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Anatomy Midterm 2 > The CNS & Spinal Cord > Flashcards

The CNS & Spinal Cord Flashcards

1
Q

Spinal Cord

A
  • cylindrical cable of pathway to & from brain and rest of body
  • extends from base of skull (medulla) to L(1-2 - between the vertebrae)
  • has cervical (brachial plexus) & lumbar (lumbosacral plexus) enlargements
  • meninges cover it like the brain (identical)
  • central canal continuous with ventricles of the brain
  • organized into inner gray & outer white matter (opposite to brain)
  • Dorsal & Ventral roots join up to form a SPINAL nerve (mixed)
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2
Q

Dorsal Horns & Roots

A

posterior, sensory input

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3
Q

Ventral Horns & Roots

A

anterior, motor output

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4
Q

Lateral Horn

A

protrusion = sympathetic

  • pre-ganglionic nerve cell bodies
  • enlargement due to appendages
  • normally about diameter of little finger
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5
Q

Parts of the Spinal Tract

A

Medulla Oblongata –> L1-L2 Conus Medullaris –> Cauda Equina –> Filum Terminale

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6
Q

Conus Medullaris

A

Spinal nerves extending directly from the end of the spinal cord

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7
Q

Cauda Equina

A

part of the spinal tract between the conus medullaris and the filum terminale

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8
Q

Sensory & Motor Pathways

A
  • communication between CNS, PNS, and peripheral organ systems
  • involves ascending and descending pathways - relay sensory and motor information between the periphery & higher centres
  • ascending = sensory, descending = motor
  • each pathway consists of a chain of neurons and associated nuclei or ganglia
  • the number of neurons and synapses (inter-neuronal connections) vary from one pathway to another
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9
Q

Pathway Nomenclature

A

pathways are names according to their site or origin and destination

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10
Q

Somatic Sensory Pathways (3)

A
  1. Dorsal Column/Medial Lemniscal Pathway
  2. Spinothalamic (anterolateral) Pathway
  3. Spinocerebellar Pathway
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11
Q

Dorsal column/medial lemniscal Pathway

A

somatic sensory pathway
two names - depends on location (dorsal column within spinal column, medial lemniscal within brain stem)
- joint position & vibration sense (proprioception) & discriminative touch (3D + fine touch), stereogenesis & graphethesia (can build mental images of structures we touch - not all parts of body have the same ability to do this)

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12
Q

Discriminative Touch

A

ability to discriminate 2 points of contact (before no longer able to separate them)

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13
Q

Proprioception

A

awareness of position of body in space

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14
Q

Spinothalamic (anterolateral) Pathway

A

somatic sensory pathway

  • pain, temperature & crude touch
  • unable to describe structure
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15
Q

Spinocerebellar Pathway

A

somatic sensory pathway

- unconscious proprioception

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16
Q

Dorsal Columns (2)

A
  1. Fasciculus Cuntaneous

2. Fasciculus Gracilis

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17
Q

Function of the Dorsal Columns

A
  • conveys perception & discriminant touch + stereogenesis (3D recognition of objects) from trunk and extremities
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18
Q

Fasciculus Gracilis

A

info from the lower extremities and lower trunk (more medial - longer)

19
Q

Fasciculus Cutaneous

A

info from the upper extremities and upper trunk (more lateral)

20
Q

Pathway of the Dorsal Columns

A
  • 1st order neuron from skin/joint receptor –> medulla (same side) (fasciculus gracilis and cutaneous)
  • 2nd order neuron from medulla –> crosses to opposite side –> ascends as the medial lemniscus –> thalamus
  • 3rd order neuron from thalamus –> primary sensory cortex (thalamocortical projections)
21
Q

Anterior Spinothalamic Tract

A

crude touch (non-discriminant)

  • 1st synapse in posterior (dorsal) horn, then passes contralateral to ventral horn –> up anterior spinothalamic tract
  • 2nd synapse at ventral nuclei of thalamus
22
Q

Dorsal Columns Pathway

A
  • 1st neuron travels in dorsal horn and up dorsal column to medulla (1st synapse) –> passes contralateral to medial lemniscus –> 2nd synapse at ventral nuclei of thalamus
23
Q

Lateral Spinothalamic Tract

A

pain and temperature (often linked)
- 1st synapse in dorsal horn –> crosses contralateral up lateral spinothalamic tract –> 2nd synapse at ventral neuclei of thalamus

24
Q

Spinocerebellar Pathway

A

unconscious proprioception (tone of muscles & stress of tendons)

  • *synapses ipsilaterally and contralaterally
  • posterior (ipsilateral) tract and anterior (contralateral) tract
  • 1st synapse for both is in the dorsal horn –> travels to cerebellum (regulates posture)
25
Q

Upper Motor Neuron (UMN)

A

cell body in CNS processing centres of a somatic motor pathway

26
Q

Lower Motor Neuron (LMN)

A

cell body in ventral horn of spinal cord or motor cranial nerve nucleus in brainstem of a somatic motor pathway

27
Q

Motor Systems

A
  • CNS issues motor commands
  • commands are distributed to the body by the PNS
  • somatic motor commands effect contraction of skeletal muscle (conscious)
  • always involve at least 2 motor neurons: UMN & LMN
28
Q

Modulation of the LMN by UMN

A

UMN –excitatory/inhibitory synapse–> LMN

CNS –brainstem/spinal cord–> periphery

29
Q

UMN Lesion

A

in most cases, causes UMN to only synapse in an inhibitory way
- leads to dis-inhibition –> SPASTIC PARALYSIS

30
Q

LMN Lesion

A

UMN produces excitatory or inhibitory synapse but no response by LMN
- leads to flaccid paralysis (no muscle tone)

31
Q

Common Final Pathway

A

LMN, the only axon to extend to the skeletal muscle for motor contraction

32
Q

Pathways of Motor Systems (2)

A
  1. Corticospinal (pyramidal) pathway

2. Corticonuclear (corticobulbar) pathway

33
Q

Corticospinal Pathway

A

Aka Pyramidal Pathway

  • UMNs extend from the cerebral cortex (cortico) to the spinal cord (spinal)
  • regulate distal musculature in limbs & trunk
  • convergences from motor & sensory cortex –> internal capsule –> CRUS CEREBRI in midbrain –> pyramids in medulla –> decussation of the pyramids –> synapses 85% to lateral LMN & 15% to anterior LMN
34
Q

Corticonuclear Pathway

A

Aka Corticobulbar Pathway

  • UMNs extend from the cerebral cortex (cortico) to motor cranial nerve nuclei in the brainstem (Nuclear (bulbar))
  • regulate muscles of the head & neck
35
Q

Extrapyramidal Pathways

A

subsidiary descending pathways important as back-up systems

36
Q

Basal Nuclei and Cerebellum

A

modulate and modify activity in the corticospinal tract to ensure smooth, coordinated, purposeful movement

37
Q

Central Motor Program

A
  1. Identification and localization of targets in space –> posterior parietal cortex
  2. Formation of a plan of action –> premotor cortex & supplementary motor cortex
38
Q

Primary Motor Cortex

A

receives info from cortex (central motor program), conveys motor commands by descending motor pathways (execution of the movement)

39
Q

Simple Finger Flexion (Performance)

A

involves motor cortex and somatic sensory cortex

40
Q

Finger Movement Sequence (Performance)

A

involves premotor area & supplementary motor area of cortex + motor cortex

41
Q

Finger Movement Sequence (Mental Rehearsal)

A

involves premotor & supplementary motor area ONLY

42
Q

Origins of the Corticospinal Pathway

A

1/3 Primary Motor Cortex
1/3 Premotor + Supplementary Motor Cortex
1/3 Primary Sensory Cortex

43
Q

LMN Injury

A

spinal nerve injury

44
Q

UMN Injuries

A
  • Middle Cerebral Artery Stroke
  • Internal Capsule lesion
  • Brainstem Lesion (above red nucleus = decorticate & spastic, below red nucleus = decerebret & flaccid)
  • spinal cord injury

Anatomy Midterm 2 (7 decks)

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