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Medicine Year 1 - Semester 2 - Part 1 > Ascending Neural Pathways > Flashcards

Ascending Neural Pathways Flashcards

1
Q

State how sensations are divided into categories

A

Divided into :

  • Conscious (Somatic)
  • Unconscious
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2
Q

State what conscious sensations are divided into

A

(Based on locations of receptors)

Exteroceptive (Superficial)
Proprioceptive (Deep)

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3
Q

State what the exteroceptive sensations are divided into

A

Touch
Pain
Temperature

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4
Q

Touch

A

Protopathic - crude touch
Epicritic - discriminative touch

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5
Q

Distinction between protopathic and epicritic touch

A

They are carried in different pathways.

One can be spared and vice versa

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6
Q

State what the proprioceptive sensations are divided into

A

Joint position
Vibration
Kinaesthesia (sensation originating from muscles)
2-Point Discrimination

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7
Q

Feature of unconscious sensations

A

Do not reach the cerebral cortex, do not reach the brain.

Therefore, we are not aware of these sensations, however these sensations end up in different parts of the CNS.

Cerebellum deals with it.

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8
Q

State what unconscious sensations are divided into

A

Proprioceptive (from the joints)
Visceral (from the organs)

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9
Q

Free Nerve Endings

A

Pain, temperature

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10
Q

Pacinian Corpuscles

A

Vibration
Rapidly adapting

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11
Q

Encapsulated nerve endings

A

Pacinian corpuscles
Meissner corpuscles
Merkels discs
Ruffini endings

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12
Q

Meissner corpuscles

A

Texture
Rapidly adapting

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13
Q

Merkel discs

A

Sustained pressure
Slowly adapting

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14
Q

Ruffini endings

A

Drag (Stretch)
Slowly adapting

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15
Q

Describe transmission of somatic senses

A

Sensations are relayed to the CNS by 3 neurones.

1st order neurones pick up sensations with their peripheral branches from the receptors/free nerve endings.

To the dorsal root ganglion.

The central extensions of the 1st order neurone, bring the sensations to the spinal cord or brainstem, where they synapse with 2nd order neurones.

2nd order neurones cross the midline and ascend to terminate in the thalamus.

3rd order neurone projects from the thalamus to the somatosensory cortex.

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16
Q

Where are sensory nerves found ?

A

Dorsal Root ganglion

Houses:
- Afferent/ Sensory/ 1st order neurones

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17
Q

Function of the peripheral branch of the 1st order neurone

A

Carries sensations from the receptor/ free nerve ending.

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18
Q

Function of the central branch of the 1st order neurone

A

Enters the spinal cord / brainstem via the dorsal root ganglion.

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19
Q

Where is the cell body of the 2nd order neurone found ?

A

Located in the grey matter of the spinal cord / brainstem on the same side.

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20
Q

Where is the 3rd order neurone found ?

A

The thalamus

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21
Q

State the locations of the 1st, 2nd and 3rd order neurones

A

1: Dorsal Root Ganglion
2: Spinal cord or Brainstem
3: Thalamus

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22
Q

What does sensory information travel to the brain via ?

A

The dorsal column-medial lemniscus system

The anterolateral system

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23
Q

Where do the dorsal column-medial lemniscus system and the anterolateral system come back together ?

A

Partially at the level of the thalamus

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24
Q

State the sensations that travel together

A

Conscious proprioceptive sensation
Vibration
Discriminative touch

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25
Q

What is the pathway that carries :

Conscious proprioceptive sensation
Vibration
Discriminative touch

called ?

A

Dorsal column medial lemniscus pathway

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26
Q

Describe the dorsal column-medial lemniscus pathway

A

Carries signals up to the medulla (brainstem) in the dorsal columns of the spinal cord.

Synapse

Cross to opposite side of medulla, become medial lemniscus.

Up the brainstem to thalamus (VPL) via medial lemniscus.

The axons of the 3rd order neurones travel to the cerebral cortex.

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27
Q

Sensory decussation

A

Axons that cross the midline

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28
Q

1st order neurones in the dorsal column-medial lemniscus pathway

A

Central branches of 1st order neurones enter the dorsal column and ascend to the medulla as fasciculus gracilis (3a) or cuneatus (3b)

29
Q

2nd order neurones in the dorsal column-medial lemniscus pathway

A

Found in the ipsilateral gracile and cuneate nuclei in the medulla

30
Q

State the 2 types of pain

A

Fast pain
Slow pain

31
Q

Describe fast pain

A
  • 0.1s after a painful stimulus
  • carried by A-delta axons
  • Not felt in deep tissues (felt in skin)
32
Q

State some types of fast pain

A

Sharp pain
Stabbing pain
Prickling pain
Acute pain
Electric pain

33
Q

Describe slow pain

A
  • Begins >1s after a painful stimulus
  • Increases slowly
  • Carried by unmyelinated C axons
  • Felt both in skin and deep tissue/organs
  • Usually associated with tissue destruction
34
Q

State some types of slow pain

A

Slow burning pain
Aching pain
Throbbing pain
Nauseous pain
Chronic Pain

35
Q

What is nociception ?

A

Detection of stimuli that can cause tissue injury.

It can involve pain.

36
Q

Describe unmyelinated type C axons

A

Not localised (dull pain)

  • Respond to intense heat/cold
  • Slow pain
  • Dull, poorly localised
  • Terminate in reticular formation
37
Q

What is reticular formation ?

A

A network of cells and connections that are scattered all around the brainstem.

The nuclei can be found in the medulla/pons/midbrain etc.

No direct connection with the cortex.

38
Q

Spinoreticular tract

A

Carries pain from the spinal cord to the reticular formation.

39
Q

Describe finely myelinated Adelta axons

A

Ends up in the cortex

  • Sharp, fast pain
  • Well localised
  • Terminate in NVPL (spinothalamic/ anterolateral tract)
40
Q

What is the pathway that carries :

Pain
Temperature
Crude Touch

called ?

A

Anterolateral tract

41
Q

Anterolateral tract

What does it carry ?
(i.e. what sensations)

A

Receptors: Nerve endings

Pain, temperature and crude touch

42
Q

Describe the anterolateral tract

A

Enter the spinal cord via dorsal root nerves

Synapse w 2nd order neurones in the dorsal horns of spinal grey matter

Cross to the opposite side of the cord

Ascend through the anterior and lateral white columns of the cord

Terminate at all levels of the lower brainstem and thalamus.

43
Q

State the 2 spinothalamic tracts

A

Anterior spinothalamic tract
Lateral spinothalamic tract

44
Q

Anterior spinothalamic tract

A

Crude touch and pressure

45
Q

Lateral spinothalamic tract

A

Pain and Temperature

46
Q

Describe referred pain

A

Noxious stimuli originating in an organ are perceived as pain arising from a superficial part of the body (skin)

47
Q

Mechanism of referred pain

A

Branches of anterior pain fibres synapse in the spinal cord on same 2nd order neurones that receive signals from the brain.

When anterior pain receptors are stimulated, pain signals from the viscera are conducted through some of the same neurones conducting pain signals from the skin.

So the person feels sensations originate in skin.

48
Q

Do organs have pain receptors ?

A

NO !

They have nociceptors and stretch receptors.

Stretch - uncomfortable sensation, referred as pain

49
Q

T10

A

Umbilicus

50
Q

Summary of dorsal column-medial lemniscus

A

Conscious proprioception
Vibration
2-Point discrimination
Fine touch

51
Q

Summary of anterolateral (spinothalamic) system

A

Pain
Temperature
Crude touch

52
Q

Features dorsal column-medial lemniscus

A

Large, myelinated fibres
30-110 m/s
Discriminative mechanoreceptive sensation
High degree of spatial orientation

53
Q

Unconscious Proprioception function

A

Essentail for smooth motor coordination

Very fast conduction is required

54
Q

Features of anterolateral system

A

Smaller fibres
Up to 40 m/s
Broad spectrum of sensory modalities
Less spatial orientation

55
Q

Unconscious Proprioception

A

Sensations do not reach the cortex, the cortex is not aware of what’s going on.

Cerebellum is the most important structure involved.

56
Q

Describe unconscious proprioception

A

Afferent sensory information from muscle spindles and Golgi tendons terminate in IPSILATERAL cerebellum, rather than cerebral cortex.

57
Q

Clarke’s nucleus

A

Found in T1 to L2 spinal cord segments

Where the spinocerebellar tracts originate

58
Q

Anterior spinocerebellar tract

A

Carries input from the trunk, upper and lower limbs

59
Q

Posterior spinocerebellar tract

A

Carries input from lower trunk and lower limbs

60
Q

Cunocerebellar tract

A

Carries input from upper limbs

61
Q

Stereognosis

A

Ability to recognise and identify objects by feeling them

62
Q

Graphesthesia

A

Ability to recognise symbols written on the skin

63
Q

Anaesthesia

A

Total loss of touch sensation

64
Q

Hypoesthesia

A

Decrease in touch sensation

65
Q

Hyperesthesia

A

Increase in touch sensation

66
Q

Astereognosis

A

Loss of stereognosis

67
Q

Analgesia

A

No pain

68
Q

Thermanalgesia

A

Loss of temperature sensation

69
Q

Sensory Ataxia

A

GAIT disorder resulting form sensory impairment

  • severe swaying when eyes closed
  • impaired joint sense and discriminative touch
  • broad based gait

Medicine Year 1 - Semester 2 - Part 1 (51 decks)

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