B7.003 Sensory Transduction

Question 1

types of senses

Answer 1

vision
hearing
touch
taste
smell
somatic proprioception
pain
itch
temperature
visceral sensation
vestibular senses

Question 2

how are sensations processed

Answer 2

processed by complex neuronal systems which transform simple forms into complex images and cognition

Question 3

what is perception

Answer 3

all senses knit together to form a unified experience of the self and the external world

Question 4

what do sensory systems do?

Answer 4

detect and discriminate information about
-modality
-intensity
-duration
-location
of sensory stimuli

Question 5

4 types of sensations

Answer 5

superficial
deep
visceral
special

Question 6

superficial sensations

Answer 6

touch
pain
temp
2 point discrimination

Question 7

deep sensations

Answer 7

proprioception
deep muscle pain
vibration

Question 8

visceral sensations

Answer 8

mostly autonomic
hunger
nausea
visceral pain

Question 9

special sensations

Answer 9

smell
vision
hearing
taste
equilibrium

Question 10

sensory receptors

Answer 10

specialized cells for detecting particular changes in the environment
NOT receptor proteins

Question 11

externoreceptors

Answer 11

affected mainly by the external environment

• Meissner’s corpuscles, merkel’s corpuscles, and hair cells for touch
• Krause end bulbs for pressure and vibration
• ruffini endings for stretch
• free nerve endings for pain and temp

Question 12

proprioceptors

Answer 12

convey state of internal environment

-Pacinian corpuscles, joint receptors, muscle spindles, and Golgi tendon organs

Question 13

simple receptors

Answer 13

neurons with free nerve endings

Question 14

complex neural receptors

Answer 14

have nerve endings enclosed in a connective tissue capsule

Question 15

special senses receptors

Answer 15

cells that release neurotransmitter onto sensory neurons initiating an action potential

Question 16

modality specificity of sensory receptors

Answer 16

1. mechanoreceptors (touch, stretch, vibration, sound)
2. chemoreceptors (taste, smell, pain)
3. photoreceptors (vision)
4. thermoreceptors (temp)
   each is optimally selective for a single type of energy
   usually relies on specialized anatomical structure

Question 17

what is somatotopy/ tonotopy / retinotopy

Answer 17

anatomical location reflects position of stimulus in space (body surface or visual field)

Question 18

what are psychophysics

Answer 18

relates physical characteristics of stimulus to attributes of sensory perception / experience

• sensation is proportional to power of stimulus intensity
• decisions are probabilistic, and latency depends on cognitive process

Question 19

power curves

Answer 19

relate stimulus intensity to perception

Question 20

function of electrophysiology

Answer 20

reveals nature of neuronal transduction

neuronal firing patterns transmit sensory info into the CNS

Question 21

when do receptors generate action potentials?

Answer 21

spatial and temporal integration of excitatory and inhibitory post synaptic potentials across the neuron’s membrane, resulting in the action potential being reached
called the “generator potential”

Question 22

result of an action potential in a receptor

Answer 22

sensory stimulation / transduction

Question 23

what is the “neural code”

Answer 23

sensory input is represented in the firing patterns of populations of neurons

Question 24

what determines the intensity of a signal

Answer 24

number or rate of action potentials

number of neurons activated (parallel processing)

Question 25

contrast enhancement

Answer 25

parallel processing of cells of different thresholds refines the acuity of a signal

Question 26

electrophysiology (tuning) curves

Answer 26

relates stimulus intensity to neuronal activity

Question 27

discuss a receptor's adaptation to persistent stimuli

Answer 27

varies across different receptor subtypes slow and rapid adaptors -tonic = slow -phasic = rapid adaptation leads to a decrease in neural response to maintained stimulation

Question 28

how is spatial information encoded into the neural code

Answer 28

function of "receptive fields" - populations of neurons have endings in different locations within the modality "space" - position of the neuron in the sense organ is the primary element of topography

Question 29

receptive field

Answer 29

area of the skin where stimulation produces activation of a neuron generally coincides with a perceptive field defined by receptive neuron branching patterns can overlap

Question 30

variations in receptive fields

Answer 30

vary in size, orientation, and sensitivity can be defined at different levels (peripheral, cord, thalamus, cortex) become more complex at higher levels topography is retained through projections and in central nuclei

Question 31

somatotopic organization

Answer 31

retained topography of nerves throughout nervous system into central nuclei - dermatomes: define relationship between body regions and the spinal cord segment innervating them - sensory homunculus: define relationship between body regions and corresponding area of sensory cortex

Question 32

vision retinotopy

Answer 32

visual receptive field of a single photoreceptor can trace back to the occipital lobe light outside of the region will have no effect on the specific cell

Question 33

tonotopy

Answer 33

relative lengths of fibers in basilar membrane convey different frequencies

Question 34

function of receptive fields

Answer 34

dimensions and overlap are important small = higher acuity overlap = increases resolution

Question 35

pattern theory of sensory codes

Answer 35

populations of neurons play a critical role in encoding sensory information coding can occur because of a pattern of activation across multiple receptor types

Question 36

example of a sense that may be impacted by pattern theory

Answer 36

color vision

Question 37

what is convergence

Answer 37

sensory receptors make connections with structures in the CNS multiple neuronal inputs will converge onto central cells, establishing a higher level receptive field

Question 38

manipulation of convergence

Answer 38

individual inputs may have different strength in stimulating the subsequent neurons - interneurons (often inhibitory) can modify the interactions between receptors and nucleus - allows for modification of simple information (processing)

Question 39

surround inhibition example of convergence manipulation

Answer 39

surround inhibition stimulus > primary neuron response is proportional to stimulus strength > pathway closest to the stimulus inhibits neighbors > inhibitors of lateral neurons enhances the perception of stimulus *results in increased acuity or contrast enhancement

Question 40

other examples of convergent controls

Answer 40

descending pain controls reflex suppression attention *all are ways to process an incoming signal into more complex, meaningful information

Question 41

how is perception initiated

Answer 41

sensory systems with discrete, specific peripheral receptors break down the complex world surrounding us into very simple components (modality, location, intensity, duration) percept is formed when these bits are merged together convergence starts this process

Question 42

describe hierarchical processing

Answer 42

subsequent, more convergent connection provide a hierarchy combine attributes of transduced information form recognizable features ultimately information becomes more polymodal and more cognitive

Question 43

parallel processing

Answer 43

allows simultaneous inputs to different specialized parts of the brain

Question 44

structures associated with higher levels of perception

Answer 44

superior colliculus associative cortex can recognize very complex patterns due to associations with previous experience, prediction, and "templates"

Question 45

features of construction of perception

Answer 45

- dependent on knowledge - partially creative - includes decision making (form vs background) - experience helps resolve ambiguity - template matching

Question 46

stereogenesis

Answer 46

ability to identify objects based solely on touch