Special Senses Flashcards
Which Cranial Nerves conduct taste and smell to the brain?
I- Olfaction
VII- Facial
IX- Glossopharyngeal
X- Vagus
What are the 3 types of cells involved in olfaction & role of each?
1) Olfactory Sensory Neurons- site of transduction
2) Supporting Epithelial Cells- give physical support to epithelium
3) Basal Cells- undergo cell division to make new sensory neurons every 2 months.
What is the name of the region where olfactory receptors pass through the ethmoid?
Cribriform Formina
Why are secretions necessary for olfaction & taste to occur?
Both are chemical senses that require dissolving of molecules to stimulate sensory neurons and trigger action potential to occur.
What is the neural pathway of taste?
Tastant → Gustatory epithelial cells →Gustatory Microvilli aka site of Transduction →Nerve impurlse to First-Order Sensory neurons → option of 3 Cranial Nerve Routes
1) Facial (VII) serves anterior ⅔ of tongue
2) Glossopharyngeal (IX) serves posterior ⅓ of tongue
3) Vagus (X) epiglottis & throat
→ Medulla Oblongata → SOME go to Limbic System & Hypothalamus (detects sugar) OR to Thalamus ( → from Thalamus to Primary Gustatory Cortex in Parietal Cortex of Cerebrum. )
What is the neural pathway of Smell?
Odor molecules →Receptors → (inside receptors, Transduction occurs which triggers → Nerve impulse) →Receptor axons →olfactory nerves → olfactory bulb →olfactory tract → primary olfactory area of temporal lobe
How do smell receptors differ from receptors in the neuromuscular junction?
NMJ receptors are stimulated by a nerve impulse whereas smell receptors are stimulated by chemical odorants (???)
What are the 4 types of papillae on the tongue?
1) Vallate Papillae- 12 total in V-shaped row at back of tongue, contain 100-300 taste buds.
2) Fungiform Papillae- Mushroom-shaped, entire surface of tongue, contain 5 taste buds each.
3) Foliate Papillae- degenerate in early childhood
4) Filiform Papillae- pointed structures, no taste buds (tactile receptors that make it easier to move food with tongue)
Physiology of Hearing
Auricle → Extrenal Acoustic Meatus → Tympanic membrane → Ossicles (Malleus → Incus → Stapes) →Vestibular Window → Cochlea → Hair Bundles
What is the purpose of the Auditory (Eustachian) tube?
Equalizes air pressure on both sides of the tympanic membrane so it can vibrate freely. If pressure is not equalized it can cause pain & popping sound & ringing in ears.
3 Structures of Outer Ear & Function
1) Auricle- Collects sound waves.
2) External Acoustic Meatus- Directs sound waves to eardrum.
3) Tympanic Membrane- sound waves cause it to vibrate, which in turn causes malleus to vibrate.
2 Structures of Middle Ear & Function
1) Auditory Ossicles (Malus, Incus, Stapes)- Transmit & amplify vibrations from tympanic membrane to vestibular window.
2) Auditory Tube- Equalizes pressure on both sides of tympanic membrane.
2 Main Structures of Inner Ear & Function
1) Cochlea- spiral organ that contain the hair cells for hearing (elicit nerve impulese in cochlear branch of vestibulocochlear (VIII) nerve)
2) Vestibular Apparatus- structures that send nerve impulses to vestibular branch of vestibulocochlear (VIII) nerve) for balance & equilibrium
3 Structures of Vestibular Apparatus & Function
1) Semicircular Ducts- detect rotation
2) Utricle- Detects linear movement in horizontal direction & head tilt.
3) Saccule- Detects linear movement in vertical direction.
What structures in the ear convert vibrations into nerve impulses & how?
Hair cells convert mechanical vibrations into a receptor potential, which releases neurotransmitter that can initiate nerve impulses in first-order sensory neurons.
How does the ear differentiate between various frequencies?
Different frequencies cause certain regions of the basilar membrane to vibrate more intensely than other regions. High frequencies detected at base of cochlea and low frequencies detected more inside cochlea.
What is the maximum range of hearing? What frequencies are humans most & least sensitive to?
Most sensitive to female voice (2000-3000 Hertz)
What are the differences between Perilymph & Endolymph of inner ear?
Perilymph- fluid between bony & membranous labyrinths of inner ear. When WAVES form, strikes VESTIBULAR membrane
Endolymph- fluid inside membranous labyrinth of inner ear. When increases in PRESSURE, vibrates the BASILAR membrane & stimulate hairs.
Static vs. Dynamic Equilibrium
Static Balance- detected by which direction the hairs within the otolithic membrane bend as the fluid moves (which way is up aka position)
Dynamic Eqilibrium- detects movement, occurs within semicircular canals, hair cells move but fluid doesn’t move
What is the purpose of tears? What is the route they follow?
Protective mechanism in response to irritant.
Lacrimal Glands → Excretory Lacrimal Ducts → Over eyeball into Lacrimal Puncta → Lacrimal Canaliculi → Lacrimal Sac → Nasolacrimal Duct.
What are the 6 extraocular muscles and their direction of movement?
1) Inferior Oblique- Up and Laterally
2) Superior Oblique- Down and Laterally
3) Lateral Rectus- Lateral
4) Superior Rectus- Up and Medially
5) Inferior Rectus- Down and Medially
6) Medial Rectus- Medially
What structures maintain the shape of the eyeball?
1) Sclera (white part of eyeball)
2) Vitreous Chamber behind the lens is filled with Vitreous Humour & Aqueous Humour of anterior segment which gives rise to intraocular pressure that holds shape.
