Fuctional Nervous System Flashcards
Sensory neurons (2 types)
Visceral sensory neurons - monitor environment inside body (pH, etc.)
Somatic sensory neurons - monitor environmental stimuli external to the body
Interoceptors
Modified nerve endings to detect changes of the internal environment on the body; form the GVA sensory portion of nervous system
Exteroceptors (3 types)
- 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
Nociception
Sensing pain and temp
Proprioception (2 types)
Spatial orientation
- GP = general proprioception - from receptors in trunk and limbs
- SP = special proprioception - from receptors in inner ear
Motor neurons (2 types)
LMN - make mm. move, innervate skeletal m., spinal and cranial nn., brainstem or spinal cord
UMN - control LMN, entirely w/in CNS
Reflex pathway
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)
Relay pathway
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)
nn/pathways that carry sensory info (nociception, proprioception) from head and face
Sensory info travels via cranial nn., used in reflex and relay pathways
nn/pathways that carry sensory info from the trunk and limbs
Sensory info travels via spinal nn., used in reflex and relay pathways
Components of sensory input
Sensory input, interneuron (variable), motor output
Monosynaptic reflex pathway
Direct sensory synapse on the LMN (no interneuron), uncommon
Ex. Patellar reflex or “knee jerk”
Polysynaptic reflex pathway
Sensory info first synapses on interneuron, most common
Role of the interneuron (4)
-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
2 kinds of Proprioception (relay pathway)
- conscious pathways - works while body at REST
- unconscious pathways - works while body in MOTION
Proprioception
Position awareness and kinesthesia (detect changes in limb position), spinal and cranial nerve systems
GP proprioceptors (specialized exteroceptors)
Respond to movement, pressure, and stretch
Located in mm., tendons, and joints
Ex. Muscle spindles, Golgi tendon organs, joint receptors
Conscious proprioception pathways (2)
- fasciculus gracilis (pelvic limb)
- fasciculus cuneatus (thoracic limb)
Unconscious proprioception pathways (4)
- dorsal spinocerebellar tract (pelvic limb)
- ventral spinocerebellar tract (pelvic limb)
- cuneocerebellar tract (thoracic limb)
- rostral spinocerebellar tract (thoracic limb)
Pathway/neurons of fasciculus gracilis (conscious proprioception, pelvic limb)
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
Pathway/neurons of fasciculus cuneatus (conscious proprioception, thoracic limb)
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
Pathway/neurons of dorsal spinocerebellar tract (unconscious proprioception, pelvic limb)
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
Pathway/neurons of ventral spinocerebellar tract (unconscious proprioception, pelvic limb)
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
Pathway/neurons of cuneocerebellar tract (unconscious proprioception, thoracic limb)
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
Pathway/neurons of rostral spinocerebellar tract (unconscious proprioception, thoracic limb)
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
Spinothalamic tract
Noxious stimuli and nociception, in ventrolateral funiculus
Propriospinal tract
Motor neurons necessary for reflexes
Clinical signs - conscious deficit
Knuckling
Clinical signs - unconscious deficit
Wide stance, wobbly, limbs swing out wide while moving
How are problems with proprioception detected?
By testing postural reactions such as placing, hopping, hemiwalking
Motor nuclei in telencephalon (3)
Caudate nucleus, putamen, pallidum
Symptoms on the right side of the body indicate what (fasciculus gracilis, conscious proprioception)
Spinal cord problem on right side or brainstem problem on left side
Fasciculus gracilis and fasciculus cuneatus form what
Dorsal funiculus
