sensory physiology- general principals

Question 1

what are the types of sensory receptors?

Answer 1

Mechanoreceptors

Thermoreceptors

Photoreceptors

Chemoreceptors

Nociceptors

Question 2

Physical (direct) transduction:

Answer 2

Interaction of stimulus with membrane protein opens ion channel

Question 3

examples of direct/physical transduction

Answer 3

somatosensory, vestibular, auditory, taste

Question 4

Molecular transduction:

Answer 4

molecular interaction of stimulus with membrane protein

e.g. G-protein

Question 5

examples of molecular transduction

Answer 5

vision, taste, olfaction

Question 6

what are the steps that occur during “direct” transduction in the taste system?

Answer 6

1. Na+ enters through “ENaCs”
   (epithelial Na+ channels)
2. Action potentials lead to Ca++ entry
3. Release of ATP as neurotransmitter

Question 7

what taste utilizes molecular transduction?

Answer 7

sweet, amino acids, bitter

Question 8

what are the steps involved in molecular (g-protein coupled) transduction of taste?

(give the example for “sweet” tastes)

Answer 8

1.Sugars bind to receptor coupled to G-protein

2. Release of intracellular Ca++ activates TRPm5 channel
   (Transient Receptor Potential)
3. Depolarization leads to action potentials &
   release of neurotransmitter ATP

Question 9

which molecule is the “key” in the pathway for sensing sweetness?

Answer 9

TRPm5 channel

transient receptor potential channel

Question 10

TRP channels are Cation ion channel that can pass _______ with a large variety of activating mechanisms

Answer 10

calcium ions

Ca2+

Question 11

what are some examples of activating mechanisms for TRP channels?

Answer 11

Intracellular Ca++
temperature
chemicals
sound
light
pH and osmolarity
mechanical

Question 12

how can the nervous system code for the intensity of a stimulus?

Answer 12

A) increase stimulus intensity
B) increase receptor potential
C) increase the number of action potentials

Question 13

T/F: the threshold value is a known, quantifiable number for a neuron

Answer 13

False- it is not a precise value, its a statistical concept

defined as the stimulus intensity detected on 50% of trials

Question 14

the ________ Can be affected by psychological, neurological, or pharmacological factors

Answer 14

threshold

Question 15

what are the common stimulus attributes coded by sensory systems?

Answer 15

A) Modality & quality (what?)
B) intensity (how much?)
C) location (where?)
D) duration (when?)

Question 16

the _________ is what a receptor (or neuron) is sensitive to

Answer 16

receptive field

Question 17

T/F: in a single neuron, location and intensity can be confounded (confused)

Answer 17

true

Question 18

how does our body prevent the confounding of location and intensity?

Answer 18

Across neuron coding

use multiple neurons to identify location

Question 19

how is olfactory quality determined?

Answer 19

Comparing activity across olfactory fibers

Question 20

what is lateral inhibition?

Answer 20

the capacity of an excited neuron to reduce the activity of its neighbors

-vital for determining the location of a stimulus

Question 21

what type of inhibition occurs when a hyperpolarized axon terminal leads to less Ca++ entry and less neurotransmitter release

Answer 21

Presynaptic inhibition

Question 22

what occurs during postsynaptic inhibition?

Answer 22

EPSPs and IPSPs interact: spatial & temporal summation

Question 23

describe the sensory pathway for the auditory system:

start at the hair cell

Answer 23

1. Hair cells (receptor cells) in cochlea (inner ear)
2. Innervation by CN VIII nerve
3. CN VIII nerve synapses in cochlear nuclei
4. Ascending sensory pathway to cortex
5. Efferent pathway from superior olivary nuclei

Question 24

T/F: Superior olivary nucleus has descending

Pathway to auditory receptor cell

Answer 24

true

Question 25

Efferents from the __________ synapse on hair receptor cells

Answer 25

superior olive

Question 26

what type of synapse occurs between fibers of the superior olive and hair receptor cells?

Answer 26

Synapse is an inhibitory nicotinic receptor

Ca++ activated K+ channel leads to hyperpolarization

Question 27

what is the result of innervation of the hair receptor cells by the superior olive?

Answer 27

functions to “set the gain” of receptor neuron

-can lessen its firing rate (loud concert—- superior olive limits signals coming from hair cells)

Question 28

what are the 3 types of Topographic Maps? what does each represent?

Answer 28

Somatotopic map
body representation

Tonotopic map
auditory pitch representation

Retinotopic map
visual field representation

Question 29

the __________ is a visual representation of our bodies somatotopic map (body representation)

Answer 29

homunculus

Question 30

what can effect sensory maps?

Answer 30

• injury

- experience

Question 31

what occurs during “central sprouting”?

what type of sensory mapping is it associated?

Answer 31

• in the event of a lesion to one neuron, its neighbor may project a dendrite and replace its function
• associated with neurological injury of the sensory map

Question 32

how can experience affect the sensory map of an individual?

Answer 32

Synaptic efficacy: long-term potentiation

New synapses

Loss of inhibition