The human brain, or encephalon, is composed of the forebrain, the midbrain and the hindbrain. The forebrain includes the cortex, the latest to appear in evolutionary development, and deeper structures. The cortex is responsible for the higher functions, those relating to conscious thought and sentience, while the other parts of the brain control the more primitive and automatic functions.
The Cortex
The cortex has two hemispheres, each composed of four lobes. The right and left hemispheres are connected by the corpus callosum. The frontal lobe is responsible for the ability to reason, to plan ahead and to act in a way suited to the environment. It controls voluntary movement and the motor part of speech. The parietal lobe is where sensory input is received. It interprets sensations and integrates them into an awareness of the body and its surroundings. The temporal lobe is the seat of memory, emotion and interpretation of language. The occipital lobes are where visual signals from the eyes are integrated and interpreted, allowing for the ability to see and identify the shape, color and movement of objects and people.
The Deeper Parts of the Forebrain
Beneath the cortex lie the deeper parts of the forebrain. The basal ganglia are responsible for integrating movement and for unconscious, or involuntary, movements.
The thalamus is a sensory relay station, transmitting sensations from the body and the auditory and optic nerves to the processing centers in the cortex. It also participates in regulating the level or alertness, sleep and wakefulness.
The hypothalamus is the relay station between the brain and the endocrine functions of the body. It regulates the circadian rhythm and helps control hunger, thirst and temperature.
The Brainstem and Cerebellum
The hindbrain is composed of the midbrain, pons and medulla oblongata, collectively known as the brainstem, and the cerebellum. The brainstem is responsible for the automatic functions of the body, such as breathing and heart rate. Level of awareness is also centered here. Cranial nerves originating from the midbrain control the facial muscles, eye movements and sensation in the face and scalp.The motor impulses from the brain pass through here on their way to the body. The sensory input from the body passes through the brainstem on its way to the brain.
The cerebellum is responsible for integrating motor and sensory input in order to create smooth and balanced movement.
References
- "Sobotta - Atlas of Human Anatomy"; Reinhard Putz: 2008
- "Adams and Victor's Principles of Neurology"; Maurice Victor and Allan H. Ropper; 2001
