Sensory physiology- basics and chemosensation

Question 1

What are the 4 steps of chemosensation?

Answer 1

Reception
Transduction
Transmission
Perception

Question 2

What are the 7 types of receptors?

Answer 2

Chemoreceptors
Mechanoreceptors
Photoreceptors
Thermoreceptors
Electroreceptors
Magnetoreceptors
Nociceptors

Question 3

What do chemoreceptors detect?

Answer 3

Chemical stimuli- smell and taste

Question 4

What do mechanoreceptors detect?

Answer 4

Mechanical stimuli- touch and sound

Question 5

What do photoreceptors detect?

Answer 5

Electromagnetic stimuli- vision

Question 6

What do thermoreceptors detect?

Answer 6

Temperature related stimuli

Question 7

What do electroreceptors detect?

Answer 7

Electrical stimuli

Question 8

What do magnetoreceptors detect?

Answer 8

Magnetic stimuli

Question 9

What do nociceptors detect?

Answer 9

Chemical stimuli-pain

Question 10

Describe the reception step of chemosensation

Answer 10

The reception of the stimulus by a receptor

Question 11

Describe the transduction step of chemosensation

Answer 11

The conversion of the stimulus into a change in the membrane potential

Question 12

Describe the transmission step of chemosensation

Answer 12

The signal is sent to an integration centre

Question 13

Describe the perception step of chemosensation

Answer 13

The stimulus is perceived at the integration centre

Question 14

What is lateral inhibition?

Answer 14

A relatively weak stimulus across multiple receptors will produce a response in each afferent neuron
A strong stimulus in the middle of these receptors will trigger the horizontal interneurons to inhibit signals at the outer receptors

Question 15

Why is lateral inhibition important?

Answer 15

Allows sharper discrimination of the boundaries of a stimulus

Question 16

What is dynamic range?

Answer 16

The range of stimuli intensities a sensory receptor is able to encode stimuli

Question 17

What is the threshold intensity?

Answer 17

The weakest stimulus that produces a response in a receptor 50% of the time

Question 18

What is range fractionation?

Answer 18

Groups of receptors that are each sensitive to a different range of stimulus that work together to cover the whole range of stimulus intensity

Question 19

What does encoding signals logarithmically do?

Answer 19

It allows a receptor to have a constant response to a given percentage change in stimulus intensity
Prevents the saturation of receptors

Question 20

What are tonic receptors?

Answer 20

They fire action potentials as long as the stimulus occurs and can provide information about how long a stimulus lasts

Question 21

What are phasic receptors?

Answer 21

They adapt very quickly and depolarise at the beginning of a stimulus and allow the tuning out factors in the environment that aren’t changing

Question 22

Give an example of a stimulus that is controlled by tonic receptors

Answer 22

A paper cut

Question 23

Give an example of a stimulus that is controlled by phasic receptors

Answer 23

A hot/cold bath

Question 24

What is the sense of smell called?

Answer 24

Olfaction

Question 25

What are the chemicals that are detected by the olfactory system called?

Answer 25

Odorants

Question 26

What is the name of the receptors that detect odorants?

Answer 26

Odorant receptors

Question 27

What is the sense of taste called?

Answer 27

Gustation

Question 28

What are the chemicals that are detected by the gustatory system called?

Answer 28

Tastants

Question 29

Where are taste receptors located?

Answer 29

The taste buds

Question 30

Describe signal transduction in vertebrate olfactory receptor cells

Answer 30

Thee binding of odorant chemicals to the receptor causes a conformational change The activated Golf protein moves through the membrane and activates adenylate cyclase The adenylate cyclase converts ATP to cAMP cAMP opens cAMP gated ion channels Ca2+ and Na+ enter the cell and cause a generator potential Ca2+ opens Ca2+ activated Cl- channels causing Cl- to leave the cell increasing the depolarisation The generator potential opens voltage-gated Na+ channels triggering action potentials

Question 31

What is the vomeronasal organ?

Answer 31

A small paired tubular structure embedded in the nasal epithelium of amphibians, reptiles, and many mammals

Question 32

Where is the vomeronasal organ located in mammals?

Answer 32

In the septum and has a pore that opens into the nasal cavity

Question 33

What does the vomeronasal organ do in rodents?

Answer 33

Detects pheromones that signal the sex, strain, identity, and sexual receptivity of another individual

Question 34

What is the vomeronasal organ called in snakes?

Answer 34

Jacobson's organ

Question 35

Where is the Jacobson's organ located in snakes?

Answer 35

In the oral cavity

Question 36

How do snakes use their Jacobson's organ?

Answer 36

They use their tongues to transfer pheromones to it by flicking their tongue in their mouth

Question 37

How are pheromones released and detected in insects?

Answer 37

The female releases a pheromone from a gland at the tip of her abdomen and it can travel thousands of meters in the air The male detects it by air passing over their antennae

Question 38

What are the hairs that cover an insect's antennae called?

Answer 38

Chemosensitive sensilla

Question 39

Describe how insects use their sensilla

Answer 39

Olfactory sensilla have a small pore at the tip to allow odorants to enter and sensory neurons express odorant receptors to detect those molecules

Question 40

How do we taste salty things?

Answer 40

Na+ from salty food enters through Na+ channel Resulting depolarisation opens voltage-gated Ca2+ channels Influx of Ca2+ causes neurotransmitter to be released

Question 41

How do we taste sweet things?

Answer 41

The sweet substance binds to its receptor causing a conformational change The activated G protein gustducin activated adenylate cyclase Adenylate cyclase catalyses the conversion of ATP to cAMP cAMP activates a protein kinase that phosphorylates and closes a K+ channel Resulting depolarisation opens voltage-gated Ca2+ channels Influx of Ca2+ causes neurotransmitter release

Question 42

How do we taste sour things?

Answer 42

H+ ions from sour foods block the K+ channel This prevents the K+ from leaving Resulting depolarisation opens voltage-gated Ca2+ channels Influx of Ca2+ causes neurotransmitter release

Question 43

How do we taste bitter things?

Answer 43

Bitter substance binds to its receptor causing a conformational change The activated G protein transducin activated PLC PLC catalyses the conversion of PIP2 into the second messenger IP3 IP3 causes the release of Ca2+ from intracellular stores Influx of Ca2+ causes neurotransmitter release