Quiz 2 (19-38)

Question 1

Where are cell bodies of Primary Sensory Neurons almost always located?

Answer 1

In peripheral ganglia of spinal and cranial nerves
i.e. DRG’s
(19)

Question 2

Where do free nerve endings, Merkel endings, and peritrichial nerve endings end?

Answer 2

-Free nerve endings = ends “freely” b/t cells (highly branched)
-Merkel endings = terminals that end as expansions/discs on Merkel cells in deep epidermis (mostly in glaborus/hairless skin)
-Peritrichial = distributed along the root of a hair follicle
(20)

Question 3

What class of receptors are free nerve endings, merkel endings, and peritrichial nerve endings?

Answer 3

Nonencapsulated

20

Question 4

What class of receptors are Pacinian corpuscles, Meissner’s corpuscles, Ruffini endings, and End bulbs?

Answer 4

Encapsulated endings

20-21

Question 5

What type of stimuli do free nerve endings, peritrichial endings, Merkel’s endings, Ruffini endings, Meissner’s and Pacinian corpuscles monitor?

Answer 5

Free nerve endings = thermal, painful and tactile (touch) stimuli
Peritrichial endings = tactile r/c
Merkel’s endings = tactile of deep epidermis
Ruffini endings = tactile of dermis/subcutaneous tissue
Meissner’s corpuscles = tactile in fingertips and other hairless skin
Pacinian = vibration of dermis and hypodermis
(22)

Question 6

What 2 types of receptors are found in joints?

Answer 6

-Nocioceptors; free nerve endings
-Proprioceptors; pacinian corpuscles, ruffini-like endings, and neurotendinous spndles (golgi tendon organs) in ligaments
(22)

Question 7

What type of receptors are in skeletal muscle?

Answer 7

-Nociceptors; free nerve endings
-Proprioceptors; neuromuscular spindles (mostly at muscle/tendon junction)
(22)

Question 8

What type of receptors are in tendons?

Answer 8

-Nociceptors; free nerve endings
-Proprioceptors; golgi tendon organs (aka neurotendinous spindles)
(22)

Question 9

What type of receptors are in the Viscera?

Answer 9

-Nociceptors; free nerve endings
-Pacinian Corpuscles; mechanoreceptors for stretch/distention
(22)

Question 10

What is the trend of myelin from A-alpha, A-beta, A-gamma, A-delta, to B fibers?

Answer 10

Thick to thin
*Conduction speed is greatest for A-alpha, slowest for B fibers
(23)

Question 11

What type of sensations are carried through the Spinothalamic System?

Answer 11

*Antero-lateral system
Pain, temperature, non-discriminative touch
(25)

Question 12

What sensations are carried through the Medial Lemniscus System (Dorsal Column System)?

Answer 12

Discriminative touch
Proprioception
Vibration
(25)

Question 13

What is Graphesthesia? What part of spinal cord will this information be traveling?

Answer 13

Ability to identify a familiar pattern traced on the skin w/ eyes closed = part of discriminative touch
-Medial Lemniscus System
(26)

Question 14

What is Kinesthesia?

Answer 14

Proprioception

27

Question 15

What is the pathway for Fine Touch (and vibration) for the body (except the face) for the Primary Neurons?

Answer 15

Sensory r/c in peripheral tissue travels (made up of A-beta fibers) to large pseudounipolar neuron in DRG
-travel through dorsal rootlets of spinal nerve (dorsal zone of spinal cord)
-enters ipsilateral dorsal funiculus and branches into ascending and descending collaterals (terminate in spinal cord gray and modify reflexes, sensory, and motor activity)
**if below T6, travel through Nucleus Gracilis and terminate in Nucleus Gracilis (on posterior surface of Medulla)
**if above T6, travel through ipsilateral Fasciculus Cuneatus to terminate in Nucleus Cuneatus (on post. surface of Medulla)
(28)

Question 16

What is the pathway for Fine Touch (and vibration) for the body (except the face) for the Secondary Neurons?

Answer 16

Cell bodies in nucleus Gracilis and Cuneatus receive ipsilateral information. Neuron fibers project ventrally, decussate, and form the Medial Lemniscus (which ascends the contralateral side of brain stem)
Fibers ascend, and terminate on tertiary neurons in the Thalamus
(29)

Question 17

What is the pathway for Fine Touch (and vibration) for the body (except the face) for the Tertiary Neurons?

Answer 17

Third order neurons comprise the Ventral Lateral Posterior (VPL) nucleus of the thalamus.
Fibers project through Posterior Limb of Internal Capsule to the Post Central Gyrus and the posterior part of the Paracentral Lobule of the parietal lobe
This data in the parietal lobe initiates the process of subjective (conscious) assessment of the data
(30)

Question 18

Where does fine touch information go from ipsilateral to contralateral part of the body?

Answer 18

Primary fine touch Neurons = Ipsilateral
Secondary = receives ipsilateral info and projects to contralateral side
Tertiary = Receives info on contralateral side and stays contralateral side
(28-30)

Question 19

What nucleus do 3rd order neuron cell bodies make up in the fine touch pathway?

Answer 19

VPL of the Thalamus
Ventral Posterior Lateral
(30)

Question 20

What is the entire pathway for fine touch and vibration of the body (accept the face)?

Answer 20

Receptor -> A-beta fibers -> DRG -> Funiculus Gracilis (or Cuneatus above T6) -> Nucleus Gracilis or Cuneatus; Secondary fibers decussate and form Medial Lemniscus -> VPL of Thalamus -> Tertiary neurons travel to Post. limb of Internal Capsule -> Postcentral Gyrus and posterior part of paracentral lobule

Question 21

In the pathway for Proprioception for the body (except the face), what do the primary and secondary neurons do?
**Upper body is same as fine touch/vibration; Lower body is different

Answer 21

Receptor sends signal through A-alpha and A-beta fibers to cell body in DRG = (peripheral process)
Central process = neuron travels through dorsal rootlets of spinal nerves and enters cord through dorsal root zone
Enters Ipsilateral Dorsal Funiculus and branch into ascending and descending collaterals which terminate in spinal cord gray
**Long ascending collaterals for lower body enter ipsilateral fasicuclus gracilis, and terminate on ipsilateral Nucleus Dorsalis (Clarke’s Nucleus, C8-L3)
Neurons then travel through ipsilateral Dorsal Spino-Cerebellar tract into medulla. (Some will then go strait to cerebellum via ICP)
Others terminate on tertiary neurons of Nucleus Z.

Question 22

In the pathway for Proprioception for the body (except the face), what do the tertiary neurons do?

Answer 22

Neurons in Medulla (Nucleus Cuneatus for upper body and Nucleus Z for lower body) send axons ventrally into Contralateral Medial Lemniscus
***The medial lemniscus includes fibers transmitting fine touch/vibration AND proprioceptive information
Fibers terminate on VPL nucleus of Thalamus
(31-32)

Question 23

In the pathway for Proprioception for the body (except the face), what do the final neurons do (from thalamus to cerebral cortex)?

Answer 23

Neurons of VPL nucleus send axons through post. limb of internal capsule
Fibers terminate on postcentral gyrus and the posterior paracentral lobule of the parietal lobe
(32)

Question 24

Give the highlights for the proprioceptive pathway for the body (except the face)

Answer 24

Upper limb = receptor -> DRG -> fasiculus cuneatus -> nucleus cuneatus
Lower limb = receptor -> DRG -> fasiculus gracilis -> Clark’s Nucleus -> Dorsal SpinoCerebellar tract -> Nucleus Z
BOTH LIMBS decussate from Medulla and enter Medial Lemniscus -> VPL nucleus -> Post. limb of internal capsule -> terminate on posctentral gyrus and paracentral lobule of parietal lobe
(30-32)

Question 25

Where are cell bodies for primary neurons that innervate the face?

Answer 25

Trigeminal Sensory Ganglion -or- (Gasserion)
*A-beta fibers
(33)

Question 26

Where are cell bodies for primary neurons that provide proprioception innervation for the face?

Answer 26

Mesencephalic Nucleus in the brainstem
*unique b/c cell bodies are typically in a ganglion, not in brainstem
(33)

Question 27

Where do the central processes of primary neurons for fine touch and proprioception for the face terminate?

Answer 27

Pontine Trigeminal Nucleus

33

Question 28

Where do the secondary neurons for fine touch and proprioception of the face go as they leave the Pontine Trigeminal Nucleus?
Where do they terminate?

Answer 28

Trigeminothalamic Tract on **contralateral side of brainstem
They terminate in the VPM Ventral Posterior Medial nucleus of the thalamus
(34)

Question 29

Once in the Thalamus, where do tertiary fibers of fine touch and proprioception of the face go as they leave the VPM?

Answer 29

VPM -> post. limb of internal capsule -> terminate in the inferior lateral part of Post Central Gyrus (near lateral sulcus)
(34)

Question 30

What is the functional significance of projections to the cerebral cortex for fine touch and proprioception from the face?

Answer 30

Permits conscious appreciation of qualities of somato-sensory data
(34)

Question 31

Which somatosensory cortex of the parietal lobe is involved w/ *general awareness of all somatosensory data?
Which is involved w/ complex assessment of data?

Answer 31

Primary somatosensory cortex = general info
Somatosensory Association Cortex (in superior parietal lobe and precuneate gyri) = complex assessment of data
i.e. stereogenesis (3D) and graphestesia
(36)