Cranial Nerves I through VIII

This week we covered anatomy of the brain and spinal cord and the blood flow to and from the brain. We the first Discussed seven cranial nerves; The Olfactory I, Optic II, Oculomotor III, Trochlear IV, Trigeminal V, Abducens VI, Facial Nerves VII.

Cranial nerves III, IV and VI are all motor nerves that pass through the Superior Orbital Fissure and control movement of the muscles that move the eyeball and eyelids. The Oculomotor nerve III controls the Superior Rectus, Inferior Rectus, Inferior Oblique and the Medial Rectus muscles of the eye. The Trochlear nerve IV controls the Superior Oblique muscle of the eye. The Abducens nerve VI controls the Lateral Rectus muscle of the eye.

Cranial Nerves I, II, and VIII are all sensory nerves with afferent impulses. The Olfactory Nerve I function is the sense of smell and passes through the Olfactory Foramina of the cribriform plate of the Ethmoid bone. The Optic nerve II is for vision and passes through the Optic Foramen of the Sphenoid bone. The Vestibulocochlear nerve VIII conveys impulses related to equilibrium and hearing and passes through the Internal Acoustic Meatus of the Temporal bone.

Cranial nerve V, the Trigeminal nerve, is a mixed nerve and has three branches, the Ophthalmic, Maxillary, and the Mandibular branch. The Ophthalmic (V1) branch passes through the Superior Orbital Fissure and is a sensory nerve. It has axons in the skin of the forehead, nasal cavity, upper eyelid, and eyebrow. The Maxillary (V2) branch is also sensory and passes through the Foramen Rotundum of the sphenoid bone. It has axons in the Superior lip, superior gums superior teeth, and palate. And the Mandibular (V3) branch is both motor and sensory and passes through the Foramen Oval of the sphenoid bone. The sensory axons are found in the inferior lip, inferior gums, and inferior teeth. The motor axons are found in the Masseter, Temporalis, and the Pterygoids muscles.

If you're still awake I applaud you. Because that is about the most boring read there is so I'm not going to put in the pathway the blood flows to the brain. And I can't think of anything in my life that I can relate to the cranial nerves

Autonomic Nervous System

The ANS consists of the parasympathetic Nervous System and the Sympathetic Nervous System. The impulses are all efferent to the effector tissue. The Parasympathetic Nervous System stimulates the rest and digests response. The cranial nerves associated with it are the Oculomotor nerve III, Facial Nerve VII, Glossopharyngeal Nerve IX, and the Vagus nerve X. There are two neurons in ANS pathways, Preganglionic neurons and postganglionic neurons, to the effector tissues. Preganglionic neurons of the ANS always release the neurotransmitter Ach. In the Parasympathetic division they have long axons, and the postganglionic neurons also release Ach and have short axons. Preganglionic neurons of the Sympathetic division are short, and postganglionic neurons are long and release Norepinephrine or epinephrine. The Adrenal medulla is part of the Sympathetic division but the postganglionic neurons release Epinephrine, Norepinephrine, and dopamine directly into the blood stream. These neurotransmitters bind to Muscarinic receptors on the effector tissue. These are secondary messenger systems and are found in the membrane of Cardiac Muscle cells, Smooth Muscle cells, and glands.

I was diagnosed with IBS last year due to a prolonged period of cronic diarrhea. I did have all the symptoms of IBS but I noticed when I was on vacation the symptoms went away and the medicine they gave me did nothing. So I believe this was due to prolonged high levels of stress. When we talked about cortisol levels being high with long term stress it made wonder if cortisol could cause that.