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Equine Special Senses - Horse Anatomy (view source)
Revision as of 12:12, 22 November 2012
, 12:12, 22 November 2012→Ear
The external ear receives sounds, which cause vibrations of the tympanic membrane. These vibrations move along the ossicles of the middle ear, to be transmitted to the inner ear. The stapes is connected to the oval window, so when the stapes transmits vibrations, this causes movement of '''perilymph''' that is in the inner ear. The movement of the perilymph is transmitted via the '''scala vestibuli''' and the '''scala tympani''', to the '''round window''', where it induces movement of the '''secondary tympanic membrane'''. This results in the movement of the '''endolymph''' of the '''cochlear duct''', causing pressure on the '''tectorial membrane''', which then induces pressure on the sensory hairs, stimulating the receptor cells within the cochlear duct to send impulses to the '''spiral ganglion'''. The axons of the spiral ganglion form part of the '''vestibulocochlear nerve'''.
The external ear receives sounds, which cause vibrations of the tympanic membrane. These vibrations move along the ossicles of the middle ear, to be transmitted to the inner ear. The stapes is connected to the oval window, so when the stapes transmits vibrations, this causes movement of '''perilymph''' that is in the inner ear. The movement of the perilymph is transmitted via the '''scala vestibuli''' and the '''scala tympani''', to the '''round window''', where it induces movement of the '''secondary tympanic membrane'''. This results in the movement of the '''endolymph''' of the '''cochlear duct''', causing pressure on the '''tectorial membrane''', which then induces pressure on the sensory hairs, stimulating the receptor cells within the cochlear duct to send impulses to the '''spiral ganglion'''. The axons of the spiral ganglion form part of the '''vestibulocochlear nerve'''.
===Central Auditory Pathways===
[[Image:Central Auditory Pathway.jpg|thumb|right|150px|Central Auditory Pathway - Copyright David Bainbridge]]
The signal that has been created from the sound waves that were picked up by the ear is carried to the brain by the '''vestibulocochlear nerve''' ([[Equine Cranial Nerves - Horse Anatomy#Vestibulocochlear Nerve (VII)|CN VIII]]), which synapses in the '''cochlear nucleus'''. From here, the auditory information is then split. Those nerve fibres that travel to the '''ventral cochlear nuclear cells''' synapse on their target cells. The ventral cochlear nuclear cells then project to a group of cells within the {Equine Brain - Horse Anatomy#Hindbrain|medulla]], called the '''superior olive nucleus'''. It is here that the timing and loudness of the sound that was picked up in each ear is compared, allowing determination of the direction that the sound came from. This information is then transferred via the '''lateral lemniscus''' to the '''inferior colliculus'''. The other nerve fibres start in the '''dorsal cochlear nucleus'''. It is here that the quality of sound is determined, as it compares the frequency differences. This pathway leads directly to the '''inferior colliculus''', via the '''lateral lemniscus'''. Both of these pathways are bilateral. This means that if there is a lesion at any point along the pathway, it usually has no effect on hearing. Deafness is only usually caused if there is damage to either the auditory nerve, the cochlea, or the middle ear. From the inferior colliculus, the information from both pathways is sent to the '''medial geniculate nucleus''' of the [[Equine Brain - Horse Anatomy#Forebrain|thalamus]], which then leads on to the primary auditory cortex of the [[Equine Brain - Horse Anatomy#Forebrain|cerebral cortex]].
==Gustatory System==
==Gustatory System==