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The brain is arguably the most important organ in the human body. It controls and coordinates actions and reactions, allows us to think and feel, and enables us to have memories and feelings – all the things that make us human.

brain_portions_illus20While the brain only weighs about 3 pounds, it is a highly complex organ made up of many parts. Years of scientific study of the brain have made it possible for scientists to identify the various areas of the brain and determine their specific functions. The following information gives a brief description of some of the major parts of the human brain.

The cranium

The brain is protected by a bony covering called the cranium (which, along with the bones of the face, make up the skull). Inside the cranium, the brain is surrounded by the meninges. The meninges is made up of 3 layers of tissue:

  • Pia mater – the layer closest to the surface of the brain
  • Arachnoid membrane – the middle layer of tissue
  • Dura mater – the outer-most layer

The cerebrum – the front of the brain

The largest part of the brain located in the front is called the cerebrum. The cerebrum is responsible for:

  • Movement
  • Body temperature
  • Touch
  • Vision
  • Hearing
  • Judgment
  • Reasoning
  • Problem solving
  • Emotions
  • Learning

The cerebrum has 2 parts: the right cerebral hemisphere and the left cerebral hemisphere. They are connected at the bottom and have a deep groove running between them. In general, the right cerebral hemisphere controls the left side of the body, and the left cerebral hemisphere controls the right. The right side is involved with creativity and artistic abilities. The left side is important for logic and rational thinking.

The hemispheres of the cerebrum are divided into lobes, or broad regions of the brain. Each lobe is responsible for a variety of bodily functions:

  • Frontal lobes are involved with personality, speech, and motor development
  • Temporal lobes are responsible for memory, language and speech functions
  • Parietal lobes are involved with sensation
  • Occipital lobes are the primary vision centers

The surface of the cerebrum appears wrinkled and is made up of deep grooves (called sulci) and bumps or folds (called gyri). The outer part of the cerebrum is called gray matter and contains nerve cells. The inner part is called white matter and contains connections of nerves.

The brainstem – the middle of the brain

The brainstem is located in front of the cerebellum. The brainstem is like the hard-drive of a computer. It is the main control panel for the body that passes messages back and forth between the brain and other parts of the body. The cerebrum, the cerebellum, and the spinal cord are all connected to the brainstem. The brainstem has three main parts, the midbrain, the pons, and the medulla oblongata.

The brainstem controls vital functions of the body, including:

  • Breathing
  • Consciousness
  • Cardiac function
  • Involuntary muscle movements
  • Swallowing
  • Movement of the eyes and mouth
  • Relaying sensory messages (pain, heat, noise, etc.)
  • Hunger

The cerebellum – the back of the brain

Behind the cerebrum at the back of the head is the cerebellum. In Latin, cerebellum means “little brain.” However, the cerebellum contains more nerve cells than both hemispheres combined. The cerebellum is primarily a movement control center, responsible for:

  • Voluntary muscle movements
  • Fine motor skills
  • Maintaining balance, posture, and equilibrium

Unlike the cerebrum, the left cerebellum controls the left side of the body, and the right cerebellum controls the right side of the body.


Other important parts of the brain

Ventricular system
The brain is not a solid organ. There are fluid-filled cavities within the brain called ventricles. The ventricles are important in providing nourishment to the brain. The ventricular system produces and processes cerebrospinal fluid – a clear, watery substance that flows around the brain and helps cushion and protect it.

Cranial nerves
The brain also contains 12 pairs of cranial nerves each responsible for specific functions in the body:

  • Olfactory nerve – smell
  • Optic nerve – vision
  • Oculomotor – eye movements, eyelid opening
  • Trochlear – eye movements
  • Trigeminal – facial sensations, chewing
  • Abducens – eye movements
  • Facial – taste, facial expressions
  • Vestibulocochlear – hearing, balance
  • Glossopharyngeal – taste, swallowing
  • Vagus – swallowing, taste
  • Accessory – neck and shoulder muscles
  • Hypoglossal – tongue movement

Pituitary gland

The pituitary gland is located in the center of the brain and is about the size of a dime. The pituitary gland, often referred to as the “master gland,” is responsible for a number of functions including producing hormones for the thyroid and adrenal glands, as well as the hormones responsible for normal growth and sexual maturation.

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