8. Ascending sensory I (senses + conscious proprioception) Flashcards
What information relays the SOMATOSENSORY system
- Info from SKIN receptors (pain, touch, warmth, temp)
- Info from DEEPER structures such as muscles, tendons, joints, viscera (pressure, vibration, proprioception, deeper pain)
Sensory receptors
Sensory receptors are found in every tissues except…
Nervous tissues
Sensory receptors
2 means of classification of sensory receptors
- Type of NERVE endings (free vs encapsulated)
- STIMULI (mechano, chemo, thermo, noci, proprio)
Note; encapsulated are all mechanoreceptors
Sensory receptors
2 modes of adaptations of sensory receptors (slide 6)
- Phasic - rapidly adapting (stops firing for constant stimulus)
- Tonic - slow adapting (continues firing)
Sensory receptors
For each receptor, describe info conveyed and adaptation (table slide 14)
- HAIR FOLLICLE TERMINALS (free nerve endings): touch, fast
- MEISSNER’s CORPUSCLE: touch/vib, fast
- MERKEL’s CORPUSCLE: touch/press, slow
- RUFFINI’s CORPUSCLE: stretch, slow
- MUSCLE SPINDLE: prop, fast iniitial; slow sustained
- GTO: prop and muscle tension, slow
Difference between
* Dermatome
* Cutaneous zone
* Autonomous zone
* Receptor field
- DERMATOME: sensory zone represented by a single spinal nerve (nerve root) - overlap
- CUTANEOUS ZONE: sensory zone represented by a single peripheral nerve - overlap
- AUTONOMOUS ZONE: skin area detected by a single peripheral nerve with NO OVERLAP (applies to only few spinal nerves)
- RECEPTIVE FIELD: sensory zone represented by a single neuron.
What properties of a receptive field affects precision of localization (slide 21)
- Size of receptive field (larger = more overlap)
- Number of 1ary sensory neurons merging per 2nd-order neurons
Name the ascending/sensory tracts:
* General proprioception - conscious
- Fasciculus cuneatus
- Spinomedullary
Name the ascending/sensory tracts:
* General proprioceptiion - unconscious
- Dorsal spinocerebellar (PL)
- Ventral spinocerebellar (PL)
- Spinocuneocerebellar (TL)
- Cranial spinocerebellar (C1-T1)
- Cervicospinocerebellar (C1-C4, de lahunta)
Name the ascending/sensory tracts
* Pain, touch, temperature
- Spinothalamic
- Spinocervicothalamic
- Spinoreticular
Name the ascending/sensory tracts:
* Deep pain
- Spinothalamic tract (+ men)
- Ascending reticular formation (+ mammals)
Medial lemniscus - location, role
- Conveys afferents from the gracile-cuneate system + spinothalamic system (not reticular formation)
- Medulla –> thalamus
Pain
Difference between pain and nociception
- Pain: subjective response to stimulation of nociceptors (not tested)
- Nociception: behavioral response to noxious stimuli
Pain
Difference between neuropathic vs nociceptive pain
- Nociceptive: stimulation of nociceptors
- Neuropathic: stimulation of PNS or CNS
Difference between superficial vs deep pain in terms of
* Fibers
* Localization
* Tracts
SUPERFICIAL:
* Ad fibers, thinly myelinated, fast
* Accurately localized
* Spinothalamic
DEEP`
* C fibers, thinner, non-myelinated
* Poorly localized
* Ascending reticular +/- spinothalamic tract
Pain, touch, temp
Spinothalamic tract (slide 32)
- DRG (N1) -> dorsal horn (N2) -> decussates
- Dorsolateral fasciculus
- Medial lemniscus
- Thalamus (N3) -> internal capsule -> SI
Touch»_space; pain (5%)
Spinocervicothalamic tract (slide 32)
- DRG (N1) -> dorsal horn (N2)
- Ipsilateral spinocervicothalamic tract
- Lateral cervical nucleus (C1-2) –> decussates
- Medial lemniscus
- Thalamus (N4) -> internal capsule -> SI
Pain, touch, temperature
Spinoreticular tract
- DRG (N1) -> dorsal horn (N2)
- Bilateral ventral funiculi
- Various nuclei (N3) (olivary -> dentate; reticular formation)
Touch
Fasciculus gracilis & cuneatus (slide 35-6)
- DRG (N1, Aβ fibers) -> dorsal horn (N2)
- Dorsal funiculus, in gracile (PL, medial) + cuneatus (TL, lateral) fasciculus
- Gracile + medial cuneate nucleus (N3) -> decussates
- Medial lemniscus
- Thalamus -> internal capsule -> SI
Conscious proprioception - TLs (C1-T5)
Fasciculus cuneatus
- DRG C1-T5 (N1, Aα fibers) -> dorsal horn
- Dorsal funiculus, in cuneatus (TL, lateral) fasciculus
- Medial cuneate nucleus (N3) -> decussates
- Medial lemniscus
- Thalamus -> internal capsule -> SI
Conscious proprioception (PLs, caudal to T5)
Spinomedullary tract (slide 44)
N.b. nucleus Z is just next to nucleus gracilis
- DRG (N1, caudal to T5)
- Nucleus thoracicus (N2, T1-L4)
- Lateral funiculus, along dorsal spinocerebellar tract
- Nucleus Z (N3) rostral to nucleus gracilis -> decussates
- Thalamus -> internal capsule -> SI
Name the 6 sensory nuclei of the brainstem (slide 49)
- V-midbrain: Nucleus of the mesencephalic tract of trigeminal nerve (face proprioception)
- V-pons: Pontine sensory nucleus of the trigeminal nerve (face tactile sensation)
- V-medulla: Nucleus of the spinal tract of the trigeminal nerve (facial pain and temp)
- VIII-medulla: Cochlear + vestibular nuclei
- VIII-medulla: nucleus of solitary tract
Face proprioception
Mesencephalic tract of trigeminal nerve
- Mesencephalic nucleus (N1-exception, not DRG!) -> decussates
- Trigeminal lemniscus (quintothalamic tract)
- Thalamus (N2)-> SI or cerebellum
Where is the mesencephalic nucleus (nucleus of the mencephalic tract of V)? slide 51
Lateral edge of periaqueductal gray
What is the quintothalamic tract
Trigeminal lemniscus (from mesencephalic nucleus to thalamus)
Face tactile sensation
Pontine sensory tract of the trigeminal nerve
- Trigeminal ganglion (N1, lateral to cavernous sinus)
- Pontine sensory trigeminal nucleus (N2, pons) -> decussates
- Trigeminal lemniscus (quintothalamic tract)
- Thalamus (N3) -> SI
Facial pain and temp
Spinal tract of the trigeminal nerve
- Trigeminal ganglion (N1)
- Nucleus of spinal tract of trigeminal nerve (N2, long, entire length of medulla) -> decussates
- Trigeminal lemniscus (quintothalamic tract)
- Thalamus -> SI
GBA
Role of the general visceral afferent system (GVA)
- Perceives changes in internal environment
- Digestion, circulation, respiration, micturition, body temp
Fiber types of GVA (viscerosensory fibers)
Free nerve endings (Ad + C) - either nociceptors or physiologic receptors (baroreceptors, chemoreceptors, …)
GVA
Thoracic viscera (lungs & heart) - slide 61
- Reach SYMPATHETIC TRUNK (via middle cervical & cervicothroacic cervical ganglia + ansa subclavia) -> DRG
- Synapse on dorsal horn -> decussates
- merge with SPINOTHALAMIC TRACT or intermediolateral nucleus (reflex)
GVA
Abdominal viscera (slide 62)
- Fibers in SPLANCHNIC NERVES
- Reach SYMPATHETIC TRUNK -> DRG
- Synapse on dorsal horn -> decussates
- Merges with SPINOTHALAMIC TRACT or intermediolateral nucleus (reflex)
GVA
Pelvic viscera (slide 63)
distal rectum, pelvic cavity, bladder, penis/clitoris
* Pelvic nerve -> pelvic ganglion -> DRG
* Synapse on dorsal horn -> decussates
* Merges with SPINOTHALAMIC TRACT or sacral parasympathetic nucleus (reflex)
GVA
Alternative (to spinothalamic tract) route for abdominal and pelvic viscera to reach cerebral cortex
**ARAS ** (receives spinoreticular tract + collaterals from spinothalmic tract)
GVA
Which CNs carry GVA fibers
IX, X
GVA
Which GVA modalities are carried by CN IX + X
- GLOSSSOPHARYNGEAL: taste (lingual nerve) + carotid body (carotid sinus branch)
- VAGUS: Aortic arch, palate, pharynx, larynx, trachea, oesophagus & thoracic and abdominal viscera
GVA
Which ganglia receive GVA afferents from CN IX and X
- Glossopharyngeal: DISTAL ganglion (jugular foramen)
- vagus: Distal and PROXIMAL ganglion (ventromedial to tympanic bulla)
GVA
WHere do GVA afferents from CN IX+X terminate
- Most: nucleus of solitary tract (medulla)
- Few: cortex, via solitariothalamic tract
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