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SF2- Exam 2 > Ascending Pathways > Flashcards

Ascending Pathways Flashcards

1
Q

Conscious info is being sent the ________ and makes us aware of the stimulus

Unconscious info about position sense is being sent to the ___________.

A

brain; cerebellum

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2
Q

List the conscious and nonconscious tracts that make up the ascending sensory pathways.

A
  • Conscious
    • ​Dorsal column-medial lemniscal pathway
    • The anterolateral system
      • Spinothalamic
      • Spinoreticular
      • Spinomesencephalic
  • Nonconscious
    • ​Spinocerebellar (proprioception)
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3
Q

Pathway for discriminative touch and kinesthesia.

A

Dorsal Column/Medial Lemniscus system

  • Tactile information
  • Vibration
  • Sense of position
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4
Q

Pathway for Pain and temperature.

A

Anterolateral system

  • Spinothalamic (main)
  • Spinoreticular
  • Spinomesencephalic

*•The spinoreticular and spinomesencephalic are ways for periphery to communicate with brainstem to control arousal and breathing and other functions that are mediated by the brainstem

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5
Q

___________,_______, and _________ cells are encapsulated receptors.

A

Pacinian corpuscle, Meissner’s corpuscle, and Merkel’s cell

*Free nerve endings are not encapsulated

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6
Q

What type of cells are found the dorsal root ganglion, as relates to the ascending sensory pathway?

A
  • Pain and temp cells
  • Small reflex cells with caliber
  • Tactile cells.
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7
Q

What are the receptors for the dorsal column medial lemniscus system?

A

Receptors: Mechano- and Proprioceptive receptors

(encapsulated nerve endings and hair follicle receptors)

  • Tactile: specialized epithelial cells of Merkel, Ruffini’s & Meisner’s corpuscle, hair follicle Rs
  • Vibration: Pacinian corpuscles
  • Position sense: Proprioceptive receptors (muscle spindles and Golgi tendon organs) in joints tendons… muscles.
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8
Q

Third order neurons finally relay the touch/pressure information to the ___________ lobe

A

Parietal

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9
Q

What is the dorsal column/ medial lemniscus pathway?

A

1) Receptors
2) Primary sensory neurons - (pseudo) unipolar neurons with cell bodies in DRG of the spinal cord, or the trigeminal ganglion of the head.
3) Second order neurons – send signals across the midline to the other side of the central nervous system. The crossed axons end in the thalamus.
4) Third order neurons finally relay the touch/pressure information to the parietal lobe

NOTE: *The primary somatosensory system is in the parietal lobe

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10
Q

The third order neurons are in the ___________

A

thalamus

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11
Q

After dorsal column nuclei decussate, they are called ___________

A

Medial lemniscus

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12
Q

The fibers of second order neurons (in the dorsal column/ medial leminscus pathway) synapse on_____________.

A

Ventro-postero-lateral nucleus (of the thalamus)

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13
Q

What fibers are sent out by the primary neurons of the dorsal column/medial leminscus pathway?

A

A beta (touch)

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14
Q

F. gracilis originates between______ and ________

A

T6 and S5

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15
Q

F. cuneatus originates between _____ and _____

A

C1 and T5

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16
Q

Fasciculus cuneatus and fasciculus gracilus synapse on cell bodies of ___________ nuclei. At the point where they synapse they cross over and become the medial lemniscus system

A

dorsal column (n.cuneatus and n.gracilus)

NOTE: Level of sensory decussation lose them (fibers)

•At the level of sensory decussation, decussation has not occurred yet because the nucleus cuneatus and gracilis are still intact.

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17
Q

In the fine touch system, the first order neurons carry sensory information regarding touch, proprioception or vibration from the peripheral nerves to the medulla oblongata. There are two different pathways which the first order neurones take:

Signals from the upper limb (T6 and above) – travel in the ___________ (the lateral part of the dorsal column). They then synapse in the _________ of the medulla oblongata.

Signals from the lower limb (below T6) – travel in the _________ (the medial part of the dorsal column). They then synapse in the ________ of the medulla oblongata.

A

fasciculus cuneatus; nucleus cuneatus

fasciculus gracilis; nucleus gracilis

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18
Q

In the first touch system, the second order neurons begin in the cuneate nucleus or gracilis. The fibers receive the information from the preceding neurons, and delivers it to the third order neurons in the _____________.

Within the medulla oblongata, these fibres decussate (cross to the other side of the CNS). They then travel in the contralateral ___________ to reach the thalamus.

A

thalamus; medial lemniscus

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19
Q

In the first touch system, the third order neurons transmit the sensory signals from the thalamus to the ipsilateral _____________of the brain. They ascend from the _________nucleus of the thalamus, travel through the _____________ and terminate at the sensory cortex.

A

primary sensory cortex; ventral posterolateral; internal capsule

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20
Q

At the level of open medulla, cervical regions are located more _________ (superior/inferior) to the sacral region.

At the level of the spinal cord, sacral regions are more __________ and cervical regions more __________.

A

Superior

medially; laterally

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21
Q

After peripheral nerve carries the information signal toward the CNS, the central process of the axon enters the spinal cord via a__________, or the brainstem via the ________.

A

dorsal root; trigeminal nerve

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22
Q

Where specifically is the primary sensory cortex located?

A

In the postcentral gyrus of the parietal lobe

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23
Q

What is the sensory information pathway toward the brainstem?

A

Trigeminal ganglion-> Sensory nuclei of CN V-> Medial lemniscus-> VPM (of the thalamus)-> Postcentral gyrus

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24
Q

Inputs into the medial lemniscus and come from 3 different nuclei. What are they?

A

Trigeminal ganglion

Fascilulus cuneatus (Above T6)

Fascilulus gracilus (Below T6)

NOTE: Inputs from the dermatomes project to different parts of the postcentral gyrus (i.e. areas 3,2, and 1) Thus, the functional, dermatomal organization of the postcentral gyrus reflects exactly the dermatomal organization of the peripheral nerves.

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25
Q

In the representation of the somatosensory cortex part of the parietal lobe in the postcentral gyrus, the foot is more _________ (medial/ lateral) and the face is more _________ (medial/lateral).

A

medial; lateral

26
Q

What areas of the primary sensory cortex do the following synapse on?

Muscle Spindle fibers

Golgi Tendon

Mechanoreceptors

A

Muscle Spindle fibers

  • Area 3a-> Area 2->Area 5, 7, 40

Golgi Tendon

  • Area 2->Area 5, 7, 40

Mechanoreceptors

  • Area 3b-> Area 2->Area 5, 7, 40
  • Area 3b-> Area 1->Area 5, 7, 40
27
Q

Primary Somatosensory Area Projections

A

Afferents

– VP of Thalamus

– Contralateral S1 Cortex

– Adjacent projections from M1

Efferents

– SII

– Ipsilateral Motor Cortex,

– Area 5, 7, Area 40

– Contralateral S1 Cortex

– Projection fibers to VP of thalamus, to DC nuclei and to spinal posterior gray horn (tiny)

28
Q

What are the receptors for the anterolateral system. spinothalamic tract?

A
  • Receptors: Nociceptors, thermoreceptors – free nerve endings
  • Mechanoreceptors – non-discriminative touch

NOTE:

Anterior spinothalamic tract – carries the sensory modalities of crude touch and pressure.

Lateral spinothalamic tract – carries the sensory modalities of pain and temperature.

29
Q

In the anterolateral system, the first order neurons arise from the sensory receptors in the periphery. They enter the spinal cord, ascend 1-2 vertebral levels (via the Lissauer tract) and synapse at the tip of the dorsal horn – an area known as the ____________.

A

substantia gelatinosa

NOTE: Substantia Gelatinosa & Nucleus Proprius– receives pain fibers C, A delta

30
Q

In the anterolateral system, the second order neurons carry the sensory information from the substantia gelatinosa to the ________. After synapsing with the first order neurons, these fibres decussate within the spinal cord, and then form the anterolateral spinothalamic tract.

A

thalamus

NOTE: Information comes in through DRG and travel through ventral white commissure and then decussates and goes to anterolateral system

31
Q

In the anterolateral system, the third order neurons carry the sensory signals from the thalamus to the ipsilateral ____________of the brain. They ascend from the _____________ of the thalamus, travel through the ___________ and terminate at the sensory cortex.

A

primary sensory cortex; ventral posterolateral nucleus; internal capsule

32
Q

Simple diagram of ST tract in the spinal cord. Label all defining areas.

A
33
Q

Compared to the fine touch system, what are the characterestics of the cell bodies and axons of the Pain/Temp/ Course Touch System?

A

The cell bodies of these neurons are smaller and the axons are thinner in diameter and are poorly myelinated.

34
Q

In the anterolateral system, pseudounipolar neurons in the dorsal root ganglion have axons that lead from the skin into the dorsal spinal cord where they ascend or descend one or two vertebral levels via ____________ and then synapse with secondary neurons in either the substantia gelatinosa of Rolando or the nucleus proprius.

A

Lissauer’s tract

35
Q

Pain sensation isn’t perfectly localized. There is mixing of signals. After they enter DRG they travel up/down one to two segments through the ___________.

A

Tract of lissauer

36
Q

As they join spinothalamic tract, if we take the tract and separate we can see the more lateral cells are for ________. The more medial are for _______. The pathway for ____________ is in the same tract but is more ventral medial.

A

pain; temp; crude touch

37
Q

Are there specialized receptors for the pain/temp/crude touch system?

A

No.

•There are no known specialized receptors for this system; the free nerve endings of the peripheral axons themselves being sensitive to pain and temperature.

38
Q

What is the flow of axons for the anterolateral system?

A
  • The primary sensory neurons are located in the DRG.
  • The termination of their central processes differs from the Fine Touch System in that the Spinothalamic tract axons end on cell bodies of second order neurons that are located in the spinal cord. Axons of 2nd order neurons terminate in the central core of the brainstem (the reticular activating system). The remainder of the second order axons end in the thalamus on a third order neuron. Some of the third order axons travel to the cells of the postcentral gyrus.
39
Q

In the anterolateral system, what three places can the axons of the second order neurons terminate?

A

Spinal cord

Brainstem (reticular activating system)

Thalamus (on third order neurons)

40
Q

When do axons of the spinothalamic tract decussate?

A

At the level of spinal cord that they enter

41
Q

What areas does the spinothalamic tract project to?

A
  • Intrathalamic nuclei
  • Limbic regions
  • Reticular formation of the medulla and pons
  • Mesencephalon.
42
Q

Together the spinothalamic and trigeminothalamic pathways form the ___________ and organization in the thalamus too and then you get information going to the specific areas.

A

homunculus

43
Q

Cold receptors coupled to ___________fibers while hot is couple to __________ fibers.

A

A delta & C

C only

44
Q

Which pathway is linked to the PATHWAY FOR JOINT POSITION AND KINESTHESIS?

A

Spinocerebellar tract

45
Q

The tracts that carry unconscious proprioceptive information are collectively known as the ____________.

A

spinocerebellar tracts

46
Q

What are the four individual pathways within the spinocerebellar tract?

A

Posterior spinocerebellar tract – Carries proprioceptive information from the lower limbs to the ipsilateral cerebellum.

Cuneocerebellar tract – Carries proprioceptive information from the upper limbs to the ipsilateral cerebellum.

Anterior spinocerebellar tract – Carries proprioceptive information from the lower limbs. The fibres decussate twice – and so terminate in the ipsilateral cerebellum.

Rostral spinocerebellar tract – Carries proprioceptive information from the upper limbs to the ipsilateral cerebellum.

47
Q

Which tracts of the spinocerebellar pathway convey information related to muscle contraction?

A

Dorsal (posterior) Spinocerebellar Tract and Cuneocerebellar Tract

–convey information related to muscle contraction.

•phase, rate, and strength of contraction

48
Q

Which tracts of the spinocerebellar pathway conveys information about interneuronal activity and effectiveness of descending pathways?

A

Ventral (anterior) Spinocerebellar Tract

49
Q

What are the results of lesions of the spinocerebellar tracts?

A

Patients walk with a wide base, stagger, and fall down often.

50
Q

What spinal cord level do cunocerebellar fibers come from?

A

Afferent fibers entering S. C. from C8 upward travels with the Cuneate fasciculus, synapse onto nuclei in lower medulla, & provide functional info regarding upper limbs.

NOTE: There is no nucleus of Clarke above C8.

51
Q

What are the boundaries of the nucleus of Clarke?

A

C8- L2

52
Q

What is the pathway of axon flow for the cuneocerebellar tract?

A
  1. Afferent fibers from C8 upward travels with the Cuneate fasciculus
  2. Fibers synapse onto nuclei in lower medulla
53
Q

What is the pathway of fiber flow for the dorsal spinocerebellar tract?

A
  1. Central processes of DRG axons project to the nucleus dorsalis of Clarke (C8-L2).
  2. Fibers travel ipsilaterally to inferior cerebellar peduncle in the medulla.
  3. Fibers terminate in the cerebellar vermis of anterior lobe.
54
Q

What type of info does the dorsal spinocerebellar tract convey?

A
  • Info about lower limbs
  • Conveys info regarding whole limb movement & Postural adjustments
55
Q

What is the fiber course for the anterior spinocerebellar tract?

A
  1. Central processes of DRG axons project to neurons in laminae V to VII ipsilaterally.
  2. These 2nd order neurons in base of dorsal horn, cross in the spinal cord and ascend via the lateral funiculus through the medulla and pons.
  3. Fibers join the superior cerebellar peduncle in the pons and cross again to the other side and terminate in the vermis of the anterior lobe of the cerebellum.
56
Q

What does the anterior spinocerebellar tract convey?

A

Ventral (anterior) spinocerebellar tract conveys efficacy of descending commands- only really for legs.

57
Q

What could result from a lesion of the dorsal column/medial lemniscus result in?

A
  • A loss of proprioception and fine touch.
    • However, a small number of tactile fibres travel within the anterolateral system, and so the patient is still able to perform tasks requiring tactile information processing.
  • If the lesion occurs in the spinal cord (which is most common), the sensory loss will be ipsilateral – decussation occurs in the medulla oblongata.
58
Q

What could result from a lesion in the anterolateral system?

A
  • An impairment of pain and temperature sensation. In contrast to DCML lesion
    • This sensory loss will be contralateral (the spinothalamic tracts decussate within the spinal cord).

NOTE: Lesion T8 at anterior commissure you would not get decussation of pain, temp, and crude touch at 2 segments above and below.

59
Q

What would result from a lesion to the spinocerebellar tracts?

A

Lesions of the spinocerebellar tracts present with an ipsilateral loss of muscle co-ordination.

  • However, the spinocerebellar pathways are unlikely to be damaged in isolation – there is likely to be additional injury to the descending motor tracts. This will cause muscle weakness or paralysis, and usually masks the loss of muscle co-ordination.
60
Q

What are the possible causes of syringomyelia (Chiari I)?

A
  • Trauma
  • Meningitis
  • Tumor
  • Arachnoiditis
  • A tethered spinal cord.

NOTE: Chiari I malformation syndrome where the cerebellar tonsils herniate through the foramen magnum.

ALSO: When you have a synrinx in the central canal, you are compressing the anterior commissure so the pain/temp/sensation in the area may be affected

61
Q

Mesothelioma

A

People in lots of pain. If they do cordotomy (at C1 and C2) it can relieve some pain

62
Q

Brown-Sequard Syndrome

A

A rare neurological condition characterized by a lesion in the spinal cord which results in weakness or paralysis (hemiparaplegia) on one side of the body and a loss of sensation (hemianesthesia) on the opposite side.

This is most often due to traumatic injury, and involves both the anterolateral system and the DCML pathway:

DCML pathway – ipsilateral loss of touch, vibration and proprioception.

Anterolateral system – contralateral loss of pain and temperature sensation.

It will also involve the descending motor tracts, causing an ipsilateral hemiparesis.

SF2- Exam 2 (16 decks)

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