Physiology of balance, taste, smell Flashcards
Semi circular canals
- Structure
- Function
6 altogether
- 3 in each ear
Detects rotation of the the head
- Lateral L+R are functionally paired
- Left anterior and Right posterior functionally paired [and opposite]
Canals connect to ampulla which contains cristae
- Ampulla connects to vestibular ganglion
Ampullae with sensory hair cells of semicentral canal
- Embedded in the capula
Orientation of semi-circular canals
Semi circular canals are orientated 90-degrees to one another
Otolith organs
- Structure
- Function
Saccule and utricle–> Inner ear
- Not exactly right angle to each other
- Sensory cells are embedded in gelatinous sheet with heavy crystals
Function
- Detects tilt and acceleration
Mechanism of semicircular canals
Action potentials are always firing from the hair cells
Endolymph movement in the semi-central canals moves the axis of sensory hair cells
- This affects the frequency at which action potentials fire–> CN VIII
Type I vestibular hair cells
Less common
- Receives both afferent and efferent fibres
- It is surrounded by the afferent nerve ending–> forming the calyx
- Only directly in contact with afferent fibres
Function
- Detects broad range of movements
Type II vestibular hair cells
More common than Type I
- Directly in contact with the motor and afferent fibres
Function
- More sensitive to smaller range of movement than Type I hair cells
Nystagmus
- Physiological
- Pathological
Physiological
- Slow then fast eye movements when the head rotates
Pathological–> Spontaneous
- Rapid side-to-side eye movements in the absence of head rotation
- Due to damage of a semi-circular canal [no firing]
Central vestibular pathwats
Vestibular organs–> Cerebellum and vestibular nuclei
Vestibular nuclei–>
- Neocortex
- Reticular formation [input to CN3 nuclei]
- Oculomotor nuclei [input to extra ocular muscles]
- Spinal cord
- Cerebellum [also has input to vestibular nuclei]
Causes of vestibular disorders
Ear infections
Headinjury
Whiplash
ageing
Drugs:
- aminoglycoside antibiotcs
Mechanism of olfactory transduction
- Odorant molecule binds to ciliated receptor cell
- cAMP is produced in intracellular signalling–> Binds to non-selective cation channel
- Influx of Na+ and Ca2+ into cell–> Depolarisation
- Ca2+ binds to Cl- channels–> Efflux of Cl-
Olfactory bulb targets
Areas where olfactory tract synapses
Pyriform cortex–> oribitofrontal cortex
Olfactory tubercle–> Thalamus, OFC, Hypothalamus
Amygdala–> Thalamus, OFC, Hypothalamus
Entorhinal cortex–> Hippocampus
Sweet taste transduction
- Sweet molecule binds
- cAMP made
- Closes K+ channel –>Depolarisation
Sour taste transduction
- pH binds
- cAMP made
- Closes K+ channel –>Depolarisation
Bitter/Umami taste transduction
- Bitter/ umami molecule binds
- IP3 made–> Opens Ca2+ stores
- Increase in Ca2+ intracellularly–> release of NT
Salty taste transduction
Na+ moves into the receptor passively
- Uses Na+ equilibrium