Chapter 7: Sensation & Perception

Question 1

how does amplitude and wavelength alter sound?

Answer 1

amplitude determines how loud a sound is in decibels (dB), wavelength determines pitch in hertz (Hz)

Question 2

timbre vs noise

Answer 2

timbre: complex tones combining multiple waves
noise: waves that do not regularly repeat

Question 3

what are the components of the outer ear?

Answer 3

pinna (auditory canal) that focuses sound

Question 4

what are the components of the middle ear?

Answer 4

tympanic membrane (eardrum), ossicles (malleus, incus, stapes), oval window, forms the boundary between the middle and inner ear

Question 5

what are the components of the inner ear?

Answer 5

semicircular canal, cochlea, fluid filled cavities

Question 6

what are the three chambers of the cochlea?

Answer 6

vestibular canal (perilymph), tympanic canal (perilymph), cochlear duct (endolymph), and organ of corti (inner and outer hair cells)

Question 7

what are the two membranes of the ear?

Answer 7

reissner’s and basilar membranes

Question 8

what does the basilar membrane do?

Answer 8

translates sound frequencies by vibrating in a wave motion, high frequency sounds cause peak vibration of the basilar membrane near its base, low frequency sounds will cause a peak vibration closer to the apex

Question 9

how do hair cells regulate hearing?

Answer 9

movement of the basilar membrane is sensed by hair cells attached to the organ of corti, movement of cilia in the endolymph alternatingly hyperpolarizes and depolarizes the hair cells away from their resting states

Question 10

what is the function of inner vs outer hair cells?

Answer 10

inner: located between the tectorial membrane and cochlear ducts and act as auditory receptors
outer: amplify the sound

Question 11

what is the central auditory pathway?

Answer 11

1. spiral ganglia neurons communicate with cochlear hair cells and the dorsal and ventral cochlear nuclei of the medulla
2. spinal ganglion neurons synpase directly or indirectly with the inferior colliculus
3. the inferior colliculus projects ot the medial geniculate nucleus
4. the medial geniculate nucleus projects to the primary auditory cortex

Question 12

how does the primary auditory cortex respond to sound?

Answer 12

columns in the primary auditory cortex respond to single frequencies, low frequencies activate rostral columns while higher frequencies activate more caudal columns

Question 13

what does the secondary auditory cortex do?

Answer 13

activated by complex stimuli and separate pathways process the “what” and “where” of sound

Question 14

how is pitch perceived?

Answer 14

tonotopic organization where neurons responding to one frequency are located next to neurons that respond to similar frequencies

Question 15

how is loudness perceived?

Answer 15

single neuron can respond to about 40 decibels but humans can received a range of 130 decibels, recruitments of multiple auditory neurons contribute to our perception of loudness, while neurons have a preferred frequency they respond to they will still respond to similar frequencies if the amplitude is high enough

Question 16

what are some causes of hearing loss?

Answer 16

age-related, poor circulation in the inner ear, damage to outer, middle, inner ear of auditory cortex, congenital hearing loss, genetics, birth-related injuries, prenatal exposure to infection or drugs/alcohol

Question 17

how do cochlear implants work?

Answer 17

cochlear implants allow sound to be picked up by an external microphone and sent to the electrode array wired through the cochlea, signals from the array are then picked up by the spiral ganglion fibers and transmitted to the brain

Question 18

what are the different types of mechanoreceptors?

Answer 18

1. encapsulated: meissner’s corpuscles (pressure), pacinian corpuscles (vibration)
2. nonencapsulated: merkel’s disks (pressure), ruffini’s endings (stretch)
3. free nerve endings

Question 19

what do alpha-alpha fibers detect?

Answer 19

feedback from muscle fibers

Question 20

what do alpha-beta fibers detect?

Answer 20

the mechanoreceptors (meissner’s corpuscles, merkel’s disks, pacinian corpuscles, ruffini’s endings)

Question 21

how do touch signals travel?

Answer 21

signals from mechanoreceptors travel from skin along Aβ axons to the dorsal roots of the spinal cord

Question 22

what are dermatones?

Answer 22

the area of the skin surface served by the dorsal roots of one spinal nerve

Question 23

what is the touch pathway?

Answer 23

from the spinal cord axons travel along the dorsal column-medial lemniscal pathway to the dorsal column nuclei of the medulla, then to the contralateral ventral posterior nucleus of the thalamus, from there they project to the primary somatosensory cortex, finally touch information from the head travels to the VP nucleus via the cranial nerves

Question 24

what are the ascending pain fibers?

Answer 24

myelinated alpha-delta fibers (quick, sharp pain) and unmyelinated C fibers (dull ache)

Question 25

what is the ascending pain pathway?

Answer 25

spinal cord -> substantia gelatinosa -> spinothalamic pathway -> VP nucleus or intralaminar nuclei of the thalamus, communicate with the anterior cingulate cortex and somatosensory cortex

Question 26

how does the descending pain pathway work?

Answer 26

higher level brain structures project to the periaqueductal gray of the midbrain (where there are high levels of opioid receptors) which allows you to respond to painful stimuli, PAG projects to the raphe nuclei of the medulla and the spinal cord

Question 27

how is chronic pain different from regular pain?

Answer 27

chronic pain usually doesnt respond to pain medicators, instead it is associated with increased activity in the prefrontal areas, whereas physical pain produces more activity in the thalamus, this suggests that chronic pain is more of a memory problem

Question 28

what is the process of detecting a smell?

Answer 28

olfactory receptors line the olfactory epithelium in the dorsal nasal cavity, molecules dissolve in mucus surrounding olfactory receptors, depolarization sends action potentials to the olfactory bulb via the olfactory nerve, olfactory neurons form the olfactory nerve

Question 29

what is the olfactory pathway?

Answer 29

olfactory bulb axons form olfactory tracts which project to the olfactory cortex, olfactory cortex connects to the medial dorsal nucleus of the thalamus, which projects to the insula and the orbitofrontal cortex where the olfactory signals are interpreted as odor identification, and also influence motivation, emotion, and memory

Question 30

what is the gustatory pathway?

Answer 30

cranial nerves synapse with gustatory nucleus of the medulla, axons from gustatory nucleus synapse in the ventral posterior medial (VPM) nucleus of the thalamus, projects to the gustatory cortex in the parietal lobe for identification of primary taste qualities, projects to the orbitofrontal cortex in the frontal lobe for combination with olfaction and vision to produce flavor perceptions

Question 31

what does damage to the primary and secondary somatosensory cortex result in?

Answer 31

primary: sensation and movement defects (numbness, loss of proprioception, defective localization) secondary: neglect syndrome (cannot process stimuli from both sides)