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Neuroanatomy > 9. Ascending sensory II > Flashcards

9. Ascending sensory II Flashcards

1
Q

Most neurons of the grey matter are classified as…

A

Multipolar neurons

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2
Q

What are the neuron types of the grey matter

A
  • Primary sensory
  • Motor (alpha, gamma, visceral)
  • Interneurons
  • Projection neurons
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3
Q

What is the role of projection neurons

A

Relay signals to distant CNS areas; form a tract as they ascend

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4
Q

What is the role of interneurons

A

Local circuit neurons; relay sensory info to motorneuron, other interneuron or projection neuron

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5
Q

Where is the cell body of alpha (extrafusal)/gamma (intrafusal) motorneurons vs visceral motorneurons

A
  • Alpha/gamma: ventral horn of C6-T2 and L4-S3
  • Visceral: intermediate substance of T1-L3 (intermediolateral nucleus) and S2-S3 (parasympathetic nucleus)
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6
Q

Organization of SC grey matter

What are the 3 ‘horns’/ zone of the SC grey matter

A
  • DORSAL (sensory)
  • INTERMEDIATE ZONE (autonomic) - contains a lateral horn, which is a bulge formed by lamina VI
  • VENTRAL HORN (motor)
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7
Q

Organization of SC grey matter

What are the two schemes of oraganization of the spinal cord

A
  • Nuclear - based on groups of cell bodies
  • Laminar - 10 laminae of Rexed based on cell structure
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8
Q

Organization of SC grey matter

Describe the localization of each laminae

Slide 22

A
  • Lamina I-VI: dorsal horn
  • Lamina VII + X: intermediate zone
  • Lamina VIII: ventral horn
  • Lamine IX: embedded in intermediate zone + ventral horn
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9
Q

Organization of SC grey matter

Name the SC grey matter nuclei

A

Dorsal horn
* Marginal nucleus
* Substantia gelatinosa
* Nucleus proprius
* Nucleus thoracicus
* Lateral cervical nuclus

Lateral horn/intermediate zone
* Intermediolateral nucleus
* Sacral parasympathetic nucleus

Ventral horn
* Medial & medial motor nuclei

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10
Q

Organization of SC grey matter

Marginal nucleus

A
  • Lamina I
  • Pain, touch, temp (exteroceptive)
  • Entire SC
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11
Q

Organization of SC grey matter

Substantia gelatinosa

A
  • Lamina II
  • Interneurons (pain, touch, temp)
  • Entire SC
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12
Q

Organization of SC grey matter

Nucleus proprius

A
  • Lamina III-IV
  • Interneurons + projection neurons
  • Entire SC
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13
Q

Organization of SC grey matter

Nucleus thoracicus

A
  • Lamina VI
  • Proprioceptive info from PLs
  • Unonscious - dorsal/ventral (PL) spinocerebellar tracts
  • Conscious - spinomedullary tract (PL)
  • T1-L4
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14
Q

Organization of SC grey matter

Lateral cervical nucleus

A
  • Dorsolateral edge of dorsal horn
  • Projection neurons
  • Part of spinocervicothoracic tract (touch > pain)
  • C1-C2
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15
Q

Organization of SC grey matter

Intermediolateral nucleus

A
  • Lamina VII (intermediate zone)
  • Sympathetic preganglionic neurons
  • T1-L3
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16
Q

Organization of SC grey matter

Sacral parasympathetic nucleus

A
  • Lamina VII (intermediate zone)
  • Parasympathetic preganglionic neurons (to pelvic viscera)
  • S2-3
17
Q

Organization of SC grey matter

Know table slide 32!

A

okay okay

18
Q

Unconscious ascending afferents

2 ascending pathways that do NOT reach conscious perception

Do not reach cerebral cortex directly

A
  1. Spinocerebellar tracts (muscle proprioception)
  2. Ascending reticular formation (all other senses)
19
Q

Name the 5 spinocerebellar tracts

A

Pelvic limbs:
* Dorsal spinocerebellar tract
* Ventral spinocerebellar tract

Thoracic limbs:
* Spinocuneocerebellar tract
* Cranial spinocerebellar tract

Neck: (De lahunta)
* Cervicospinocerebellar tract

20
Q

Spinocerebellar tracts

DORSAL spinocerebellar tract

A
  • Muscle spindle
  • DRG
  • Nucleus thoracicus
  • Ipsi dorsal spinocerebellar tract
  • Caudal c.p
21
Q

Spinocerebellar tracts

VENTRAL spinocerebellar tract

A
  • GTO
  • Base of dorsal horn
  • Immediately decussates
  • Contra ventral spinocerebellar tract
  • Rostral c.p.
  • Decussates again in the cerebellum
22
Q

Spinocerebellar tracts

SpinoCUNEOcerebellar tract

A
  • Muscle spindle
  • Ascends ipsi cuneate fascicle
  • LATERAL CUNEATE NUCLEUS (medulla)
  • Caudal c.p.
23
Q

Spinocerebellar tracts

CRANIAL spinocerebellar tract

A
  • GTO
  • Base of dorsal hon
  • ipsi cranial sinocerebellar tract
  • Either rostral or caudal c.p.
24
Q

Which spinocerebellar tract is called the DIRECT pathway and why?

A

DORSAL spinocerebellar tract.
* No decussation
* Remains close to dorsal horn
* closest (caudal) c.p.

25
Q

Which spinocerebellar tract is the INDIRECT pathway and why?

A

VENTRAL spinocerebellar tract
* Decussates twice
* Remains far from dorsal horn
* Farthest (rostral) c.p.

26
Q

How do spinocerebellar tract collaterals reach conscious perception (somatosensory cortex)?

A
  • DORSAL spinocerebellar: reaches nucleus Z (medulla) -> medial lemniscus - > thalamus -> SI
  • VENTRAL spinocerebellar: nuclear X -> ..
27
Q

Ascending reticular formation

What are the components of the ascending reticular formation

A
  • Spinal part, cranial part (medullary, pontine, midbrain, thalamic)
  • Project to cortex via central group of thalamic nuclei

N.b. is a midline system
- Cell bodies lie in the grey matter surrounding the central canal
Axons have short collaterals projecting to both sides of the reticular formation
- Contains an ascending and descending system which are intimately interconnected via reticular neurons

Relays all sensory modailities from SC to cerebrum except proprioception

28
Q

Name the 5 gate mechanisms of pain

A

Presynaptic inhibition
Enkephalinergic activation from superficial pain
Enkephalinergic activation through raphe spinal tract
Intense physical activity (endorphin release)
Hypnosis (unclear mechanism)

29
Q

Gate mechanism of pain

PRESYNAPTIC INHIBITION from mechanoreceptors (rubbing)

A
  • Inhibitory collaterals from gracile and cuneate fasciles carrying info from mechanoreceptors (e.g. rubbing) synapse on C-fiber terminals in the substantia gelatinosa
30
Q

Gate mechanism of pain

Enkephalic activation from SUPERFICIAL PAIN (acupuncture)

A

Excitatory collaterals from superficial pain afferents synapse on inhibitory enkephalinegic interneurons in the substantia gelatinosa, which them synapse on neurons projecting to the spinoreticular tract

31
Q

Gate mechanism of pain

Enkephalic activation from raphe spinal tract (2nd mechanism of acupuncture)

A

Excitatory serotoninergic collaterals from raphe spinal tract synapse on inhibitory enkephalinergic interneurons in the substantia gelatinosa

Neuroanatomy (20 decks)

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