Sensory physiology- basics and chemosensation Flashcards

1
Q

What are the 4 steps of chemosensation?

A

Reception
Transduction
Transmission
Perception

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2
Q

What are the 7 types of receptors?

A
Chemoreceptors
Mechanoreceptors
Photoreceptors
Thermoreceptors
Electroreceptors
Magnetoreceptors
Nociceptors
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3
Q

What do chemoreceptors detect?

A

Chemical stimuli- smell and taste

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4
Q

What do mechanoreceptors detect?

A

Mechanical stimuli- touch and sound

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5
Q

What do photoreceptors detect?

A

Electromagnetic stimuli- vision

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6
Q

What do thermoreceptors detect?

A

Temperature related stimuli

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7
Q

What do electroreceptors detect?

A

Electrical stimuli

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8
Q

What do magnetoreceptors detect?

A

Magnetic stimuli

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9
Q

What do nociceptors detect?

A

Chemical stimuli-pain

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10
Q

Describe the reception step of chemosensation

A

The reception of the stimulus by a receptor

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11
Q

Describe the transduction step of chemosensation

A

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

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12
Q

Describe the transmission step of chemosensation

A

The signal is sent to an integration centre

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13
Q

Describe the perception step of chemosensation

A

The stimulus is perceived at the integration centre

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14
Q

What is lateral inhibition?

A

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

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15
Q

Why is lateral inhibition important?

A

Allows sharper discrimination of the boundaries of a stimulus

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16
Q

What is dynamic range?

A

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

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17
Q

What is the threshold intensity?

A

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

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18
Q

What is range fractionation?

A

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

19
Q

What does encoding signals logarithmically do?

A

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

20
Q

What are tonic receptors?

A

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

21
Q

What are phasic receptors?

A

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

22
Q

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

A

A paper cut

23
Q

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

A

A hot/cold bath

24
Q

What is the sense of smell called?

A

Olfaction

25
Q

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

A

Odorants

26
Q

What is the name of the receptors that detect odorants?

A

Odorant receptors

27
Q

What is the sense of taste called?

A

Gustation

28
Q

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

A

Tastants

29
Q

Where are taste receptors located?

A

The taste buds

30
Q

Describe signal transduction in vertebrate olfactory receptor cells

A

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

31
Q

What is the vomeronasal organ?

A

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

32
Q

Where is the vomeronasal organ located in mammals?

A

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

33
Q

What does the vomeronasal organ do in rodents?

A

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

34
Q

What is the vomeronasal organ called in snakes?

A

Jacobson’s organ

35
Q

Where is the Jacobson’s organ located in snakes?

A

In the oral cavity

36
Q

How do snakes use their Jacobson’s organ?

A

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

37
Q

How are pheromones released and detected in insects?

A

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

38
Q

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

A

Chemosensitive sensilla

39
Q

Describe how insects use their sensilla

A

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

40
Q

How do we taste salty things?

A

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

41
Q

How do we taste sweet things?

A

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

42
Q

How do we taste sour things?

A

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

43
Q

How do we taste bitter things?

A

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