MT2 Chap 15 - Special senses Flashcards
Function of Olfactory receptors
Stimulus – dendrites – specialized olfactory neuron
The function of receptors for the senses of
taste, vision, equilibrium, and hearing
Olfactory Pathway to the cerebellum
Olfactory organ – olfactory epithelium – olfactory bulb - – olfactory tract – olfactory cortex, hypothalamus
The olfactory epithelium consists of 3 kinds of cells
- olfactory receptors
- Supporting columnar epithelial cells
- Basal cells
Olfactory Receptors
-bipolar sensory neurons w/ cilia responds to odorant molecules
Supporting columnar epithelial cells
provide support & nourishment
Basal cells
stem cells that replace olfactory receptors (monthly)
Olfactory Apparatus can detect about
10,000 different odors, often in concentrations as low as 4 molecules
Olfaction process
Nerve impulses travel from olfactory neuron –> mitral cell neuron in olfactory bulb –> axons of olfactory tract –> Primary olfactory area in temporal lobe
Olfaction is the ___ sensory system that has direct cortical projections w/o first going through relay stations in the ____
only
thalamus
Olfactory sensory pathways are
rapidly adapting
Olfactory supporting cells and glands are innervated by the Facial (VII) nerve, a component of which provides parasympathetic motor innervation to lacrimal glands and the mucous membranes.
why certain odor will make our nose run or eyes tear up
Gustation: 5 primary tastes
sour, sweet, bitter, salty, umami
Umami is believed to arise from taste receptors that are stimulated by
monosodium glutamate (MSG)
Each taste bud is composed of about
50 gustatory receptor cells, then surrounded by a number of supporting cells
Basal cells
first to become supporting cells, then gustatory receptor cells inside the taste bud
Gustatory hair
a single, long microvillus projects from each receptor cell to the surface through the taste pore
Each gustatory receptor cell has a lifespan of about
10 days
Taste buds are found in 3 diff types of papillae
- Circumvallate papillae: form a row at the back of the tongue (100-300 taste buds in each)
- Fungiform papillae: scattered all over (5 taste buds in each)
- Foliate papillae: in small trenches on lateral margins of the tongue, most taste buds degenerate in early childhood
Filiform Papillae
- all over
- contains tactile receptors but NO taste buds
- increase friction btwn tongue and food,
Our visual perception is dependent on the
eye, its accessory structures, the optic tracts, and the 1 degree visual cortex and its association areas
Vision is possible bc of
photoreceptors that are able to catch photons of EM radiation (what we perceive as visual light)
Flow of tears
Lacrimal gland –> lacrimal ducts –> Superior or inferior lacrimal canal –> lacrimal sac –> nasolacrimal duct –> nasal cavity
Wall consists of 3 layers or tunics
- Fibrous tunic: outer layer, composed of sclera and cornea
- Vascular tunic: middle layer, composed of choroid, ciliary body, and iris
- Nervous tunic: inner retinal layer
Anterior Cavity
- Anterior chamber
- posterior chamber
- filled w/ aqueous humor
Posterior cavity
-contains the vitreous body
Giliary body consists of 2 parts
- ciliary processes - secrete aqueous humor
- ciliary muscle - changes shape of lens to adapt to near vision
Iris
coloured portion of eye
-has circular and radial smooth muscle fibres
Cornea
- superficial layer of epithelial cells
- multiple layers of collagen fibres
- transparent
- lacks blood vessels
Lens
- consists of concentric layers of cells
- filled with crystallins (transparent proteins)
Suspensory ligaments
resists tendency of lens the assume spherical shape
Ciliary body
-supports and controls its shape
Retina
-contains photoreceptors, pigments cells, supporting cells, neurons
Choroid blood vessels
directly or indirectly provide nutrients to all structures within eye
Sclera
-stabilizes shape of eye during movements
Aqueous humor
- maintains intraocular pressure (IOP)
- replaced every 90 min
- produced at giliary body
Aqueous humor flow
posterior chamber –> anterior chamber –> reabsorbed in scleral venous sinus –> returned to venous system
Vitreous body (humor)
- maintains intraocular pressure (IOP)
- ONLY formed during embryological development
- NOT replaced
- shrinkage of vitreous body may lead to detachment of retina
Normal image formation depends on
refraction of light waves, accommodation of lens, constriction of pupil, convergence of 2 eyes
Refraction
- process of bending light rays
- cornea aqueous humor and lens refracts light rays
Focal distance
determined by shape of lens and distance btwn lens and object
An increase in the curvature of the lens for near vision is called
accommodation
accommodation is made possible by
contracting ciliary muscle and relaxing suspensory ligaments
Exact centre of the retina is called the
Macula lutea
in centre of macula lutea is a small depression called
the central fovea (or fovea centralis)
there are no ___ in the fovea, only high concentration of ___
rods, cones
3 principle regions
- External
- middle
- internal
External includes
- Auricle (pinna)
- external auditory canal
Structures of middle ear
- ossicles: Malleus, Incus, Stapes
- Tensor tympani and stapedius muscle
- Tympanic membrane
structures of inner ear (labyrinth)
- cochlea
- vestibule
- semicircular canals
Labyrinth has 2 main divisions
-outer bony labyrinth that encloses an inner membranous labyrinth
bony labyrinth is sculpted out of the petrous part of the temporal bone and divided into 3 areas
- semicircular canals
- vestibule
- cochlea
vestibule consists of 2 sacs
-utricle and saccule
Order of cochlea
vestibular duct –> cochlear duct –> tympanic duct
Fluid in cochlea, ___ and ____ fills the 3 different internal channels ____, ____, and _____
perilymph and endolymph,
scala vestibuli, scala tympani, cochlear duct
Organ of Corti hair cells only have
sterocillia
Equilibrium is another function of the inner ear, its controlled by
vestibular apparatus
What equilibrium refers to a state of balance relative to the force of gravity?
Static Equilibrium - linear acceleration
What equilibrium involves the maintenance of balance during sudden movements?
Dynamic equilibrium - rotational acceleration
Static equilibrium is controlled by
sensory hairs within the macula of the:
- utricle – detects horizontal motion
- saccule – detects vertical motion
An otolithic membrane of static equilibrium is studded with dense
calcium carbonate crystals
Dynamic equilibrium is controlled by the
sensory hairs within the ampulla of the semicircular canals
within each ampulla is a small elevation called
crista or crest
each crista is covered in
cupula
Equilibrium pathway
-nerve impulse travel up the vestibular branch of CN VIII –> most axons synapse in medulla and pons (which also receive input from the eyes and proprioceptors) –> ascending neurons continue –> primary auditory area in parietal lobe to provide us with conscious awareness of the position and movements of the head and limbs
