Sensory transduction

Question 1

All sensory systems convey which 4 basic types of information when stimulated?

Answer 1

Modality
Location
Intensity
Time course

Question 2

What are the 2 superficial mechanoreceptors?

Answer 2

Meissner corpuscles

Merkel cells

Question 3

What are the 2 deep mechanoreceptors?

Answer 3

Pacinian corpuscles

Ruffini endings

Question 4

What are the 2 rapidly adapting mechanoreceptors?

Answer 4

Meissner corpuscles

Pacinian corpuscles

Question 5

What are the 2 slowly adapting mechanoreceptors?

Answer 5

Merkel cells

Ruffini endings

Question 6

Describe the 3 ways in which pressure opens ion channels on mechanoreceptors.

Answer 6

The force of the pressure causes the cell membrane to stretch and pull ion channels open:

1. Change in tension in the lipid bilayer
2. Changes in extracellular matrix
3. Changes in intracellular cytoskeleton

Question 7

Which specific mechano-sensitive ion channel is present on Merkel’s discs?

Answer 7

Piezo 2

Question 8

Describe the process of sensory transduction in a Merkel’s disc.

Answer 8

Stretch opens Piezo 2, which causes receptor potential depolarization

This receptor potential depolarization opens voltage-gated Ca2+ channels, leading to the release of neurotransmitter

Action potentials are produced in SA1 neuron

Question 9

What do slowly adapting mechanoreceptors detect?

Answer 9

Object pressure and form

Question 10

What do rapidly adapting mechanoreceptors detect?

Answer 10

Object motion and vibration

Question 11

When are nerve action potentials fired when receiving input from Pacinian corpuscles?

Answer 11

At the start and end of the stimulus

Question 12

What is found in the layers of Pacinian corpuscles?

Answer 12

Viscous fluid

Question 13

What is the peak sensitivity of Pacinian corpuscles?

Answer 13

200 to 300 Hz

Question 14

Describe the size of the receptive fields of superficial receptors.

Answer 14

Small

Question 15

Describe the size of the receptive fields of deep receptors.

Answer 15

Large

Question 16

Distinguishing between two points of contact on the skin is termed what?

Answer 16

Tactile acuity

Question 17

Where on the body is tactile acuity the best and why?

Answer 17

Fingertips - receptors are dense

Question 18

When light passes through the retina, which cells does it first pass through?

Answer 18

Ganglion cells

Question 19

What are the 4 common regions in rods and cones?

Answer 19

1. Outer segment
2. Inner segment
3. Cell body
4. Synaptic terminal

Question 20

What type of receptors are rods and cones?

Answer 20

Photoreceptors

Question 21

Which part of rods and cones contains photopigment?

Answer 21

Outer segment (contains light sensitive discs)

Question 22

Which type of photoreceptor is more sensitive to light?

Answer 22

Rods

Question 23

How many rods and cones are in the retina?

Answer 23

Rods - 100 million

Cones - 5 million

Question 24

Which type of photoreceptor detects colour perception?

Answer 24

Cones

Question 25

Which type of cell is concentrated in the fovea?

Answer 25

Cones

Question 26

Why is resolution best in the fovea?

Answer 26

Due to 1:1 connections with bipolar and ganglion cells

Question 27

In dark conditions, what is the resting potential of photoreceptors? What is this known as?

Answer 27

-30mV 'Dark current' - Na+

Question 28

In dark conditions, what is the activity level of glutamate in photoreceptors?

Answer 28

Glutamate is released

Question 29

Which molecule keeps Na+ channels open in the 'dark current'?

Answer 29

cGMP

Question 30

What affect does light have on the membrane potential of photoreceptors?

Answer 30

Hyperpolarises the cells

Question 31

Describe how light causes hyperpolarization of photoreceptors.

Answer 31

Light causes a conformational change in the rhodopsin molecules This causes the release of phosphodiesterase Phosphodiesterase reduces the levels of cGMP, leading to the closure of Na+ channels, causing hyperpolarization

Question 32

Which fluid is found in the scala vestibuli?

Answer 32

Perilymph

Question 33

Which fluid is found in the scala tympani?

Answer 33

Perilymph

Question 34

Which fluid is found in the scala media?

Answer 34

Endolymph

Question 35

Describe the composition of perilymph in terms of Na+ and K+.

Answer 35

High Na+ Low K+

Question 36

Describe the composition of endolymph in terms of Na+ and K+.

Answer 36

Low Na+ High K+

Question 37

Which structure lies on the basilar membrane and contains the auditory receptor cells?

Answer 37

Organ of Corti

Question 38

Which cells are found in the Organ of Corti?

Answer 38

Hair cells

Question 39

Hair cells have which specialised feature?

Answer 39

Stereocilia

Question 40

What are stereocilia on hair cells attached to?

Answer 40

Tectorial membrane

Question 41

Hair cells synapse onto what?

Answer 41

Spiral ganglion cells

Question 42

What do stereocilia contain and how does this affect their form?

Answer 42

Aligned actin filaments - they are rigid and bend only at the base

Question 43

What connects the mechanosensitive ion channels to adjacent stereocilia?

Answer 43

Tip links

Question 44

Describe the process of auditory transduction.

Answer 44

Displacement of the stereocilia increase tension on the tip links and cause ion channels to open - this allows the influx of K+ and depolarizes the hair cell Receptor potentials stimulate neurotransmitter release which goes on to generate AP in neurons

Question 45

In auditory transduction, why does K+ move into the hair cells?

Answer 45

Because the endolymph has a high concentration of K+

Question 46

What structure divides the endolymph from the perilymph?

Answer 46

Reticular lamina

Question 47

How does the base of the basilar membrane differ from the apex?

Answer 47

Base is stiff Apex is soft

Question 48

The base of the basilar membrane detect which kind of frequency?

Answer 48

High frequency

Question 49

The apex of the basilar membrane detects which kind of frequency?

Answer 49

Low frequency

Question 50

What is Piezo 2?

Answer 50

A mechano-sensitive ion channel present on Merkel's discs

Question 51

When light passes through the retina, what is the order of the 3 cells it passes through?

Answer 51

Ganglion cells Bipolar cells Photoreceptors (rods + cones)

Question 52

In the dark current, is Na+ moving in or out of the cell?

Answer 52

Na+ moves in