- The cerebrum – the largest part of the human brain. The cerebrum enables sensory

perception and controls voluntary motor actions. - The cerebellum – the cerebellum lies inferior

to the cerebrum at the back of the head. It is mostly involved in coordination of movement

and fine tuning of motor activities. - The brainstem - the brainstem is located

at the base of the brain and is continuous to the spinal cord. It houses all nerve connections

between different parts of the central nervous system. The brainstem provides innervation

to the head and neck via cranial nerves. It also contains nuclei associated with important

body functions such as regulation of blood pressure, respiration, swallowing, bladder

control, sleep cycle, … among others. On top of the brainstem, and sometimes classified

as part of it, is the diencephalon. The main components of the diencephalon are:

- The thalamus – the thalamus serves as a gateway relaying sensory signals originated

throughout the body to the cerebral cortex. It is also involved in emotional and memory

functions. - The hypothalamus – the hypothalamus is

the major control center of the autonomic nervous system and plays essential role in

homeostatic regulation. The hypothalamus links the nervous system to the endocrine system

via the pituitary gland. It also contains nuclei involved in regulation of body temperature,

food and water intake, sleep and wake cycle, memory and emotional behavior.

The cerebrum consists of two cerebral hemispheres. The left hemisphere controls the right half

of the body. The right hemisphere controls the left half of the body. The two hemispheres

are separated by a deep groove called the longitudinal fissure. Each hemisphere has

a number of folds called gyri separated by grooves called sulci. A major landmark is

the central sulcus. The cerebrum has four major lobes. The frontal

lobe is situated anterior to the central sulcus. It is associated mainly with voluntary motor

functions, planning, motivation, emotion and social judgment.

Posterior to the central sulcus is the parietal lobe. This lobe is mainly concerned with sensory

functions of the somatosensory category such as touch, stretch, movement, temperature and

pain. The temporal lobe is separated from the frontal

and parietal lobes by the lateral sulcus. The temporal lobe is associated with hearing,

learning, visual memory and language. The occipital lobe is located at the rear

of the cerebrum. This is the visual processing center of the brain.

At first glance, the two hemispheres look identical, but research has found a number

of differences between them. This is called lateralization of brain function. For example,

the language formation areas - the Wernicke’s and Broca’s areas - are usually located

in the left hemisphere of right-handed people. Lesions to these areas result in language

comprehension deficits or speech disorders. The corresponding areas in the right hemisphere

are responsible for emotional aspect of language. Lesions to these areas do not affect speech

comprehension and formation, but result in emotionless speech and inability to understand

the emotion behind the speech such as sarcasm or a joke.