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Systems: Neurology AB > The Spinal Cord and the Periphery > Flashcards

The Spinal Cord and the Periphery Flashcards

1
Q

How is the grey matter arranged?

A

Central

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2
Q

How is the white matter arranged?

A

Peripheral

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3
Q

What does the grey matter have on each side?

A

Dorsal and ventral horn

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4
Q

What enters through the dorsal root into the dorsal horn of the grey matter?

A

The axons of sensory fibres enter through the dorsal root into the dorsal horn of grey matter.

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5
Q

Where do motor neurones have their cell bodies?

A

Ventral horn

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6
Q

What is motor neuron disease?

A
  • Group of diseases affecting the motor neuron in the ventral horn of spinal cord. (This neuron is called as the Lower Motor Neuron.)
  • The neuron dies and as a result muscle supplied by it atrophies.
  • Progressive, incurable disease.
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7
Q

What is white matter made up of?

A

White matter is made up of tracts.(axons transmitting information between higher centres in the brain and peripheral nerves)

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8
Q

What are tracts?

A

Pathways

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9
Q

How do tracts differ?

A

Different tracts carry different bits of information. Ascending pathways are sensory, descending pathways are motor.

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10
Q

What are the 3 columns of the white matter?

A

The white matter is arranged as 3 columns – posterior,lateral & anterior. Each column has in it various tracts.

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11
Q

What do the ascending spinal tracts carry?

A

Carries sensory information to the brain (cerebral cortex and cerebellum)

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12
Q

What are the common characteristics of pathways reaching conscious level?

A
  • There are 3 neurons between peripheral receptor and cortex.
  • 2nd order neuron nucleus in grey matter of spinal cord or medulla
  • Crosses over to contralateral side in spinal cord or medulla (2nd order neuron)
  • 3rd order neuron nucleus in contralateral thalamus
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13
Q

What is the posterior/dorsal column responsible for?

A
  • Fine touch
  • Tactile localisation
  • Vibration sense
  • Proprioception
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14
Q

What is the lateral spinothalamic tract of the right side responsible for?

A

Pain and temperature from Left side of body

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15
Q

What is the posterior column of the right side responsible for?

A

Touch, pressure, proprioception from Right side of body.

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16
Q

Where do the motor/descending tracts of the spinal cord originate from?

A

Cerebral cortex and brainstem

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17
Q

What are motor/descending tracts of the spinal cord responsible for?

A

Are concerned with control of movement, muscle tone, spinal autonomic functions.

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18
Q

How many neurons do ascending sensory tracts have in their pathway

A

3

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19
Q

Where do the motor/descending tracts of the spinal cord decussate?

A

They decussate to the opposite side in the brainstem.

20
Q

What is the corticospinal/pyramidal tract responsible for?

A

Control of voluntary skilled movements.

21
Q

Where do corticobulbar fibres go?

A

Corticobulbar fibres go to contralateral cranial n nucleii.

22
Q

Where is the decussation of corticospinal fibres?

A

Corticospinal fibres mostly cross in decussation of pyramids (Lateral corticospinal tract).

23
Q

Where is the corticospinal/pyramidal tract located?

A

Posterior limb of Internal Capsule (blood supply MCA).

24
Q

What is the LMN responsible for?

A

The lower motor neuron (LMN) is responsible for muscle tone and reflexes

25
Q

What happens if the UMN is damaged with the LMN intact?

A

If the upper motor neuron (UMN) is damaged with LMN intact, then reflexes and tone are exaggerated

26
Q

What is a reflex?

A

A reflex is an involuntary stereotyped pattern of response brought about by a sensory stimulus.

27
Q

Where are many reflexes mediated?

A

Many reflexes are mediated at the level of the spinal cord (spinal reflexes).

28
Q

How can reflexes differ anatomically?

A

Anatomically they may be monosynaptic (eg: stretch reflex) or polysynaptic (eg: flexor reflex).

29
Q

When is some sensory information not sent to the brain?

A
  • Not all sensory information needs to be sent to the brain for decisions to be made
  • In certain instances where an immediate response in needed, the spinal cord or other lower centres themselves can take these decisions.
  • These make up some of our reflexes.
30
Q

What is stretch reflex important in the control of?

A

Stretch reflex is important in control of muscle tone and posture.

31
Q

Briefly describe the steps in the stretch reflex (and reciprocal innervation).

A
  • Tendon stretched
  • Intrafusal muscle fibres stimulated
  • Sensory neuron activated
  • Monosynaptic reflex arc
  • Polysynaptic reflex are to inhibitory interneuron
  • Muscle contraction
  • Reciprocal innervation
32
Q

What does the flexor reflex help to do?

A

Flexor reflex helps protect the body from painful stimuli.

33
Q

Briefly describe the steps in the flexor (and crossed extensor) reflex.

A
  • Pain stimulus
  • Sensory neuron activated
  • Polysynaptic reflex arc
  • Flexion and withdrawal from noxious stimulus
  • Crossed extensor response to contralateral limb (only in weight bearing limbs
34
Q

Why does someone have exaggerated reflexes with an UML?

A
  • A motor response was brought about (reflexively) without using the upper motor neuron.
  • So even if the upper motor neuron is damaged, one still does have reflexes – which become EXAGGERATED
35
Q

What are the characteristics of UMN lesions?

A
  • Exaggerated reflexes

- Increased muscle tone (spasticity)

36
Q

At the spinal cord level what tracts are crossed/uncrossed?

A
  • Pyramidal tract crossed
  • Spinothalamic tract crossed
  • Posterior column uncrossed
37
Q

What would hemisection of spinal cord on the left side result in?

A
  • Pyramidal tract, spinothalamic tract, posterior column all abrupted on left side
  • Right sided loss of temperature and pain
  • Left sided paralysis (spastic)
  • Left sided loss of touch, vibration sense
  • Reflexes on left side exaggerated
38
Q

What are the divisions of the motor PNS?

A
  • Somatic motor (skeletal muscles)

- Autonomic motor (smooth muscle, cardiac muscle, glands)

39
Q

What does the autonomic nervous system refer to?

A

Autonomic nervous system refers to nerve cells within both CNS & PNS concerned with innervation & control of visceral organs,smooth muscles & secretory glands.

40
Q

What is the outflow of the sympathetic system?

A

Thoracolumbar

41
Q

What is the outflow of the parasympathetic system?

A

Cranisacral

42
Q

Where are the preganglionic fibres in the sympathetic system?

A

Ganglia near spinal cord

43
Q

Where are the preganglionic fibres in the sympathetic system?

A

Ganglia near target organ

44
Q

Where are the postganglionic fibres in the sympathetic system?

A

Target - every cell in body

45
Q

Where are the postganglionic fibres in the parasympathetic system?

A

Target- exocrine glands, heart, other selected organs

46
Q

How many neurons do the descending motor tracts have in their pathway?

A

2

Systems: Neurology AB (51 decks)

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