Brain Anatomy

The brain is a remarkably complex organ comprised of billions of interconnected neurons and glia. It is a bilateral, or two-sided, structure that can be separated into distinct lobes. Each lobe is associated with certain types of functions, but ultimately, all of the areas of the brain interact with one another to provide the foundation for our thoughts and behaviors. In this section, we discuss the overall organization of the brain and the functions associated with different brain areas.


TL; DR

  • The brain is divided into three distinct parts: the forebrain, the midbrain and the hindbrain. 
  • The cerebrum is further classified in distinct lobes that as groups areas of the brain by their location and function. 
  • Some structures of the cerebrum are sub-cortical, also known as deep brain structures. 
  • The limbic system is a combination of structures from different lobes that processes emotional memory.
  • The hindbrain consists of structures at the base of the brain including the cerebellum, the medulla and pons. 

The Brain Separated into Three Division


The brain is a large organ and you’ll soon see that each of are divided according to:
    •  
    • Forebrain
    • Midbrain
    • Hindbrain

The two hemispheres of the cerebral cortex are part of the forebrain,  which 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): thalamus, hypothalamus, pituitary gland, and the limbic system (a collection of structures). The midbrain is comprised of structures located deep within the brain, between the forebrain and the hindbrain. The hindbrain is located at the back of the head and looks like an extension of the spinal cord. It contains the medulla, pons, and cerebellum.

forebrain, midbrain and hindbrain
Author/Source: CNX OpenStax | License: CC BY 4.0

Forebrain Structures:  

    • Cerebrum
    • Thalamus
    • Hypothalamus
    • Pituitary gland
    • Limbic system

Midbrain Structures

    • Tectum
    • Cerebral Aqueduct
    • Tegmentum
    • Cerebral Peduncles

Hindbrain Structures

    • Medulla (also part of the brainstem)
    • Pons (also part of the brainstem)
    • Cerebellum

The Forebrain


The two hemispheres of the cerebral cortex are part of the forebrain, which is the largest part of the brain. The forebrain contains the cerebrum and a number of other deep brain structures that lie beneath the cortex including the: thalamus, hypothalamus, pituitary gland, and the limbic system. The cerebral cortex, which is the outer surface of the brain, is associated with higher level processes such as consciousness, thought, emotion, reasoning, language, and memory. 


One thing you’ll notice about the cerebral cortex, is how uneven – or ‘bumpy’ – it actually is. There are  distinct patterns of folds and bumps known as gyri. Between each gyrus are these grooves, which we call sulci. Take a look at the figure to the right, the gyri These gyri and sulci form important landmarks that allow us to separate the brain into functional centers.


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. There is evidence of some specialization of function—referred to as lateralization—in each hemisphere, mainly regarding differences in language ability. Beyond that, however, the differences that have been found have been minor. What we do know is that the left hemisphere controls the right half of the body, and the right hemisphere controls the left half of the body.


 

Brain Lobes


There are two hemispheres of the cerebral cortex connected by a thick band of nearly 200 million neural fibers known as the corpus callosum. The corpus callosum allows for communication between the hemispehres. Each cerebral hemisphere can be subdivided into four lobes (frontalparietaltemporal, and occipital). Each brain lobe is associated with unique set functions, but either directly or indirectly, all lobes either communicate to produce behavior.

Frontal Lobe


The frontal lobe is the most rostral part of the brain and extends back to a fissure known as the central sulcus (where the orange and blue lobes meet). The frontal lobe is involved in what is described as higher cognitive functions and executive control.  Reasoning, emotion, self-control, flexible thinking, planning problem solving, personality and emotion are all functions that fall under the frontal lobe’s higher cognitive function. These function are processed by a particular structure called the prefrontal cortex. A very unique accident that happened to a man named Phineas Gage, gave us our first understandings of the prefrontal cortex and the frontal lobe.


The frontal lobe also controls voluntary movement through the primary motor cortex and production of speech through a region known as Broca’s area. interesting feature of the frontal lobe is it’s involvement in the production of speech. It’s important to distinguish the difference between the production of speech and the interpretation of speech; Broca’s area only invovled in the former.  

    •  

Parietal Lobe


The brain’s parietal lobe is located immediately caudal to the frontal lobe, and is involved in processing information from the body’s senses. It contains the primary somatosensory cortex, which is essential for processing sensory information from the entire body. Anything from touch, temperature, and pain is processed here. An interesting feature of the primary somtaosensory cortex is that it is topographical. This means that spatial relationships that exist in the body are mapped on the surface of the somatosensory cortex. For example, the portion of the cortex that processes sensory information from the hand is adjacent to the portion that processes information from the wrist.

Temporal Lobe


The temporal lobe is located on the sides of the head (temporal means “near the temples”), and is associated with hearing, memory, emotion, and some aspects of language. Deep within the temporal lobe are structures like the hippocampus (which processes memory) and the amygdala (which processes emotion/fear). The auditory cortex, the main area responsible for processing auditory information, is also located within the temporal lobe. A specialized area called Wernicke’s area is important for speech comprehension and also located here.

 

Occipital Lobe


The occipital lobe is located at the very back of the brain. It contains the primary visual cortex, which is responsible for interpreting incoming visual information. The visual cortex can process a range of visual information including color, motion, texture, shape and facial recognition. The organization of the visual cortex is called retinotopical. This means there’s a close relationship between the position of an object in a person’s visual field and the position of that object’s representation on the cortex. You will learn much more about how visual information is processed in the occipital lobe when you study sensation and perception.

 

→ Click here for the Brain Lobes Cheat Sheet 

labelled brain lobes
Author/Source: CNX OpenStax | License: CC BY 4.0

 


 

The Limbic System


Location
: Frontal and temporal lobes.
Function: Motivation; learning; emotion; memory.
Notable Structures: Hippocampus; amygdala; hypothalamus; cingulate gyrus.

The limbic system is not technically a ‘lobe’ but its an important cerebral cortex structure. It spans both the frontal and temporal lobes and can only be seen through a longitudinal cross section (this is where the brain is sliced from the front to back down the center). The limbic system processing both emotion and memory and building connections between the two. Interestingly, the sense of smell projects directly to the limbic system. Therefore, smell can evoke emotional responses in ways that other sensory modalities cannot.


The limbic system is made up of a number of different structures, but three of the most important are the hippocampus, the amygdala, and the hypothalamus. The hippocampus is an essential structure for learning and memory. The amygdala is involved in our experience of emotion and in tying emotional meaning to our memories. The hypothalamus regulates a number of homeostatic processes, including the regulation of body temperature, appetite, and blood pressure. The hypothalamus also serves as an interface between the nervous system and the endocrine system and in the regulation of sexual motivation and behavior.

limbics system
Author/Source: CNX OpenStax | License: CC BY 4.0

The Midbrain


The midbrain is comprised of structures located deep within the brain, between the forebrain and the hindbrain. The reticular formation is centered in the midbrain, but it actually extends up into the forebrain and down into the hindbrain. The reticular formation is important in regulating the sleep/wake cycle, arousal, alertness, and motor activity.


The substantia nigra (Latin for “black substance”) and the ventral tegmental area (VTA) are also located in the midbrain. Both regions contain cell bodies that produce the neurotransmitter dopamine, and both are critical for movement. Degeneration of the substantia nigra and VTA is involved in Parkinson’s disease. In addition, these structures are involved in mood, reward, and addiction

brainstem
Author/Source: CNX OpenStax | License: CC BY 4.0

The Hindbrain


The hindbrain is located at the back of the head and looks like an extension of the spinal cord. It contains the medulla, pons, and cerebellum. 
The medulla, pons, and midbrain together are known as the brainstem, but know that the midbrain is not consider part of the hindbrain.


The word pons literally means “bridge,” and as the name suggests, the pons serves to connect the forebrain with the cerebellum and spinal cord. It also is involved in regulating brain activity during sleep. 


The medulla controls the automatic processes of the autonomic nervous system, such as breathing, blood pressure, and heart rate.  The initial portion of the name, “myel,” refers to the significant white matter found in this region, which is continuous with the white matter of the spinal cord. 


The cerebellum (Latin for “little brain”) receives messages from muscles, tendons, joints, and structures in our ear to control balance, coordination, movement, and motor skills. The cerebellum is also thought to be an important area for processing some types of memories. In particular, procedural memory, or memory involved in learning and remembering how to perform tasks, is thought to be associated with the cerebellum.

→ Click here for the Hindbrain Cheat Sheet.

OpenStax - CNX
Author/Source: OpenStax | License: CC BY 4.0

Pons

Function: relay signals from forebrain to cerebellum; facial movements and sensations.

Medulla

Function: autonomic functions; breathing; heart rate; blood pressure; vomiting; sleep/wake cycles.

Cerebellum

Function: coordination of voluntary movement; precise movements; balance; gait; posture; ‘muscle memory.’

Brain Anatomy & Structures Review Questions

Coming soon!

Conclusion Questions

Brain Lobes

  1. Consider the function of each brain lobe: how might the lobes communicate to coordinate a function or behavior?
  2. The pre-frontal cortex does not fully develop well into an individual’s 20s, how might this explain differences in behavior between adults and teenagers?
  3. What parts of the human brain do you think might be similar/different from other animals? Why?

Hindbrain

  1. Consider the function of hindbrain structure: how might these structure control behavior?
  2. How might the hindbrain structures communicate with other regions of the brain/body to coordinate behavior?
  3. What other brain regions/body parts might the cerebellum communicate with given its function?
  4. What parts of the human hindbrain do you think might be similar/different from other animals? Why?

Key Words

  1. Spielman RM, Dumper K, Jenkins W, Lacombe A, Lovett M, Perlmutter. “”3.4 The Brain and Spinal Cord.” Psychology. OpenStax CNX. 2014. Houston, TX. https://openstax.org/books/psychology/pages/3-4-the-brain-and-spinal-cord. License: CC BY 4.0 License Terms: Edited & Adapted | Access for free at https://openstax.org/books/psychology/pages/1-introduction.
  2. OpenStax, Biology. OpenStax CNX. May 27, 2016 http://cnx.org/contents/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.53License: CC BY 4.0 License Terms: Edited & Adapted | Access for free at https://openstax.org/books/psychology/pages/1-introduction.
  3. Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH, Korol O, Johnson JE, Womble M, DeSaix P. “13.2 The Central Nervous System.” Anatomy and Physiology. OpenStax, 2013. Houston, TX. https://openstax.org/books/anatomy-and-physiology/pages/13-2-the-central-nervous-system. License TermsEdited & Adapted | Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction.