Ascending Neural Pathways Flashcards Preview

MD2002 > Ascending Neural Pathways > Flashcards

Flashcards in Ascending Neural Pathways Deck (37):
1

What are the 3 principal ascending tract systems of the spinal cord?

1. dorsal column - medial lemniscus
2. spinothalamic
3. spinocerebellar

2

What tract carries information from the lower body extremities?

fasciculus gracilis (up to T6)

3

Where does fasciculus cuneate carry information from?

upper body (from above T6)

4

Where does the first order neuron/first afferent terminate?

the spinal cord or brainstem

5

Where does the second order neuron project to?

the thalamus

6

Where does the third order neuron project to?

primary sensory cortex

7

What is the dorsal column - medial lemniscal pathway for?

MECHANICAL STIMULI
1. conscious proprioception
2. discriminative touch
3. vibration
4. pressure

8

What fibres is the medial lemniscal pathway composed of?

large diameter, fast A-beta fibres

9

In the dorsal columns, how do the 1st order neurons ascend?

ipsilaterally

10

What are the steps in the medial lemniscal pathway?

1. 1st order neurons ascend dorsal colum
2. at gracile and cuneate nuclei, they synapse with 2nd order neurons
3. they then decussate and form medial lemniscus
4. project to VPL of thalamus

11

What pathological process occurs when the brain is deprived of information about the position of the feet?

gait ataxia

12

What can lesions in the cervical cord cause?

upper extremity ataxia

13

What does paraesthesia usually result from?

ectopic discharge in damaged dorsal column axons

14

What is the spinothalamic pathway for?

NOCICEPTIVE STIMULI
1. mech/chem/therm detection of coarse or non-discriminating touch
2. pain
3. temperature

15

What sort of fibres are spinothalamic pathways composed of?

+ smaller diameter
+ A-delta or C fibres
+ no specialised sensory endings
+ myelinated fibres (quick to cross)

16

What do A-delta fibres detect?

+ non-discriminative touch (strong stimuli that does not damage skin)
+ heat/cold
+ sharp pain

17

What do C fibres detect?

+ dull, aching pain
+ itch (histamine sensitive)

+ thermal
+ mechanical

18

What are the steps in the spinothalamic pathway?

1. 1st and 2nd order neurons synapse in dorsal horn
2. decussate then ascend lateral OR ventral tracts
3. synapse with 3rd order neurons at thalamus
4. project to sensory cortex

19

What are the features of the spinothalamic LATERAL route?

+ mix of A-delta and C fibres
+ carries info about:
- pain/heat and cold (A-delta)
- dull pain/itch (C)

20

What are the features of the spinothalamic VENTRAL/ANT. route?

only C fibres carrying info about coarse/non-discriminating touch via mechanosensitive fibres

21

What are the 4 types of nociceptor?

+ polymdal
+ mechanical
+ chemical
+ thermal

22

What are the features of pricking/stabbing pain?

+ fast
+ conducted along A-delta fibres
+ arrives first in CNS (fast conduction velocity)

23

What are the features of burning/aching pain?

+ slower
+ conducted along C fibres
+ arrives later in CNS (slow conduction velocity)

24

What is the role of substance P?

+ modulates the peripheral neuronal response to noxious stimuli

+ released from pain neurons when stimulated in fast succession

+ increase sensitivity to noxious stimuli

25

What is referred pain?

+ signals of noxious and normal cutaneous stimuli enter spinal cord at same point

+ cross talk in dorsal horn between modalities common

+ signals from viscera picked up by ascending nerve fibres mapped cortically to dermis

26

What is the role of the spinocerebellar pathway?

PROPRIOCEPTIVE INFO

takes info about body's position and movements to cerebellum for integration (for control of posture and co-ordination of movement)

27

What are the two principal routes for info in the spinocerebellar pathway?

+ ventral/anterior route
+ dorsal/posterior route

28

Where is information carried from in the spinocerebellar pathway?

Dorsal route: from muscle spindles (muscle tension)

Ventral route: from golgi organs (proprioception) and touch receptors

29

How many neurons does each pathway contain along its length (1st and 2nd order)

only 2 neurons

30

Where are the 2nd order cell bodies located?

dorsal horn of spinal cord, and terminate in vermis of cerebellum

31

How do dorsal tract neurons ascend?

ipsilaterally

32

How do dorsal tract neurons enter the cerebellum?

via the inferior peduncle

33

How do ventral tract neurons ascend?

contralaterally

34

How do ventral tract neurons enter the cerebellum?

via the superior peduncle

35

What is Friedreich's ataxia

Inherited disease where spinocerebellar tract becomes increasingly ineffective

36

What causes Friedreich's ataxia

multiple repeats of gene for protein (Frataxin) responsible for iron metabolism in mitochondria

37

What does Friedreich's ataxia result in?

1. progressively uncoordinated arm and leg movements
2. wide based 'reeling' gait
3. intention tremor

Decks in MD2002 Class (85):