Sensory Receptors: Tactile, Temperature, Proprioceptive Input

Question 1

Function somatosensory system

Answer 1

Provides information to CNS about the state of the body and its contact with the environment

Question 2

Function receptors

Answer 2

Transduce mechanical or thermal stimuli (extracellular info into intracellular response)

Question 3

Where is a receptor potential generated

Answer 3

Distal tips of first order neuron (cell bodies in dorsal root)
Passive potential

Question 4

Describe first order neurons

Answer 4

Unipolar
Primary neuron
Encode information as APs

Question 5

What kind of info do APs relay

Answer 5

Info about magnitude and duration

Question 6

Spinothalamic- Where do first order sensory neurons synapse onto second order neurons

Answer 6

Spinal cord

Question 7

DCML- Where do first order sensory neurons synapse onto second order neurons

Answer 7

Medulla (brain stem)

Question 8

Spinothalamic- Where do second order sensory neurons synapse onto third order neurons

Answer 8

Thalamus

Question 9

DCML- Where do second order sensory neurons synapse onto third order neurons

Answer 9

Thalamus

Question 10

Where do third order neurons project

Answer 10

Somatosensory cortex (S1)

Question 11

Name the ascending somatosensory pathways

Answer 11

Dorsal column medial lemniscus DCML
Spinothalamic

Question 12

What kind of info does dorsal column medial lemniscus propagate

Answer 12

Fine discriminatory touch
Proprioception

Question 13

What kind of info does spinothalamic propagate

Answer 13

Pain
Temperature

Question 14

Two Sensory fiber types for skin mechanoreceptor, thermal receptor, nociceptor

Answer 14

III- larger diameter, larger conducting velocity
IV- smaller diameter, smaller conducting velocity
- tactile info and pain, temperature, crude touch

Question 15

Dermatome

Answer 15

Map for regions of skin sensory neuron responsible for
- specific dorsal root supplies specific cutaneous region

Question 16

What is found in dorsal and ventral root

Answer 16

Dorsal root- contains sensory neuron (afferent)
Ventral root- contain motor neuron (efferent)

Question 17

What is found rostral and caudal regarding nerves

Answer 17

Rostral- enters spinal tract
Caudal- afferent limb of reflex arcs

Question 18

Proof of dermatones

Answer 18

Shingles are found in bands

Question 19

Name sensory receptor afferents found in glabrous skin

Answer 19

Meissner corpuscles (superficial)
Merkel’s disk (superficial)
Pacinian corpuscles (deeper)
Ruffini endings (deeper)

Question 20

Name sensory receptor afferents found in hairy skin

Answer 20

Hair and nerve fibers
Free nerve endings

Question 21

State adaptability and size of receptive field for glabrous skin

Answer 21

Meissner’s corpuscles- fast, small receptive field
Pacinian corpuscles- fast, large receptive field
Merkel’s disk- slow, small receptive field
Ruffini endings- slow, large receptive field

Question 22

Describe fast receptors

Answer 22

filter steady stimuli
filter slowly changing stimuli
- selectively sensitive to changing stimuli

Question 23

DCML afferent pathway

Answer 23

First order neuron enters the spinal cord and projects to dorsal column nuclei of medulla
Second order neuron decussate (cross over) at medualla then project to thalamic nuclei
Third order neuron in thalamus and project to S1 (somatosensory cortex)

Question 24

Name other pathways that project via thalamus

Answer 24

Trigeminal- facial sensation
Spinocerebellar- muscle tone and coordination

Question 25

Regions of thalamus for 3 specific types of information

Answer 25

VPS- proprioception (DCML) VPM and VPL- fine touch and vibration (DCML) VPI- pain and temperature (spinothalamic)

Question 26

Monkey experiment: What did recording one cortical neuron (in S1) responding to a variety of stimuli identify

Answer 26

There is a favour stimulus for a specific projection pathway - labeled line coding - specific directionality preference - feature extraction

Question 27

What is feature extraction

Answer 27

Higher order processing in S1 cortical neurons Specific S1 neurons respond to specific stimuli - all stimuli have a favourable pathway

Question 28

What does labeled line coding prove

Answer 28

If you provide the same stimulus, you will get the same projection pathway and sent to the same S1 location

Question 29

What kind of info do III and IV sensory fibers carry

Answer 29

Tactile - remember different tracts carry these types of info, therefore they don’t have same pathway Pain Temperature Crude touch

Question 30

Spinothalamic tract pathway

Answer 30

First order neuron enter spinal cord - 2nd order decussate (cross over) - second order neuron in spinal cord - project to third order in VPI thalamus - then S1 (and other areas for emotional responses)

Question 31

Free nerve endings of nociceptors express what kinds of channels

Answer 31

Chemo, mechano, thermo sensitive ion channels - pain and temperature sensation Transient receptor potential (TRP) ion channels

Question 32

What do transient receptor potential ion channels produce? What kinds of things can activate the types

Answer 32

Receptor potential- passive potential can sum to make AP in afferent neuron TRPV1- heat sensitive (heat temp, wasabi, capsaicin - chilli peppers) TRPM8- cold sensitive (cold temp, mental) Both are temp gated- perception of cold or hot

Question 33

Location S1

Answer 33

Immediately posterior to central sulcus in post central gyrus

Question 34

State medial to lateral for sensory homunculus and what is heavily innervated

Answer 34

Medial- genitals, feet Hands at shoulders Lateral- head, mouth Big- toes, hands, lips, face

Question 35

Wilder Penfield

Answer 35

Mapped various brain regions including S1 - developed treatments for epilepsy (electrode to brain to pinpoint what region cause seizure- Montreal technique)

Question 36

What sensory fiber type carries proprioceptive information from muscle spindles and GTOs

Answer 36

Ia Ib- GTO II- smaller diameter, smaller conducting velocity

Question 37

Where are muscle spindles found and what is their shape

Answer 37

Found in skeletal muscle Fusiform shaped muscle fibers Sensory and motor axons

Question 38

Muscle spindle vs GTO lie in parallel/series with muscle

Answer 38

Muscle spindle- parallel GTO- series

Question 39

Function muscle spindles

Answer 39

Detect changes in muscle length

Question 40

What kind of fibers do muscle spindles have

Answer 40

Nuclear bag fibers Nuclear chain fibers

Question 41

Name type of fibers that innervate muscle spindle

Answer 41

Sensory Ia and II Motor gamma

Question 42

What is alpha gamma co stimulation

Answer 42

Maintain sensitivity over range of fiber lengths

Question 43

GTO function

Answer 43

Monitor muscle force

Question 44

What innervates GTO

Answer 44

Ib afferents sensory

Question 45

How does GTO measure force

Answer 45

Hooke’s law Force is proportional to stretch