Picture of the Brain

Human Anatomy

Medically Reviewed by Carol DerSarkissian, MD on June 23, 2021

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The brain is one of the largest and most complex organs in the human body.
It is made up of more than 100 billion nerves that communicate in trillions of connections called synapses.

The brain is made up of many specialized areas that work together:
• The cortex is the outermost layer of brain cells. Thinking and voluntary movements begin in the cortex.
• The brain stem is between the spinal cord and the rest of the brain. Basic functions like breathing and sleep are controlled here.
• The basal ganglia are a cluster of structures in the center of the brain. The basal ganglia coordinate messages between multiple other brain areas.
• The cerebellum is at the base and the back of the brain. The cerebellum is responsible for coordination and balance.

The brain is also divided into several lobes:
• The frontal lobes are responsible for problem solving and judgment and motor function.
• The parietal lobes manage sensation, handwriting, and body position.
• The temporal lobes are involved with memory and hearing.
• The occipital lobes contain the brain's visual processing system.

The brain is surrounded by a layer of tissue called the meninges. The skull (cranium) helps protect the brain from injury.

Brain Conditions

  • Headache: There are many types of headaches; some can be serious but most are not and are generally treated with analgesics/painkillers.
  • Stroke (brain infarction): Blood flow and oxygen are suddenly interrupted to an area of brain tissue, which then dies. A blood clot, or bleeding in the brain, are the cause of most strokes.
  • Brain aneurysm: An artery in the brain develops a weak area that swells, balloon-like. A brain aneurysm rupture can causes a stroke.
  • Subdural hematoma: Bleeding within or under the dura, the lining inside of the skull. A subdural hematoma may exert pressure on the brain, causing neurological problems.
  • Epidural hematoma: Bleeding between the tough tissue (dura) lining the inside of the skull and the skull itself, usually shortly after a head injury. Initial mild symptoms can progress rapidly to unconsciousness and death, if untreated.
  • Intracerebral hemorrhage: Any bleeding inside the brain.
  • Concussion: A brain injury that causes a temporary disturbance in brain function. Traumatic head injuries cause most concussions.
  • Cerebral edema: Swelling of the brain tissue in response to injury or electrolyte imbalances.
  • Brain tumor: Any abnormal tissue growth inside the brain. Whether malignant (cancer) or benign, brain tumors usually cause problems by the pressure they exert on the normal brain.
  • Glioblastoma: An aggressive, malignant brain tumor (cancer). Brain glioblastomas progress rapidly and are very difficult to cure.
  • Hydrocephalus: An abnormally increased amount of cerebrospinal (brain) fluid inside the skull. Usually this is because the fluid is not circulating properly.
  • Normal pressure hydrocephalus: A form of hydrocephalus that often causes problems walking, along with dementia and urinary incontinence. Pressures inside the brain remain normal, despite the increased fluid.
  • Meningitis: Inflammation of the lining around the brain or spinal cord, usually from infection. Stiff neck, neck pain, headache, fever, and sleepiness are common symptoms.
  • Encephalitis: Inflammation of the brain tissue, usually from infection with a virus. Fever, headache, and confusion are common symptoms.
  • Traumatic brain injury: Permanent brain damage from a traumatic head injury. Obvious mental impairment, or more subtle personality and mood changes can occur.
  • Parkinson's disease: Nerves in a central area of the brain degenerate slowly, causing problems with movement and coordination. A tremor of the hands is a common early sign.
  • Huntington's disease: An inherited nerve disorder that affects the brain. Dementia and difficulty controlling movements (chorea) are its symptoms.
  • Epilepsy: The tendency to have seizures. Head injuries and strokes may cause epilepsy, but usually no cause is identified.
  • Dementia: A decline in cognitive function resulting from death or malfunction of nerve cells in the brain. Conditions in which nerves in the brain degenerate, as well as alcohol abuse and strokes, can cause dementia.
  • Alzheimer’s disease: For unclear reasons, nerves in certain brain areas degenerate, causing progressive dementia. Alzheimer’s disease is the most common form of dementia.
  • Brain abscess: A pocket of infection in the brain, usually by bacteria. Antibiotics and surgical drainage of the area are often necessary.

Brain Tests

  • Computed tomography (CT scan): A scanner takes multiple X-rays, which a computer converts into detailed images of the brain and skull.
  • Magnetic resonance imaging (MRI scan): Using radio waves in a magnetic field, an MRI scanner creates highly detailed images of the brain and other parts of the head.
  • Angiography (brain angiogram): A special substance doctors call "a contrast agent" is injected into the veins, and travels into the brain. X-ray videos of the brain are taken, which can show problems in the brain's arteries.
  • Magnetic resonance angiography (MRA): A special MRI scan of the brain's arteries. An MRA scan may show a blood clot or another cause for stroke.
  • Lumbar puncture (spinal tap): A needle is inserted into the space around the spinal nerves, and fluid is removed for analysis. Lumbar puncture is often done if meningitis is suspected.
  • Electroencephalogram (EEG): Brain activity is monitored through electrodes placed on the skin on the head. EEG can help diagnose seizures, or other brain problems.
  • Neurocognitive testing: Tests of problem-solving ability, short-term memory, and other complex brain functions. Usually, neurocognitive testing is done through questionnaires.
  • Brain biopsy: In rare situations, a very small piece of the brain is needed to make the diagnosis of a brain condition. Brain biopsies are generally done only when the information is needed to provide proper treatment.

Brain Treatments

  • Thrombolytics: Clot-busting medicines injected into the veins can improve or cure some strokes if given within a few hours after symptoms start.
  • Antiplatelet agents: Medicines like aspirin and clopidogrel (Plavix) help prevent blood clots. This can reduce the chance of a stroke.
  • Cholinesterase inhibitors: These medicines can improve brain function slightly in mild or moderate Alzheimer’s disease. They do not slow or prevent Alzheimer’s disease.
  • Antibiotics: When a brain infection is caused by bacteria, antibiotics can kill the organisms and make a cure more likely.
  • Levodopa: A medicine that increases brain levels of dopamine, which is helpful in controlling symptoms of Parkinson’s disease.
  • Brain surgery: An operation on the brain can cure some brain tumors. Brain surgery may be performed any time increased pressure in the brain threatens brain tissue.
  • Ventriculostomy: A drain is placed into the natural spaces inside the brain (ventricles). Ventriculostomy is usually performed to relieve high brain pressures.
  • Craniotomy: A surgeon drills a hole into the side of the skull to relieve high pressures.
  • Lumbar drain: A drain is placed into the fluid around the spinal cord. This can relieve pressure on the brain and spinal cord.
  • Radiation therapy: If cancer affects the brain, radiation can reduce symptoms and slow the cancer's growth.