The awe-inspiring complexity of the brain is impressive in the abstract, but even more amazing when you consider the specifics. This organ weighs less than 3 pounds, on average,1 but contains a network of about 86 billion neurons and 85 billion glial cells2 that guides our ability to walk upstairs, sense the coldness of ice cubes and appreciate Mozart.
The brain’s five subsections include the brainstem, which connects to spinal cord and helps manage heart rate, breathing, eating and sleeping; the cerebellum, which helps with balance and posture; limbic system, which helps manage emotions, movement and memories; diencephalon, which helps with perception, movement and hormone regulation; and the cerebral cortex, which is the center of thinking and perception, language and reason as well as processing our senses.3
To understand how each brain region works alone and together, think of electrical wiring. The brain's neurons connect with one another to form large electrical circuits that transmit signals. For example, when the eye detects motion, neurons in the back of the eye fire electrical impulses along a circuit back to the brain. The eye's nerve cells are specialized, so their signals can convey to the brain's visual cortex4 exactly what the eye saw -- something red, round and moving left. Similar nerve circuits convey information detected by our other senses.
Just like the plastic that encases electrical cords, the fatty protein mylein coats neurons.5 If mylein is damaged through disease or trauma, its ability to protect and insulate neurons is hindered. Subsequently, the neurons lose their ability to pass signals quickly or at all, manifesting in symptoms such as numbness, inability to move or lost of speech. Adrenoleukodystrophy (ALD) and multiple sclerosis are both demyelinating disorders and their treatments are designed to halt mylein damage and allow the brain try to repair mylein, which may reduce symptoms.
The brain's glial cells are the neurons' support system. Named for the Greek word for glue,6 glial cells in the brain include star-shaped astrocytes that give structural support to neurons and help provide nourishment.7 Another glial cell type, oligodendrocytes, produce and install mylein on neurons.
The brain also is home to neurotransmitters, chemical messengers that carry signals from neuron to neuron, and sometimes from neurons to other cell types. These molecules include dopamine, glutamate and serotonin.8 If the brain's quantities of neurotransmitters are not maintained, mental health disorders such as schizophrenia can develop, as can diseases such as Parkinson's. Treatments to rebalance neurotransmitter levels include SSRI antidepressants, which are designed to increase serotonin to have a positive effect on mood.
Understanding the root causes of neurotransmitter imbalance, neuronal damage or glial malfunction are dynamic areas of research that may yield improved diagnostics and treatments.
Going forward, that research will be especially important and key to addressing unmet medical need in debilitating or deadly diseases that have a cognitive component. As research reveals more knowledge of the genetic, molecular and cellular levels of brain function, insights will shed light on the intersection of mental activity, brain health and disease.
- http://www.ncbi.nlm.nih.gov/pubmed/8072950 1336 grams = 2.9 lbs; 1198 grams = 2.7 lbs.
- Azevedo. http://www.ncbi.nlm.nih.gov/pubmed/19226510
- The Brain Lesson 1. https://science.education.nih.gov/supplements/nih2/addiction/guide/lesson1-1.html
- Hubel. https://nei.nih.gov/news/briefs/david_hubel
- Myelin. https://www.nlm.nih.gov/medlineplus/ency/article/002261.htm
- Neuroglial cells. http://www.ncbi.nlm.nih.gov/books/NBK10869/
- SEER. http://training.seer.cancer.gov/brain/tumors/anatomy/neurons.html
- NIMH. http://www.nimh.nih.gov/health/educational-resources/brain-basics/brain-basics.shtml