The human brain can be anatomically divided into three main sections, or layers. The outermost part is called the forebrain (the prosencephalon); the middle layer is called the midbrain (the messancephalon); and the innermost part of the brain is called the hindbrain (the rhombencehalon). Each layer contains different main structures which serve different purposes.
Forebrain
The forebrain has two primary parts, the telencephalon and the diencephalon. The telencephalon contains the cerebral cortex, the hippocampus and basal ganglia. The cerebral cortex is the outermost part of the brain. The cortex is responsible for developing memory, and maintaining attention and awareness. The hippocampus is just below the cerebral cortex. Its role is long-term memory and spatial awareness. The basal ganglia, at the base of the forebrain, is responsible for motor control and is closely linked to learning. The other part of the forebrain is the diencephalon, which contains the thalamus, hypothalamus and the pineal gland. The thalamus' purpose is to relay information from the midbrain to the forebrain. It also regulates sleep and alertness. The hypothalamus controls metabolic processes, secretes neurohormones, and regulates thirst, hunger and body temperature. It also regulates the circadian cycle (natural sleep-wake pattern). The pineal gland, located at the center of the brain, produces the hormone melatonin, which regulates waking and sleeping patterns.
Midbrain
The midbrain contains two main parts, the tectum and the tegmentum. The tectum is responsible for visual and auditory reflexes. The tectum has two parts, the inferior and the superior colliculi. Although the visual center of the brain is in the cerebral cortex, it is the superior colliculi which processes visual signals and controls eye movement. The inferior colliculi processes auditory information. Through a series of interconnected neural structures, it gathers information from various parts of the brain involved in hearing and then relays the information to the cerebral cortex. Both of the colliculi extend into the spinal cord, which allows for faster processing of sensory information. The tegmentum is at the base of the midbrain, and is a complex neural network which regulates body homeostasis and physical reflexes.
Hindbrain
The hindbrain is composed of the metencephalon and the myelencphalon. The metencephalon is divided into the pons and the cerebellum. The pons is responsible for swallowing, bladder control, respiration, facial expressions and posture. The cerebellum is the part of the brain primarily responsible for integrating information from the senses into the brain and coordinating responses. The myelencephalon contains the medulla oblongata and several nerves which connect to it from the spinal cord, including the vagus and hypoglossal nerves. This part of the brain controls and regulates the essential body functions of breathing, the heart, digestion and blood vessels.
References
- "The Human Brain: An Introduction to its Functional Anatomy"; John Nolte, Ph.D.; 2008
