Module B: Sensory Systems

Question 1

Processing centres of sensory systems are found in the

Answer 1

spinal cord, thalamus, brainstem, and cerebral cortex

Question 2

Common features of senses are

Answer 2

• they require a physical stimulus
• events transform stimulus into nerve impulses
• response of signal gives rise to perception of sensation

Question 3

Definition of sensation is

Answer 3

the detection of a physical stimulus

Question 4

Definition of perception is

Answer 4

the interpretation modified by experience

Question 5

Some senses that we do not posses are

Answer 5

fish - pressure (mechanoreceptors) magnetic electrical fields and electrosensory systems
insects: hearing organs on legs

Question 6

What is involved in modality?

Answer 6

signal transduction, action potential, receptor specificity

neurons from specific receptors are modality specific

Question 7

Classes of receptors in humans

Answer 7

mechanoreceptors, chemoreceptors, thermoreceptors, photoreceptors

Question 8

Intensity of stimulus is determined by

Answer 8

Stimulus amplitude. This is coded by the number of activated neurons and the frequency of impulses

Question 9

How many taste receptors in one taste bud?

Answer 9

50-150

Question 10

How many taste buds are in the tongue?

Answer 10

2000-5000

Question 11

At what concentrations are papillae most selective?

Answer 11

low concentrations, they lose selectivity at higher concentrations

Question 12

Taste receptors/cells synapse with…

Answer 12

gustatory afferant axons at basal end

Question 13

Activation of taste receptor leads to…

Answer 13

hyperpolarisation or depolarisation

which leads to an increase in neurotransmitter or decrease in activity

allows two or more taste stimuli to be responded to by a single receptor cell

Question 14

Describe transduction mechanisms of bitterness, sweetness, and umami

Answer 14

• Specific G-protein receptors
• Activate Phospholipase C & 2nd messenger IP3
• Na channels open, depolarisation
• Voltage gated calcium channels release internal calcium stores
• Neurotransmitter release (serotonin, ATP, glutamate)

Question 15

Receptors for bitterness are..

Answer 15

T2R
30 types
Can’t distinguish bitter compounds

Question 16

Receptors for sweetness are..

Answer 16

T1R

Need two types (T1R2 and T1R3) together

Question 17

Receptors for amino acids/umami are…

Answer 17

T1R
Need two types (T1R1 and T1R3)
Detects only some amino acids (i.e. in protein such as glutamate and aspartate)

Question 18

Receptors for saltiness are…

Answer 18

Amiloride-sensitve sodium channels are used, causing depolarisation and calcium release

ENaC

Question 19

Receptors for sourness are…

Answer 19

Protons are transported through amiloride-sensitive sodium channels, inhibiting potaassium influx.

Question 20

Nerves associated with taste are:

Answer 20

7: Facial, majority of tongue
9: Glossopharyngeal, back of tongue
5: Vagus, start of throat

Question 21

Taste nerves go to

Answer 21

the nucleus of the solitary tract/gustatory nucleus

all information is then carried to the ventral posterior medial nucleus of the thalamus before moving to the bustatory cortex (both insula and frontal operculum)

Question 22

Mucous secreted by the oflactory glands contain…

Answer 22

• Mucopolysaccharides
• Antibodies
• Odorant binding proteins

Question 23

Oflactory cells are created from basal stem cells every…

Answer 23

4-8 weeks

Question 24

Olfactory receptors when activated…

Answer 24

• Activate adenylyl cyclase
• Increase cAMP levels
• Activates Ca/Na channels
• Chloride leaves cell through Ca gated Cl channels
• Calcium can also leave the cell through Na/Ca exchangers
• Membrane depolarisation

Question 25

Olfactory receptors are specific to…

Answer 25

One or a few types of odorant molecules

Question 26

Vomeronasal organ has….

Answer 26

V1R and V2R genes