The brain and spinal cord (CNS) are connected to parts of the body by nerves and cell bodies called the peripheral nervous system. The PNS contains all of the nervous tissue outside the brain and spinal cord.
Afferent (sensory) nerve fibers-conduct nerve impulses toward the CNS Efferent (motor) nerve fibers-conduct nerve pulses away
Sensory Somatic System – Carries nerve impulses from the senses to the CNS and also carries the impulses to the skeletal muscles and glands (this allows us to react to the environment)
Sensory Somatic System – Composed of 12 pairs of cranial nerves and 31 pairs of spinal nerves.
Cranial Nerve| Fibers| Function|
Olfactory (I)| SensoryReceptors in roof/walls of nasal cavity| Smell| Optic (II)| SensoryReceptors in Retina of eye| Vision|
Oculomotor (III)| Motor| Eyeball movement|
Trochlear (IV)| Motor| Muscle of the eyeballTurns eye downward and lateral| Trigeminal (V)| Both| Sensory scalp, face and mouth.Motor muscles of mastication (chewing) and soft palate and the middle ear.| Abducens (VI)| Motor| Muscle of the eyeballMoves eye latterally| Facial (VII)| Motor| Motor muscles of facial expressions| Vestibulocochlear (VIII) Auditory| Sensory| HearingBalance| Glossopharyngeal (IX)| Both| Sensory: Taste, tongue, pharynx, tonsils and middle ear.Motor: Muscles of the pharynx (swallowing).| Vagus (X)| Both| Sensory: pharynx, larynx, thoracic and abdominal organs and taste.Motor: Soft palate, pharynx, voice and tongue muscle.Stimulates digestive organs, slows heart rate, senses blood pressure| Spinal Accessory (XI)| Motor| Neck muscle (sternocleidomastoid and trapezius).Muscles of swallowing (pharynx and soft palate).| Hypoglossal (XII)| Motor| Muscles of the tongue and hyoid muscles| Some