The NERVOUS System Organization

The Peripheral Nervous System
1.) Sensory Neurons-(Afferent)
2.) Motor Neurons-(efferent)
2a. Autonomic nervous system
2b. Somatic nervous system
b1.) Sympathetic nervous system
b2.) Parasympathetic Nervous system

The Central Nervous System
a.) Brain
b.) Spinal Cord

The Cranial Nerves

Cranial nerves are nerves that emerge directly from the brain in contrast to spinal nerves which emerge from segments of the spinal cord. Although thirteen cranial nerves in humans fit this description, twelve are conventionally recognized. The nerves from the third onward arise from the brain stem. Except for the tenth and the eleventh nerve, they primarily serve the motor and sensory systems of the head and neck region. However, unlike peripheral nerves which are separated to achieve segmental innervation, cranial nerves are divided to serve one or a few specific functions in wider anatomical territories.

Whereas most major nerves emerge from the spinal cord, the 12 pairs of cranial nerves project directly from the brain. All but 1 pair relay motor or sensory information (or both); the tenth, or vagus nerve, affects visceral functions such as heart rate, vasoconstriction, and contraction of the smooth muscle found in the walls of the trachea, stomach, and intestineCorporation.

Cranial Nerves:

1. olfactory nerves - smell

2. optic nerve - vision

3. ocumulator - eye movements

4. trochlear - eye movements

5. abducent nerves - eye movements

6. trigeminal-Facial sensation and jaw movements

7. Acoustic (vestibulocochlear nerve) - hearing and balance

8. Glossopharyngeal nerve -Taste and throat sensations

9. Vagus nerve - Breathing,circulation and digestion

10. Spinal accessory nerve -Movements of neck and back muscles

11. hypoglossal nerve- Tonge movements

12. Facial nerve - facial expressions and taste

courtesy of: 3D science.com.

source: wiki/encarta encyclopedia