17 External Brain Anatomy

The brain is comprised of the cerebrum, cerebellum, and brainstem. The cerebrum is the most prominent region of the brain. It is divided into left and right hemispheres. The hemispheres have many of the same functions, for example, each perceives touch on one side of the body, but some functions demonstrate laterality, meaning they are primarily controlled on one side of the brain. The cerebral hemispheres in humans have many folds to increase the surface area of the brain. The ridges are called gyri and the grooves are called sulci. Large sulci are often called fissures.

Illustration of the brain. Details in caption.
Figure 17.1 An external, side view of the parts of the brain. The cerebrum, the largest part of the brain, is organized into folds called gyri and grooves called sulci. The cerebellum sits behind (posterior) and below (inferior) the cerebrum. The brainstem connects the brain with the spinal cord and exits from the ventral side of the brain. ‘External Brain Regions’ by Casey Henley is licensed under a Creative Commons Attribution Non-Commercial Share-Alike (CC BY-NC-SA) 4.0 International License.

Frontal Lobe

The cerebral hemispheres of the brain are divided into four lobes. The frontal lobes are the most rostral, located in the front of the brain and are responsible for higher level executive functions, like attention, critical thinking, and impulse control. They are the last brain region to fully develop, not completing development until individuals reach their 20s. The frontal lobes are also the location of the primary motor cortex, the region of the brain responsible for planning and executing movement. The primary motor cortex is located in the precentral gyrus.

Illustration of the brain showing the frontal lobe. Details in text.
Figure 17.2. The frontal lobe is located in the front of the brain. It includes the precentral gyrus, the location of the primary motor cortex. ‘Frontal Lobe’ by Casey Henley is licensed under a Creative Commons Attribution Non-Commercial Share-Alike (CC BY-NC-SA) 4.0 International License.

View the frontal lobe using the BrainFacts.org 3D Brain

Parietal Lobe

The central sulcus lies caudal to the frontal lobe and divides the frontal lobes from the parietal lobes. The parietal lobes are important for processing sensory information. The primary somatosensory cortex is located in the postcentral gyrus of the parietal lobe and is responsible for the perception of touch and pain. The parietal lobes also perform higher-level visual processing.

Illustration of the brain showing the parietal lobe. Details in text.
Figure 17.3. The parietal lobe is located on the top of the brain. It includes the postcentral gyrus, the location of the primary somatosensory cortex. The central sulcus divides the parietal lobe from the frontal lobe. ‘Parietal Lobe’ by Casey Henley is licensed under a Creative Commons Attribution Non-Commercial Share-Alike (CC BY-NC-SA) 4.0 International License.

View the parietal lobe using the BrainFacts.org 3D Brain

Temporal Lobe

The temporal lobes are located on the side of the brain, separated from the frontal and parietal lobes by the lateral fissure. Like the parietal lobe, the temporal lobe plays a role in sensory processing, specifically with hearing, smell, taste, and higher-level visual processing. The temporal lobe is also important for speech and memory. Beneath the cerebral cortex, deep in the temporal lobes, lie the hippocampus and amygdala, two regions of the limbic system, a circuit important for emotion and memory.

Illustration of the brain showing the temporal lobe. Details in text.
Figure 17.4. The temporal lobe is located on the side of the brain. The lateral fissure divides the temporal lobe from the frontal and parietal lobes. ‘Temporal Lobe’ by Casey Henley is licensed under a Creative Commons Attribution Non-Commercial Share-Alike (CC BY-NC-SA) 4.0 International License.

View the temporal lobe using the BrainFacts.org 3D Brain

Occipital Lobe

The last lobes are the occipital lobes, the most caudal lobes located in the back of the brain. The occipital lobes’ primary function is processing of visual information.

Illustration of the brain showing the occiptial lobe. Details in text.
Figure 17.5. The occipital lobe is located in the back of the brain. ‘Occipital Lobe’ by Casey Henley is licensed under a Creative Commons Attribution Non-Commercial Share-Alike (CC BY-NC-SA) 4.0 International License.

View the occipital lobe using the BrainFacts.org 3D Brain

Non-Cerebral Components

The cerebellum lies inferior to the occipital lobes. The cerebellum is also divided into two hemispheres, like the cerebral cortex. The cerebellum is best known for its role in regulation and control of movement, but it is also involved in cognitive functions like emotions.

The brainstem is located between the cerebrum and the spinal cord. It is important for regulating critical functions like heart rate, breathing, and sleep. It is also the location of most of the cranial nerves.

The spinal cord, which is part of the central nervous system but not part of the brain, is responsible for receiving sensory information from the body and sending motor information to the body. Involuntary motor reflexes are also a function of the spinal cord, indicating that the spinal cord can process information independently from the brain.

Illustration of the brain showing the cerebellum, brainstem, and spinal cord. Details in text.
Figure 17.6. The cerebellum, brainstem, and spinal cord are located below the brain. ‘Hindbrain’ by Casey Henley is licensed under a Creative Commons Attribution Non-Commercial Share-Alike (CC BY-NC-SA) 4.0 International License.

View the brainstem using the BrainFacts.org 3D Brain

View the cerebellum using the BrainFacts.org 3D Brain

Key Takeaways

  • The four lobes of the cerebral cortex each have specific functions
  • The cerebral cortex has gyri and sulci to increase the surface area
  • The cerebral cortex, underlying structures, cerebellum, brainstem, and spinal cord form the central nervous system

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