Week 6 (How do we hear, taste, and smell?) Flashcards
What are the properties of sound
-Frequency & Pitch
-Amplitude & Loudness
-Complexity & Timbre
What is Frequency & Pitch
Rate of vibration n cycles per second (Hertz, Hz)
What is Amplitude & Loudness
Intensity of sound (Decibels, Db)
What is Complexity & Timbre
Complexity determines Timbre, (e.g. difference between violin and flute)
What are the three sections of the ear?
Outer ear, Middle ear, Inner ear
What are the components of the outer ear?
Pinnae: Funnel-like structure channels sound into ear.
Ear canal: Narrowing amplifies sound waves toward membrane (tympanic membrane)
What are the components of the middle ear?
Osssicles:
-Malleus (Hammer)
-Incus (Anvil)
Stapes (Stirrup)
What are the components of the inner ear?
Cochlea:
-Converts vibrational energy into waves of fluid
-The auditory part of the vestibulocochlear nerve
Inner ear includes vestibular apparatus.
Structure and function of the Cochlea
-Coiled structure, bony exterior, hollow compartments, filled with fluid.
-Vibrations from the ossicles to oval window membrane sends waves through fluid filled cochlea.
-Vibration is transmitted to organ of court via basilar membrane (structures in cochlea)
-Movement in sensory hair cells transduce sound waves into neural activity, which is sent along auditory nerve to the brain.
Structure and function of the tonotopic basilar membrane.
The basilar membrane vibrates when stapes moves the fluids of the inner ear. Different sound wave frequencies cause peak pending f the membrane at different points along its length.
What does the Organ of Corti
Sends vibrations to auditory nerve.
What is the auditory pathway to the brain?
-Ear (cochlea)
-Cochlear nuclei (brainstem)
-Superior olive (brainstem)
-Inferior Colliculi (midbrain)
-Medial geniculate nucleus (thalamus)
-Auditory cortex (Temporal cortex
Where are the primary and secondary auditory cortex located?
Primary:
Located in the temporal lobe, within the Heschl’s gyrus, within the Sylvia fissure, tonotopic.
Secondary:
-Surrounds primary auditory cortex,
What allows us to hear pitch
Tonotopic organisation in the basilar membrane.
What allows us to hear loudness
Louder sounds produce larger pressure changes, produces more intense basilar vibration.
How do we detect location
-Difference in timing in each ear
-Relative loudness
Detected by nuclei in the brainstem that receive input from both left and right ventral cochlear nuclei.
-Superior olive (medial part) neurons respond to difference in arrival time between each ear.
-Superior olive (lateral part) and trapezoid body neurons respond to differences in loudness.
Two types of deafness
Conduction deafness
-Pathology of the outer/middle ear: prevent vibrations reaching cochlear
Sensorineural deafness/ hearing loss
-Originate from cochlear or nerve lesions
-Cochlear losses most common
Damage to auditory cortex
Left primary auditory cortex damage:
-Deficit in differentiating speech sounds
Right primary auditory cortex damage
-Deficit in discriminating musical sounds
Bilateral auditory cortex damage
-Agnosia for sound (everything sounds the same)
Fancy word for smell
Olfaction
Olfactory segment
-Along the roof of the nasal cavity
-Lined with the olfactory epithelium, which contains receptors for smell.
Olfactory receptors
Each olfactory receptor has a short thick dendrite, ending in 10 to 20 cilia, that projects into a mucous layer (olfactory mucosa)
-Chemicals in air dissolve into mucosa to interact with cilia
Olfactory bulbs
Receptor cells project to olfactory bulbs
Theolfactory nervesare non-myelinatedand consist of bundles of slenderfibresheldtogether by thin strips of connectivetissue; form olfactory cranial nerve
Receptors form synapses with dendrites of mitral cells at glomeruli
Mitral cells send axons from olfactory bulb to a broad range of forebrain areas
Path from olfactory bulbs to the brain.
Mitral cells send axons from olfactory bulb to a broad range of forebrain areas
Amygdala & pyriform cortex have no connection through thalamus
Orbitofrontal cortex (role in emo & social behaviours) has thalamic connection
Abnormalities of olfaction
Anosmia (absence of the sense of smell)
-Can be anosmic for certain odours
-Can be temporary or permanent
Hyposmia (diminished olfactory sensitivity)
-Hyposmia might be very early sign of Parkinson’s disease
Dyosmia (distorted sense of smells)
-Misinterpreted smells of hallucination of smells
The tongue
Covered in papillae and taste buds
What are the different taste senses?
Sweet, salty, sour, bitter, umami
Taste pathways to the brain
Pathway one:
-Through posterior medulla to ventroposterior medial nucleus of thalamus
Then through two sub pathways
-one to primary somatosensory cortex (tactile information )
-one to gustatory cortex of insult (flavour)
Pathway two:
-projects through pons to hypothalamus & amygdala
Hypothesised to play a role in feeding behaviour.