It is the largest part of the human brain (makes up to 85 percent of the brain’s weight) and is linked with higher brain function like action and thought. It develops prenatally, from the prosencephalon of the embryo.
The surface of the cerebrum is called the cortex. It appears wrinkled and is made up of bumps (called gyri) and deep grooves (called sulci). The cortex contains 16 billion neurons which are arranged in specific layers.
It is located in the uppermost region of the central nervous system and contains:
- olfactory bulb – a structure of the forebrain involved in the sense of smell;
- basal ganglia – a group of nuclei (clusters of neurons);
- hippocampus – it is composed of several subregions, that include the dentate gyrus, the cornu ammonis (CA1–4), and the subiculum;
- the cerebral cortex – it is responsible for directing motor activity, integrating sensory impulses, and controlling higher intellectual functions.
The cerebrum is divided into a left hemisphere and a right hemisphere by the longitudinal fissure, a deep groove. These hemispheres are joined by the corpus callosum, a bundle of fibers which transmits messages from one side to the other.
Each hemisphere can be broken down into 4 functionally and spatially defined lobes: occipital, temporal, parietal, and frontal.
Occipital lobes – they are located in the back of the brain and are involved in the capacity to recognize and read printed words, along with other functions of vision.
Temporal lobes – they are located on either side of the head on the same level as the ears. The temporal lobes coordinate:
- the interpretation of the emotions and reactions of others;
- verbal memory (like understanding language);
- visual memory (like facial recognition).
Parietal lobes – they are located behind the frontal lobes and are involved in interpreting and organizing sensory information from other parts of the brain.
Frontal lobes – they are the largest of the lobes. You can divide the frontal lobe into 3 sections – the premotor area, the motor area, and the prefrontal cortex. The frontal lobes control a number of functions, such as:
In addition, the frontal lobes manage impulse control and emotions.
White Matter & Grey Matter
- white matter consists of myelinated axons and glial cells which connect the various grey matter areas. It forms the bulk of the deeper parts of the brain.
- grey matter is associated with processing and cognition. It forms the surface of each cerebral hemisphere.
The cerebrum is dominated by the paired cerebral hemispheres that are mainly responsible for language, memory, cognition, behavior, and emotion.
It receives information from the balance system of the sensory nerves, inner ear, and the visual and auditory systems. It is comprised of small lobes.
The cerebellum is a lot smaller than the cerebrum at only 1/8 of its size, however, it contains over 50% of its neurons. Evolutionarily speaking, the cerebellum is an older portion of the brain.
It is located behind the top part of the brain stem, the part of the brain that provides the main sensory and motor innervation to the neck and face.
The cerebellum consists of 2 hemispheres that are connected by a narrow midline area, called the vermis. In addition, the cerebellum consists of white matter and grey matter:
- white matter – embedded in the white matter are the 4 cerebellar nuclei (the globose, dentate, fastigial nuclei, and emboliform). It is located underneath the cerebellar cortex.
- grey matter – it is tightly folded, forming the cerebellar cortex and is located on the surface of the cerebellum.
The cerebellum can also be subdivided into 3 lobes which coordinate information received from different areas of the brain and from the spinal cord. These three lobes include:
- the flocculonodular lobe receives input from the cranial nuclei of the vestibular nerve. Lesions of the flocculonodular lobe cause postural ataxia of trunk and head during standing, sitting, and walking.
- the posterior lobe receives input mainly from the cerebral cortex and brainstem. It is the newest part of the cerebellum.
- the anterior lobe receives input mainly from the spinal cord. It is responsible for mediating unconscious proprioception.
This part of the brain has a few roles that are related to coordination and movement, including:
- motor learning – it helps the body learn movements which need fine-tuning and practice. For instance, this part of the brain plays an important role in learning the movements required to ride a bicycle.
- vision – it is responsible for coordinating eye movements.
- maintaining balance – it has special sensors which detect shifts in movement and balance. After, the cerebellum transmits signals for the body to adjust.
- coordinating movement – most body movements need the coordination of multiple muscle groups. The cerebellum manages muscle actions so that the body can move smoothly.
It communicates with the rest of the central nervous system by six cerebellar peduncles (3 on each side), including:
- the inferior cerebellar peduncle – it occupies the upper part of the posterior district of the medulla oblongata;
- middle cerebellar peduncles – it connects the cerebellum to the pons;
- superior cerebellar peduncle – it connects the cerebellum to the midbrain.
Unlike the cerebrum, the right cerebellum controls the right side of the body, while the left cerebellum controls the left side of the body.
The cerebrum is the largest part of the brain and is divided into 4 sections called lobes: the temporal, parietal, frontal, and occipital. Functions of the cerebrum include:
- speech and language;
- coordination of movement;
- initiation of movement.
The cerebellum is a hindbrain structure which is composed of 3 layered cortex and deep nuclei. It plays a vital role in the coordination of motor movements and balance as well as motor control.
People who have suffered from damaged cerebellums frequently struggle with maintaining proper muscle coordination and keeping their balance.