Sensory Physiology Ch. 10

Question 1

Sensing the environment

Answer 1

Receptors are tuned to specific stimuli (modalities)
Chemoreceptor
Mechanoreceptor
Photoreceptor
Thermoreceptor
Nociceptor
Proprioceptor

Question 2

Function of Sensory System

Answer 2

1.Signal detection
2.Discrimination of some aspects of the sensory input
Estimation

Question 3

What must be estimated from the input: of Sensory System

Answer 3

1. Qualitative features: modality: what is stimulus?
2. Quantitative features: intensity
3. Temporal features: duration or frequency
4. Spatial location: where

Question 4

Sensory estimation
Depends on:

Answer 4

Specific receptor cell activity
Specific processing area in the brain
Sender and receiver!

Question 5

Sensory coding

Answer 5

Receptor cell sends type of stimulus
Remember: Kind of receptor activated + brain processing determine perception
Receptor cell sends intensity of stimulus
frequency of APs
Receptor cell sends location of stimulus
receptive field

Question 6

Receptive Field

Answer 6

Area of skin that, when stimulated, changes the firing rate of a neuron
Size of area depends on density of receptors in that region of skin
The more receptors, the smaller the field, the larger the brain area for processing.

Question 7

Sensory Acuity

Answer 7

Ability to detect details
A small receptive field = greater tactile acuity – sharpness of the sensation

Question 8

Two-point discrimination threshold

Answer 8

Receptive fields can be determined by measuring at what distance a person can perceive two separate points of touch.
Measurement of tactile acuity.

Question 9

Generator potential or receptor potential

Answer 9

Equivalent to EPSPs
Produced in response to strong enough stimulus
Generates action potential if it reaches threshold

Question 10

Sensory physiology

Answer 10

A signal from a specific sensory cell is sent to a specific processing center in brain.
Because of specific anatomical connection, signal indicates sensory modality and location of the stimulus.
Stimulus intensity is indicated by the frequency of APs.

Question 11

Input-Output Relations

Answer 11

Receptor response is proportional to logarithm of the stimulus intensity (semi-log).
Meaning: high-intensity end of scale becomes compressed Extending dynamic range of detection.
Sunlight is 109 times more intense than moonlight!
Human auditory system capable of detection sound intensity differing 12 orders of magnitude!

Question 12

Range fractionation:

Answer 12

different cells with different but overlapping sensitivities, extending dynamic range

Question 13

Function of sensory adaptation?

Answer 13

Extending dynamic range of detection, allowing detection of weak and strong stimuli.

Question 14

Phasic response:

Answer 14

Firing activity only when stimulus strength changes (on/off)

Question 15

Tonic response:

Answer 15

Firing activity continues for the duration of the stimulus

Question 16

Lateral Inhibition

Answer 16

Can occur with a group of adjacent receptor cells, such as found in the eye.
Neighboring cells may be connected with each other by inhibitory synapses.
Result: Enhanced Contrast

Question 17

Sensory Pathways

Answer 17

Convey the type and location of sensory stimulus.

Type of stimulus: because of type of receptor activated.
Location: because brain has a map of location of each receptor.

Question 18

Sensory Pathways

Answer 18

Olfactory pathways from the nose project directly to the cortex
All other pathways pass through the thalamus before they project to their relevant cortical area

Question 19

Sensory Processing

Answer 19

Somatosensory cortex: somatic senses
Sensory association areas (integration of all sensory input)
Visual cortex
Auditory cortex
Olfactory cortex

Question 20

Somatosensory Processing

Answer 20

Somatic Senses: somesthetic (“body feelings”) sensations:
touch, pressure, heat, cold, pain, from surface of the body
This information is “projected” to the somatosensory cortex in mammals.

Question 21

Somatotopic order in human primary sensory cortex

Answer 21

More brain area means more information processing and relatively more important.

Question 22

Sensory Physiology: Big Picture

Answer 22

Stimulus energy is “converted” to action potential energy.
Same response for all different stimuli.
Signals are interpreted as sight, sound, taste, depending on which sensory cells send the signal and which tissue in CNS receives it!
Note, modality is not coded for by AP!

Question 23

Free

Answer 23

Free