Week 2 Lecture 2: Introduction to the Senses

Question 1

What are the five special senses?

Answer 1

Vision, hearing, equilibrium, taste and smell

Question 2

What is the 4 somatic senses?

Answer 2

Touch, temperature, proprioception and nociception

Question 3

Are we totally conscious of our senses?

Answer 3

No, we are only partly conscious of the data coming from our special and somatic senses and largely unconscious of all other senses e.g. blood pressure, pH etc.

Question 4

What are receptors?

Answer 4

Cells that convert stimuli into electrical signals

Question 5

What is the process by which receptors convert stimuli into electrical signals called?

Answer 5

Transduction

Question 6

Are receptors cells always neurons?

Answer 6

Not always, in some sensory systems e.g. vision receptors are neurons however in hearing, receptors are non-neuronal epithelial cells

Question 7

What is receptor potential?

Answer 7

When a receptor changes stimuli energy into graded change in membrane potential. The result is the release of neurotransmitter or the firing of an action potential

Question 8

What is an adequate stimulus?

Answer 8

The form of energy which a receptor is most sensitive to e.g. thermoreceptors respond most to temperature but may be able to respond to other forms of energy.

Question 9

What are the different types of receptors and their adequate stimuli?

Answer 9

• Chemoreceptors: chemical molecules or ions e.g. glucose, H+
• Mechanoreceptors: mechanical energy e.g. pressure and vibration
• Thermoreceptors: temperature
• Photreceptors: light

Question 10

What is the receptor threshold?

Answer 10

The weakest stimulus that will cause a response in the receptor e.g. photoreceptors can detect a single photon of light, chemoreceptors for smell may respond to single odorant molecule

Question 11

What is the perceptual threshold?

Answer 11

The weakest stimulus that will cause a conscious perception in the organism e.g. 40 odorant molecules required to perceive a smell

Question 12

What do sensory systems involve?

Answer 12

Series of neurons (primary, secondary, tertiary sensory neurons) that synapse onto each other

Question 13

What is the result of sensory systems involving series of neurons?

Answer 13

Convergence, presynaptic cells contact any one post-synaptic cell allowing for secondary and higher neurons to combine data from many receptors.

Question 14

What is stimulus modality?

Answer 14

The type of sense e.g. whether it is a light, sound, touch

Question 15

How do sensory systems indicate modality?

Answer 15

By labeled lines, the modality is revealed by which axons carry the signals e.g. activity of neurons in the visual pathway mean light

Question 16

What are the two ways groups of neurons represent intensity?

Answer 16

Population and frequency coding

Question 17

What is population coding of intensity?

Answer 17

Representing stimulus intensity by the number of active neurons (stronger stimuli may activate more neurons)

Question 18

What is frequency coding?

Answer 18

Stronger stimuli make individual neurons fire at a faster rate, more action potential

Question 19

Does population and frequency coding work together or seperately?

Answer 19

Both mechanisms may work together since a stronger stimulus may increase firing rate or cause neurons to be more active

Question 20

What are receptor-neuron dynamics?

Answer 20

Their activities depends on how stimuli changes through time e.g when a stimulus suddenly increases or decreases

Question 21

What are the different types of dynamic seen in cells?

Answer 21

Phasic: cell responds briefly to change then ceases in activity
Tonic: cell maintains their activity when the stimulus is not changing
Phasic-tonic: cell reacts to change but does not do not cease firing when stimulus is constant

Question 22

What is an example of phasic cells?

Answer 22

Retinal cells, report changes in visual world when something moves, when there is little change, phasic retinal cells to reporting

Question 23

Why are phasic signals significant?

Answer 23

Make communication more efficient, our world is very stable so it is more efficient to report change than repeat similar messages over and over

Question 24

What are temporal and spatial changes?

Answer 24

Temporal changes are changes through time and spatial changes (contrast) are difference between neighbouring regions in space

Question 25

What are locations with strong contrast called?

Answer 25

Edges

Question 26

How do sensory systems utilize edges?

Answer 26

Lateral inhibition

Question 27

What is lateral inhibition?

Answer 27

When cells inhibit their neighbours or the cells their neighbours excite, with lateral inhibition edges are detected by the sensory system while excitation and inhibition cancel out

Question 28

Which sensory pathways pass through the thalamus and which do not?

Answer 28

Visual, auditory, somatosensory, and gustatory pathways travel through the thalamus. The olfactory pathway bypasses the thalamus and equilibrium pathways project mainly in the cerebellum

Question 29

What does sensory processing involve?

Answer 29

Inference (educated-guessing), senses guide our behaviour and help us avoid danger but this is hard to do so inference is required, which is unconscious and fast

Question 30

What is consequences of the brain inferring?

Answer 30

The brain can be fooled and mistrusts coincidences