A delta fibers are responsible for signaling "new" sharp pain. The body sends this sensory information to Rexed Laminae I and II. *I and II are called the substantia gelatinosa.

Fasciculus gracilus is one of the component to the dorsal columns. Remember that anything that is dorsal of the spinal cord is associated with sensation. In addition, the dorsal columns control touch while the spinothalamic tract carries pain and temperature information.

Unlike the body, where the spinothalamic tract sends pain and temperature information, the trigeminal nerve does this for the face. This is processed through the trigeminal ganglion which then synapsis to the spinal trigeminal nucleus before going to the thalamus.

The face is unique in which the sensation of touch is processed through the trigeminal nerve through the trigeminal ganglion which later synapses to the chief nucleus. Don't confuse this with fasciculus gracilus, which transmits touch info from T8 and down and cuneatus that does T8 and up.

C fibers are the least myelinated fibers that carry sensory information. They are responsible for the "slow" more excruciating pain that people tend to experience after the initial pain occurs with an injury. They are known as the slow fibers because the less myelinated a fiber is the slower the conduction speed it has to send the information.

Visceral afferent and somatic afferent axons are found in the dorsal roots of spinal nerves. The dorsal root emerges directly from the spinal cord and travels to the dorsal root ganglion. It then joins fibers with the ventral root to make a mixed spinal nerve. The dorsal root relays sensory information (thus has afferent axons).

The somatic nervous system is the voluntary nervous system and part of the peripheral nervous system. It is associated with voluntary skeletal muscle control over body movements and is associated with involuntary reflex arcs. The somatic nervous system consists of afferent (relay sensations to central nervous system) and efferent (relays commands from central nervous system to the body) nerves stimulating muscle contractions. Thus muscle contraction ceases when neural stimulation ceases.

The conus medullaris is the cone-shaped ending of the spinal cord and it is found at the level of the second lumbar vertebrae (L2). It is located superior to the cauda equina.

The cauda equina is the bottom of the conus medullaris. It extends from the conus medullaris and terminates at C0 vertebrae.

The Dorsal root is responsible for sensory information because it contains the somae of sensory neurons. The Ventral root, on the other hand, contains the somae of motor neurons and therefore is responsible for the motor division.