The Nervous System
Pp. 256-322 (67)
Robert E. Smith
The first year of life is critical in brain development, for the total brain
volume doubles, as measured by MRI. This is when the brain is most susceptible to
damage by genetic defects and environmental insults. It is also the time in which
therapeutic intervention can have its maximum effect. A principal component of the
nervous system is the neuron. Neurons are arranged in networks and circuits. The
normal human brain has many local regions, or centers, and many pathways between
them. The autonomic nervous system is organized into three divisions: the sympathetic,
parasympathetic and enteric . These maintenance activities are usually performed
without conscious control or sensation. The sympathetic and parasympathetic nervous
systems work to maintain a type of balance. They have opposite effects on the body.
The sympathetic division is used in actions requiring quick responses. The
parasympathetic division is used in actions that do not require immediate reaction .
Messages are sent to and from neurons in the form of primary messengers, called
neurotransmitters. L-DOPA is used to treat Parkinson’s disease, which affects about
1% of the population over 65. Alzheimer’s disease (AD) is the most common
neurodegenerative disease. Phenobarbital, carbamazepine, valproic acid and its sodium
salt, gabapentin, ethosuximide, lamotrigrine, and tiagabine are anti-epileptics.
Diazepam, buspirone, b-blockers, tricyclic antidepressants and monoamine oxidase
inhibitors treat anxiety disorders. Currently the first-line treatment is either SSRIs or
SNRIs. The four main classes of antidepressant drugs are MAOIs, TCAs, SSRIs and
Alzheimer’s disease, Autonomic nervous system, Neuron,
Park University, Parkville, USA.