Viscerosomatic Sensation/Somatosensory Pathways Flashcards
Somatosensory information from most cranial structures is transmitted by ____, with cell bodies located in ____.
Trigeminal sensory neurons (CNV)
Trigeminal (semilunar) ganglion
Encapsulated terminal of DRG neurons are responsible for ____
sensations of touch and proprioception
Bare nerve endings of DRG neurons are responsible for ____
Thermal and painful sensations
4 elementary attributes of stimuli
Modality
Location
Intensity
Duration
Group 1 axons
Originate from:
Sensory receptors:
Speed of transduction:
Muscles
Proprioceptors of skeletal msucles
Fastest transduction
Axon from skin: A-beta axons
Axons from muscles: Group ___
Sensory receptors:
Responsible for:
Group II
Mechanoreceptors of skin
Discriminative touch
Axon from skin and viscera: A-delta axons
Axons from muscles: Group ___
Responsible for:
Group III
Cool, sharp pain
Axons from skin: C axons
Axons from msucles: Group ___
Responsible for:
Speed of transduction:
Group IV
Warm and cool, aching pain, itch
Slowest
Meissner's corpuscle Fiber group: Modality: Adaption speed: Location
A beta
Stroking, fluttering
Fast
Superficial skin
Merkel's disk receptor Fiber group: Modality: Adaption speed: Location:
A beta
Pressure
Slow
Superficial skin
Pacinian corpuscle Fiber group: Modality: Adaption speed: Location:
A beta
Vibration
Fast
Deep subcutaneous tissue
Ruffinin ending Fiber group: Modality: Adaption speed: Location:
A beta
Skin stretch
Slow
Deep subcutaneous tissue
____-conducting Type Ia fibers are ___-adapting. Respond to ____. They excite ____ during the ___ reflex, which causes ___.
Fast, fast Changes in muscle length Alpha motor nuerons Deep tendon reflex Increasing muscle tension
Type of muscle fiber active during steady state after a change in muscle length.
Type II fibers
Fast-conducting fibers that respond to stretch on tendon, which ____ alpha motor neurons.
Type Ib fibers
Inhibit
Thermal nociceptors
Activated by:
Fibers used:
Extreme temperature
Alpha delta
Mechanical nociceptors
Activated by:
Fibers used:
Intensive pressure applied to skin
Alpha delta
Polymodal nociceptors
Activated by:
Fibers used:
High intensity chemical, mechanical or thermal stimuli
Nonmyelinated C fibers
Visceral afferent nerves
Cell bodies located:
Majority of fibers:
DRG or CN ganglia
Alpha delta and C fibers (slow conducting)
Dorsal root fibers enter spinal cord through medial bundle contain _____ which convey impulses from _______. Ex: ____
thickly myelinated fibers Large encapsulated somatic receptors Muscle spindles (Ia) Golgi tendon organs (Ib) Pacinian corpuscles (Abeta) Meissner's corpuscles (Abeta)
Golgi tendon organs (GTOs)
Signal tendon tension
Diminshed or absent deep tendon reflex indicates lesion that affects ____
Afferent or efferent neurons for that specific spinal cord segment
Exaggerated deep tendon reflex indicates lesion that affects ____
Upper motor neuron (disrupted inhibition on LMN)
Golgi tendon reflex involves:
Ib afferent, 1 or 2 interneurons
Dorsal column system transmits:
Tactile sensation
Conscious proprioception
Kinesthesia
Dorsal column system’s spinal cord components are _____ which is made up of ____ and ____. Composed of ____.
The dorsal columns
Gracile and cuneate fasciculi
Heavily myelinated axons of DRG fibers
Dorsal column system
_____ cable together more medially, _____ more laterally
Sacral fibers
Cervical fibers
Dorsal column system
Gracile and cuneate fasciculi ascend to the ____ and synapse on the ___ and ___.
Lower medulla
Nucleus gracilis and nucleus cuneatus
Medial lemniscus
Formed from decussated second-order neurons in gracile/cuneate nuclei in medulla
Location of neuron 2 in dorsal column system
Location of neuron 3 in dorsal column system: ____
Fibers ultimately end in _____
Ventral posterolateral nucleus in that thalamus
Limb and trunk areas of primary somatosensory cortex in postcentral gyrus
Lesion of dorsal column result in (ipsilateral or contralateral) loss of ______ (4) in body segments ____ the level of the lesion
Ipsilateral
Conscious proprioception, kinesthesia, 2-point discrimination, vibration sense
Below
Lesion of the medial lemniscus result in (ipsilateral or contralateral) loss of ______ (4)
Contralateral (b/c it has already crossed in the medulla)
Conscious proprioception, kinesthesia, 2-point discrimination, vibration sense
Romberg’s test
Test of DCML dysfunction. Relies on fact that w/o visual clues, balance requires conscious proprioception. Lose awareness of proprioception when eyes are closed.
Spinothalamic system runs in ____ and ____
Anterior (ventral) and lateral funiculi
Spinothalamic system
Ascending 2nd order fibers mostly cross in _____
Spinal cord
Lesions of spinothalamic tract result in loss of ____ on ____ side of body ____ the level of lesion
Pain and temperature
Contralateral
Below, 1-2 segments below level of lesion (Lissauer’s tract)
Lissauer’s tract
Some A beta and C fibers of spinothalamic system ascend spinal cord in this tract before entering dorsal horn and synapse.
Spinothalamic tract neurons (2nd order) are mostly found in _____. Their axons cross in ____.
Laminae 1, 4, 5, 6
Ventral (anterior) white commissure
Spinothalamic system
_____ cable together more medially, _____ more laterally
Cervical
Sacral
Spinothalamic tract fibers end in _____
Ventral postlateral nucleus and other thalamic nuclei
Spinothalamic system
Locations of neuron 2
Posteromarginal nucleus
Substantia gelatinosa
Nucleus proprius
Lesion of anterior white commissure results in ___
bilateral segmental loss of pain and temperature, 1-2 segments below the level of the lesion.
Will still have sensation above and below the lesion
Visceral pain pathway
2nd order neurons run in _____ to reach higher centers. They (do/do not) cross
Gracile fasciculi, lesser exten in cuneate fasciculi
Do NOT cross
3 pathways of spinocerebellar pathways
Dorsal (posterior) spinocerebellar tract: lower extremities
Cuneocerebellar tract: upper extremities
Ventral (anterior) spinocerebellar tract: whole limb position and kinesthesia
Location of neuron 2 of dorsal spinocerebellar tract
Dorsal nucleus of Clarke
Dorsal nucleus of Clarke is part of ____ pathway
Dorsal spinocerebellar tract
Dorsal spinocerebellar tract axons (do/do not) cross the spinal cord to enter (contralateral/ipsilateral) ____ via the _____
Do not
Ipsilateral
Inferior cerebellar peduncle
Dorsal nucleus of Clarke exits in ______
Thoracic/upper lumbar cord
Dorsal spinocerebellar tract conveys information from _____
Only trunk and lower limb
Neuron 1 of the dorsal spinocerebellar tract enters the spinal cord through ____
dorsal column
Neuron 1 of the cuneocerebellar tract enters the spinal cord through ____ and ascends to the ___ to synapse on ____
Fasciculus cuneatus
Medulla
Accessory cuneate nucleus
2nd order fibers of the cuneocerebellar tract form ____ at the accessory cuneate nucleus to enter the (contralateral/ipsilateral) ___ via the ___.
Cuneocerebellar tract
Ipsilateral cerebellum
Inferior cerebellar peduncle
Venral spinocerebellar tract conveys ____
Nonconscious proprioceptive information about movement and posture of whole (lower) limb
Which pathway has its neurons cross twice to end up on the same side?
Ventral spinocerebellar tract
2nd order fibers of the ventral spinocerebellar tract are located at _____ at ____ levels. They cross in the ____ and ascend in the _____ to the ____ where they ____ to enter the _____ via the ____.
The base lateral to dorsal gray horn Lumbosacral levels ventral white commissure Anterolateral white matter upper pons cross the midline again cerebellum superior cerebellar peduncle
3 systems of trigeminal sensory complex
Spinal tract and nucleus
Main sensory nucleus
Mensencephalic nucleus
Spinal tract and nucleus functions:
Pain, temp, crude touch from face, head, nasal and oral cavities
Like spinothalamic tract of spinal system
Main sensory nucleus
Discriminative touch sensation from head and face
Like DCML system w/o conscious proprioception
Mesencephalic nucleus
All conscious and nonconscious proprioception from mm. of mastication, periodontal ligament, facial and tongue muscles
Location of main sensory nucleus
Pons, adjacent and lateral to motor nucleus of V
Mesencephalic nucleus contains ____ that end up in the ____
primary afferent neurons
Midbrain
*only structure in CNS to contain primary afferent cell bodies
Neurons of the mesencephalic nucleus communicate by _____
electrical gap junctions
Mesencephalic nucleus sends axons to the ____, located between the ___ and ___.
This transmits _____ about _____
Supra-trigeminal nucleus (S-TN)
Motor nucleus and main sensory nucleus
Conscious proprioception
Jaw and tongue position
Major output target of mesencephalic nucleus is the ____ for participation in ____
Motor nucleus of V (MoV)
Jaw-jerk reflex
Jaw-jerk reflex is exaggerated in ____
___ signs resulting from damage to ____ inputs to ____
Corticobulbar lesions
UMN, corticobulbar inputs, MoV
Ventral trigeminothalamic tract (VTT) formed from:
2n order fibers of spinal nucleus, main sensory nucleus, supra-trigeminal nucleus
VTT terminates in ____
Ventral posteromedial (VPM) nucleus of thalamus
VTT fibers from spinal nucleus run alongside ___ aspect of the ____
medial
Spinothalamic tract
VTT fibers from main sensory nucleus and supra-trigeminal nucleus run alongside the ____
medial leminiscus
Trigeminal lemniscus formed from
VTT (ventral trigemino-thalamic tract) and DTT (dorsal trigemino-thalamic tract)
Dorsal trigemino-thalamic tract (DTT) formed from
Ascending uncrossed main sensory nucleus
