week 7

Question 1

sensory organs are very diverse but all senses use the same type of energy: ___ ___.

Answer 1

action potentials

Question 2

out of a trillion nanometers, human sensory mechanisms can perceive about ___ nanometers of wavelength.

Answer 2

400

Question 3

how many colour receptors do humans have?

Answer 3

3

Question 4

which of the following animals has the most colour receptors + what does this entail?

a) cat
b) honeybee
c) pigeon

Answer 4

c) pigeon – entails seeing millions more colours than humans.

Question 5

define transduction

Answer 5

the generation of neural signals that can be used by the brain.

Question 6

the pacinian corpuscle is a skin receptor that responds to ___ and ___.

Answer 6

vibration and pressure

Question 7

describe the process of transduction of the pacinian corpuscle (2)

Answer 7

1. stimulus opens sodium channels and produces a graded generator potential.
2. when potential is big enough, receptor reaches threshold and generates an AP.

Question 8

know how a generator potential vs action potential look like, see slide 10

Answer 8

know how a generator potential vs action potential look like, see slide 10

Question 9

describe the process of transduction of a photoreceptor.

Answer 9

1. photopigment absorbs light.
2. photopigment changes shape in response to light (i.e., bent to straight).

Question 10

describe the process of transduction of a hair cell.

Answer 10

• mechanical transduction
• ion channels open and close

Question 11

T or F: perception is an absolute measure.

Answer 11

FALSE!!!
perception is relative

Question 12

why did one square look darker than the other, despite being the same colour? (2)

Answer 12

• combined with the contrasting shading in between the two blocks, our brain interprets the top block as dark and the bottom one as light.
• it’s what our brains expect due to the other surrounding elements.

Question 13

T or F: the # of colour-sensitive cones in the human retina differ by up to 40 times, yet people appear to perceive colour in the same way.

Answer 13

true!
thus, sensory input is not only thing brain considers – context plays a role.

Question 14

why is relative perception important? (2)

Answer 14

• sensory adaptation
• without adaptation, there would be no way to distinguish A from B.

Question 15

define adaptation

Answer 15

the progressive loss of receptor sensitivity as stimulation is maintained.

Question 16

benefits of adaptation (2)

Answer 16

1. helps to ignore constant/innocuous stimuli, reducing distraction.
2. allows detection of larger range of stimulus intensities.

Question 17

define range fractionation + label diagram on slide 25.

Answer 17

• skin contains array of receptors that transduce different forms of energy to provide our sense of touch.
• e.g., pacinian corpuscles = fast adaptors.
• e.g., ruffini corpuscles = slow adaptors.
• e.g., merkel’s disc = contrasts.
• e.g., meissner’s corpuscle = texture.

Question 18

the dorsal column medial lemniscus system delivers __ information.

Answer 18

touch

Question 19

what are the 2 major somatosensory pathways?

Answer 19

• (dorsal column) medial lemniscus system
• anterolateral system

Question 20

describe process of dorsal column medial lemniscus system (3).

Answer 20

1. info travels up the dorsal column.
2. first synapses in the caudal medulla of brainstem.
3. crosses over (decussation) in the medial lemniscus and projects up to the thalamus.

Question 21

what do labelled lines do? (3)

Answer 21

• allow spatial organization b/c uniquely convey spatial information.
• neurons arranged in an orderly, map-like manner.
• the map at each sensory level is not exact, but reflects spatial positions and receptor density.

Question 22

what is the montreal procedure? (3)

Answer 22

• wilder penfield treated patients with severe epilepsy by destroying nerve cells in the brain where the seizures originated.
• before operating, he stimulated the brain with electrical probes while the patients were conscious (under only local anesthesia), and observed their responses.
• could more accurately target the areas of the brain responsible, reducing the side-effects of the surgery.

Question 23

areas of the body that are more sensitive are ___ in the cortex.

Answer 23

magnified

Question 24

what is a two-point threshold test?

Answer 24

• approximate measure of the density and receptive field properties of touch receptors.
• e.g., thumb: less than 3.5mm only one point is perceived (very sensitive) vs less than 45mm on calf.

Question 25

what is the hierarchy of sensory system organization (bottom to top)?

Answer 25

receptors
thalamic relay nuclei
primary SC
secondary SC
association cortex

Question 26

was dr P’s problem one of sensation or perception? (2)

Answer 26

• perception.
• without a holistic sense of his wife as a person, he confuses his sensory data all too easily.