Sensory Receptors / Ascending Pathways

Question 1

Somatosensory Systems ~

Answer 1

Touch, Pain, Temperature, Vibration, Proprioreception

Question 2

Protopathic Somesthesis

Sensory:

Answer 2

pain, temperature, crude touch

Question 3

Protopathic Somesthesis

Spatial/Temporal Resolution:

Answer 3

low (“crude”)

Question 4

Protopathic Somesthesis

Fiber Type:

Answer 4

small, slow, little/no myelin

Question 5

Protopathic Somesthesis

Ascending Tract:

Answer 5

Spinothalamic Tract / Anterolateral Funiculi (Spinal Cord)

Question 6

Epicritic Somesthesis

Sensory:

Answer 6

fine/discriminative touch (form, texture, slippage, pressure), position (proprioception), vibration

Question 7

Epicritic Somesthesis

Spatial/Temporal Resolution:

Answer 7

high (“fine”)

Question 8

Epicritic Somesthesis

Fiber Type:

Answer 8

large, rapid, myelinated

Question 9

Epicritic Somesthesis

Ascending Tract:

Answer 9

Posterior / Posterolateral Columns (Spinal Cord)

—> Medial Lemniscus (Brainstem)

Question 10

Arrangement of Spinal Cord Efferent:

Answer 10

motor neuron cell bodies (ventral horn) —> axon via ventral root —> peripheral nerve —> target ~ Final Common Path

Question 11

Arrangement of Spinal Cord Afferent:

Answer 11

sensory receptors (skin, muscle, viscera) linked to sensory processes of pseudounipolar nerves ---> dorsal horn
Next Step Depends: receptor type dictates whether peripheral process synapses in dorsal horn or ascends

Question 12

Fiber Types ABC Classification ~

Answer 12

Organized Fastest Conductive Velocity (A) to Slowest (C)

Question 13

Fiber Type Aɑ:

Answer 13

motor to skeletal muscle ~ “ɑ motor neuron” + sensory from muscle spindle (~Ia)

Question 14

Fiber Type Aβ:

Answer 14

sensory from Golgi Tendon Organs (GTO) and Ruffini Endings

Question 15

Fiber Type Aɣ:

Answer 15

motor to intrafusal fibers

Question 16

Fiber Type Aδ:

Answer 16

Sensory from free nerve endings for pain, temp, hair follicles

Question 17

Fiber Type B:

Answer 17

preganglionic autonomic fibers

Question 18

Fiber Type C:

Answer 18

postganglionic autonomics + free nerve endings for pain, temperature, smell

Question 19

Roman Numeral Classification ~

Answer 19

Organized Based on Axon Diameter (I = Larges)

Question 20

Roman Numeral Classification Ia:

Answer 20

sensory from muscle spindles

Question 21

Roman Numeral Classification Ib:

Answer 21

sensory from Golgi Tendon organ and Ruffini Endings ~ Aβ

Question 22

Roman Numeral Classification II:

Answer 22

sensory from skin receptors

Question 23

Roman Numeral Classification III:

Answer 23

sensory from free nerve endings for pain, temperature, hair follicles ~ Aδ

Question 24

Roman Numeral Classification IV:

Answer 24

postganglionic autonomics + sensory from free nerve endings for pain, temperature, smell

Question 25

Somatosensory Receptors Detect:

Answer 25

chemoreceptors, thermoreceptors, mechanoreceptors, photoreceptors, nociceptors

Question 26

Somatosensory Receptors FUNCTION:

Answer 26

stimulus —> receptor —> graded potential ==> AP
Important: somatosensory receptor transduces (converts environmental energy —> electrical energy) + integrates (==> AP)

Question 27

Pacinian Corpuscle: Function/Location:

Answer 27

lamellar (Shwann Cells), rapidly adapting mechanoreceptors
Function: gross touch + vibratory skin stimuli (250 Hz optimal)
Location: subcutaneous skin, joints/muscle, mesentery

Question 28

Missner’s Corpuscle: Function/Location:

Answer 28

rapidly adapting mechanoreceptors
Function: light touch + vibratory skin stimuli (< 50 Hz)
Location: glabrous* skin (just below epidermis)

Question 29

Merkel’s Disks: Function/Location:

Answer 29

SLOWLY adapting mechanoreceptors
Glabrous Skin: clustered beneath fingertips
Hairy Skin: grouped into specialized epithelium ~ “Touch Domes” or “Hair Disks”

Question 30

Ruffini Organs: Function/Location:

Answer 30

SLOWLY adapting mechanoreceptors
Function: sustained pressure and skin stretch (slippage / position sense)
Location: glabrous skin (deep)

Question 31

Free Nerve Endings ~

Answer 31

no accessory structures / usually respond to pain / temp

Question 32

Transient Response

Answer 32

ADAPTATION ~ ↓response with constant and continued stimulus ==> Transient Response

1. No Adaptation: constant stimulus —> AP fire at constant rate —> no adaptation
2. Adaptation: constant stimulus —> AP frequency slows —> +adaptation

Question 33

Collaterals ~

Answer 33

Branches of 1° Afferent Axons ~ Represent Intrinsic Spinal Refelx

Question 34

Polysynaptic (Poly)

Answer 34

Enter Dorsally —> Synapse with Interneuron —> Synapse in Ventral Horn

Question 35

Monosynaptic (Mono)

Answer 35

Enter Dorsally —> Synapse in Ventral Horn

Question 36

Rexed Laminae ~

Answer 36

Layers of Spinal Cord Gray Matter

Question 37

Rexed Laminae I - V =

Answer 37

Dorsal Horn (I = marginal zone; I+II = Substantia Gelatinosa - pain modulation)

Question 38

Rexed Laminae VI - VII =

Answer 38

Intermediate Zone

Question 39

Rexed Laminae VIII - IX =

Answer 39

Anterior Horn

Question 40

Rexed Laminae X =

Answer 40

Central Canal

Question 41

ventral posterolateral nucleus (VPL) ~

Answer 41

Somatosensory Thalamus for Body

Medial Lemniscus / Spinothalamic Tract —> VPL —> Post-Central Gyrus

Question 42

ventral posteromedial nucleus (VPM) ~

Answer 42

Somatosensory Thalamus for Head)

Trigeminal Lemniscus / Trigeminothalamic Tract (and taste) —> VPM—> Post-Central Gyrus