Lecture 20 - Introduction to the Senses

Question 1

senses:
- what are the 5 special senses
- what are the 4 somatic senses
- what is our state of consciousness for these 9 senses?
- how about our consciousness for other sense data from our body?

Answer 1

slide 4
- 5 special senses: vision, hearing, equilibrium, taste, and smell
- 4 somatic senses: touch, temperature, proprioception (body position), and nociception (pain)
- we are at least partly conscious of all 9 senses
- we are largely unconscious of other sense data from our body – blood pressure, lung inflation etc.

Question 2

receptors:
- what is transduction in receptor cells?
- what are two types of receptor cells in sensory systems?
- what is a receptor potential? what are the two options of what may happen as a result of a receptor potential change?

Answer 2

slide 6
- transduction: receptor cells that convert stimuli into electrical signals
- we can have neuronal or non-neuronal epithelial receptor cells (ex. vision, hearing respectively)
- receptor potential: a receptor cell converts stimulus energy to a graded change in membrane potential. this can release a neurotransmitter or fire action potentials

Question 3

adequate stimulus:
- what is an adequate stimulus?
- can a receptor only respond to one form of energy?
- explain using the example of thermoreceptors

Answer 3

slide 7
- adequate stimulus: the main stimulus/ the form of energy to which it is most responsive. ex. thermoreceptors adequate stimulus is temperature
- receptors with an adequate stimulus can also respond to other forms of energy - ex. thermoreceptors also respond to certain chemicals

Question 4

classification of receptors:
- state what form of energy the following receptors respond to:
chemoreceptors, mechanoreceptors, thermoreceptors, photoreceptors

Answer 4

slide 8
- Chemoreceptors: respond to specific molecules or ions, e.g. to glucose, or oxygen, or H+.
- Mechanoreceptors: respond to mechanical energy such as pressure, vibration, gravity, and sound.
- Thermoreceptors: respond to temperature.
- Photoreceptors: respond to light.

Question 5

sensitivity of receptors:
- what is the receptor threshold? ex with photoreceptors and chemoreceptors
- what is the perceptual threshold? ex with odorant molecules?

Answer 5

slide 9
- receptor threshold: the weakest stimulus that will cause a response in the receptor. ex. some photoreceptors can respond to a single photon / chemoreceptors for smell can respond to a single odorant molecule
- perceptual threshold: the weakest stimulus that will cause a conscious perception in the organism. ex. takes abt 40 odorant molecules for you to perceive a smell

Question 6

series of neurons in a sensory system:
- what are the first neurons in a sensory system called?
- where do these neurons synapse?
- what is convergence and what does it allow for?

Answer 6

slide 10
- the first neurons = primary sensory neurons
- synapse to secondary sensory neurons and that synapses to tertiary sensory neurons
- convergence allows for secondary and higher neurons to combine data from many neurons/receptors (ie. tertiary gets info from 3 secondary neurons wherein each secondary gets info from three primary - thus 1 tertiary get info from 9 primary neurons)

Question 7

sensory neurons carry info about many aspects of the stimulus:
- what is the first info neurons send? how is this indicated physiologically?
- what is the second info it sends? what are the two ways it does this?
- can the two ways act together?

Answer 7

slide 11-12
- 1st piece of info: the type of information AKA stimulus modality (is it light, sound, touch). it does this through labelled lines –> modality is revealed by which axons carry the signal (activity on neurons in the visual pathway means light; activity on neurons in the auditory pathway means sound.)
- 2nd piece of info: intensity of the information – does this by: (1) population coding of intensity (stronger stimuli = inc. intensity = activate more neurons), and/or (2) frequencing coding (stronger stimuli = inc. rate of firing of neurons)
- Both mechanisms may operate together: a stronger stimulus may increase the firing rates of neurons and also cause more neurons to be active.

Question 8

receptor and neuronal dynamics:
- what are dynamics with respect to receptors and neurons?
- what are the three cellular dynamics? what do they do and how do they differ with respect to steady levels and response?

Answer 8

slide 14-15
- dynamic = activities may depend on how a stimulus changes through time
-

Question 9

retinal cells:
- what type of cellular dynamic are retinal cells?
- what does this mean in the real world?
- how does this cellular dynamic make communication more efficient?
- what do temporal changes mean?

Answer 9

slide 16-18

Question 10

spatial changes:
- what are spatial changes?
- what are edges?
- what is an example of spatial changes with skin?

Answer 10

slide 19

Question 11

lateral inhibition:
- what is lateral inhibition with primary, secondary, and tertiary neurons?
- what does lateral inhibition accentuate?
- what do sensory neurons at an edge look like without lateral inhibition and with lateral inhibition?
- which neurons are an edge detector?
- where do neurons cancel out? what does this mean for phasic cellular dynamics?

Answer 11

slide 20-23

Question 12

sensory pathways:
- what brain region do most sensory pathways run though and where is this located?
- where do these pathways end up? give 4 examples
- state the exceptional pathway that doesn’t run though the main brain region
- state the exceptional pathway that runs though the main brain region but ends up elsewhere for the most part

Answer 12

slide 25

Question 13

brain inference:
- why does the brain have to infer?
- is an inference conscious or unconscious, fast or slow
- we can identify things visually in BLANK ms. fill in the BLANK
- can the brain be fooled? use an example
- does the brain mistrust coincidences? use an example

Answer 13

slide 26-28