Fuctional Nervous System

Question 1

Sensory neurons (2 types)

Answer 1

Visceral sensory neurons - monitor environment inside body (pH, etc.)
Somatic sensory neurons - monitor environmental stimuli external to the body

Question 2

Interoceptors

Answer 2

Modified nerve endings to detect changes of the internal environment on the body; form the GVA sensory portion of nervous system

Question 3

Exteroceptors (3 types)

Answer 3

• Modified nerve endings to detect changes of the external environment on the body (senses); contribute to SSA (special somatic afferent) and SVA (special visceral afferent)
• specialized nerve endings to detect pain in body or in head/face; contribute to GSA as nociception
• specialized nerve endings to detect spatial orientation of the limbs, head and trunk; contribute to GSA as proprioception

Question 4

Nociception

Answer 4

Sensing pain and temp

Question 5

Proprioception (2 types)

Answer 5

Spatial orientation

• GP = general proprioception - from receptors in trunk and limbs
• SP = special proprioception - from receptors in inner ear

Question 6

Motor neurons (2 types)

Answer 6

LMN - make mm. move, innervate skeletal m., spinal and cranial nn., brainstem or spinal cord
UMN - control LMN, entirely w/in CNS

Question 7

Reflex pathway

Answer 7

Sensory info operates at local level, usually through interneuron; travels short distance up spinal cord or brainstem through propriospinal tract to integrate spinal cord segments (to cerebellum or cerebral cortex)

Question 8

Relay pathway

Answer 8

Sensory info travels long distance up spinal cord to reach various levels in brain, thereby forming the named tracts of the spinal cord (synapses at LMN at same level)

Question 9

nn/pathways that carry sensory info (nociception, proprioception) from head and face

Answer 9

Sensory info travels via cranial nn., used in reflex and relay pathways

Question 10

nn/pathways that carry sensory info from the trunk and limbs

Answer 10

Sensory info travels via spinal nn., used in reflex and relay pathways

Question 11

Components of sensory input

Answer 11

Sensory input, interneuron (variable), motor output

Question 12

Monosynaptic reflex pathway

Answer 12

Direct sensory synapse on the LMN (no interneuron), uncommon

Ex. Patellar reflex or “knee jerk”

Question 13

Polysynaptic reflex pathway

Answer 13

Sensory info first synapses on interneuron, most common

Question 14

Role of the interneuron (4)

Answer 14

-contributes to both reflex and relay pathways
-local cord segment
-adjacent cord segments to recruit/inhibit motor units
-relay to higher levels
Ex. L3, L4, L5 - interneuron at L4 must interact with L3 and L5

Question 15

2 kinds of Proprioception (relay pathway)

Answer 15

• conscious pathways - works while body at REST

- unconscious pathways - works while body in MOTION

Question 16

Proprioception

Answer 16

Position awareness and kinesthesia (detect changes in limb position), spinal and cranial nerve systems

Question 17

GP proprioceptors (specialized exteroceptors)

Answer 17

Respond to movement, pressure, and stretch
Located in mm., tendons, and joints
Ex. Muscle spindles, Golgi tendon organs, joint receptors

Question 18

Conscious proprioception pathways (2)

Answer 18

• fasciculus gracilis (pelvic limb)

- fasciculus cuneatus (thoracic limb)

Question 19

Unconscious proprioception pathways (4)

Answer 19

• dorsal spinocerebellar tract (pelvic limb)
• ventral spinocerebellar tract (pelvic limb)
• cuneocerebellar tract (thoracic limb)
• rostral spinocerebellar tract (thoracic limb)

Question 20

Pathway/neurons of fasciculus gracilis (conscious proprioception, pelvic limb)

Answer 20

DRG -> fasciculus gracilis -> nucleus gracilis -> deep arcuate fibers -> contralateral medial lemniscus -> brainstem -> VCL -> IC -> sensory cortex

• 1st neuron = dorsal root ganglion (DRG) - axons ascend ipsilaterally forming fasciculus gracilis
• 2nd = nucleus gracilis - axons cross midline as deep arcuate fibers, form contralateral medial lemniscus and ascend through brainstem
• 3rd = ventral caudal lateral nucleus (VCL) of thalamus - axons contribute to formation of internal capsule (IC), terminate in appropriate part of sensory (somesthetic) cortex in parietal lobe

Question 21

Pathway/neurons of fasciculus cuneatus (conscious proprioception, thoracic limb)

Answer 21

DRG -> fasciculus cuneatus -> medial cuneate nucleus -> deep arcuate fibers -> contralateral medial lemniscus -> brainstem -> VCL -> IC -> sensory cortex

• 1st neuron = DRG - axons ascend ipsilaterally forming fasciculus cuneatus
• 2nd = medial cuneate nucleus - axons cross midline as deep arcuate fibers, form contralateral medial lemniscus and ascend through brainstem
• 3rd = VCL of thalamus - axons contribute to formation of IC, terminate in appropriate part of sensory cortex in parietal lobe

Question 22

Pathway/neurons of dorsal spinocerebellar tract (unconscious proprioception, pelvic limb)

Answer 22

DRG -> dorsal gray column in Clarke’s Nucleus -> lateral funiculus forming tract -> superficial arcuate fibers -> caudal cerebellar peduncle -> cerebellum

• 1st neuron = DRG
• 2nd = dorsal gray column in Clarke’s Nucleus (aka thoracic nucleus) - axons ascend ipsilaterally in lateral funiculus forming DSCT, pass through superficial arcuate fibers, enter caudal cerebellar peduncle, terminate in appropriate area of cerebellum

Question 23

Pathway/neurons of ventral spinocerebellar tract (unconscious proprioception, pelvic limb)

Answer 23

DRG -> dorsal gray column -> crosses ventral white commissure -> lateral funiculus forming tract -> rostral cerebellar peduncle -> cerebellum

• 1st neuron = DRG
• 2nd neuron = dorsal gray column - axons cross in ventral white commissure, ascend contralaterally in lateral funiculus forming VSCT, enter rostral cerebellar peduncle, recross to terminate in appropriate area of cerebellum

Question 24

Pathway/neurons of cuneocerebellar tract (unconscious proprioception, thoracic limb)

Answer 24

DRG -> lateral part of fasciculus cuneatus -> lateral cuneate nucleus -> brainstem -> caudal cerebellar peduncle -> cerebellum

• 1st neuron = DRG - axons ascend ipsilaterally in most lateral part of fasciculus cuneatus
• 2nd = lateral cuneate nucleus - axons ascend ipsilaterally through brainstem, enter caudal cerebellar peduncle, terminate in appropriate area of cerebellum

Question 25

Pathway/neurons of rostral spinocerebellar tract (unconscious proprioception, thoracic limb)

Answer 25

DRG -> dorsal gray column -> lateral funiculus forming tract -> caudal and rostral cerebellar peduncles -> cerebellum

• 1st neuron = DRG
• 2nd = dorsal gray column - axons ascend ipsilaterally in lateral funiculus as RSCT, enter caudal and rostral cerebellar peduncle, terminate in appropriate area of cerebellum

Question 26

Spinothalamic tract

Answer 26

Noxious stimuli and nociception, in ventrolateral funiculus

Question 27

Propriospinal tract

Answer 27

Motor neurons necessary for reflexes

Question 28

Clinical signs - conscious deficit

Answer 28

Knuckling

Question 29

Clinical signs - unconscious deficit

Answer 29

Wide stance, wobbly, limbs swing out wide while moving

Question 30

How are problems with proprioception detected?

Answer 30

By testing postural reactions such as placing, hopping, hemiwalking

Question 31

Motor nuclei in telencephalon (3)

Answer 31

Caudate nucleus, putamen, pallidum

Question 32

Symptoms on the right side of the body indicate what (fasciculus gracilis, conscious proprioception)

Answer 32

Spinal cord problem on right side or brainstem problem on left side

Question 33

Fasciculus gracilis and fasciculus cuneatus form what

Answer 33

Dorsal funiculus