Sensory Physiology

Question 1

General senses

Answer 1

Touch, temp, pressure, pain, itch

Question 2

Special senses

Answer 2

Vision, hearing, smell, taste

Question 3

Visceral senses

Answer 3

pH, osmolarity, chemoreceptors

Question 4

Proprioceptors

Answer 4

Stretch, position, over-contraction

Question 5

Two types of sensory receptors

Answer 5

-Specialized endings of neuron
-Separate cell that signals to afferent neuron

Question 6

Receptor field

Answer 6

Area of skin that a sensory receptor innervates

Question 7

Characteristics of sensory receptors

Answer 7

-Modality
-Intensity
-Adaptation
-Localization

Question 8

Modality

Answer 8

-Receptor type
-Each responds to one type of stimulus only (except pain)
Ex: chemoreceptors, mechanoreceptors, proprioceptors, thermoceptors

Question 9

How do sensory receptors code for intensity?

Answer 9

-Coded by frequency of APs
-More APs = more intense
-Higher stimulus (pressure) also stimulates more fibres

Question 10

Adaptation

Answer 10

-When the neuron stops sending APs in response to a continuous stimulus
-Over time the frequency decreases

Question 11

Phasic or fast-adapting receptors

Answer 11

-Responds to a change in stimulus
ex: temp, touch, smell

Question 12

Tonic or slow-adapting receptors

Answer 12

-Continues to send APs in response to constant stimulus
-APs may go away slowly or not at all
ex: pain, vision, proprioceptors

Question 13

What do proprioceptors detect?

Answer 13

Changes in position and movement of body

Question 14

What sized receptor fields are found in sensitive areas such as the finger?

Answer 14

Very small

Question 15

Acuity

Answer 15

-Ability to distinguish between two stimulus points

Question 16

Factors that affect acuity

Answer 16

-Receptor field size (smaller = better)
-Receptor field overlap (more = better)
-Area of representation in cortex (more = better)
-Lateral inhibition (increases contrast and acuity)

Question 17

Lateral inhibition

Answer 17

-When neuron sends inhibitory messages to neighbours
-Narrows down the search for where the stimulus occurred by inhibiting surrounding neurons

Question 18

How is pain related to memory?

Answer 18

-Involves limbic system, which gets an emotional reaction, creating an emotional memory (sensitization) and behavioural change

Question 19

Nociceptors

Answer 19

-Pain receptors
-Do not adapt to sustained stimulation

Question 20

Cytokines

Answer 20

-Lower nociceptor’s threshold, so we are more likely to get a pain AP
-Present in inflammation response
-Hyper-algesia (more sensitive to pain)
ex: prostaglandins, bradykinin, histamines)

Question 21

3 types of nocireceptors

Answer 21

1. Mechanical nociceptors: respond to damage such as cutting, crushing, or pinching
2. Thermal nociceptors: respond to temperature extremes
3. Polymodal nocicpetors: respond equally to all kinds of damaging stimuli, creates secondary throbbing response that sticks around

Question 22

Fast pain vs slow pain

Answer 22

Fast pain:
-Mechanical or thermal nociceptors
-A-delta fibres
-Easily localized
-Occurs first

Slow pain:
-Polymodel nociceptors
-C fibers
-Dull and aching
-Poorly localized
-Occurs second, persists for longer

Question 23

Two best known pain NT

Answer 23

-Substance P: activates ascending pathways
-Glutamate: major excitatory NT

Question 24

What is the brain’s build in analgesic system?

Answer 24

-Suppresses transmission in pain pathways
-Uses opiates in descending pathways

Question 25

Referred pain

Answer 25

-The sensation of pain at a site other than the injured or diseased tissue -Critical to diagnosis -Occurs on skin -Brain interprets pain from organs as pain coming from skin because the two nerves are so close together

Question 26

What do chemoreceptors do?

Answer 26

-Help with smell and taste -Binding of molecules will trigger GPs and APs

Question 27

Which nerves work for smell and taste?

Answer 27

Smell: olfactory nerve Taste: glossopharyngeal nerve

Question 28

What is the role of mucous in smell?

Answer 28

Scent molecules must be dissolved in mucous made by support cells

Question 29

What is the lifespan of scent receptors?

Answer 29

2 months

Question 30

Which system does smell input to?

Answer 30

Limbic - emotional response and memories

Question 31

Taste buds are the receptors for _____

Answer 31

Taste

Question 32

Life span of taste buds

Answer 32

10 days

Question 33

5 types of taste

Answer 33

-Salty -Sweet -Sour -Bitter -Umani

Question 34

Gustatory transduction

Answer 34

-Involves the interaction of tastant molecules in saliva with the receptor cells in the taste buds on the papillae of the tongue -These receptor cells undergo only GPs during this process

Question 35

Facial nerve innervates which part of the tongue? Which tastes?

Answer 35

Front 2/3 Salty and sweet

Question 36

Glossopharygeal nerve innervates which part of the tongue? Which tastes?

Answer 36

Back 1/3 Sour and bitter