Audition and Somatosenses Flashcards
week 8
what is sound?
changes in air pressure produced by objects that vibrate, alternating compression and expansion of air molecules.
what are th physical and perceptual dimensions of sound?
- sound is percieved differently by everyone.
- low pitch= wave forms are less frequent than high pitch sounds
- amplitude= (intensity) if a sound is lough the wave form will be higher in comparison to a soft sound.
- complexity= the timbre of the sound will be more for complex sounds compared to simple sounds (more jaggered)
what unit is sound measured in?
hertz
what are the 3 parts of the ear?
the outer ear
the middle ear
the inner ear
what are the functions of the outer ear?
- External ear = pinna
○ Protects the middle and inner ear
○ The part of the ear we can see - Sound is funnelled through pinna and ear canal
○ Runs to the ear drum (tunnel)
○ Vibrates when sound hits it
pinna= causes spectral modification and detects sound.
ear canal= amplifies frequencies so that the middle and inner ear can percieve it.
what is the function of the middle ear?
- Middle ear increases efficiency of sound transfer into the cochlea
○ Translator to the inner ear- helps sound get there so it can be perceived and we don’t loose it.
what is impedence matching?
increases its efficiency of the sound by maximising the frequencies from the outer ear to the inner ear.
what are the two types of impedence matching?
○ Area effect: greater pressure is exerted at the oval window than at the tympanic membrane
○ Lever effect: ossicles (middle ear bones) act as a lever, amplifying the force exerted on the tympanic membrane
→ 74% of the sound energy is transmitted to the cochlea (without impedance matching < 1%)
○ Crucial for the transfer of sound
what is the middle ear reflex?
- Muscles attached to ossicles contract when exposed to intense sounds
- Protection from loud sounds and reduction from self-generated sounds (e.g. speech)
- Contract providing protection for the loud noise.
what are the 2 sections of the inner ear?
- Cochlea (receptive organ)
- Vestibular system (involved in balance)
what is the cochlea?
made up of 3 fluid filled canals:
○ Scala vestibula (upper canal)
○ Scala media (middle canal)
○ Scala tympani (lower canal)
and recpetive organs, including:
○ Basilar membrane
○ Hair cells
○ Tectorial membrane
what is the organ of corti?
a sensory organ of the inner ear located within the cochlea which contributes to audition
how many different hair cells are in the organ of corti?
- 3500 inner hair cells (IHC) arranged in one row
○ Actual sensory receptors
○ Play the role in the transmission of sound waves - 12000 outer hair cells (OHC) arranged in 3-5 rows
○ Amplify the movement of the basilar membrane
○ Positioned closer
what is the auditory nerve responsible for?
sending sound vibrations to the brain
what does the auditory nerve contain?
30000 afferent (outside world into the brain) nerve fibres that are tonotopically organized
○ i.e., different fibres correspond to different frequencies: element of variation within the organisation
○ Allows us to distinguish between different sounds
what is the difference between the fibres innervating IHC responding to high and low frequencies of the auditory nerve?
- Fibres innervating IHC responding to low frequencies are near the centre of the nerve
- Fibres innervating IHC responding to high frequencies are near the periphery of the nerve
what is an auditory pathway and where does this occur?
the movement of soumd through the air
organ of corti -> cochlear nucleus -> superior olivary comples -> inferior colliculus -> medial geniculate nucleus -> auditory cortex.
what is the cohlear nucleus?
the first central auditory structure to receive input from the cochlea via the auditory nerve
what is the superior olivary complex?
a group of auditory nuclei in the brainstem of amphibians, reptiles, and mammals
what is the inferior colliculus?
a paired structure in the midbrain, which serves as an important relay point for auditory information as it travels from the inner ear to the auditory cortex.
what is the medial geniculate nucleus?
It acts as the principal relay nucleus for the auditory system between the inferior colliculus and auditory cortex. Together with the lateral geniculate body, it forms the metathalamus
what is the auditory cortex?
the part of the temporal lobe that processes auditory information in humans and many other vertebrates
what is the core region of the auditory cortex?
○ Contains the primary auditory cortex (A1)
○ Tonotopically organized is of frequency bands
§ DIFFERENT PARTS RECEIVE DIFFERENT FREQUENCIES
what is the hierarchal arrangement of the auditory cortex?
- core region
- belt region
- parabelt region
what is the belt region of the auditory cortex?
First level of auditory association cortex
what is the parabelt region of the auditory cortex?
Highest level of auditory association cortex
what happens as you move to higher-level association areas within the auditory cortex?
○ Auditory information is integrated with that from others systems
○ Better perception of what the sound is and where it came from
○ Understand what we are actually hearing
what are the two different processing streams of the auditory cortex?
- ventral stream
- dorsal stream
what is the ventral stream?
○ Anterior parabelt → anterior temporal lobe
○ The what pathway
§ THE WHAT.
○ Helps us understand what we are hearing
what is the dorsal stream?
○ Posterior parabelt → posterior parietal cortex
○ The where pathway
§ THE WHERE
□ The location of the sound
○ Where is the sound coming from
how is loudness percieved?
by the rate of firing of the auditory nerve activity
the louder the noise, the more firing of signals involved
corresponds to physical diension of amplitude of sound waves
what is the perception of pitch?
corresponds to physical dimensions of frequency
what is perception of pitch signalled by?
place coding
temporal coding
what is place coding?
information is carried by which neurons fire
§ Different neurons fire depending on which part of the basilar membrane are triggered.
§ Where the place of the basilar membrane (where noise if fired from) is the place coding
what is temporal coding?
information carried by the timing of the AP fired
§ Depends on the time of the information being fired from an action potential.
what is the structure of the vestibular system?
in the inner ear
* Comprised of: (structures)
○ Vestibular sacs
○ Semi circular canals
* Each containing hair cells
what are the fucntions of the vestibular system?
○ Balance
§ Plays integral role in balance
○ Maintenance of head position
○ Eye movements for image stability
§ Prevents blurry images when we are moving
what are vestibular sacs?
○ Saccule and utricle
Sensitive to the force of gravity and inform about the head’s orientation
what are semicircular canals?
○ Ring-like structures approximate the three major planes of the head (sagittal, transverse and horizontal)
○ Receptors in each canal respond to angular acceleration in one plane
○ Changes in rotation to the head in each plane of movement.
what is the funcrtion of the somatosenses?
- A subset of the sensory nervous system
○ Part of the sensory system - Provides information about the surface of the body as well as the inside.
○ Involved in perception of temperature, touch, body position, pain - Network of neural structures
what are the 3 sections of the somatosenses?
- Organic senses
§ Provide information about pleasant and unpleasant sensations- internal organs - Proprioception and kinaesthesia
§ Provide sensory information about body position and movement - Cutaneous sense (skin senses)
§ Commonly referred to as “touch”
§ Includes perception of temperature and pain
what arte the 3 main layers of skin?
epidermis (top), dermis (middle) and subcutaneous tissue (bottom)
has free nerve endings
what are the variable appearances of the skin?
mucous membrane, hairy or glabrous (smooth and hairless)
what does the skin contain?
variety of morphologically diverse sensory receptors:
what are the somatosensory receptors the skin is encapsulated in?
○ Ruffini corpuscles
○ Pacinian corpuscles
○ Meissner’s corpuscles
○ Merkel’s disks
what are touch receptors called?
mechanoreceptors
what are mechanoreceptors?
○ a type of somatosensory receptors which relay extracellular stimulus to intracellular signal transduction through mechanically gated ion channels
* Respond to vibration in the skin & changes in pressure against it
→ movement of dendrites of mechanoreceptors
→ opening of ion channels: influx/efflux of ions
→ receptor potential (change in membrane potential)
Use large myelinated Aβ fibres (i.e., high conduction velocity)
what are merkel’s disks?
slowly adapting, small receptive fields that have high spatial resolution
where ate merkel’s disks found?
Hairy and glabrous skin, dense in the fingertips
what do merkel’s disks respond to?
indentation of skin
what are merkel’s disks responsible for?
Detecting pressure; static discrimination of
shapes and edges, process info about shape and texture.
what are ruffini corpuscles (endings)?
slowly adapting fields
where are ruffinin endings found?
Hairy and glabrous skin
what do ruffini endings respond to?
stretching of skin
what are ruffinin endings responsible for?
Maintaining grip to avoid slippage, generating awareness of finger and hand position.
what are meissner’s corpuscles?
rapidly adapting receptors, relatively small receptor fields, spatial resolution is inferior to Merkel’s discs.
where are meissner’s corpuscles found?
glaborous skin
what do meissner’s corpuscles respond to?
Low-frequency vibrations and light tough
what are meissner’s corpuscles responsible for?
Detecting surface roughness when
textured objects move across skin (important for maintaining grip), transmit info about movement between the skin and another surface.
what are pacinian corpuscles?
rapidly-adapting receptors with very large receptive fields
where are pacinian corpuscles found?
Hairy and glabrous skin
what do pacinian corpuscles respond to?
High-frequency vibration
what are pacinian corpuscles responsible for?
Discrimination of fine surface
textures or moving stimuli/vibrating machines- most effective at transmitting information about vibrations objects cause when they are in contact with the hand.
what is the perception of touch?
- Accuracy with which tactile stimuli can be sensed varies across the body surface which is due to:
○ Density of mechanoreceptors
○ Receptive field size
Different level of sensitivity in where we may be touched- better signals to the brain.
what are temperature receptors called?
thermoreceptors (have free nerve endings)
what are the two types of thermoreceptors?
○ “Warm” receptors
§ Located deeply in the skin
§ Use unmyelinated C fibres
○ “Cold” receptors
§ Located just beneath the epidermis- located closer to the surface
§ Use unmyelinated C fibres and lightly myelinated Aδ fibres
* some thermoreceptors also respond to chemicals
what are pain receptors called?
nociceptors (have free nerve endings)
what is pain information conveyed via?
○ Lightly myelinated Aδ fibres (sharp pain)
○ Unmyelinated C fibres (dull pain)
what are the different types of nociceptors?
○ Mechanical nociceptors
§ Sensitive to strong pressure (e.g. pinch)
§ Intense pressure on a small surface area
○ Thermal nociceptors
§ Sensitive to burning heat and extreme cold
○ Chemical nociceptors
§ e.g. sensitive to histamine
○ Polymodal nociceptors
§ Respond to mechanical, thermal and chemical stimuli
§ Respond to all different types of pain- multiple different sources
what are somatosensory pathways?
- Two distinct ascending pathways:
○ Dorsal column-medial lemniscus pathways- touch and proprioception pathway
○ Spinothalamic pathway- pain and temperature sensations
what is the samotosensory cortex?
- Within the brain
- Two main cortical areas
○ primary (blue)(S1) & secondary (S2) somatosensory cortex - Somatotopic representation of the body parts
- Amount of somatosensory cortex not proportionate to body surface
- Two main cortical areas
what are the 3 different perceptual and behavioural effects of pain?
- Sensory component (perception of pain intensity) involving pathway to S1 and S2
- Immediate emotional component (unpleasantness of stimulus) involving pathways including the insular cortex and anterior cingulate cortex
- Long-term emotional component in case of chronic pain involving pathways to the prefrontal cortex
what are the psychological factors influencing pain?
- previous experience
- percieved self-efficacy
- attentionanaxiety
- depression
- percieved helplessness
what is olfaction?
the action or capacity to smell (sense of smell)
