The Brain: Learn It 1—The Forebrain

  • Identify the location and function of the lobes of the brain
  • Describe the functions of the midbrain and hindbrain
  • Describe the function of the parts of the limbic system

The Central Nervous System: Looking at the Brain as a Whole

The brain is the largest single part of the central nervous system. It is here that most of your sensing, perception, thinking, awareness, emotions, and planning take place.

Even though the brain makes up only about 2% of your body weight, it uses nearly 20% of your body’s oxygen and energy—a reflection of how constantly active it is.

Sections of the Brain

An illustration shows the position and size of the forebrain (the largest portion), midbrain (a small central portion), and hindbrain (a portion in the lower back part of the brain).
Figure 1. The brain and its parts can be divided into three main categories: the forebrain, midbrain, and hindbrain.

Scientists often organize the brain into major parts based on location and function. One common approach divides it into three main regions:

  • Forebrain – responsible for complex thought, emotion, memory, and reasoning
  • Midbrain – involved in movement, sensory processing, and reflexes
  • Hindbrain – controls vital functions like breathing, balance, and coordination

Another useful way to describe the brain’s structure is to look at its major components:

  • The cerebrum (cerebral cortex) – the largest part, responsible for higher thought and perception
  • The cerebellum (at the back) – coordinates movement and balance
  • The brain stem (even further back)– connects the brain to the spinal cord and regulates basic life functions
  • The limbic system (an area that is less regionally defined in the center of the brain) – a network involved in emotion, motivation, memory, and smell
A model shows a cross section of the human brain with areas labeled - cerebral cortex, limbic system, cerebellum, and brain stem
Figure 2. General areas of the brain [Image: Biology Corner, https://goo.gl/wKxUgg, CC-BY-NC-SA 2.0, https://goo.gl/Toc0ZF, labels added]

We’ll start by looking at the big part—the forebrain.

Forebrain Structures

the forebrain

An illustration of the brain’s exterior surface shows the ridges and depressions, and the deep fissure that runs through the center.
Figure 3. The surface of the brain is covered with gyri and sulci. A deep sulcus is called a fissure, such as the longitudinal fissure that divides the brain into left and right hemispheres. (credit: modification of work by Bruce Blaus)

The forebrain is the largest part of the brain. The forebrain contains the cerebral cortex and a number of other structures that lie beneath the cortex (called subcortical structures). This is the largest part of the brain you might typically think of if asked to picture the brain.

The cerebral cortex (also called the cerebrum) is the “newest,” most advanced portion of the brain associated with higher-level processes such as consciousness, thought, emotion, reasoning, language, and memory.

 

The surface of the brain is characterized by a distinctive pattern of folds or bumps, known as gyri (singular: gyrus), and grooves, known as sulci (singular: sulcus). The most prominent sulcus, known as the longitudinal fissure, is the deep groove that separates the brain into two halves or hemispheres: the left hemisphere and the right hemisphere.

 

These two hemispheres are connected to one another by a thick bundle of axons called the corpus callosum.

There are instances in which people—either because of a genetic abnormality or as the result of surgery—have had their corpus callosum severed so that the two halves of the brain cannot easily communicate with one another. The rare split-brain patients offer helpful insights into how the brain works.
For example, we now understand that the brain is contralateral, or opposite-sided. This means that the left side of the brain is responsible for controlling a number of sensory and motor functions of the right side of the body, and vice versa.

Each cerebral hemisphere can be subdivided into four lobes, each associated with different functions.