CH 10 - Sensory physiology

Question 1

What is a free nerve ending receptor?

Answer 1

• simple receptor
• may be myelinated or unmyelinated

Question 2

What is a complex neural receptor?

Answer 2

• have nerve endings enclosed in connective tissue capsules

Question 3

What are most special senses receptor cells?

Answer 3

• release neurotransmitter onto sensory neurons, initiating action potential
• have specialized receptor hair

Question 4

What are the 4 sensory accessory structures and what they respond to?

Answer 4

1. Chemoreceptors: respond to chemical ligands (smell, taste)
   - oxygen, pH, glucose, etc
2. Mechanoreceptors: respond to mechanical energy, pressure, and sound (ex: hearing)
   - cell stretch, pressure, vibration, acceleration, and sound
3. Thermoreceptors: respond to temperature
4. Photoreceptors: for vision, respond to light

Question 5

What is transduction?

Answer 5

• stimulus energy converted into information processed by nervous system
• ion channels or second messengers initiate membrane potential change

Question 6

What is an adequate stimulus?

Answer 6

a form of energy to which a receptor is most responsive

Question 7

What is a receptor potential?

Answer 7

• another name for a graded potential
• change in sensory receptor membrane potential

Question 8

What is a receptor field?

Answer 8

• the physical area where a stimuli activates a neuron
• primary sensory neuron and secondary sensory neuron
• receptor fields frequently overlap
• neighboring fields may exhibit convergence
• the size determines sensitivity (2 point discrimination test)
• Sensitive areas have smaller receptive fields
• less sensitive areas have larger receptive fields
  (figure 10.2)

Question 9

What is perceptual threshold?

Answer 9

level of stimulus necessary to be aware of particular sensation

Question 10

What is habituation?

Answer 10

• decreased perception through inhibitory modulation
• falls below perceptual threshold

Question 11

Where do most sensory pathways project to?

Answer 11

The thalamus

Question 12

Where do equallibrium pathways primarily project to?

Answer 12

the cerebellum

Question 13

How does the brain distinguish between stimuli that are converted to action potentials?

Answer 13

• sensory modality
• the location of the stimulus
• the intensity of the stimulus
• the duration of the stimulus

Question 14

How does the brain use sensory modality to distinguish between stimuli?

Answer 14

• depends on which sensory neurons are activated and where neurons terminate in the brain
• the type of stimulus
• Label coding —> 1:1 association of receptor with sensation

Question 15

How does the brain use the location of the stimulus to distinguish between stimuli?

Answer 15

• which receptive fields are activated
• lateral inhibition and population coding
• sound waves hits each ear at a different rate but your brain hears them together

Question 16

How does the brain use the intensity of the stimulus to distinguish between stimuli?

Answer 16

• the number of receptors activated and frequency coding

Question 17

How does the brain use the duration of the stimulus to distinguish between stimuli?

Answer 17

• duration of action potentials
• receptors adapt: tonic receptors v. phasic receptors

Question 18

What is population coding?

Answer 18

The number of sensory receptors activated encodes the intensity of the stimulus

Question 19

What is lateral inhibition?

Answer 19

Process in which sensory neurons close to a stimulus are inhibited to intensify the perception of the stimulus

Question 20

What is the difference between tonic and phasic receptors?

Answer 20

• Tonic: slowly adapting receptors that respond for the duration of the stimulus
• Phasic:Rapidly adapt to a constant stimulus and turn off

Question 21

Where are receptors for somatic senses located?

Answer 21

• skin and viscera

Question 22

Where do primary sensory neurons synapse?

Answer 22

in the CNS with secondary neurons

Question 23

Where do the secondary sensory neurons synapse & what are they?

Answer 23

• interneurons in CNS
• synapse with tertiary sensory neurons in thalamus

Question 24

Where are the tertiary sensory neurons?

Answer 24

project to somatosensory cortex and many project to cerebellum somatosensory cortex

Question 25

What initiates touch receptors? where are they found?

Answer 25

• most common/frequent in the body
• Found in skin or deeper regions
• stretch
• steady pressure
• fluttering or stroking movements
• vibrations
• texture

Question 26

What kind of receptors regulate skin temperature, and at what temperatures?

Answer 26

• thermoreceptors are free nerve endings that terminate in the subcutaneous layers
• Thermoreceptors use cation channels
• cold receptors = colder then body temp
• warm = above 45 deg. C, anything below is pain receptors

Question 27

What are nociceptors and where are they found?

Answer 27

• neurons with free nerve endings
• respond to strong noxious stimulus that may damage tissue
• found in skin, joints, muscles, bones, and viscera
• not found in CNS
• Activation initiates adaptive reflex (integrated in spinal cord)

Question 28

How is pain recognized?

Answer 28

• in nociceptors
• subjective perception per person
• fast or slow pain

Question 29

How are itches recognized?

Answer 29

• from skin nocioceptors
• histamine (and other substances) cause itch

Question 30

Where do reflexive protective responses integrate?

Answer 30

at the level of the spinal cord

Question 31

How do nocioceptors help with inflammation?

Answer 31

local chemicals respond at the injury site

Question 32

What is the withdrawl reflex?

Answer 32

protective reflex in response to pain