4a. Sensory Systems

Question 1

Taste Receptors

Answer 1

Characteristic distribution, regions are a mixture

Some overlap in response

Taste is a combination of the categories

Tongue also has mechanoreceptors and thermoreceptors

Question 2

Taste Receptors: Categories

Answer 2

sour (foliate papillae)
sweet (fungiform papillae)
salty (fungiform papillae)
bitter (circumvallate papillae)
umami (fungiform papillae)

Question 3

Taste Buds

Answer 3

Location of taste receptors

On tongue and other areas of mouth

Grouped in each of 3 types of papillae on tongue

1 bud = ~50 receptors

Question 4

Taste Receptor: Hairs

Answer 4

Project into taste pore - pick up taste stimuli

Question 5

Taste Transduction

Answer 5

1. Dissolved substances initiate transduction (substance must be dissolved in saliva to come in contact with R)
2. Depolarizing R potentials
3. Some taste R have voltage gated Na channels, make AP and release ATP
4. Other taste R have voltage gated Ca channels and release vesicles of ATP (ATP release as NT - depolarizes primary afferent nerve ending)
5. Peripheral endings of CN VII, IX, X depolarize - fire faster

Question 6

CN for Conscious Perception of Taste

Answer 6

CN VII Facial
CN IX Glossopharnygeal
CN X Vagus

Mostly 7 and 9

Question 7

Taste Receptors: Modified Epithelial Cells

Answer 7

Depolarizing receptor potentials –> release of NT ATP –> AP in primary neuron

Question 8

Salt

Answer 8

NaCL

Question 9

Sour

Answer 9

H+ in citric acid

Question 10

Sweet

Answer 10

Sugar (glucose)

Question 11

Bitter

Answer 11

Alkaloids (quinine)

Question 12

Umami

Answer 12

L glutamate

Question 13

Taste Pathways

Answer 13

1. taste receptors
2. cranial nerves (1 neuron)
3. brainstem - nucleus solitarius (2 neuron)
4. Thalamus (3 neuron)
5. Gustatory cortex - insula

Question 14

Limbic System

Answer 14

Provides affective dimension of taste (emotional context)

Question 15

Olfactory Receptors

Answer 15

primary afferent neurons - not a separate cell

In olfactory mucosa

Odorant molecules bind to receptors in cilia in mucus layer

CN I (olfactory) goes through cribriform plate to connect with olfactory receptor in olfactory mucosa

Question 16

Olfactory Transduction

Answer 16

1. Olfactory R binds odorant molecules –> activates G protein
2. Increase in intracellular cAMP
3. cAMP gated cation channels open - Ca2+ enters
4. Depolarization - Cl- leaves through Ca2+ gated Cl- channels
5. Depolarization travels to initial segment of olfactory nerve
6. AP generated

Question 17

Axons from olfactory receptors leave olfactory epithelium …

Answer 17

Travel ventrally to olfactory bulb - pass through cribriform plate

fractures of cribriform plate can sever olfactory neurons –> disorders

Question 18

Odor Discrimination

Answer 18

Enabled by variations in receptor molecule

Question 19

Olfactory Pathway

Answer 19

1. olfactory receptors (1 neuron: CNI (olfactory))
2. olfactory bulb: apical dendrites of mitral cells (2 neuron)
3. primary olfactory cortex (piriform cortex)

Also project to amygdala, limbic system

NO RELAY IN THALAMUS

Question 20

Outer Ear (anatomy, function)

Answer 20

Direct sound through ear canal to tympanic membrane

helix
auricle
auditory canal
earlobe

Question 21

Middle Ear (function, anatomy)

Answer 21

Begins process of transmitting vibrations to inner ear

tympanic membrane?
ossicles (stapes, incus, malleus)

Question 22

Inner Ear (function, anatomy)

Answer 22

Transmits sound and balance information to brain

semicircular ducts?
vestibular nerve
cochlear nerve
cochlea
round window?
tympanic cavity?
tensor tympani muscle
auditory tube

Question 23

Cochlea

Answer 23

Contains receptor cells

Coils 2.5 around modiolus (bony pillar)

3 chambers:

• scala tympani
• scala media
• scala vestibuli

2 fluids:

• perilymph
• endolymph

Hair cells sit in cochlear duct

Question 24

Perilymph

Answer 24

Fills scala vestibuli and scala tympani (continuous)

Similar composition to ECF

Movement –> bulges in cochlear duct –> activation of basilar membrane

Question 25

Endolymph

Answer 25

# Fill scala media (cochlear duct) Chemically similar to ICF (K+ rich) Produced continuously via active pumping mechanism --> positive electrical potential inside ear (+80mV)

Question 26

Membranes of Cochlea

Answer 26

- Reissner's/vestibular membrane - Basilar membrane - Tectorial membrane

Question 27

Reissner's Membrane

Answer 27

Roof of cochlear duct

Question 28

Basilar Membrane

Answer 28

Fibrous floor of cochlear duct Supports organ of corti Near oval window: narrow, thick Near cochlear apex: wider, thinner

Question 29

Tectorial Membrane

Answer 29

Overhanging membrane of organ of corti In contact with stereocilia of hair cells

Question 30

Role of Sense of Hearing

Answer 30

Translate pressure waves of perilymph and endolymph to electrical signal and acoustic sensation

Question 31

Bending of cilia produces change in K+ conductance

Answer 31

Toward kinocilium: increases K+ influx Away from kinocilium: decreases K+ influx Kinocilium = tallest sterocilia

Question 32

Basilar Membrane: Fibers

Answer 32

Span the width like the strings of a harp Near oval window: short, stiff -resonate with HIGH frequency waves Near cochlear apex: longer, floppier -resonate with lower frequency waves

Question 33

Sound

Answer 33

Pressure disturbance originated from a vibrating object Propagated by molecules of medium (air, liquid) Normally manifests as pressure or sound wave

Question 34

Frequency

Answer 34

Number of sound waves that pass a given point in a given time Hertz Shorter wavelength = high frequency

Question 35

Pitch

Answer 35

Our ears perceive different frequencies as pitch higher frequency = higher pitch ability to distinguish pitch and loudness depends on ability of cochlea to respond differently to vibrations of different amplitude and frequency

Question 36

Tuning Fork

Answer 36

Pure sound - single frequency Most sounds are a mixture of frequencies

Question 37

Place Coding

Answer 37

Frequency sensitivity of IHCs depends on their position along basilar membrane of cochlea

Question 38

Loudness

Answer 38

An increase in AP firing Related to amplitude of sound waves Measure of sound intensity Decibels

Question 39

Severe Hearing Loss

Answer 39

Frequent/prolonged exposure to sound greater than 90 dB

Question 40

Sound source directly in front, in back, over midline of head...

Answer 40

Intensity and timing cues will be the same for both ears

Question 41

Sound coming from one side...

Answer 41

Nearer hair cells activated: - slightly earlier - more vigorously

Question 42

Superior Olivary Nucleus

Answer 42

Functions in biaural hearing Compares signals from R and L ear to identify direction from which a sound is coming

Question 43

Conductive Deafness

Answer 43

BC>AC Sound vibrations don't go from air to ossicles as well as they should (loss of air conduction) Effects auditory canal and middle ear

Question 44

Conductive Deafness: Causes

Answer 44

Ear wax buildup Fluid buildup from infection Puncture of eardrum

Question 45

Conductive Deafness: Results

Answer 45

Loss of loudness Loss of clarity Sounds are weak, muffled, distorted

Question 46

Nerve Deafness

Answer 46

Sensorineuronal Both air and bone conduction decreased Auditory nerve damage (loss of air and bone conduction) Effects cochlea, nerve, cochlear nucleus

Question 47

Nerve Deafness: Causes

Answer 47

Ototoxic drugs Prolonged exposure to loud sounds Inner ear infections

Question 48

Rinne Test

Answer 48

Use a tuning fork to determine air conduction (AC) and bone conduction (BC)

Question 49

Normal Hearing in Adults

Answer 49

0-25 dB

Question 50

Most Important Frequencies for Speech

Answer 50

250-6000 Hz

Question 51

Presbycusis

Answer 51

Gradual loss of hearing associated with aging Due to gradual cumulative loss of hair cells and neurons

Question 52

Presbycusis: Loss

Answer 52

Loss of ability to hear consonants Loss of high frequency sounds Difficulty screening out background noise