Anatomy of the Brain

The human brain is an incredibly complex and delicate organ. Weighing in at approximately three pounds (1.5 kilograms) and consisting of more than 100 billion nerves, the human brain is one of the largest and most important organs in the body. Intelligence, creativity, emotion, and memory are just a few of the several things governed by the brain, crucial to the essence of our lives.

Understanding the anatomy and structure of the brain is the key to understanding the various functions it performs. Protected within the cranial vault of the skull, the human brain is comprised of three main sections:

• Forebrain

• Midbrain

• Hindbrain (brainstem)

Forebrain

The forebrain contains the cerebral cortex, which surrounds the midbrain and brainstem. It has two hemispheres (left hemisphere and right hemisphere) which are joined by the corpus callosum, a white matter tract consisting of a bundle of nerve fibres which transmits messages from one side to the other. Each hemisphere of the cerebral cortex controls the opposite site of the body. Furthermore, the left and right hemispheres differ in their functions. The left hemisphere controls speech, comprehension, arithmetic and writing, while the right hemisphere controls creativity, spatial ability, artistic, and musical skills.

The cerebral cortex is divided into four lobes which are each responsible for different cortical functions:

• Frontal lobe:

  • Determining personality, emotions and behaviour

  • Judgment

  • Planning

  • Problem solving

  • Speech

  • Body movement

  • Intelligence

  • Concentration

  • Self awareness

• Parietal lobe:

  • Interpreting of words and languages

  • Sensing touch, pain and temperature (sensory strip)

  • Interpreting sensory and memory signals

  • Spatial and visual perception

• Occipital lobe:

  • Interpreting vision (color, light, movement)

• Temporal lobe:

  • Understanding language

  • Hearing

  • Sequencing and organization

Midbrain

The midbrain is located in the central part of the brain and connects the brainstem to the thalamus. This allows for the brain to relay information from the senses to the brain and back to the muscles. The midbrain is responsible for:

• Vision,

• Hearing,

• Temperature control,

• Motor control

• Alertness.

The limbic system is also part of the midbrain, which contains a number of interrelated structures that regulate temperature control, hormones, emotions and long- term memory. Included in this system are the following:

• Cingulate gyrus - responsible for emergency responses , eg. the“fight or flight response”, and processes such as feeding and reproduction

• Hypothalamus - neurons associated with heart rate and respiration are concentrated here

• Amygdala - responsible for emotional reactions and behavior

• Hippocampus - responsible for memory formation, storage and organisation

Hindbrain

The hindbrain is one of the three major regions of the brain, located in the lower back part of the brain. It consists of the majority of the brainstem, the cerebellum, the pons and the medulla. Most of the 12 cranial nerves are found in the hindbrain, which is generally responsible for the oldest and most primitive body functions.

• Cerebellum:

  • The cerebellum has two hemispheres with a dense layer or grey matter surrounding an internal section of white matter.

  • Its function is to coordinate muscle movements (enabling most of our voluntary movements). It also processes nerve impulses from the inner ear, which is responsible for helping us maintain balance and posture.

• Pons:

  • The pons connects the brainstem to the cerebral cortex

  • It serves as the coordination center for signals and communications that flow between the two brain hemispheres and the spinal cord.

  • Four cranial nerves are found in the pons: the abducens nerve (coordinates eye movement); the facial nerve (coordinates movement and sensation in the face); the vestibulocochlear nerve (processes sounds, helps us maintain balance); and the trigeminal nerve (coordinates chewing and carries sensory information from the face and the head, face sensations).

• Medulla (oblongata)

  • Arguably the most vital part of the entire brain, sitting at the lowest part of the brainstem, containing important control centers for the heart and lungs.

  • This is where the brain transitions to the spinal cord.

  • Contains the control centers for: heart rate, blood pressure, breathing, and many involuntary reflexes such as sneezing and swallowing.

  • Contains both white and grey matter, and four cranial nerves: the glossopharyngeal nerve (coordinates taste sensations and mouth movements); the vagus nerve (mouth movements, voice and the gag reflex); the accessory nerve (coordinates head and neck movements); and the hypoglossal nerve (controls tongue movements and muscles involved in our speech.)

References

• Brain Anatomy, Anatomy of the Human Brain (2020). Available at: https://mayfieldclinic.com/pe-anatbrain.htm (Accessed: 16 August 2020).

• Structure and Function of the Brain | Boundless Psychology (2020). Available at: https://courses.lumenlearning.com/boundless-psychology/chapter/structure-and-function-of-the-brain/ (Accessed: 16 August 2020).

• Dr. Ananya Mandal, M. (2010) Human Brain Structure, News-Medical.net. Available at: https://www.news-medical.net/health/Human-Brain-Structure.aspx (Accessed: 16 August 2020).

• Anatomy of the Brain (2020). Available at: https://www.hopkinsmedicine.org/health/conditions-and-diseases/anatomy-of-the-brain (Accessed: 18 August 2020).

• The Hindbrain (2018). Available at: https://qbi.uq.edu.au/brain/brain-anatomy/hindbrain#:~:text=The%20hindbrain%20(developmentally%20derived%20from,back%20part%20of%20the%20brain.&text=There%20are%20three%20main%20parts,are%20found%20in%20the%20hindbrain. (Accessed: 22 August 2020).

• Resources, B., Myths, C. and 101, T. (2020) The Brain 101 - BrainHQ from Posit Science, BrainHQ from Posit Science. Available at: https://www.brainhq.com/brain-resources/cool-brain-facts-myths/brain-101/ (Accessed: 2 September 2020).