Sensory Organs Flashcards
What does the term olfaction refer to?
Olfaction = sense of smell
What does the olfactory organ consist of?
The olfactory mucosa in the dorsacaudal nasal cavity
What type of epithelium covers the conchae?
Pseudostratified columnar epithelium
What is the benefit of turbinate bones in terms of olfaction?
Air coming through the nostrils can be redirected using turbinate bones to ensure it reaches the olfactory mucosa.
Where would you find the dendrites of olfactory neurones?
They reach into the epithelium of the nasal cavity and are present as cilia.
What do that axons of olfactory neurones pass through and what do they connect to?
Axons pass through the cribiform plate and connect directly to the olfactory bulb on the brain.
What is the function of olfactory (Bowman’s) glands that sit below the epithelium?
- They produce lipid rich mucus that binds to odorants
- Odorants are then able to dissolve to reach sensory receptors
- Also help to wash away odour to the nasopharynx and humidify epithelium.
What do olfactory cells synapse with in the olfactory bulb?
Synapse with mitral cells in the olfactory bulb.
Complete the sentence:
There are multiple… per mitral cell in a… of nerve endings
- Olfactory neurons
- Glomerulus
What do mitral cells link to?
One type of olfactory receptor
How does the brain distinguish odours?
Compares signal frequencies of different mitral cells.
Where is the vomeronasal organ?
It is embedded within the hard palate and opens into the incisive ducts.
It is a blind ending caudally.
What is the purpose of the incisive ducts that the vomeronasal organ opens into?
Connect the oral and nasal cavities through the hard palate.
(This oral opening is absent in horses)
What is the role of the vomeronasal organ?
It detects pheromones and thus has a role in reproductive and social behaviours (e.g., the Flehman reaction
Where are the sensory cells for taste located?
Within the tongue.
Which two cranial nerves innervate the sensory cells?
Cranial nerves 7 & 9
Which parts of the brain are linked to the gustatory inputs?
Cerebral cortex, brain stem + limbic stem.
What is the specific function of these 3 parts of the brain?
1) Cerebral cortex
2) Brain stem
3) Limbic system
1) Conscious perception of taste and smell
2) Helps with unconscious reflexes such as salivation and digestive juices
3) Emotional response
Which nerve carries information between the eye and the brain?
Optic nerve
What is the passageway of light through the eye?
Cornea -> Aqueous humour -> Lens -> Vitreous humour -> Retina
What are the 3 different layers of the eye?
Retina, vascular tunic, fibrous tunic
What is the function of the retina?
It is connected to the brain and converts light information to nerve signals.
What is the function of the vascular tunic?
Contains blood vessels as well as structures that hold the lens, regulate pupil size and produce fluid that fills the eyeball.
What is the function of the fibrous tunic?
A dense, tough collagen tissue which protects and holds the eyeball’s shape.
Extravascular muscles that move the eye attach here.
What does the retina develop from?
From the neural tube.
What are the 2 layers of the retina?
- Pigmented layer (prevents light scattering)
- Nervous layer (Contains photoreceptors and neurones)
What type of receptor cells are found in the eye and what do they contain?
- Rods contain rhodopsin (black and white vision)
- Cones contain photopsins (colour vision)
What structures does the outer ear consist of?
- Pina, auricular muscles, external auditory meatus (ends at the tympanic membrane)
What is the function of the outer ear?
To direct and transmit sound to the middle ear.
What structures are present within the middle ear?
- Ossicles (chains of 3 small bones called the hammer, anvil and stirrup)
- These bones transmit vibrations from the tympanic membrane to the inner ear.
Describe the structure of the inner ear.
- Membranous labyrinth filled with endolymph
- Surrounded by a bony labyrinth filled with perilymph.
What are the 2 main functions of the inner ear?
- Hearing (using the cochlear and cochlear duct)
- Balance (by the vestibular system)
What is unique about the equine auditory tube?
- Horses have outpouchings of the auditory tubes connecting the middle ear to the pharynx
- These guttural pouches re divided into medial and lateral compartments by the stylohyoid bone.
What are the 3 subsections of the cochlea?
Cochlea duct
Scala vestibuli
Scala tympani
What happens when the stapes vibrate in the oval window?
- It compresses the perilymph in the scala vestibuli
- This pressure wave then travels into the scala tympani
- This causes the basilar membrane to vibrate, moving the hair cells relative to the tectorial membrane.
How do impulses travel from the cochlea to the brain?
Along the vestibulocochlea nerve to the brain
What do the saccule and utricle help to detect
(Parts of the inner ear)
Linear accelerations.
There are 3 semi-circular canals within the inner ear that detect rotation, what are the 3 axis?
Pitch (head up and down)
Yaw (head left to right)
Roll (rotating head from side to side)
What do head rotations cause?
Cause endolymph current inside the canals, moving hair cells in the ampulla (expanded portion) of the canal.
The saccule and utricle are expansions of the membranous labyrinth that help to detect linear accelerations such as gravity and vertical movements. What do they contain?
They contain hair cells in thickened patches (maculae)
The hair cells are covered with a gel-like layer containing otolith crystals.
