Difference between revisions of "Cranial Nerves - Anatomy & Physiology"
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− | + | [[Image:brainstemcranialnervespyramids.jpg|thumb|right|150px|The brainstem, cranial nerves and pyramids. © BioMed Archive.]] | |
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==Introduction== | ==Introduction== | ||
− | Cranial nerves are those nerves which arise from the brain and | + | Cranial nerves are those nerves which arise from the brain and brain stem rather than the spinal cord. Nerves arising from the spinal cord are the [[PNS Structure - Anatomy & Physiology|peripheral nerves]]. There are 12 pairs of cranial nerves and these pairs of nerves passage through foramina in the skull, either individually or in groups. Cranial nerves are traditionally referred to by Roman numerals and these numerals begin cranially and run caudally. |
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− | The most cranial nerve is the '''Olfactory nerve (I)''' which runs from the nasal cavity through to the olfactory bulb. The next most cranial is the '''Optic nerve (II)''' which runs from the eyes to the | + | The most cranial nerve is the '''Olfactory nerve (I)''' which runs from the nasal cavity through to the olfactory bulb. The next most cranial is the '''Optic nerve (II)''' which runs from the eyes to the thalamus. Cranial nerves III to XII all exit from the brain stem and innervate the head, neck and organs in the thorax and abdomen. In order of most cranial to caudal, these include the '''Oculomotor nerve (III)''', the '''Trochlear nerve (IV)''', the '''Trigeminal nerve (V)''', the '''Abducens nerve (VI)''', the '''Facial nerve (VII)''', the '''Vestibulocochlear nerve (VIII)''', the '''Glossopharyngeal nerve (IX)''', the '''Vagus nerve (X)''', the '''Accessory nerve (XI)''' and the '''Hypoglossal nerve (XII)'''. |
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Many of the cranial nerves with nuclei within the brain stem contain sensory and motor neurone components. The sensory fibre components have their cell bodies located in ganglia outside the central nervous system and the motor fibre element have their cell bodies within the central nervous system. | Many of the cranial nerves with nuclei within the brain stem contain sensory and motor neurone components. The sensory fibre components have their cell bodies located in ganglia outside the central nervous system and the motor fibre element have their cell bodies within the central nervous system. | ||
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==Cranial Nerves== | ==Cranial Nerves== | ||
− | There are three main groups of cranial nerves; special senses, innervation of the head muscles and innervation of structures originating from | + | There are three main groups of cranial nerves; special senses, innervation of the head muscles and innervation of structures originating from brancial arches. The special senses cranial nerves include the olfactory, ocular and vestibulocochlear. Cranial nerves related to the innervation of the head muscles include the oculomotor, trochlear, abducens and the hypoglossal nerves. Cranial nerves related to innervation of structures originating from branchial arches includes the trigeminal, facial, glossopharyngeal, vagus and accessory nerves. |
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===Olfactory Nerve (I)=== | ===Olfactory Nerve (I)=== | ||
− | Olfaction is part of the special senses cranial nerve group and represents the chemical senses of olfaction (smell) and gustation (taste). When chemical substances interact with our bodies they stimulate special sensory cells which in turn generate an action potential. The resultant impulse is sent to the brain via sensory afferent fibres and it is these fibres that represent the olfactory cranial nerve. Note: an action potential is only generated where a special sensory cell for that particular chemical substance exists. | + | Olfaction is part of the special senses cranial nerve group and represents the chemical senses of olfaction (smell) and gustation (taste). When chemical substances interact with our bodies they stimulate special sensory cells which in turn generate an action potential. The resultant impulse is sent to the brain via sensory afferent fibres and it is these fibres that represent the olfactory cranial nerve. Note: an action potential is only generated where a special sensory cell for that particular chemical substance exists. The special sensory cells are found within the olfactory mucous membrane in the nasal fundus and the olfactory neurosensory cells are found within the olfactory epithelium. The olfactory epithelium contains cilia on the surface of the cells to increase the surface area for chemical interactions. |
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− | The olfactory nerve runs to the olfactory bulb which is found within the [[ | + | The olfactory nerve runs to the olfactory bulb which is found within the [[Forebrain_-_Anatomy_%26_Physiology#Olfactory_Bulb|telencephalon]]. The olfactory nerve is a sensory nerve and is composed of many '''Special Visceral Afferent''' fibres. The fibres are formed into bundles that are referred to as 'Olfactory filaments'. The olfactory nerve passes through the '''Cribiform plate''' and is surrounded by meningeal sheets including the sub-arachnoid space. Therefore the route of the olfactory nerve represents a potential site for an infection to track towards the brain. Injury of this nerve can lead to 'anosmia', or loss of smell. |
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− | The olfactory organ in dogs is extremely well developed and species such as | + | The olfactory organ in dogs is extremely well developed and species such as dogs use olfaction to orientate themselves in an environment in a way that humans do not. Olfactory cells are continuously replaced and are only viable sensory cells for between 30 - 60 days. This point is of importance as this is the only area in which nerve cells are able to be replaced or regenerated in adult animals and this area is now under research at Cambridge University for the treatment of damaged nerves and/or nerve disorders in nerves other than those involved in olfaction. |
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===Optic Nerve (II)=== | ===Optic Nerve (II)=== | ||
− | The optic nerve is part of the special senses cranial nerves and represents the connection between the receptor cells of the [[ | + | The optic nerve is part of the special senses cranial nerves and represents the connection between the receptor cells of the [[Eye_-_Anatomy_%26_Physiology#The_Wall_.28retina.2C_uvea_and_sclera.29|retina]] and the diencephalon. The optic nerve is a sensory nerve and is composed of '''Special Somatic Afferent fibres'''. The optic nerve passes through the '''optic chiasm''' which is an area of the ventral brain where both optic nerves run in a medial direction and eventually decussate. The optic nerve runs through the '''optic canal'''. |
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− | The optic nerve can be examined clinically via a | + | The optic nerve can be examined clinically via a menace response and anopsia (loss of vision) can be seen in injury. |
===Oculomotor nerve (III)=== | ===Oculomotor nerve (III)=== | ||
− | The oculomotor nerve is part of the group of cranial nerves responsible for innervating the | + | The oculomotor nerve is part of the group of cranial nerves responsible for innervating the muscles of the head. The nerves originate from the ventral [[Midbrain_-_Anatomy_%26_Physiology|midbrain]] and is a motor nerve. It is composed of '''general somatic efferent fibres''' and '''general visceral efferent fibres'''. The general somatic efferent fibres of the oculomotor nerve are responsible for the motor function of four of the six external muscles of the eyeball; the 'dorsal rectus', 'medial rectus', 'ventral rectus', 'ventral oblique' and 'levator of the upper eyelid'. The general visceral efferent fibres of the oculomotor nerve are responsible for the control of pupil diameter and therefore control the 'spincter pupillae' muscle and the 'ciliaris' muscle. |
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− | The oculomotor nerve has a pre-ganglionic nucleus in the midbrain and the nerve passes through the | + | The oculomotor nerve has a pre-ganglionic nucleus in the midbrain and the nerve passes through the '''orbital fissure''', along with the trochlear, abducens and opthalmic branch (V1) of the trigeminal nerve. It synapses in the ciliary ganglion of the eye. During a clinical examination, horizontal eye movements (strabismus) or an abscent pupillary light reflex (PLR) may indicate a problem. |
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===Trochlear nerve (IV)=== | ===Trochlear nerve (IV)=== | ||
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===Vestibulocochlear nerve (VIII)=== | ===Vestibulocochlear nerve (VIII)=== | ||
− | The vestibulocochlear nerve is part of the special senses group of cranial nerves and is made up of two components; the vestibular nerve and the cochlear nerve. The vestibular nerve is responsible for balance whilst the cochlear nerve is responsible for hearing. The nerves send impulses from the inner ear which contains the [[ | + | The vestibulocochlear nerve is part of the special senses group of cranial nerves and is made up of two components; the vestibular nerve and the cochlear nerve. The vestibular nerve is responsible for balance whilst the cochlear nerve is responsible for hearing. The nerves send impulses from the inner ear which contains the [[Ear_-_Anatomy_%26_Physiology#Vestibular_Receptors_and_Balance|vestibular apparatus]] and [[Ear_-_Anatomy_%26_Physiology#The_Cochlea|cochlear]]. The vestibulocochlear nerve is a sensory nerve made up of '''special somatic afferent fibres'''. It passes through the '''internal acoustic meatus''' and into the '''petrosal bone'''. The facial nerve also takes this route. |
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− | + | Clinical problems with the vestibulocochlear nerve would be indicated on examination by changes in hearing and/or horizontal and verticle eye movements (strabismus and nystagmus). A head tilt is also associated with this nerve. | |
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− | + | ==Cranial Nerve Location and Routes== | |
− | + | A summary of the cranial nerves is shown below: | |
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{| style="width:100%; height:200px" border="1" | {| style="width:100%; height:200px" border="1" | ||
Line 189: | Line 54: | ||
| Olfactory bulb | | Olfactory bulb | ||
| Cribriform plate | | Cribriform plate | ||
− | | | + | | SVS |
| Olfactory epithelium | | Olfactory epithelium | ||
| Olfactory epithelium | | Olfactory epithelium | ||
Line 195: | Line 60: | ||
| '''II - Optic''' | | '''II - Optic''' | ||
− | | | + | | Optic chiasma |
| Optic canal | | Optic canal | ||
− | | | + | | SSS |
| Retina | | Retina | ||
| Retina | | Retina | ||
|- | |- | ||
− | | '''III - | + | | '''III - Occulomotor''' |
| Midbrain | | Midbrain | ||
− | | Orbital fissure | + | | Orbital fissure and Round Foramen |
− | | | + | | GSM + GVM |
− | | | + | | Nuculi III |
− | + | parasympathetic nuculi III | |
| Extraoccular mm. | | Extraoccular mm. | ||
− | Constrictor | + | Constrictor pupulli |
|- | |- | ||
| '''IV - Trochlear''' | | '''IV - Trochlear''' | ||
| Midbrain (dorsal) | | Midbrain (dorsal) | ||
− | | | + | | Round Foramen |
− | | | + | | GSM |
− | | | + | | Nuc IV |
| Dorsal oblique mm. | | Dorsal oblique mm. | ||
|- | |- | ||
Line 223: | Line 88: | ||
| Pons | | Pons | ||
| V1 - Orbital fissure | | V1 - Orbital fissure | ||
− | V2 - Round Foramen | + | V2 - Round Foramen and Orbital Fissure |
V3 - Oval Foramen | V3 - Oval Foramen | ||
− | | V1 - | + | | V1 - GSS |
− | V2 - | + | V2 - GSS |
− | V3 - | + | V3 - SVM |
− | | V1 - Trigeminal gangion | + | | V1 - Trigeminal gangion |
− | V2 - Trigeminal ganglion | + | V2 - Trigeminal ganglion |
− | V3 - | + | V3 - Nuculi V |
| V1 - Eye region | | V1 - Eye region | ||
V2 - Upper jaw inc. teeth | V2 - Upper jaw inc. teeth | ||
− | V3 - mm. of arch 1 | + | V3 - mm. of arch 1 |
|- | |- | ||
Line 243: | Line 108: | ||
| Medulla oblongata | | Medulla oblongata | ||
| Orbital fissure | | Orbital fissure | ||
− | | | + | | GSM |
− | | | + | | Nuc IV |
| Lateral rectus and retractor bulbi mm. | | Lateral rectus and retractor bulbi mm. | ||
|- | |- | ||
Line 251: | Line 116: | ||
| '''VII - Facial''' | | '''VII - Facial''' | ||
| Medulla oblongata | | Medulla oblongata | ||
− | | | + | | Stylomastoid foramen |
− | | | + | | SVM + GVM + SVS |
− | | | + | | Nuc III |
− | + | (Taste - gleniailate ganglion) | |
| mm. of arch 2 | | mm. of arch 2 | ||
Submaxillary and sublingual glands | Submaxillary and sublingual glands | ||
− | Rostral 2/3 | + | Rostral 2/3 taste |
|- | |- | ||
Line 264: | Line 129: | ||
| '''VIII - Vestibulocochlear''' | | '''VIII - Vestibulocochlear''' | ||
| Medulla oblongata | | Medulla oblongata | ||
− | | | + | | Inner accoustic meatus |
− | | | + | | SSS |
− | | Vestibular | + | | Vestibular ganglion |
| Maculae and cristae | | Maculae and cristae | ||
|- | |- | ||
Line 273: | Line 138: | ||
| '''IX - Glossopharyngeal''' | | '''IX - Glossopharyngeal''' | ||
| Medulla oblongata | | Medulla oblongata | ||
− | | Jugular foramen | + | | Jugular foramen |
− | | | + | | G/S V M/S |
− | | | + | | Ganglia IX - SVM |
− | + | Nuculi ambiguous - mm. arch 3 | |
| Carotid gland | | Carotid gland | ||
− | Caudal 1/3 | + | Caudal 1/3 taste |
mm. of arch 3 | mm. of arch 3 | ||
Line 287: | Line 152: | ||
| '''X - Vagus''' | | '''X - Vagus''' | ||
| Medulla oblongata | | Medulla oblongata | ||
− | | Jugular foramen | + | | Jugular foramen |
− | | | + | | GVM + SUM + GVS + GSS |
− | | | + | | Ganglion X - (amongst others) |
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| Thoracic and abdominal organs | | Thoracic and abdominal organs | ||
mm. of arches 4-6 | mm. of arches 4-6 | ||
Line 300: | Line 164: | ||
| '''XI - Accessory''' | | '''XI - Accessory''' | ||
| Medulla oblongata | | Medulla oblongata | ||
− | | Jugular foramen | + | | Jugular foramen |
− | | | + | | GSM |
− | | | + | | Cervical spinal cord |
| Trapezius m. etc | | Trapezius m. etc | ||
|- | |- | ||
Line 310: | Line 174: | ||
| Medulla oblongata | | Medulla oblongata | ||
| Hypoglossal canal | | Hypoglossal canal | ||
− | | | + | | GSM |
− | | | + | | Medulla nuculi XII |
| Tongue mm. | | Tongue mm. | ||
|- | |- | ||
+ | | | ||
|} | |} | ||
− | ===Cranial | + | ==Cranial Nerve Fibre Types== |
− | + | ||
+ | Cranial nerves are best explained by function: | ||
+ | |||
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+ | *'''General Somatic Motor (GSM)''' | ||
+ | |||
+ | Motor cortex —→ Motor nuculi —→ Muscle | ||
+ | |||
+ | |||
+ | *'''General Visceral Motor (GVM)''' | ||
+ | |||
+ | Brainstem —→ Parasympathetic nuculi —→ Parasympathetic ganglion —→ Gland etc | ||
+ | |||
+ | |||
+ | *'''"Branchial motor" - Special Visceral Motor (SVM)''' | ||
+ | |||
+ | Motor cortex —→ Motor nuculi —→ Muscle | ||
+ | |||
+ | |||
+ | *'''General Somatic Sensory (GSS) and General Visceral Sensory (GVS)''' | ||
+ | |||
+ | Sensory cortex —→ Thalamus —→ Trigeminal nuculi —→ Trigeminal ganglion —→ Skin etc | ||
+ | |||
+ | |||
+ | ===Special sensory fibres (SSS + SVS):=== | ||
+ | |||
+ | '''[[Nose - Anatomy & Physiology|Smell]]''' '''SVS''' | ||
+ | |||
+ | Priform cortex —→ Olfactory tubercle —→ Olfactory Bulb —→ '''SMELL''' | ||
+ | |||
+ | |||
+ | '''[[Eye - Anatomy & Physiology|Vision]]''' '''SSS''' | ||
+ | |||
+ | Occipital cortex —→ Thalamus MGN —→ Rostral colliculus/Retinal ganglion cell —→ Bipolar cell —→ '''VISION''' | ||
+ | |||
+ | |||
+ | '''[[Ear - Anatomy & Physiology|Hearing/Balance]]''' '''SSS''' | ||
+ | |||
+ | Temporal cortex —→ Thalamus MGN —→ Caudal colliculus and hindbrain —→ Spiral ganglion —→ '''HEARING''' | ||
+ | |||
+ | |||
+ | '''[[Gustatory System - Anatomy & Physiology|Taste]]''' '''SVS''' | ||
+ | |||
+ | Sensory cortex —→ Thalamus —→ Hindbrain (VII, IX, X) —→ Ganglion —→ '''TASTE''' | ||
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+ | ==Cranial Nerves and their Functions== | ||
{| border="1" cellpadding="7" | {| border="1" cellpadding="7" | ||
|-style="background:#B0E0E6; color:black" | |-style="background:#B0E0E6; color:black" | ||
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− | + | {{unfinished}} | |
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[[Category:Nervous System - Anatomy & Physiology]] | [[Category:Nervous System - Anatomy & Physiology]] | ||
− | [[Category:A&P | + | [[Category:To Do - A&P]] |
Revision as of 10:55, 11 August 2011
Introduction
Cranial nerves are those nerves which arise from the brain and brain stem rather than the spinal cord. Nerves arising from the spinal cord are the peripheral nerves. There are 12 pairs of cranial nerves and these pairs of nerves passage through foramina in the skull, either individually or in groups. Cranial nerves are traditionally referred to by Roman numerals and these numerals begin cranially and run caudally.
The most cranial nerve is the Olfactory nerve (I) which runs from the nasal cavity through to the olfactory bulb. The next most cranial is the Optic nerve (II) which runs from the eyes to the thalamus. Cranial nerves III to XII all exit from the brain stem and innervate the head, neck and organs in the thorax and abdomen. In order of most cranial to caudal, these include the Oculomotor nerve (III), the Trochlear nerve (IV), the Trigeminal nerve (V), the Abducens nerve (VI), the Facial nerve (VII), the Vestibulocochlear nerve (VIII), the Glossopharyngeal nerve (IX), the Vagus nerve (X), the Accessory nerve (XI) and the Hypoglossal nerve (XII).
Many of the cranial nerves with nuclei within the brain stem contain sensory and motor neurone components. The sensory fibre components have their cell bodies located in ganglia outside the central nervous system and the motor fibre element have their cell bodies within the central nervous system.
Cranial Nerves
There are three main groups of cranial nerves; special senses, innervation of the head muscles and innervation of structures originating from brancial arches. The special senses cranial nerves include the olfactory, ocular and vestibulocochlear. Cranial nerves related to the innervation of the head muscles include the oculomotor, trochlear, abducens and the hypoglossal nerves. Cranial nerves related to innervation of structures originating from branchial arches includes the trigeminal, facial, glossopharyngeal, vagus and accessory nerves.
Olfactory Nerve (I)
Olfaction is part of the special senses cranial nerve group and represents the chemical senses of olfaction (smell) and gustation (taste). When chemical substances interact with our bodies they stimulate special sensory cells which in turn generate an action potential. The resultant impulse is sent to the brain via sensory afferent fibres and it is these fibres that represent the olfactory cranial nerve. Note: an action potential is only generated where a special sensory cell for that particular chemical substance exists. The special sensory cells are found within the olfactory mucous membrane in the nasal fundus and the olfactory neurosensory cells are found within the olfactory epithelium. The olfactory epithelium contains cilia on the surface of the cells to increase the surface area for chemical interactions.
The olfactory nerve runs to the olfactory bulb which is found within the telencephalon. The olfactory nerve is a sensory nerve and is composed of many Special Visceral Afferent fibres. The fibres are formed into bundles that are referred to as 'Olfactory filaments'. The olfactory nerve passes through the Cribiform plate and is surrounded by meningeal sheets including the sub-arachnoid space. Therefore the route of the olfactory nerve represents a potential site for an infection to track towards the brain. Injury of this nerve can lead to 'anosmia', or loss of smell.
The olfactory organ in dogs is extremely well developed and species such as dogs use olfaction to orientate themselves in an environment in a way that humans do not. Olfactory cells are continuously replaced and are only viable sensory cells for between 30 - 60 days. This point is of importance as this is the only area in which nerve cells are able to be replaced or regenerated in adult animals and this area is now under research at Cambridge University for the treatment of damaged nerves and/or nerve disorders in nerves other than those involved in olfaction.
Optic Nerve (II)
The optic nerve is part of the special senses cranial nerves and represents the connection between the receptor cells of the retina and the diencephalon. The optic nerve is a sensory nerve and is composed of Special Somatic Afferent fibres. The optic nerve passes through the optic chiasm which is an area of the ventral brain where both optic nerves run in a medial direction and eventually decussate. The optic nerve runs through the optic canal.
The optic nerve can be examined clinically via a menace response and anopsia (loss of vision) can be seen in injury.
Oculomotor nerve (III)
The oculomotor nerve is part of the group of cranial nerves responsible for innervating the muscles of the head. The nerves originate from the ventral midbrain and is a motor nerve. It is composed of general somatic efferent fibres and general visceral efferent fibres. The general somatic efferent fibres of the oculomotor nerve are responsible for the motor function of four of the six external muscles of the eyeball; the 'dorsal rectus', 'medial rectus', 'ventral rectus', 'ventral oblique' and 'levator of the upper eyelid'. The general visceral efferent fibres of the oculomotor nerve are responsible for the control of pupil diameter and therefore control the 'spincter pupillae' muscle and the 'ciliaris' muscle.
The oculomotor nerve has a pre-ganglionic nucleus in the midbrain and the nerve passes through the orbital fissure, along with the trochlear, abducens and opthalmic branch (V1) of the trigeminal nerve. It synapses in the ciliary ganglion of the eye. During a clinical examination, horizontal eye movements (strabismus) or an abscent pupillary light reflex (PLR) may indicate a problem.
Trochlear nerve (IV)
Vestibulocochlear nerve (VIII)
The vestibulocochlear nerve is part of the special senses group of cranial nerves and is made up of two components; the vestibular nerve and the cochlear nerve. The vestibular nerve is responsible for balance whilst the cochlear nerve is responsible for hearing. The nerves send impulses from the inner ear which contains the vestibular apparatus and cochlear. The vestibulocochlear nerve is a sensory nerve made up of special somatic afferent fibres. It passes through the internal acoustic meatus and into the petrosal bone. The facial nerve also takes this route.
Clinical problems with the vestibulocochlear nerve would be indicated on examination by changes in hearing and/or horizontal and verticle eye movements (strabismus and nystagmus). A head tilt is also associated with this nerve.
Cranial Nerve Location and Routes
A summary of the cranial nerves is shown below:
Nerve | Attatchment to brain | Exit Foramen | Fibre Type | Location of cell bodies | Distribution |
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I - Olfactory | Olfactory bulb | Cribriform plate | SVS | Olfactory epithelium | Olfactory epithelium |
II - Optic | Optic chiasma | Optic canal | SSS | Retina | Retina |
III - Occulomotor | Midbrain | Orbital fissure and Round Foramen | GSM + GVM | Nuculi III
parasympathetic nuculi III |
Extraoccular mm.
Constrictor pupulli |
IV - Trochlear | Midbrain (dorsal) | Round Foramen | GSM | Nuc IV | Dorsal oblique mm. |
V - Trigeminal | Pons | V1 - Orbital fissure
V2 - Round Foramen and Orbital Fissure V3 - Oval Foramen |
V1 - GSS
V2 - GSS V3 - SVM |
V1 - Trigeminal gangion
V2 - Trigeminal ganglion V3 - Nuculi V |
V1 - Eye region
V2 - Upper jaw inc. teeth V3 - mm. of arch 1 |
VI - Abducens | Medulla oblongata | Orbital fissure | GSM | Nuc IV | Lateral rectus and retractor bulbi mm. |
VII - Facial | Medulla oblongata | Stylomastoid foramen | SVM + GVM + SVS | Nuc III
(Taste - gleniailate ganglion) |
mm. of arch 2
Submaxillary and sublingual glands Rostral 2/3 taste |
VIII - Vestibulocochlear | Medulla oblongata | Inner accoustic meatus | SSS | Vestibular ganglion | Maculae and cristae |
IX - Glossopharyngeal | Medulla oblongata | Jugular foramen | G/S V M/S | Ganglia IX - SVM
Nuculi ambiguous - mm. arch 3 |
Carotid gland
Caudal 1/3 taste mm. of arch 3 Carotid body |
X - Vagus | Medulla oblongata | Jugular foramen | GVM + SUM + GVS + GSS | Ganglion X - (amongst others) | Thoracic and abdominal organs
mm. of arches 4-6 Pharynx and larynx External ear |
XI - Accessory | Medulla oblongata | Jugular foramen | GSM | Cervical spinal cord | Trapezius m. etc |
XII - Hypoglossal | Medulla oblongata | Hypoglossal canal | GSM | Medulla nuculi XII | Tongue mm. |
Cranial Nerve Fibre Types
Cranial nerves are best explained by function:
- General Somatic Motor (GSM)
Motor cortex —→ Motor nuculi —→ Muscle
- General Visceral Motor (GVM)
Brainstem —→ Parasympathetic nuculi —→ Parasympathetic ganglion —→ Gland etc
- "Branchial motor" - Special Visceral Motor (SVM)
Motor cortex —→ Motor nuculi —→ Muscle
- General Somatic Sensory (GSS) and General Visceral Sensory (GVS)
Sensory cortex —→ Thalamus —→ Trigeminal nuculi —→ Trigeminal ganglion —→ Skin etc
Special sensory fibres (SSS + SVS):
Smell SVS
Priform cortex —→ Olfactory tubercle —→ Olfactory Bulb —→ SMELL
Vision SSS
Occipital cortex —→ Thalamus MGN —→ Rostral colliculus/Retinal ganglion cell —→ Bipolar cell —→ VISION
Hearing/Balance SSS
Temporal cortex —→ Thalamus MGN —→ Caudal colliculus and hindbrain —→ Spiral ganglion —→ HEARING
Taste SVS
Sensory cortex —→ Thalamus —→ Hindbrain (VII, IX, X) —→ Ganglion —→ TASTE
Cranial Nerves and their Functions
# | Name | Nuclei | Function |
---|---|---|---|
I | Olfactory nerve | Anterior olfactory nucleus | Transmits the sense of smell |
II | Optic nerve | Lateral geniculate nucleus | Transmits visual information to the brain |
III | Oculomotor nerve | Oculomotor nucleus, Edinger-Westphal nucleus | Innervates the dorsal rectus, medial rectus, ventral rectus, and ventral oblique, which collectively perform most eye movements |
IV | Trochlear nerve | Trochlear nucleus | Innervates the superior oblique muscle, which depresses, pulls laterally, and intorts the eyeball |
V | Trigeminal nerve | Principal sensory trigeminal nucleus, Spinal trigeminal nucleus, Mesencephalic trigeminal nucleus, Trigeminal motor nucleus | Receives sensation from the face and innervates the muscles of mastication |
VI | Abducens nerve | Abducens nucleus | Innervates the lateral rectus, which abducts the eye and the retractor bulbi which forces the third eyelid across the surface of the cornea as a protective mechanism. |
VII | Facial nerve | Facial nucleus, Solitary nucleus, Superior salivary nucleus | Provides motor innervation to the muscles of facial expression and stapedius, receives the special sense of taste from the anterior 2/3 of the tongue, and provides secretomotor innervation to the salivary glands (except parotid) and the lacrimal gland |
VIII | Vestibulocochlear nerve | Vestibular nuclei, Cochlear nuclei | Senses sound, rotation and gravity (essential for balance & movement) |
IX | Glossopharyngeal nerve | Nucleus ambiguus, Inferior salivary nucleus, Solitary nucleus | Receives taste from the posterior 1/3 of the tongue, provides secretomotor innervation to the parotid gland, and provides motor innervation to the stylopharyngeus |
X | Vagus nerve | Nucleus ambiguus, Dorsal motor vagal nucleus, Solitary nucleus | Supplies branchiomotor innervation to most laryngeal and pharyngeal muscles; provides parasympathetic fibers to nearly all thoracic and abdominal viscera down to the splenic flexure; and receives the special sense of taste from the epiglottis |
XI | Accessory nerve | Nucleus ambiguus, Spinal accessory nucleus | Controls muscles of the neck and overlaps with functions of the vagus |
XII | Hypoglossal nerve | Hypoglossal nucleus | Provides motor innervation to the intrinsic muscles of the tongue and other glossal muscles |
This article is still under construction. |