Sensory Perception

Question 1

Steps to Sensation

Answer 1

1. Stimulation
2. Transduction
3. Conduction
4. Perception

Question 2

Stimulation

Answer 2

Application of stimulus

Sensors most sensitive to one particular
stimulus modality (adequate stimulus)

Question 3

Transduction

Answer 3

– Induction of an action potential
– If strong enough depolarization, AP results
– ↑ stimulus strength above threshold → ↑ AP firing rate

Question 4

Conduction

Answer 4

– Relay of information through a sensory pathway to specific region of CNS 1st order neuron
– from stimulation point to CNS 2nd order neuron
– e.g., from entry into CNS to thalamus 3rd order neuron
– e.g., from thalamus to perception site

Question 5

Perception

Answer 5

– Detection of environmental change by CNS

Question 6

Receptor Properties

Answer 6

Adequate Stimulus-Sensors most sensitive to one particular stimulus modality

Sensory Adaptation
Phasic receptors
Tonic receptors

Acuity

Question 7

Sensory Adaptation

Answer 7

Response of sensors to constant stimulation

Question 8

Phasic Receptors

Answer 8

exhibit sensory adaptationfiring rate of receptor (# AP’s)
Decreases with constant stimulus

Question 9

Tonic Receptors

Answer 9

Exhibit little adaptation
Maintain constant firing rate as long as stimulus is applied

Question 10

Sensory System

Answer 10

Touch (Mechanoreceptors)
Temperature (Thermoreceptors)
Pain (Nociceptors)
Body position (Proprioceptors)
Photoreceptors
Osmoreceptors
Chemoreceptors

Question 11

Touch (Mechanoreceptors)

Answer 11

stretch, tension and indentation

Question 12

Temperature (Thermoreceptors)

Answer 12

changes in temperature

Question 13

Pain (Nociceptors)

Answer 13

damaging stimuli – extreme temperature, sudden or severe overdistension, chemicals

Question 14

Body position (Proprioceptors)

Answer 14

changes in joint and muscle tension and signal body position

Question 15

Receptors of the skin

Answer 15

Slow adapting or Fast adapting
1. Free nerve ending
2. Merkel’s disk
3. Meissner’s corpuscle
4. Pacinian corpuscle
5. Ruffin’s ending

Question 16

Slow adapting

Answer 16

Receptor is slow to give a response to a stimuli, and when a stimulus is removed, the response falls slowly

Question 17

Fast Adapting

Answer 17

Receptor will respond quickly, but will not give a sustained response

Question 18

Free nerve endings

Answer 18

Variable adapting (slow or fast)
Heat, cold, pain

Question 19

Merkel’s disk

Answer 19

Slow adapting
Expanded dendritic endings

Question 20

Meissner’s corpuscle

Answer 20

Fast adapting
Encapsulated endings
Tactile sensory input=light pressure, slow vibration (50 Hz)

Question 21

Pacinian Corpuscle

Answer 21

Fast adapting
Encapsulated endings
Tactile sensory input=heavy pressure, rapid vibration (300Hz)

Question 22

Ruffin’s ending

Answer 22

slow adapting
Expanded dendritic endings

Question 23

Tactile Sensory input

Answer 23

Respond to pressure and movement of skin
Specialized receptors that respond to particular types of inputs

Use mechanically gated ion channels ( pacinian and messiner)

Question 24

Acuity

Answer 24

• ability to discriminate size, shape of an object in the environment
  Determined by size of receptive field
  – area of the body that, if stimulated, will cause a response from a sensory neuron
• ↑ receptor density, ↓ receptive field size,↑ acuity
  – easier to define borders of an object

Question 25

Receptive Field

Answer 25

The region of the skin in which a stimulus evokes a response in a single sensory neuron

Discrimination depends on the density of receptors
- Fingers 1-4 mm
- Thigh 45 mm

Question 26

Thermoreception

Answer 26

Respond to non painful temperatures.
warm thermoreceptors
Cold thermoreceptors

Thermosensitive neurons are present in the skin, the hypothalamus and the spinal cord.

Thermoreceptors – respond to non painful temperatures. Extreme temp is detected by nociceptors