Changes

==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 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.

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 include the trigeminal, facial, glossopharyngeal, vagus and accessory nerves.

===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. 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.

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. If no sensory cell exists, that chemical substance will go undetected. 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.

<br />

<br />

<br />

<br />

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.

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 [[Skull_and_Facial_Muscles_-_Anatomy_%26_Physiology#Ethmoid_Bone_.28os_ethmoidale.29|'''Cribiform plate''']] and is surrounded by meningeal sheets including the [[Meninges_-_Anatomy_%26_Physiology#Subarachnoid_Space|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.

<br />

<br />

<br />

<br />

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.

The olfactory organ in dogs is extremely well developed and species such as canines 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)===

===Optic Nerve (II)===

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'''.

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'''.