Lecture Seven; Auditory organ

Question 1

What are the four parts of somatosensation?

Answer 1

Touch (cutaneaous senses)
Pain/temperature (nocicepsis
Position own bodyparts (propriocepsis
Organes (interocepsis

Question 2

vestibular sense:

Answer 2

balance

Question 3

The difference between eye and ear?

Answer 3

Ear is an analytic organ the eye is a synthetic organ

The ear is an analytic organ
(we perceive all individual frequencies)

The eye is a synthetic organ
(in a mix of light frequencies we perceive only a single color)

Question 4

which cranial nerve is associated with hearing?

Answer 4

the eighth

Question 5

what is analog to the brightness, hue (color), saturation the auditory organ?

Answer 5

saturation equals complexity (timbre), hue(wavelength) equals frequency (pitch) and brightness equals amplitude (loudness)

Question 6

What is the tympanic membrane?

Answer 6

(eardrum),

which vibrates with the sound.

Question 7

How is the middle ear structured?

Answer 7

The middle ear consists of a small hollow
region behind the tympanic membrane. It contains the
bones of the middle ear, called the ossicles, which are set
into vibration by the tympanic membrane. The malleus
(hammer) connects with the tympanic membrane and transmits
vibrations via the incus (anvil) and stapes (stirrup) to
the cochlea, the structure that contains the receptors. The
bottom of the stapes presses against the membrane behind
the oval window, the opening in the bone surrounding the
cochlea

Question 8

Receptors in cochlea

Answer 8

Sound detection by bending inner hair cells in organ of corti
(outer hair cells are for amplification)

Question 9

How are lower frequencies encoded vs. higher frequencies?

Answer 9

Detection high and middle high tones by “place coding “; low tones by “rate coding”
Rate coding:
tip vibrates at rate of low frequencies

Question 10

Coding: intensity

Answer 10

High and middle high sound frequencies by neuron firing frequency (rate law)
But, not possible for low frequency sounds! For these the sound frequency itself is coded by the neuron firing rate.

Intensity of low frequency sounds is coded by the number of activated haircells

Question 11

physical describtion of pitch and loudness

Answer 11

frequency and intensity/amplitude

Question 12

Intensity of low frequency sounds is coded by …?

Answer 12

by the number of activated haircells

Question 13

Coding location

Answer 13

Left-right by differences in arrival time in both ears
from right: right eardrum pulled in, left eardrum pulled out
from left: right eardrum pulled in, left eeardrum pulled out
from front or behin, botheardrums the same

Question 14

why can we distinct from front and behind sound?

Answer 14

High-low (front-behind) changes in frequency-content induced by shape of ear shell

Question 15

Higher order processing

Answer 15

In secondary auditory association cortices

1. belt region (first auditory association cortex)
2. parabelt region (second auditory association cortex)
3. prmary auditory cortex

Question 16

Information is combined for a complete percept

Answer 16

1. Where:
Auditory
Barking dog right (in front or behind?)
Visual
Nothing in front so behind

2. What:
Auditory
Rhustling in bushes (bird or mouse?)
Visual
Blue-yellow so bird

Question 17

Perception of Pitch and Loudness High-frequency sounds and Moderate-frequency sounds

Answer 17

Perception of Pitch (frequency): Place coding; firing by hair cells at location of basilar membrane
that is active
Perception of Loudness (Amplitude)Determined by rate of action potentials from hair cells

Question 18

Low-frequency sounds

Answer 18

Perception of Pitch :Rate coding; hair cells at apical end of basilar membrane
fire in synchrony with frequency of sound wave
Perception of Loudness: Determined by number of active hair cells

Question 19

the four types of encapsulated somatosensory receptors

Answer 19

Merkel’s disks, Ruffini corpuscles, Meissner’s corpuscles,

and Pacinian corpuscles).

Question 20

Merkel’s disks

Answer 20

Size and Nature of Receptive Field: Small, sharp borders
Location: Hairy and glabrous skin
Function: Detection of form and roughness, especially by fingertips

Question 21

Ruffini corpuscles

Answer 21

Size and Nature of
Receptive Field: Large, diffuse borders
Location: Hairy and glabrous skin
Function: Detection of static force against skin; skin stretching; proprioception

Question 22

Meissner’s corpuscles Glabrous

Answer 22

Size and Nature of
Receptive Field: Small, sharp borders
Location: glabrous skin
Function: Detection of edge contours; Braille-like stimuli, especially by fingertips

Question 23

Pacinian corpuscles

Answer 23

Size and Nature of
Receptive Field: Large, diffuse borders
 Location: Hairy and glabrous skin
Function: Detection of vibration; information from end of elongated object being
held, such as tool

Channels for positive ions (Na+) opened due to displacement rings: depolarisation

Question 24

Open nerve endings

Answer 24

pain, temperature

Question 25

Open nerve endings:

Answer 25

hair movement

Question 26

Dermatome

Answer 26

A part of the skin subserved by one peripheral nerve

Question 27

Shingles (Gordelroos):

Answer 27

viral infection of one nerve (dermatomes)

Question 28

Projection to the cortex
Pain/temperature:
nociception

cogitive response:

Answer 28

Spino-thalamic tract (crosses immediately)
to Thalamus ventral posterior (passes Mediale lemniscus
)
and the to primary somtosensory cortex

Via various receptors on dendrites
Cognitive response
withdrawal reflex

Question 29

Projection to the cortex

Touch:

Answer 29

Dorsal column
then nuclei of the dorsal columns
then also (as pain) Mediale lemniscus
to Thalamus ventral posterior
and then primary somatosensory cortex

Question 30

tissue damage/inflammation

1. macrophage:
2. mast cells
3. neutrophil granulocyte

Answer 30

through detection of signaling molecules

1. Clearing damaged cells
2. release of signaling chemicals
3. Clearing damaged cells

Question 31

Somatotopic map (place coding)

Answer 31

Somatosensory (and motor) homunculus