Special Senses Flashcards
what are the properties of sound
pure tone is described by two measures -
- amplitude or intensity measured as sound pressure measured in decibels (dB) –> perceived as loudness
- frequency or number of cycles per second of vibration, measured in hertz (Hz) and perceived as pitch
what are the physical properties of sound
amplitude and frequency and harmonics
what are the perceptual properties of sound
loudness and pitch
what muscles permit movement of pinna
auricularis muscles (anterior, posterior, superior)
what are the two muscles in the middle ear
tensor tympani and stapedius muscles
act to improve perception and sound protection –> both damaging sounds and those that are self produced
what are the fluid filled canals in the cochlea
- vestibuli
- media
- tympani
what causes vibrations against the oval window in the cochlea
the staples vibrations
causes fluid within the cochlea to move
what is the round window
a moveable membrane that is required to accommodate pressure that arises when the oval window is pushed
what is the organ of corti
the structure responsible for converting the vibrations produced by the ossicles into neural activity
what are the 3 components of the organ of corti
- sensory cells (hair cells)
- auditory fibres that make up the vestibulocochlear nerve
- supporting cells
what are the hair cells in the inner ear
both inner and outer
are involved in transmitting the perturbations in the basilar membrane and transmit this information to the vestibulocochlear nerve
what are the functions of the inner hair cells
associate with many auditory nerves
involved in sound perception
what are the functions of the outer hair cells
associate with few auditory nerves
are not primarily involved in sound detection, instead they fine tune information by changing tension on the basilar membrane (relax or stiffen)
what are the efferent projections from brain involved in
to inhibit input from loud sounds
what are the neurotransmitters in the inner hair cells
glutamate
what are the neurotransmitters in the outer hair cells
acetylcholine
what does inner ear hair cell movement cause
hair cell cilia cause rapid changes in ion channels
fast mechanically gated ion channels –> no second messenger systems
respond with graded potentials
channels are large (non-specific) so other cells can enter the cell
what is the basilar membrane movement
vibrates in response to sound exhibit a topographical organization
*detect different frequencies in acoustic vibrations
high frequencies cause maximal distortions in base and low frequencies cause large changes at apex
what are the auditory pathways that link the brainstem and brain
- superior olivary nucleus is the first stage when inputs from both the right and left cochlear nuclei are integrated (binaural)
- the inferior colliculus is the primary auditory center in the midbrain –> this nucleus sends outputs to medial geniculate nuclei (MGN) in the thalamus
MGN then projects to auditory cortex
what is the auditory theory –> sound localization via binaural cue
intensity differences
results from the differences in loudness that reaches the ear
head provides a barrier the sound must move around
higher freq sounds are more susceptible to intensity differences compared to low freq sounds (longer sound waves)
what are latency differences
results from the difference in the arrival times of sound waves
one ear is always a little closer to sound
thus onset disparity (difference in two ears) and ongoing phase disparity (continuous mismatch of all frequency peaks)
what is the auditory theory in mammals
the superior olivary nucleus is the main localization nucleus for sound with two divisions
- lateral superior olive processes intensity differenec
- medial superior olive (MSO) processes latency differences but encodes sounds by relative activity of the left and right sides
what are common causes of conduction deafness in the external ear and middle ear
- external ear
cerumen (excessive earwax)
otitis externa (ear infection, aka swimmers)
- middle ear
fluid accumulation in eustachian tube
where does sensorineural deafness originate from
cochlear or auditory nerve lesions
damage to hair cells (ex. outer) can result in tinnitus (a sensation or ringing in ears)
what are cochlear implants used to treat
deafness due to hair cell loss
what is word deafness
unable to recognize spoken words
speech production and simple sound discrimination are still function
what is cortical deafness
difficulty in recognizing auditory stimuli
rare bilateral damage to the auditory cortex
stroke induced damage to various nuclei in the auditory pathway
what organ do animals have for olfactory detection
vomeronasal organ
what secrete mucous at the olfactory epithelium
bowman’s glands secrete mucous that line epithelium
what do ordorants have to be
partially lipid soluble
odorant receptors are on the cilia
what replaces receptors in the olfactory epithelium
basal stem cells
how are odorants detected and activate intracellular processes
graded potential and action potentials
what are the receptors in the olfactory epithelium and bulb
large number of receptors, small number of mitral cells
means sensitivity of mitral cells is very high but spatial awareness of smell origin is poor but improved by lateral inhibition
how is olfaction is significantly different from other sensory systems
chemical detection and circuitry
olfactory epithelium –> olfactory bulb –> limbic system –> motor pathways
what are characteristics of olfaction
- highly sensitive
- shows complete adaption
- complex concentration/perception characteristics
why do dogs have a better sense of smell
- larger olfactory epithelium so more receptors
- twice as many active receptor proteins
- olfactory bulb is much larger
- vomeronasal organ show low functionally in humans
where are the taste receptor cells in the tongue
are in buds on papillae in the tongue
sensation derives from tastants (molecules giving rise to taste)
what are the taste receptors
- salty
- sour
- bitter
- sweet
what are the two types of taste receptors
each cell will have one type of receptors but buds can detect multiple types of tastants (concentrations of each receptor type will differ between buds)
- small charged particles or ions (salty and sour) –> enter taste receptor cells through ion channels in microvilli
- molecules bind to receptor (sweet and bitter)
how is taste percieved in dogs
from nasal epithelium –> olfactory bulb –> limbic system –> sensory cortex
