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A request for an overview of the cranial nerves

A request for an overview of the cranial nerves



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Is there any resource that contains motor and sensory innervations, or pathways of all the twelve cranial nerves (i.e., cranial nerve I to XII)?

I have found this book chapter on the cranial nerves, but it is too broad for me - I'm still at high school.


I am not entirely sure what you are after, but I (as have others that commented on this question) interpret your question as "The linked chapter contains too much technical information". Quite frankly, after scanning the book chapter, I have to agree with you. Therefore I have sought for a quick overview image of all the cranial nerves including their sensory and motor targets.
Encyclopedia Britannica has published all the cranial nerves and their sensory and motor innervations in a single comprehensive figure:


Cranial Nerves and their targets. Source: Encyclopedia Britannica

I can highly recommend this online encyclopedia. Their articles are more concise and better accessible than similar topics on wikipedia. Moreover, this encyclopedia is not freely editable by everyone on the planet, and everything I have seen so far on their website is credible.


If you're still learning the names and functions of all 12 cranial nerves, something like this page may help you get ready for more in depth material like the chapter you found. https://faculty.washington.edu/chudler/cranial.html
I like the fact that they include activities for each nerve to help give you one more way to remember their functions.


The Clinical Anatomy of the Cranial Nerves: The Nerves of ""On Old Olympus Towering Top""

The cranial nerves are an endlessly fascinating family of twelve nerves that have a dramatic impact on our daily lives. A dysfunction of the cranial nerves can cause loss of vision or double vision, loss of smell, poor balance, or loss of muscle function, and can also be an indicator of underlying neurological disorders. The Clinical Anatomy of the Cranial Nerves: The Nerves of "On Old Olympus Towering Top" is an engaging and accessible book on the anatomy and clinical importance of these unique nerves.

The text opens with a brief introduction of key neuroanatomical concepts that relate the clinical and anatomical sections that follow. Additionally, this book uniquely provides a detailed description of the bones of the head and face in order for the reader to understand the routes taken by the cranial nerves through the skull. Chapters then detail each nerve and its unique impact in relationship to our senses, motor function, and health. Vividly illustrated and supported by real-life clinical cases, the book will appeal to anyone wishing to gain a better understanding of the cranial nerves.

Merging anatomical and clinical information with intriguing clinical cases, The Clinical Anatomy of the Cranial Nerves: The Nerves of "On Old Olympus Towering Top" introduces readers to the anatomy and diverse function of this intriguing family of nerves.


Slide left or right to learn the labels of models.

Brain Model – Lateral View

Brain Model – Medial View

Brain Model – Ventral View

Brain Model – Cranial Nerves

Sheep Brain Specimen – Dorsal View

Sheep Brain Specimen – Lateral View

Sheep Brain Specimen – Sagittal View

Sheep Brain Specimen – Ventral View

Cranial Nerves Summery, Click here for 3D Anatomy Tutorial Video.

Click on the picture to read the Summary of Cranial Nerves.


What are the symptoms of cranial neuropathies?

Different types of neuropathies can cause different symptoms. They are based on which nerves are damaged and where they are located. Generally, neuropathies can cause:

  • Pain
  • A tingling sensation
  • Numbness
  • Skin that feels sensitive to the touch
  • Weak or paralyzed muscles. This can cause drooling or slurred speech.
  • Vision changes

Some of the symptoms of different types of cranial neuropathies include:

  • Bell palsy can cause drooping of part of the face. It usually affects only one side of the face.
  • Microvascular cranial nerve palsy can cause double vision, droopy eyelid, and other problems with eyesight.
  • Third nerve palsy can cause an eyelid to sag and droop, double vision, trouble moving the eye, and a pupil that is bigger than normal.
  • Fourth nerve palsy causes the eye or eyes to turn abnormally. It sometimes makes you see double. It may force you to tilt your head when looking.
  • Sixth nerve palsy can cause abnormal movement of the eye and double vision.

How are cranial neuropathies diagnosed?

A healthcare provider will often do a variety of tests to diagnose neuropathy. Depending on the type of cranial neuropathy your healthcare provider suspects, you may need:

  • Nervous system exam to test sensation, reflexes, balance, and mental status
  • Blood tests to look for infections or health conditions such as diabetes
  • Electromyography (EMG), which measures the electrical activity of muscles when working and at rest
  • CT or MRI scans, which are imaging tests that allow healthcare providers to see the brain
  • Nerve conduction velocity tests to help find out how and where the nerve is damaged
  • Biopsies of the skin and nerves to find out how severely nerves are damaged
  • Hearing tests
  • Spinal tap (lumbar puncture) to look for infection or inflammation in the spinal fluid
  • Angiography, which is a special X-ray that uses contrast dye and takes pictures of your heart and blood vessels

Sensory-Somatic Nervous System

The sensory-somatic nervous system is made up of cranial and spinal nerves and contains both sensory and motor neurons. Sensory neurons transmit sensory information from the skin, skeletal muscle, and sensory organs to the CNS. Motor neurons transmit messages about desired movement from the CNS to the muscles to make them contract. Without its sensory-somatic nervous system, an animal would be unable to process any information about its environment (what it sees, feels, hears, and so on) and could not control motor movements. Unlike the autonomic nervous system, which has two synapses between the CNS and the target organ, sensory and motor neurons have only one synapse—one ending of the neuron is at the organ and the other directly contacts a CNS neuron. Acetylcholine is the main neurotransmitter released at these synapses.

Humans have 12 cranial nerves , nerves that emerge from or enter the skull (cranium), as opposed to the spinal nerves, which emerge from the vertebral column. Each cranial nerve is accorded a name, which are detailed in [link]. Some cranial nerves transmit only sensory information. For example, the olfactory nerve transmits information about smells from the nose to the brainstem. Other cranial nerves transmit almost solely motor information. For example, the oculomotor nerve controls the opening and closing of the eyelid and some eye movements. Other cranial nerves contain a mix of sensory and motor fibers. For example, the glossopharyngeal nerve has a role in both taste (sensory) and swallowing (motor).


Spinal nerves transmit sensory and motor information between the spinal cord and the rest of the body. Each of the 31 spinal nerves (in humans) contains both sensory and motor axons. The sensory neuron cell bodies are grouped in structures called dorsal root ganglia and are shown in [link]. Each sensory neuron has one projection—with a sensory receptor ending in skin, muscle, or sensory organs—and another that synapses with a neuron in the dorsal spinal cord. Motor neurons have cell bodies in the ventral gray matter of the spinal cord that project to muscle through the ventral root. These neurons are usually stimulated by interneurons within the spinal cord but are sometimes directly stimulated by sensory neurons.



Contents

Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized. [2] [5] The nerves are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and the hypoglossal nerve (XII).

Terminology Edit

Cranial nerves are generally named according to their structure or function. For example, the olfactory nerve (I) supplies smell, and the facial nerve (VII) supplies the muscles of the face. Because Latin was the lingua franca of the study of anatomy when the nerves were first documented, recorded, and discussed, many nerves maintain Latin or Greek names, including the trochlear nerve (IV), named according to its structure, as it supplies a muscle that attaches to a pulley (Greek: trochlea ). The trigeminal nerve (V) is named in accordance with its three components (Latin: trigeminus meaning triplets), [6] and the vagus nerve (X) is named for its wandering course (Latin: vagus). [7]

Cranial nerves are numbered based on their position from front to back (rostral-caudal) of their position on the brain, [8] as, when viewing the forebrain and brainstem from below, they are often visible in their numeric order. For example, the olfactory nerves (I) and optic nerves (II) arise from the base of the forebrain, and the other nerves, III to XII, arise from the brainstem. [8]

Cranial nerves have paths within and outside the skull. The paths within the skull are called "intracranial" and the paths outside the skull are called "extracranial". There are many holes in the skull called "foramina" by which the nerves can exit the skull. All cranial nerves are paired, which means they occur on both the right and left sides of the body. The muscle, skin, or additional function supplied by a nerve, on the same side of the body as the side it originates from, is an ipsilateral function. If the function is on the opposite side to the origin of the nerve, this is known as a contralateral function. [9]

Intracranial course Edit

Nuclei Edit

Grossly, all cranial nerves have a nucleus. With the exception of the olfactory nerve (I) and optic nerve (II), all the nuclei are present in the brainstem. [2]

The midbrain of the brainstem has the nuclei of the oculomotor nerve (III) and trochlear nerve (IV) the pons has the nuclei of the trigeminal nerve (V), abducens nerve (VI), facial nerve (VII) and vestibulocochlear nerve (VIII) and the medulla has the nuclei of the glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI) and hypoglossal nerve (XII). [10] The olfactory nerve (I) emerges from the olfactory bulb, and depending slightly on division the optic nerve (II) is considered to emerge from the lateral geniculate nuclei. [10]

Because each nerve may have several functions, the nerve fibres that make up the nerve may collect in more than one nucleus. For example, the trigeminal nerve (V), which has a sensory and a motor role, has at least four nuclei. [10] [11]

Exiting the brainstem Edit

With the exception of the olfactory nerve (I) and optic nerve (II), the cranial nerves emerge from the brainstem. The oculomotor nerve (III) and trochlear nerve (IV) emerge from the midbrain, the trigeminal (V), abducens (VI), facial (VII) and vestibulocochlea (VIII) from the pons, and the glossopharyngeal (IX), vagus (X), accessory (XI) and hypoglossal (XII) emerge from the medulla. [12]

The olfactory nerve (I) and optic nerve (II) emerge separately. The olfactory nerves emerge from the olfactory bulbs on either side of the crista galli, a bony projection below the frontal lobe, and the optic nerves (II) emerge from the lateral colliculus, swellings on either side of the temporal lobes of the brain. [12]

Ganglia Edit

The cranial nerves give rise to a number of ganglia, collections of the cell bodies of neurons in the nerves that are outside of the brain. These ganglia are both parasympathetic and sensory ganglia. [10]

The sensory ganglia of the cranial nerves, directly correspond to the dorsal root ganglia of spinal nerves and are known as cranial nerve ganglia. [8] Sensory ganglia exist for nerves with sensory function: V, VII, VIII, IX, X. [2] There are also a number of parasympathetic cranial nerve ganglia. Sympathetic ganglia supplying the head and neck reside in the upper regions of the sympathetic trunk, and do not belong to the cranial nerves. [10]

The ganglion of the sensory nerves, which are similar in structure to the dorsal root ganglion of the spinal cord, include: [13]

  • The trigeminal ganglia of the trigeminal nerve (V), which occupies a space in the dura mater called Meckel's cave. This ganglion contains only the sensory fibres of the trigeminal nerve.
  • The geniculate ganglion of the facial nerve (VII), which occurs just after the nerve enters the facial canal.
  • A superior and inferior ganglia of the glossopharyngeal nerve (IX), which occurs just after it passes through the jugular foramen.

Additional ganglia for nerves with parasympathetic function exist, and include the ciliary ganglion of the oculomotor nerve (III), the pterygopalatine ganglion of the maxillary nerve (V2), the submandibular ganglion of the lingual nerve, a branch of the facial nerve (VII), and the otic ganglion of the glossopharyngeal nerve (IX). [14]

Exiting the skull and extracranial course Edit

Exits of cranial nerves from the skull. [10] [13]
Location Nerve
cribriform plate Terminal nerve (0)
cribriform plate Olfactory nerve (I)
optic foramen Optic nerve (II)
superior orbital fissure Oculomotor (III)
Trochlear (IV)
Abducens (VI)
Trigeminal V1
(ophthalmic)
foramen rotundum Trigeminal V2
(maxillary)
foramen ovale Trigeminal V3
(mandibular)
stylomastoid foramen Facial nerve (VII)
internal auditory canal Vestibulocochlear (VIII)
jugular foramen Glossopharyngeal (IX)
Vagus (X)
Accessory (XI)
hypoglossal canal Hypoglossal (XII)

After emerging from the brain, the cranial nerves travel within the skull, and some must leave it in order to reach their destinations. Often the nerves pass through holes in the skull, called foramina, as they travel to their destinations. Other nerves pass through bony canals, longer pathways enclosed by bone. These foramina and canals may contain more than one cranial nerve and may also contain blood vessels. [13]

  • The terminal nerve (0), is a thin network of fibers associated with the dura and lamina terminalis running rostral to the olfactory nerve, with projections through the cribriform plate.
  • The olfactory nerve (I), passes through perforations in the cribriform plate part of the ethmoid bone. The nerve fibres end in the upper nasal cavity.
  • The optic nerve (II) passes through the optic foramen in the sphenoid bone as it travels to the eye.
  • The oculomotor nerve (III), trochlear nerve (IV), abducens nerve (VI) and the ophthalmic branch of the trigeminal nerve (V1) travel through the cavernous sinus into the superior orbital fissure, passing out of the skull into the orbit.
  • The maxillary division of the trigeminal nerve (V2) passes through foramen rotundum in the sphenoid bone.
  • The mandibular division of the trigeminal nerve (V3) passes through foramen ovale of the sphenoid bone.
  • The facial nerve (VII) and vestibulocochlear nerve (VIII) both enter the internal auditory canal in the temporal bone. The facial nerve then reaches the side of the face by using the stylomastoid foramen, also in the temporal bone. Its fibers then spread out to reach and control all of the muscles of facial expression. The vestibulocochlear nerve reaches the organs that control balance and hearing in the temporal bone and therefore does not reach the external surface of the skull.
  • The glossopharyngeal (IX), vagus (X) and accessory nerve (XI) all leave the skull via the jugular foramen to enter the neck. The glossopharyngeal nerve provides sensation to the upper throat and the back of the tongue, the vagus supplies the muscles in the larynx and continues downward to supply parasympathetic supply to the chest and abdomen. The accessory nerve controls the trapezius and sternocleidomastoid muscles in the neck and shoulder.

The cranial nerves are formed from the contribution of two specialized embryonic cell populations, cranial neural crest and ectodermal placodes. The components of the sensory nervous system of the head are derived from the neural crest and from an embryonic cell population developing in close proximity, the cranial sensory placodes (the olfactory, lens, otic, trigeminal, epibranchial and paratympanic placodes). The doble-origin cranial nerves are summarized in the following Table: [15]

Contributions of neural crest cells and placodes to ganglia and cranial nerves

(Ensheating glia of Olfactory nerves)

-Inferior: geniculate, general and special afferent

-Sphenopalatine, visceral efferent

-Submandibular, visceral efferent

-1st epibranchial placode (geniculate)

-Inferior, petrosal, general and special afferent

-2nd epibranchial placode (petrosal)

-Hindbrain NCCs (from r6 into 3rd PA)

Superior laryngeal branch and recurrent laryngeal branch

-Inferior: nodose, general and special afferent

-Vagal: parasympathetic, visceral efferent

-Hindbrain NCCs (4th& 6th PA) 3rd (nodose) and 4th epibranchial placodes

-Hindbrain NCCs (4th & 6th PA)

Abbreviations: CN, Cranial Nerve m, purely motor nerve mix, mixed nerve (sensory and motor) NC, neural crest PA, pharyngeal (branchial) arch r, rhombomere s, purely sensory nerve. * There is no known ganglion of the accessory nerve. The cranial part of the accessory nerve sends occasional branches to the superior ganglion of the vagus nerve.

The cranial nerves provide motor and sensory supply mainly to the structures within the head and neck. The sensory supply includes both "general" sensation such as temperature and touch, and "special" senses such as taste, vision, smell, balance and hearing. [11] The vagus nerve (X) provides sensory and autonomic (parasympathetic) supply to structures in the neck and also to most of the organs in the chest and abdomen. [3] [2]

Terminal nerve (0) Edit

The terminal nerve (0) may not have a role in humans, [3] although it has been implicated in hormonal responses to smell, sexual response and mate selection. [5]

Smell (I) Edit

The olfactory nerve (I) conveys information giving rise to the sense of smell. [16]

Damage to the olfactory nerve (I) can cause an inability to smell (anosmia), a distortion in the sense of smell (parosmia), or a distortion or lack of taste. [16] [17]

Vision (II) Edit

The optic nerve (II) transmits visual information. [2]

Damage to the optic nerve (II) affects specific aspects of vision that depend on the location of the damage. A person may not be able to see objects on their left or right sides (homonymous hemianopsia), or may have difficulty seeing objects from their outer visual fields (bitemporal hemianopsia) if the optic chiasm is involved. Inflammation (optic neuritis) may impact the sharpness of vision or colour detection [16]

Eye movement (III, IV, VI) Edit

The oculomotor nerve (III), trochlear nerve (IV) and abducens nerve (VI) coordinate eye movement. The oculomotor nerve controls all muscles of the eye except for the superior oblique muscle controlled by the trochlear nerve (IV), and the lateral rectus muscle controlled by the abducens nerve (VI). This means the ability of the eye to look down and inwards is controlled by the trochlear nerve (IV), the ability to look outwards is controlled by the abducens nerve (VI), and all other movements are controlled by the oculomotor nerve (III) [16]

Damage to these nerves may affect the movement of the eye. Damage may result in double vision (diplopia) because the movements of the eyes are not synchronized. Abnormalities of visual movement may also be seen on examination, such as jittering (nystagmus). [17]

Damage to the oculomotor nerve (III) can cause double vision and inability to coordinate the movements of both eyes (strabismus), also eyelid drooping (ptosis) and pupil dilation (mydriasis). [18] Lesions may also lead to inability to open the eye due to paralysis of the levator palpebrae muscle. Individuals suffering from a lesion to the oculomotor nerve may compensate by tilting their heads to alleviate symptoms due to paralysis of one or more of the eye muscles it controls. [17]

Damage to the trochlear nerve (IV) can also cause double vision with the eye adducted and elevated. [18] The result will be an eye which can not move downwards properly (especially downwards when in an inward position). This is due to impairment in the superior oblique muscle. [17]

Damage to the abducens nerve (VI) can also result in double vision. [18] This is due to impairment in the lateral rectus muscle, supplied by the abducens nerve. [17]

Trigeminal nerve (V) Edit

The trigeminal nerve (V) and its three main branches the ophthalmic (V1), maxillary (V2), and mandibular (V3) provide sensation to the skin of the face and also controls the muscles of chewing. [16]

Damage to the trigeminal nerve leads to loss of sensation in an affected area. Other conditions affecting the trigeminal nerve (V) include trigeminal neuralgia, herpes zoster, sinusitis pain, presence of a dental abscess, and cluster headaches. [19] [16]

Facial expression (VII) Edit

The facial nerve (VII) controls most muscles of facial expression, supplies the sensation of taste from the front two-thirds of the tongue, and controls the stapedius muscle. [16] Most muscles are supplied by the cortex on the opposite side of the brain the exception is the frontalis muscle of the forehead, in which the left and the right side of the muscle both receive inputs from both sides of the brain. [16]

Damage to the facial nerve (VII) may cause facial palsy. This is where a person is unable to move the muscles on one or both sides of their face. [16] The most common cause of this is Bell's palsy, the ultimate cause of which is unknown. [16] Patients with Bell's palsy often have a drooping mouth on the affected side and often have trouble chewing because the buccinator muscle is affected. [3] The facial nerve is also the most commonly affected cranial nerve in blunt trauma. [20]

Hearing and balance (VIII) Edit

The vestibulocochlear nerve (VIII) supplies information relating to balance and hearing via its two branches, the vestibular and cochlear nerves. The vestibular part is responsible for supplying sensation from the vestibules and semicircular canal of the inner ear, including information about balance, and is an important component of the vestibuloocular reflex, which keeps the head stable and allows the eyes to track moving objects. The cochlear nerve transmits information from the cochlea, allowing sound to be heard. [2]

When damaged, the vestibular nerve may give rise to the sensation of spinning and dizziness (vertigo). Function of the vestibular nerve may be tested by putting cold and warm water in the ears and watching eye movements caloric stimulation. [3] [17] Damage to the vestibulocochlear nerve can also present as repetitive and involuntary eye movements (nystagmus), particularly when the eye is moving horizontally. [17] Damage to the cochlear nerve will cause partial or complete deafness in the affected ear. [17]

Oral sensation, taste, and salivation (IX) Edit

The glossopharyngeal nerve (IX) supplies the stylopharyngeus muscle and provides sensation to the oropharynx and back of the tongue. [3] The glossopharyngeal nerve also provides parasympathetic input to the parotid gland. [3]

Damage to the nerve may cause failure of the gag reflex a failure may also be seen in damage to the vagus nerve (X). [16]

Vagus nerve (X) Edit

The vagus nerve (X) provides sensory and parasympathetic supply to structures in the neck and also to most of the organs in the chest and abdomen. [2]

Loss of function of the vagus nerve (X) will lead to a loss of parasympathetic supply to a very large number of structures. Major effects of damage to the vagus nerve may include a rise in blood pressure and heart rate. Isolated dysfunction of only the vagus nerve is rare, but - if the lesion is located above the point at which the vagus first branches off - can be indicated by a hoarse voice, due to dysfunction of one of its branches, the recurrent laryngeal nerve. [10]

Damage to this nerve may result in difficulties swallowing. [17]

Shoulder elevation and head-turning (XI) Edit

Damage to the accessory nerve (XI) will lead to weakness in the trapezius muscle on the same side as the damage. The trapezius lifts the shoulder when shrugging, so the affected shoulder will not be able to shrug and the shoulder blade (scapula) will protrude into a winged position. [3] Depending on the location of the lesion there may also be weakness present in the sternocleidomastoid muscle, which acts to turn the head so that the face points to the opposite side. [16]

Tongue movement (XII) Edit

The hypoglossal nerve (XII) supplies the intrinsic muscles of the tongue, controlling tongue movement. [16] The hypoglossal nerve (XII) is unique in that it is supplied by the motor cortices of both hemispheres of the brain. [17]

Damage to the nerve may lead to fasciculations or wasting (atrophy) of the muscles of the tongue. This will lead to weakness of tongue movement on that side. When damaged and extended, the tongue will move towards the weaker or damaged side, as shown in the image. [17] The fasciculations of the tongue are sometimes said to look like a "bag of worms". Damage to the nerve tract or nucleus will not lead to atrophy or fasciculations, but only weakness of the muscles on the same side as the damage. [17]

Examination Edit

Doctors, neurologists and other medical professionals may conduct a cranial nerve examination as part of a neurological examination to examine the cranial nerves. This is a highly formalised series of steps involving specific tests for each nerve. [16] Dysfunction of a nerve identified during testing may point to a problem with the nerve or of a part of the brain. [16]

A cranial nerve exam starts with observation of the patient, as some cranial nerve lesions may affect the symmetry of the eyes or face. [16] Vision may be tested by examining the visual fields, or by examining the retina with an ophthalmoscope, using a process known as funduscopy. Visual field testing may be used to pin-point structural lesions in the optic nerve, or further along the visual pathways. [17] Eye movement is tested and abnormalities such as nystagmus are observed for. The sensation of the face is tested, and patients are asked to perform different facial movements, such as puffing out of the cheeks. Hearing is checked by voice and tuning forks. The patient's uvula is examined. After performing a shrug and head turn, the patient's tongue function is assessed by various tongue movements. [16]

Smell is not routinely tested, but if there is suspicion of a change in the sense of smell, each nostril is tested with substances of known odors such as coffee or soap. Intensely smelling substances, for example ammonia, may lead to the activation of pain receptors of the trigeminal nerve (V) located in the nasal cavity and this can confound olfactory testing. [16] [17]

Damage Edit

Compression Edit

Nerves may be compressed because of increased intracranial pressure, a mass effect of an intracerebral haemorrhage, or tumour that presses against the nerves and interferes with the transmission of impulses along the nerve. [22] Loss of function of a cranial nerve may sometimes be the first symptom of an intracranial or skull base cancer. [23]

An increase in intracranial pressure may lead to impairment of the optic nerves (II) due to compression of the surrounding veins and capillaries, causing swelling of the eyeball (papilloedema). [24] A cancer, such as an optic glioma, may also impact the optic nerve (II). A pituitary tumour may compress the optic tracts or the optic chiasm of the optic nerve (II), leading to visual field loss. A pituitary tumour may also extend into the cavernous sinus, compressing the oculuomotor nerve (III), trochlear nerve (IV) and abducens nerve (VI), leading to double-vision and strabismus. These nerves may also be affected by herniation of the temporal lobes of the brain through the falx cerebri. [22]

The cause of trigeminal neuralgia, in which one side of the face is exquisitely painful, is thought to be compression of the nerve by an artery as the nerve emerges from the brain stem. [22] An acoustic neuroma, particularly at the junction between the pons and medulla, may compress the facial nerve (VII) and vestibulocochlear nerve (VIII), leading to hearing and sensory loss on the affected side. [22] [25]

Stroke Edit

Occlusion of blood vessels that supply the nerves or their nuclei, an ischemic stroke, may cause specific signs and symptoms relating to the damaged area. If there is a stroke of the midbrain, pons or medulla, various cranial nerves may be damaged, resulting in dysfunction and symptoms of a number of different syndromes. [26] Thrombosis, such as a cavernous sinus thrombosis, refers to a clot (thrombus) affecting the venous drainage from the cavernous sinus, affects the optic (II), oculomotor (III), trochlear (IV), opthalamic branch of the trigeminal nerve (V1) and the abducens nerve (VI). [25]

Inflammation Edit

Inflammation of a cranial nerve can occur as a result of infection, such as viral causes like reactivated herpes simplex virus, or can occur spontaneously. Inflammation of the facial nerve (VII) may result in Bell's palsy. [27]

Multiple sclerosis, an inflammatory process resulting in a loss of the myelin sheathes which surround the cranial nerves, may cause a variety of shifting symptoms affecting multiple cranial nerves. Inflammation may also affect other cranial nerves. [27] Other rarer inflammatory causes affecting the function of multiple cranial nerves include sarcoidosis, miliary tuberculosis, and inflammation of arteries, such as granulomatosis with polyangiitis. [25]

Other Edit

Trauma to the skull, disease of bone, such as Paget's disease, and injury to nerves during surgery are other causes of nerve damage. [25]

The Graeco-Roman anatomist Galen (AD 129–210) named seven pairs of cranial nerves. [7] Much later, in 1664, English anatomist Sir Thomas Willis suggested that there were actually 9 pairs of nerves. Finally, in 1778, German anatomist Samuel Soemmering named the 12 pairs of nerves that are generally accepted today. [7] However, because many of the nerves emerge from the brain stem as rootlets, there is continual debate as to how many nerves there actually are, and how they should be grouped. [7] For example, there is reason to consider both the olfactory (I) and optic (II) nerves to be brain tracts, rather than cranial nerves. [7]


After obtaining her Ph.D. in Human Anatomy at the University of Kentucky in 1979, Rose Leigh Vines accepted a faculty position in the Department of Biological Sciences at the California State University, Sacramento. Dr. Vines has been instrumental in the evolution and expansion of the anatomy curriculum in her department by developing new courses and implementing multimedia in the classroom. She has also created new teaching tools, including a series of instructional videotapes. Dr. Vines is respected and admired by students and colleagues alike. In 1995, she received the peer-nominated Outstanding Teacher Award from the School of Arts and Sciences, California State University, Sacramento.

University Media Services (UMS) provides multi-media based information technology resources to support the teaching/learning, research, service and outreach missions of the California State University, Sacramento. The UMS integrated service philosophy combines state-of-the-art hardware and software, production, origination and transmission environments with the talents of a staff of technical and creative professionals dedicated to the development and implementation of appropriate applications of media/information technologies.

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Chapter 14 The Brain and Cranial Nerves

Make certain that you can define, and use in context, each of the terms listed below, and that you understand the significance of each of the concepts.

  1. Identify the principal parts of the brain, and describe how the brain is protected.
    1. neural tube
    2. primary brain vesicles
    3. secondary brain vesicles
    4. principal parts of the brain
      1. brain stem
      2. cerebellum
      3. diencephalon
      4. cerebrum
      1. cranial meninges (singular is meninx)
      2. dura mater
      3. arachnoid mater
      4. pia mater
      1. cerebrospinal fluid (CSF)
        1. subarachnoid space
        2. ventricle
          1. lateral ventricles (2)
          2. septum pellucidum
          3. third ventricle
          4. fourth ventricle
          1. interventricular foramina
          2. aqueduct of the midbrain
          3. median aperture
          4. lateral apertures
          5. arachnoid villi
          1. brain stem
            1. medulla oblongata
            2. pyramids
            3. decussation of pyramids
            4. cardiovascular center
            5. medullary respiratory center
            6. pons
            7. pontine respiratory group
            8. midbrain or mesencephalon
            9. cerebral peduncles
            10. reticular formation
            11. reticular activating system (RAS)
            1. transverse fissure
            2. vermis
            3. cerebellar hemispheres
            4. cerebellar cortex
            5. folia
            6. arbor vitae
            7. cerebellar peduncles (superior, middle and inferior)
            1. thalamus
            2. hypothalamus and functions
            3. epithalamus
              1. pineal gland
              2. melatonin
              1. cerebrum
              2. cerebral cortex
              3. gyrus or convolution (plural is gyri)
              4. fissure
              5. sulcus (plural is sulci)
              6. longitudinal fissure
              7. cerebral hemispheres
              8. corpus callosum
              1. central sulcus
              2. frontal lobe
              3. parietal lobe
              4. precentral gyrus
              5. postcentral gyrus
              6. lateral cerebral sulcus
              7. temporal lobe
              8. parieto occipital sulcus
              9. occipital lobe
              10. insula
              11. cerebral white matter
                1. association tracts
                2. commissural tracts
                3. projection tracts
                1. basal ganglia
                2. limbic system
                1. functional organization of the cerebral cortex
                  1. sensory areas
                  2. primary somatosensory area
                    1. primary visual area
                    2. primary auditory area
                    3. primary gustatory area
                    4. primary olfactory area
                    1. primary motor area
                    2. Broca&rsquos speech area

                    Note: Learn the summary of the functions of the principal parts of the brain, Table 14.2.

                    1. hemispheric lateralization
                    1. brain waves
                    2. electroencephalogram or EEG
                      1. alpha waves
                      2. beta waves
                      3. theta waves
                      4. delta waves
                      1. cranial nerves
                        1. special sensory nerves
                        2. motor nerves
                        3. mixed nerves

                        Note: There are 12 pairs of cranial nerves (originating from the brain) in the PNS. Their names indicate their distribution or function. The table below provides a brief summary of the numbers, names and major functions of the cranial nerves.

                        Although they are not described in your e-textbook, scientists have recently confirmed the presence of a 13th pair of cranial nerves in the human body. This pair is currently numbered &ldquozero&rdquo because it is located anterior to the olfactory (first) nerves. These nerves innervate a newly discovered pair of sensory organs called the vomeronasal organs, located in the anterior nasal cavity. The function of the human vomeronasal organs is not yet known however, there is some evidence that they might detect pheromones, chemical signals passed subconsciously from one individual to another. In other animals, pheromones are known to have effects on reproductive and social behaviours.


                        Definition

                        Cranial Nerves: Cranial nerves are the nerves that arise directly from the brain and pass through separate apertures in the skull.

                        Spinal Nerves: Spinal nerves are a series of paired nerves that originate from the nerve roots of the spinal cord on both sides.

                        Number of Pairs

                        Cranial Nerves: Cranial nerves comprise 12 nerve pairs.

                        Spinal Nerves: Spinal nerves comprise 31 nerve pairs.

                        Numbering

                        Cranial Nerves: Cranial nerves are numbered I to XII.

                        Spinal Nerves: Spinal nerves are classified into five groups as 8 cervical nerve pairs, 12 thoracic nerve pairs, 5 lumber nerve pairs, 5 sacral nerve pair, and one pair of coccygeal nerve pair.

                        Distribution

                        Cranial Nerves: Cranial nerves are distributed in head, neck and facial regions.

                        Spinal Nerves: Spinal nerves are distributed in the skin, sweat glands, mucosa, blood vessels, joints, and skeletal muscles.

                        Structure

                        Cranial Nerves: Cranial nerves may contain sensory/motor/mixed neurons.

                        Spinal Nerves: All spinal nerves are composed of both sensory and motor neurons.

                        Function

                        Cranial Nerves: Cranial nerves are involved in vision, sense of the smell, hearing, sense of taste, and eye movements.

                        Spinal Nerves: Spinal nerves are involved in movement, sensation, and sweat secretion.

                        Dorsal and Ventral Roots

                        Cranial Nerves: Cranial nerves form dorsal and ventral roots.

                        Spinal Nerves: Spinal nerves do not form dorsal and ventral roots.

                        Conclusion

                        Cranial and spinal nerves are the two components of the peripheral nervous system. Both types of nerves are involved in connecting the internal organs and muscles to the central nervous system to coordinate the functions of the body. Cranial nerves arise from the brain and are distributed in the brain, neck, and facial areas. In contrast, spinal nerves arise from the spinal cord and are distributed in the rest of the body. Therefore, the main difference between cranial and spinal nerves is in their paths.

                        Reference:

                        1. “Summary of the Cranial Nerves.” TeachMeAnatomy. N.p., 18 July 2017. Web. Available here. 25 July 2017.
                        2. “Spinal Nerves.” HealthPagesorg Anatomy Surgery Pregnancy Nutrition Fitness. N.p., n.d. Web. Available here. 25 July 2017.

                        Image Courtesy:

                        1. � Spinal Nerve Plexuses” By OpenStax – (CC BY 4.0) via Commons Wikimedia
                        2. “Brain human normal inferior view with labels en-2 By Brain_human_normal_inferior_view_with_labels_en.svg: *Brain_human_normal_inferior_view.svg: Patrick J. Lynch, medical illustratorderivative work: Beaoderivative work: Dwstultz (talk) – Brain_human_normal_inferior_view_with_labels_en.svg (CC BY 2.5) via Commons Wikimedia

                        About the Author: Lakna

                        Lakna, a graduate in Molecular Biology & Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things


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