- Diencephalon
- Brainstem
The cerebrum constitutes the largest part of the brain; it accounts for nearly 83%, which is two-thirds of the total weight of the brain. This large part of the brain can be seen atop the brainstem, comprising the cerebellum underneath the rear section.
The cerebrum is accountable for complex facets related to consciousness such as intelligence, memory and personality. It is involved in receiving sensory information, processing it and regulating the conscious and motor activities. It is involved in a wide range of cognitive processes.
Particular areas of the cerebrum are responsible for interpreting sensory impulses. For instance, the Wernicke’s area is the part of the cerebrum which receives spoken and written language.
Where is Cerebrum located? – Cerebrum Location
The cerebrum is situated in the upper portion of the cranial cavity in the skull. A central longitudinal fissure divides the cerebrum, wherein each of the hemispheres is connected by the corpus callosum.
In simpler words, the cerebrum in the human skill can be seen on the brain stem, while the cerebellum is under the rear part.
Structure of Cerebrum
The telencephalon or cerebrum is divided into two cerebral hemispheres – the right and the left hemisphere on either side of a fissure. The left hemisphere regulates the right side of the body and is involved in functionalities related to speech and language. Hence, it mainly deals with logic, speech, arithmetic and writing.
The right hemisphere regulates the left side of the body and is typically involved in processing spatial and visual information along with non-verbal skills. Hence, the right side is concerned with symbols, imagination, spatial relations and art. Both hemispheres are associated with nerve fibres that enable communication between each brain’s side.
The cerebral hemispheres have evident fissures dividing the brain into different lobes. Each of the hemispheres comprises 4 main lobes – frontal, parietal, temporal and occipital.
Also see: Sensory receptors
Function of Cerebrum
The cerebral cortex forms the highest level at which the motor systems could be represented. It is essential for conscious awareness, memory, thought and intellect. It is here wherein all the sensory modalities ascend and are perceived consciously; the interpretations are on the basis of previous instances or experiences.
The frontal cortex comprises the 4 main flaps, each projection having its own organization of capacities. The cerebrum in general regulates all voluntary actions. Also, it is the control centre for the following – enthusiastic control, innovativeness, visual data, cognizance and higher idea, spatial data, character, tangible preparing, learning, creative mind, critical thinking, language and discourse. The areas in the cerebrum are involved in receiving and interpreting most of the physical surroundings wherein the body is.
The cerebral fissures, several deep grooves found in the cerebral cortex, take their origin in the large folding of the surface of the brain. Found between the temporal and frontal lobes is the main cerebral fissure – the fissure of Sylvius or lateral fissure or the fissure of Rolando found between the parietal and frontal lobes separating the main sensory and motor areas of the brain.
The visual cortex is contained in the calcarine fissure found on the occipital lobe. The parieto occipital fissure divides the parietal and the occipital lobes. The cerebrum is separated from the cerebellum by the transverse fissure, while the longitudinal fissure divides the cerebrum into two hemispheres.
The 4 main lobes are involved in the following functionalities –
Frontal lobes – it is situated in front of the central sulcus. Particularly this lobe is prone to injury, typically trauma or impact, however, it can be damaged by diseases such as septicaemia or meningitis. Since this region of the brain is linked with other areas too, damage to this region can have a great impact on different activities or functions.
It deals with the following areas –
- Performing executive functionalities – attention, planning ahead, emotion, behaviour
- Intelligence and self-awareness
- Memory
- Speech and language
- Planned movement
Parietal lobes – it deals with somatic senses. They form the processing centres of the brain and are involved in –
- Sensation – cold, hot, pain, pressure or touch
- Visual perception
- Language and symbol use
- From other sensory information, giving meaning to signal
Occipital lobes – these lobes are involved in processing visual information and control the ability to identify colour, shape, faces and objects.
They are involved in –
- Visual perception
- Spatial orientation
- Colour
- Light
- Movement
Temporal lobes – these are involved in understanding speech and processing sound, auditory reception and memory. They are also a part of the system which regulates memory. While the left lobe is involved in processing receptive language, the right lobe processes musical awareness.
It concerns the following areas –
- Hearing
- Patterns and organization
- Memory
- Comprehending language
Despite the fact that the cerebellum and cerebrum sound alike, in the brain they perform different functions. The cerebellum is found below the cerebrum. It directly operates with the different areas in the cerebrum for the coordination of functions such as balance and posture. It is also involved in sending signals for the regulation of the movement of muscles.
Function of the Left hemisphere
In most people, it is deemed to be the dominant half of the brain as a result of the analytical and verbal skills it encapsulates. This hemisphere is rational and logical and is involved in the regulation of communication such as reading, talking and verbal awareness. It also deals with analyzing situations and typing, processing information in spatial and logical perceptions etc. Further, it regulates the right half of one’s body.
Function of the Right hemisphere
This hemisphere can be associated with unconsciousness awareness. Comprehending social interactions, face recognition, artistic creativity, emotions and intuitions are all regulated by the right hemisphere of the brain. The communication between both hemispheres is through the corpus callosum.
Summarizing the functions of the cerebrum, it is involved in the following activities –
- Thinking and reasoning
- Organization and planning
- Determining personality and intelligence
- Motor function
- Processing the sensory information
- Comprehending and producing language
- Interpretation of the sensory impulses
- Motor function
Cerebral Cortex
About 2 mm thick, the outer layer of the cerebrum is the cerebral cortex, with the composition of gray matter comprising nerve cell bodies. It has a surface area of 0.5 sq m. Beneath the gray matter lies the white matter made of nerve fibres with myelin sheath coverings.
At the time of embryonic development, the gray matter tends to quickly grow in comparison to the white matter, folding on itself. This imparts the distinguishing wrinkly appearance onto the brain. These folds are referred to as gyri or convolutions; the grooves between them are called sulci.
Cerebral Cortex – Functional areas
Motor areas
Almost 50% of the frontal lobe is occupied by the four motor areas. Of these, the primary motor cortex is the precentral gyrus seen anterior to the central sulcus. The motor areas are associated with the basal ganglia and the cerebellum. These regions are required for motor coordination, balance and postural stability, learned movements, planning and the execution of voluntary activities.
Association areas
Information is sorted upon receiving by the primary sensory area and is then relayed to the nearby sensory association regions to process it. These association areas recognize particular traits of a stimulus and combine the stimulus information with memory and other forms of input. While the primary auditory cortex is involved in hearing a piece of music, for its identification, the auditory association region is involved, found below the primary auditory cortex.
The human brain varies from that of the other primates in its huge amount of the association cortex. The association area does not only integrate the immediate sensory information with that of the others, but is also involved in areas such as personality, ingenuity, decision-making and judgment.
Sensory areas
The incoming sensory information is received by the primary sensory regions. The primary somatosensory cortex receives a signal for temperature, pain, pressure and touch. It is seen in the postcentral gyrus, the first gyrus of the parietal lobe following the central sulcus. On the upper margin of the temporal lobe is the primary auditory cortex deployed in hearing and is placed deep within the lateral fissure.
In the occipital lobe is the primary visual cortex, dealing with sight. The primary sensory area is arranged in the exact sensory map of the body. The primary somatosensory cortex has a point-for-point correspondence with the opposite side of the body. Likewise, the primary visual cortex has a point-for-point map of the contralateral visual field.
This was a brief on cerebrum function, functions of each cerebral lobe and the functionalities of the right and left hemispheres. For related articles on NEET preparation, visit us at BYJU’S NEET.
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