Nervous System


The nervous system consists of the brain, spinal cord, sensory organs, and all of the nerves that connect these organs with the rest of the body. Together, these organs are responsible for the control of the body and communication among its parts. \

The Central and Peripheral Nervous System

The central nervous system is the complex of nerve tissues that controls the activities of the body. In vertebrates it comprises the brain and spinal cord.

The major parts of the central nervous system are the spinal cord (serves as a conduit for signals between the brain and the rest of the body) and the brain (responsible for integrating most sensory information and coordinating body function, both consciously and unconsciously).

The peripheral nervous system is the nervous system outside the brain and spinal cord.

The major parts of the peripheral nervous system are the somatic nervous system (send sensory information to the central nervous system AND motor nerve fibers that project to skeletal muscle) and the autonomic nervous system (projects directly to a skeletal muscle).

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Simple Reflex Arc

White Matter: the paler tissue of the brain and spinal cord, consisting mainly of nerve fibers with their myelin sheaths.

Grey Matter: the darker tissue of the brain and spinal cord, consisting mainly of nerve cell bodies and branching dendrites.

Ventral Root: the efferent motor root of a spinal nerve. At its distal end, the ventral root joins with the dorsal root to form a mixed spinal nerve.

Interneuron: a neuron that transmits impulses between other neurons, especially as part of a reflex arc.

Dorsal Root Ganglion: contains the cell bodies of sensory neurons that bring information from the periphery to the spinal cord.

Sensory Neuron: nerve cells within the nervous system responsible for converting external stimuli from the organism's environment into internal electrical impulses.

Motor Neuron: a nerve cell forming part of a pathway along which impulses pass from the brain or spinal cord to a muscle or gland.

Functions of the Major Regions of the Cerebral Hemisphere

Cerebral Hemisphere: The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the medial longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres.

Diencephalon: region of the embryonic vertebrate neural tube that gives rise to posterior forebrain structures including the thalamus, hypothalamus, posterior portion of the pituitary gland, and pineal gland.

Brain Stem: sits beneath the cerebrum and in front of the cerebellum. It connects the rest of the brain to the spinal cord, which runs down your neck and back. The brain stem is in charge of all the functions your body needs to stay alive, like breathing air, digesting food, and circulating blood.

Cerebellum: does not initiate movement, but it contributes to coordination, precision, and accurate timing. It receives input from sensory systems of the spinal cord and from other parts of the brain, and integrates these inputs to fine tune motor activity.


Epilepsy is a neurological disorder marked by sudden recurrent episodes of sensory disturbance, loss of consciousness, or convulsions, associated with abnormal electrical activity in the brain.


Seizures are the only visible symptom of epilepsy.


  • The average incidence of epilepsy each year in the U. S is estimated at 150,000 or 48 for every 100,000 people.
  • Another way of saying this- each year, 150,000 or 48 out of 100,000 people will develop epilepsy.
  • The incidence of epilepsy is higher in young children and older adults. This means that epilepsy starts more often in these age groups.
  • When the incidence of epilepsy is looked at over a lifetime, 1 in 26 people will develop epilepsy at sometime in their life.


The majority of epileptic seizures are controlled through drug therapy, particularly anticonvulsant drugs. The type of treatment prescribed will depend on several factors including the frequency and severity of the seizures as well as the person's age, overall health, and medical history.


A stroke is damage to the brain from interruption of its blood supply.


Muscular: overactive reflexes, paralysis of one side of the body, difficulty walking, stiff muscles, problems with coordination, or paralysis with weak muscles

Visual: sudden visual loss, double vision, temporary loss of vision in one eye, or blurred vision

Sensory: numbness, pins and needles, or reduced sensation of touch

Speech: speech loss, difficulty speaking, or slurred speech

Limbs: weakness or numbness

Facial: muscle weakness or numbness

Whole body: lightheadedness, vertigo, balance disorder, or fatigue

Also common: inability to understand, mental confusion, headache, difficulty swallowing, or rapid involuntary eye movement


  • Stroke kills almost 130,000 Americans each year—that’s 1 out of every 20 deaths.
  • On average, one American dies from stroke every 4 minutes.
  • Every year, more than 795,000 people in the United States have a stroke.
  • About 610,000 of these are first or new strokes.
  • About 185,00 strokes—nearly one of four—are in people who have had a previous stroke.
  • About 87% of all strokes are ischemic strokes, when blood flow to the brain is blocked.
  • Stroke costs the United States an estimated $34 billion each year. This total includes the cost of health care services, medications to treat stroke, and missed days of work.
  • Stroke is a leading cause of serious long-term disability.


Ischemic Stroke Treatment. The only FDA approved treatment for ischemic strokes is tissue plasminogen activator (tPA, also known as IV rtPA, given through an IV in the arm). tPA works by dissolving the clot and improving blood flow to the part of the brain being deprived of blood flow.