Sensory

Question 1

Describe the properties of taste receptor families and their

transduction mechanism

Answer 1

• T1R3 are in the detect for both Sweet and Umami.
• G-protein-coupled receptor
• T2R’s in the detect of Bitter
• G-protein-coupled receptor
• Sour has H+ ion channels
• Salt has ENac ion channels

Question 2

Describe the cell types in taste bud and how/what they communicate to the taste fibers

Answer 2

TYPE I (“Glial-like cells”):

• wrap around other cells in the taste bud
• Do not form any apparent specialized contacts with sensory nerve fibers

TYPE II (Receptor cells);
-Express G protein-coupled Rs (GPCRs) (known as TRs) for sweet, bitter and umami taste stimuli.

TYPE III (“Pre-synaptic”)
-Sour (H+)-sensing cells

Question 3

Labelled line/Combinatorial code, explain what these coding

schemes are

Answer 3

Labelled Line code:
Narrow tuning: small different tone.
- Small areas detect different tastes

Combinatorial code:
Broad tuning: broader detection and broader tone.
Can detect many different tastes. (cross)

Question 4

Knock-out experiment showed?

Answer 4

Deletion of TRC shows loss in detection of salt in mouse: Labelled line sensory, only one sensor detects the salt.

Question 5

Olfactory receptors

Answer 5

are chemoreceptors expressed in the cell membranes of olfactory receptor neurons and are responsible for the detection of odorants which give rise to the sense of smell.

Question 6

1 step of olfactory transduction

Answer 6

An odorant dissolves through mucus and binds to an odorant binding protein. (activates OBP)

Question 7

2 step of olfactory transduction

Answer 7

Activated odorant binding protein activates thousands of adenylate cyclase. (ADC

Question 8

3 step of olfactory transduction

Answer 8

Each ADC can activate thousands of cAMP.

Question 9

4 step of olfactory transduction

Answer 9

cAMP binds to millions of +NAT channels which open. Depolarizes the (R) receptor

Question 10

How can one detect and discriminate different odors?

Answer 10

Olfactory system contains both narrowly (very specific) and broadly tuned (not very specific. ) OR’s.

Balance between dedicated channels that enables the detection and discrimination of more odarants

Question 11

Components of the olfactory bulb circuit

Answer 11

olfactory glomeruli, mitral cells, granule cells

Question 12

Function of inhibitory granule cells

Answer 12

Inhibition of granule cells plays a key role in gating the flow of signals into the cerebellum

Question 13

Odor encoding

Answer 13

odor encoding comprises three main aspects: the identity of the odor-activated neurons, the temporal evolution of the ensemble, and oscillatory synchronization

Question 14

Olfactory cortex

Answer 14

Vital for the processing and perception of odor. Is a component of the limbic system. This system is involved in the processing of our emotions, survival instincts, and memory formation and connects senses, such as odors, to our memories and emotions

Question 15

Ear anatomy

Answer 15

External, middle and inner ear

Question 16

The inner ear

Answer 16

detect both auditory and vestibular cues.

Question 17

Cochlea

Answer 17

detects auditory cues.

Question 18

Function of cochlea and basilar membrane

Answer 18

Movement of the tympanum leads to movement of the maleus/incus/stapes, which presses on the oval window. This leads to movement of water in the cochlea. The basilar membrane deflects differentially with air compression/rarefaction.

Question 19

Basilar membrane frequency detection

Answer 19

thicker/narrower at the base and wide/loose at the end. This means that different part of the basal membrane deflect depending on the frequency. Low frequency is detected at the apex (travels longer). High frequency at the base (travels less but more powerful)

Question 20

The organ of Corti and hair cells

Answer 20

Hair cells are the sensory cells of the cochlea located in the center of the cochlea in the organ of corti, located between the basilar membrane and the tectorial membrane.

There are 2 different hair cell types: inner and outer

Question 21

Hair bundles

Answer 21

Hair bundles are made of stereocilia, organized in a very specific manner and connected by tip links and are made of actin
Stereocilia are the organelles detecting the deflection of the basilar membrane

Question 22

mechanoreceptors

Answer 22

are ionotropic to be able to detect very fast signal

Question 23

Detection of intensity in sound

Answer 23

Stronger vibration, more deflection stereocilla, more neurotransmitters are released.

Question 24

How does a hair cell sense vibration

Answer 24

Stereocilium deflection

• opening of a gate upon deflection of the tip-link
• entrance of K+ and Ca+ in the cell

Question 25

What is the hair bundle of a hair cell and what is it good for?

Answer 25

• Cylinder of actin covered with plasma membrane (Stereocilium)
• Made of more than hundred of stereocilia
• Is the organ of mechanosensation of the inner ear

Question 26

What is the difference between a inner and outer hair cell?

Answer 26

• Position in organ of Corti
• Shape of stereocilia
• Function
• Nerve innervation
• Electromotility