5.2 Sensory & Motor Pathways

Question 1

What receptors are on fingers and palm of hand, plantar surface of foot and toes?

Answer 1

Meissner’s corpuscles

Question 2

What receptors are sensitive to touch and vibration?

Answer 2

Meissner’s corpuscles

Question 3

What receptors are on lips, distal parts of extremities?

Answer 3

Merkel’s receptors

Question 4

What receptors are sensitive to pressure stimuli, and low frequency vibration?

Answer 4

Merkel’s receptors

Question 5

What receptors are found on hands and feet, walls of mesenteries, vessel walls, periosteum, and joint capsules?

Answer 5

Pacinian corpuscles

Question 6

What receptors are sensitive to rapid indentation of skin (high frequency vibration)?

Answer 6

Pacinian corpuscles

Question 7

What receptors are widely distributed in dermis layer of skin?

Answer 7

Ruffini’s corpuscles

Question 8

What receptors are sensitive to stretch?

Answer 8

Ruffini’s corpuscles

Question 9

Where are proprioceptors located?

Answer 9

in joint capsules

Question 10

Where are cell bodies that mediate touch and conscious proprioception located; first order neurons of DCML?

Answer 10

dorsal root ganglia

Question 11

What fibers are located in the fasciculus gracilis?

Answer 11

central axons of sensory neurons (from receptors that mediate tactile sensation and proprioceptors of joints) at and below T6

Question 12

What fibers are located in the fasciculus cuneatus?

Answer 12

central axons of sensory neurons (from receptors that mediate tactile sensation and proprioceptors of joints) above T6

Question 13

Where do the fibers of the fasciculus gracilis and cuneatus synapse?

Answer 13

Upon 2nd order neurons in the dorsal column nuclei of the medulla (nucleus gracilis and nucleus cuneatus)

Question 14

Do the fibers in the fasciculus gracilis and cuneatus tracts stay on the same side or do they cross to the contralateral side?

Answer 14

ascend ipsilaterally in the spinal cord

Question 15

Where do the fibers of the nucleus gracilis and cuneatus decussate?

Answer 15

at the level of the medulla

Question 16

What do the fibers of the nucleus gracilis and cuneatus form after they decussate?

Answer 16

medial lemniscus

Question 17

Where do fibers from the medial lemniscus travel and project to?

Answer 17

Ascend through medulla, pons and midbrain, then project to 3rd order neurons in the VPL nucleus of thalamus.

Question 18

Where do the 3rd order neurons of the VPL project to?

Answer 18

primary somatosensory cortex = postcentral gyrus

Question 19

Where are lower motor neurons for the head from?

Answer 19

motor neurons of cranial nerves

Question 20

Where are lower motor neurons for the body from?

Answer 20

in the ventral horn of the spinal cord

Question 21

Where do upper motor neurons arise?

Answer 21

cerebral cortex

Question 22

Upper motor neurons of the Corticospinal tract from the cerebral cortex project to lower motor neurons of what?

Answer 22

spinal cord (voluntary control for movement of body)

Question 23

Upper motor neurons of the Corticobulbar tract from the cerebral cortex project to lower motor neurons of?

Answer 23

brainstem (CN i.e. facial motor nucleus, trigeminal m. n.) and (voluntary control fro movement)

Question 24

What participates in control of movement by receiving inputs from cerebral cortex and feeding back signals to different regions of the frontal cortex involved in initiation of movement?

Answer 24

Basal ganglia

Question 25

How does the basal ganglia play a role in motor function?

Answer 25

modulates activity of upper motor neurons

Question 26

What receives inputs from and gives outputs to most parts of CNS that contribute to motor functions?

Answer 26

cerebellum

Question 27

How does the cerebellum play a role in motor function?

Answer 27

Serves as the principal integrator of motor function

Question 28

What regions influence the pre central gyrus?

Answer 28

(1) motor activity regulation from several regions of CNS including cerebellum and basal ganglia via VL (2) somatosensory afferents from postcentral gyrus via VPL

Question 29

Where does the primary motor cortex (pre central gyrus) project to and via which pathways? (2)

Answer 29

(1) ventral horn of spinal cord at all levels via corticospinal tract
(2) lower motor neurons composing cranial motor nuclei of brainstem via corticobulbar tract

Question 30

What is the result of activation of the descending fibers of the primary motor cortex?

Answer 30

muscle contractions of individual muscles and controls the tone of these muscles

Question 31

What area do inputs received from basal ganglia primarily go to?

Answer 31

Supplemental motor area via VL

Question 32

What area do inputs received from the cerebellum primarily go to?

Answer 32

premotor cortex via VL

Question 33

Where do the Premotor and Supplemental Motor Cortices also receive inputs from?

Answer 33

Posterior parietal cortex, including somatosensory inputs from post central gyrus and from vestibular and visual areas

Question 34

Where do the premotor and supplemental motor cortices project to? and via which fiber pathway?

Answer 34

corticospinal tract to ventral horn

Question 35

What is the result of activating fibers of the premotor and supplemental motor cortices?

Answer 35

coordinate voluntary movements, sequencing of response patterns that are essential for producing movements

Question 36

What results from the inability to initiate specific, purposeful movements; moving planning deficits?

Answer 36

Apraxia

Question 37

What are the 3 different regions of origin of the Corticospinal tract?

Answer 37

pre central gyrus (primary motor cortex), premotor cortex, and supplemental motor area

Question 38

Axons of the corticospinal tract travel through the white matter of the cortex, followed by what 2 structures to reach the lower brainstem?

Answer 38

internal capsule (posterior limb) and then through the crus cerebri (midbrain)

Question 39

Where does the Corticobulbar tract arise from?

Answer 39

lateral aspect of primary motor cortex (pre central gyrus)

Question 40

What are the 2 exceptions to the bilateral innervation of the Corticobulbar pathway?

Answer 40

contralateral innervation of the ventral cell groups of motor nucleus of CN VII and CN XII

Question 41

Axons of the corticobulbar tract travel through the white matter of the cortex, followed by what 2 structures before exiting at their appropriate levels of the brainstem?

Answer 41

internal capsule (gene) and crus cerebri (midbrain)