The human brain is divided into three major
parts : – 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.