Anatomy lab 3

Malfunctions of the oculomotor nerve can result in

Drooping of the upper eyelid (ptosis), external strabismus (when the eyes have the same amount of deviation in whatever direction they are looking), abnormal dilation of the pupil, loss of power of accommodation, and slight bulging of the eyeball due to the relaxed eye muscles

ABDUCENS NERVE

The abducens nerve supplies the external rectus muscle - it innervates the lateral rectus muscle of the eyeball. The sixth nerve is more frequently involved in fractures of the base of the skull than any other of the cranial nerves. When injured there is, in addition to the partial or complete paralysis of the external rectus muscle, a certain amount of dilation in one of the pupils. Such a condition is often indicative of swelling and pressure in the brain.

ACCESSORY NERVE

The accessory nerve innervates the muscles of swallowing, as well as the sternocleomastoid and trapezius muscles. Damage to this nerve can result in the inability to move the head from side to side, or the inability to shrug the shoulders.

anosmia

The Olfactory nerve is a sensory nerve that carries nerve impulses related to smell. In severe injuries to the head, the olfactory bulbs may become separated from the olfactory nerves, thus producing loss of the sense of smell. This condition is referred to as "anosmia". Often accompanying this condition is a considerable loss in the sense of taste, since much of what we taste is accentuated by scent.

FACIAL NERVE

The facial nerve is the motor nerve of all the muscles of expression in the face. Motor fibers are responsible for the innervation of the muscles of the scalp and of the face, the lacrimal glands, and the sublingual and salivary glands. Sensory fibers arise from this nerve to innervate the anterior two-thirds of the tongue. The facial nerve is more frequently paralyzed than any of the twelve cranial nerves. Paralysis can be caused when blood-clots put pressure on this nerve, by middle ear disease, or upon exposure to cold or lesions. In such cases, individuals will not be able to frown, the eyelids cannot be closed, and the lower eyelid droops so that tears run down the cheeks, among other things. A good example of this is Bell's palsy which typically occurs on just one side of the face.

GLOSSOPHARYNGEAL NERVE

The glossopharyngeal nerve is a mixed nerve. The motor fibers innervate the parotid salivary gland and, along with those of the vagus nerve, innervate the muscles of swallowing. Sensory fibers are responsible for the sense of taste to all areas of the tongue to which it is distributed.

HYPOGLOSSAL NERVE

The hypoglossal nerve is the motor nerve of the tongue. It is responsible for the motor impulses to the intrinsic and extrinsic muscles of the tongue. This nerve is not responsible for the innervation of the taste buds. Damage to this nerve may result in the loss of the ability to stick your tongue out at whoever you chose. (Bummer!).

OCULOMOTOR NERVE

The oculomotor nerve is mainly a motor nerve which innervates the levator palpebrae (the muscle that raises the upper eyelid), four extrinsic eye muscles, the sphincter muscle of the iris, and the ciliary muscle that controls lens shape.

OPTIC NERVE

The optic nerve is the special nerve of the sense of sight and is distributed exclusively to the eyeball. The left and right optic nerves run from each eye to the optic chiasma where fibers from the medial half of each retina cross over to the opposite side. The optic nerve may be affected in injuries or diseases involving the eye, fractures of the anterior fossa at the base of the skull, and in tumors within the eye itself or in neighboring areas. For instance, severing the optic chiasma would result in the loss of sight in the medial portion of each eye

TRIGEMINAL NERVE

The trigeminal nerve is the great sensory nerve of the head and face, and is the motor nerve of the muscles of mastication. It is the largest of the twelve cranial nerves, and is a mixed nerve due to its sensory and motor functions. The fifth nerve may be damaged in its entirety or damaged partially where its sensory or motor root may be separately affected. In the case of an injury to the sensory root, the person would experience the following symptoms: anesthesia of the half of the face of the side of the damage, dryness of the nose, loss of sensation to anterior 2/3 of tongue, and in the case of irritation/inflammation to the nerve, intense, pulsating pain. In the case of injury to the motor root, there is impaired action of the lower jaw due to paralysis of muscles of mastication of the affected side.

TROCHLEAR NERVE

The trochlear nerve innervates the extrinsic eye muscles and is the smallest of the twelve cranial nerves. The trochlear nerve, when paralyzed, can cause loss of function in the superior oblique so that one is unable to turn his eye outward and downward. A patient attempting to do this will experience double vision when going down hill or descending a flight of stairs. Irritation of this nerve may cause spasms of one of the muscles supplied by it.

VAGUS NERVE

The vagus nerve has a more extensive distribution than any other of the cranial nerves, passing through the neck and thorax to the upper part of the abdomen. It supplies the organs of voice and respiration with its sensory fibers, and the pharynx, stomach, and heart with the motor fibers. When branches of this nerve are irritated or paralyzed a spasm of the muscles of the larynx may occur. Accompanying this is a hoarse voice that is weak in timbre, among other things.

vestibulocochlear nerve

The vestibulocochlear nerve is the special nerve of the sense of hearing and equilibrium. It is distributed exclusively to the inner ear. The nerve may either be torn, producing permanent damage, or may be bruised or damaged due to loud noises, blows on the head, etc. resulting in temporary deafness and/or ringing in the ears.