sensory physiology

Question 1

• Five major divisions based on stimuli they respond to

Answer 1

○ Mechanoreceptors 
		○ Thermoreceptors 
		○ Photoreceptors 
		○ Chemoreceptors 
		○ Nociceptors

Question 2

• Two types of receptor cells

Answer 2

○ A nerve cell

○ A specialised cell + afferent neurone

Question 3

Stimulus intensity encoded by

Answer 3

AP firing rate

Question 4

RA (phasic) neurones

Answer 4

respond poorly to steady stimuli, but very well to dynamic stimuli

Question 5

SA (tonic) neurones

Answer 5

detect continuous stimuli, but not dynamic stimuli

Question 6

C fibres

Answer 6

slow

no myelin

Question 7

Aa fibres

Answer 7

super fast

thick myelin

Question 8

Ab fibres

Answer 8

fast

Question 9

A delta fibres

Answer 9

kinda fast

Question 10

stimulus acuity

Answer 10

Ability to distinguish between two spatially separate stimuli

Question 11

stimulus acuity depends on

Answer 11

§ Density of peripheral receptors
§ Size of receptive fields
§ Central convergence and lateral inhibition

Question 12

Lateral inhibition restricts

Answer 12

spatial spread of excitation

Question 13

label line principle

Answer 13

§ Receptor does not dictate what the brain will understand, the location of the afferent nerve does
○ Action potentials in labelled lines generate specific sensory percept

Question 14

2 unencapsulated nerve endings

Answer 14

free nerve endings and Merkel’s disks

Question 15

free nerve endings

Answer 15

(slowly adaptive, variable gating)

□ Pain, warm, cold A-delta or C fibres

Question 16

merles’s disks

Answer 16

(slowly adapting, mechanoreceptor)

□ Continuous light tough (steady state info) Ab fibres

Question 17

3 encapsulated nerve endings

Answer 17

meissner’s corpuscle, lamellar corpuscle, bulbous corpusle

Question 18

miessner’s corpuscle

Answer 18

(rapidly adapting mechanoreceptor

□ Altered touch, spatial characteristics Ab fibres

Question 19

lamellar corpuscle

Answer 19

(rapidly adapting mechanosensor)

□ Deep pressure, vibration, Ab fibres

Question 20

bulbous corpusclee

Answer 20

(slowly adapting mechanosensor)

□ Heavy touch, stretch (joints) Ab fibres

Question 21

Na/Ca channels

Answer 21

§ Excitatory

Question 22

K/Cl channels

Answer 22

§ Inhibitory

Question 23

○ Golgi tendon organs

Answer 23

§ Compression, stretch
§ Rapid adapt, Aa, Ab fibres
§ Joint position, reflex response to over-flexion

Question 24

○ Muscle spindles

Answer 24

§ Compression, stretch
§ Rapid adapt of slowly adapt, Aa/Ab fibres
§ Rate of change and muscle stretch

Question 25

joint capsule receptors

Answer 25

§ Around the joint capsule § Fire information at different angles § Stretch receptors - ruffini § Joint angle information

Question 26

3 instruments for positional sense

Answer 26

joint capsule receptors muscle spindles Golgi tendon organs

Question 27

Transient receptor potential (TRP) channels

Answer 27

temperature sensitive ion channels | § Excitatory Na/Ca channels

Question 28

cold receptors

Answer 28

TRPM8 channels | § Firing rate increases as temp decreases

Question 29

cold receptors also respond to

Answer 29

eucalyptus, menthol

Question 30

cold receptors

Answer 30

§ Temperature range spanning about 10-35°C

Question 31

Warm receptors

Answer 31

TRPV1/3, TREK1 channels | § Firing rate increases as temp increases

Question 32

TRPV3

Answer 32

22-40°C

Question 33

TRPV1

Answer 33

42°C +

Question 34

2 distinct affarent pathways of somatosensory

Answer 34

DCML and anterolateral pathway

Question 35

- The dorsal column medial lemiscal pathway DCML

Answer 35

○ Larger fibres (30-110 m/s) | ○ More spatial organisation

Question 36

DCML does

Answer 36

``` § Localised touch § Fine grade touch § Vibration § Movement against skin § Joint position § Fine pressure ```

Question 37

- Anterolateral pathway

Answer 37

○ Thinner fibres (<40m/s) | ○ Less spatial organisation

Question 38

anterolateral pathway does

Answer 38

``` § Pain § Heat cold § Crude touch § Crude pressure § Tickle and itch § Sexual sensation ```

Question 39

Strong pressure/pinch/squeeze

Answer 39

§ High threshold stretch-gated Na/Ca channels

Question 40

- Temperature pain (hot, cold)

Answer 40

○ Thermally gated ion channels | ○ TRPV1/2/3 (HOT) and TRPM8 (cold) channels

Question 41

Polymodal nociceptors

Answer 41

- Receptive to all other painful stimuli ○ Respond to heat, cold, pinch and chemical stimuli ○ Express multiple receptors