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Transcript
Cranial Nerves
Brooke Roby
Anatomy and Physiology II, PCC
Vocabulary:
1. Cranial- pertaining to the brain
2. Nerve- a bundle of neuronal axons and or dendrites and associated connective
tissue coursing together outside the central nervous system.
3. Axon- the usually single, long process of a nerve cell that propagates a nerve
impulse toward the axon terminals.
4. Dendrite- a neuronal process that carries electrical signals usually graded
potentials, toward the cell body.
5. Synapse-the functional junction between two neurons or between a neuron
and an effector, such as a muscle or gland; may be electrical or chemical.
6. Sensory neurons- neurons that carry sensory information from cranial and
spinal nerves into the brain and spinal cord or from a lower to a higher level in
the spinal cord and brain. Also known as afferent neurons.
7. Motor neuron- neurons that conduct impulses from the brain toward the
spinal cord or out of the brain and spinal cord into cranial or spinal nerves to
effectors that may be either muscle or glands. Also called efferent neurons.
8. Mixed-contains both sensory and motor neurons
Introduction:
Understanding cranial nerves are very important because each has a specific
function in the body. Without nerves are body will receive no impulses from the brain,
which means our bodies will not function. There are 12 pairs of cranial nerves and each
arises from a different location and has a specific function. Understanding and
remembering where each arises from and the function it has may be very difficult. There
are so many cranial nerves and spinal nerves that it is hard to keep them all straight and
remember them all.
Explanation:
There are twelve cranial nerves. They are all named with a name, which tells a
nerve’s function, and a Roman numeral, which tells which nerve it is. The first is Cranial
Nerve I, which is the olfactory nerve. If you know what olfactory is, this one will be easy
to remember. Olfactory has to do with a person’s sense of smell. This nerve is entirely
sensory. It covers the upper part of the nasal cavity and the bottom surface of the
cribiform plate. Olfactory nerves end in the brain in paired masses of gray matter called
the olfactory bulbs. The next cranial nerve is Cranial Nerve II, the Optic Nerve. This is
also a simple on to know because optic means eye, or vision of the eye. It also is entirely
sensory. This nerve conducts impulses for vision.
The third cranial nerve is Cranial Nerve III, the oculomotor nerve. Oculo=eye,
and motor=a mover. This cranial nerve is mixed which means it contains both sensory
and motor neurons. There are a few branches of the oculomotor nerve. This nerve
innervates the superior rectus, which is an eyeball muscle, and it also innervates the upper
eyelid. The second branch is the inferior branch innervates the ciliary muscle of the
eyeball, and the circular muscle which is around the iris (the colored part of the eye).
This second branch also innervates the inferior rectus muscle of the eye. Cranial Nerve
IV is the trochlear Nerve. This nerve is mixed, and innervates the superior oblique
muscle of the eye, which also controls the movement of the eye. These axons convey
nerve impulses for proprioception.
Cranial Nerve V is the trigeminal nerve, and likes its name has 3 branches,
ophthalmic, maxillary, and mandibular. This cranial nerve conveys impulses for touch,
pain, and temperature sensations and proprioception. It is also involved in chewing. It is
a mixed nerve. Cranial nerve VI is also mixed, and is called the abducens nerve. It is
involved in movement of the eye, and propriception. It works with nerve III and IV.
The next cranial nerve is Cranial Nerve VII, the facial nerve. Like its name states,
it is involved in facial expressions, taste and secretion of saliva and tears. It is a mixed
nerve. Cranial nerve VIII is the vestibulocochlear nerve, which is also mixed. The
cochlear is a spiral, snail like shape, structure in the inner ear. It conveys impulses
related to equilibrium, conveys impulses for hearing. The Glossopharyngeal nerve is
cranial nerve IX. Glosso = tongue, and –pharyngeal = throat. It has to do with taste and
somatic sensation from the back 2/3 of the tongue. It also functions by elevating the
pharynx during swallowing and speech. Cranial nerve X is the vagus nerve and is also a
mixed nerve. Its sensory function is taste and it somatic motor function is swallowing,
coughing, and voice production.
Cranial nerve XI is the accessory nerve. This mixed nerve’s spinal part mediates
movement of the head and shoulders. The final cranial nerve is cranial nerve XII. The
hypoglossal nerve is responsible for the tongue during speech and swallowing.
Summary:
In order to remember the order of these nerves it is best to come up with a saying,
such as:
Old Opie Octopus Trocanter Tripped And Fell Very Gracefully Vanashing Always
Head-over-heels
This will help to remember the order. Knowing the functions takes some time and it is
best to practice and practice. If you break down most of the names it can help you to put
the function with the name. Good Luck!