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Brain + Behaviour > Somatosensory pathways > Flashcards

Somatosensory pathways Flashcards

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1
Q

what are the different types of somatosensation and their names

A

thermoreception= temperature
mechanoreception= pressure
nociception= pain
proprioception= position in space

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2
Q

at what spinal levels is the fasciculus gracilis present alone

A

The fasciculus gracilis carries sensory input from vertebral level T6 and below and ascends into the gracile nucleus to form the gracile tubercle. The fasciculus cuneatus carries information from T6 and above and ascends into the cuneate nucleus to form the cuneate tubercle. (so above T6 both the fasciculus gracilis + fasciculus cuneatus is present which is why at the cervical level the horns of the grey matter are thinner)

n.b. The gracile nucleus (nucleus gracilis) receives somatosensory information from the lower half of the body and the legs, and the cuneate nucleus (nucleus cuneatus) receives somatosensory information from the upper half of the body and arms

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3
Q

what is the point in the human brain at which the fourth ventricle narrows to become the central canal of the spinal cord?

A

the OBEX (latin for barrier) is the point in the human brain at which the fourth ventricle narrows to become the central canal of the spinal cord The obex occurs in the caudal medulla (it’s the lower margin of the medulla)

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4
Q

what are the following large diameter sensory nerve fibres responsible for
* 1a, 1b (Ia,Ib) or A alpha
* II or A beta

A
  • 1a, 1b (Ia,Ib) or A alpha= proprioception
  • II or A beta= touch, vibration
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5
Q
  • fibres of the dorsal columns originate from first order neurons in the _______
  • medial lemniscus fibres originate from second order neurons in the cuneate or gracile nuclei in the ______ _____
  • The thalamo-cortical fibres in the internal capsule originate from third order neurons in the ________
A
  • fibres of the dorsal columns originate from first order neurons in the DORSAL ROOT GANGLIA
  • medial lemniscus fibres originate from second order neurons in the cuneate or gracile nuclei in the LOWER MEDULLA
  • The thalamo-cortical fibres in the internal capsule originate from third order neurons in the VPL (Ventero-posterolateral thalamus)
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6
Q

what is the difference between PERCEPTION + SENSATION

A
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7
Q

Which tracts carry unconscious proprioceptive information?

A

spinocerebellar tract

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8
Q

Complete the sentence: The third order neurones of the DCML ascend from the ___________ and synapse in the sensory cortex

A

The third order neurones of the DCML ascend from the THALAMUS and synapse in the sensory cortex

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9
Q

where in the brain is the primary somatosensory cortex

A

the primary somatosensory cortex is located in the postcentral gyrus (anterior part of the parietal lobe)

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10
Q

What is spasticity?

A

Spasticity is abnormal muscle tightness due to prolonged muscle contraction. It is a symptom associated with damage to the brain, spinal cord or motor nerves, and is seen in individuals with neurological conditions, such as: Cerebral palsy (CP) Multiple sclerosis (MS)== its painful for patient

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11
Q

what is hyper-reflexia

A

Hyperreflexia= is the presence of hyperactive stretch reflexes of the muscles.
Hyperreflexia refers to hyperactive or repeating (clonic) reflexes. These usually indicate an interruption of corticospinal and other descending pathways that influence the reflex arc due to a suprasegmental lesion, that is, a lesion above the level of the spinal reflex pathways.

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12
Q

what is paresis

A

Paresis= general term referring to a mild to moderate degree of muscular weakness(can’t contract), occasionally used as a synonym for PARALYSIS (severe or complete loss of motor function). In the older literature, paresis often referred specifically to paretic neurosyphilis

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13
Q

spinal tracts are bundles of axons in CNS, these bundles are organised into specific groups with specific functions forming the tracts
ASCENDING TRACTS conduct _____________________
DESCENDING TRACTS= ____________________

A

spinal tracts are bundles of axons in CNS, these bundles are organised into specific groups with specific functions forming the tracts
ASCENDING TRACTS= conduct sensory info up to brain
DESCENDING TRACTS= motor instructions down the cord

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14
Q

Which of these tissues is NOT used in any tissue as a proprioceptor:
* Ruffini ending
* Golgi tendon organs
* Free nerve endings
* Merkel’s disks
* Muscle spindles

A

free nerve endings are NOT used in any tissue as a proprioceptor

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15
Q

Which type of nerve fibres transmit the sense of proprioception?

A

Ia + Ib (large diameter fibres originating from muscles, tendons + joints)

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16
Q

Which type of nerve fibres conveys the sense of touch?

A

II (Aβ)

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17
Q

In which spinal cord 2 laminae touch + conscious proprioceptive fibres synapse?

A

Lamina III
Lamina IV

18
Q

The ascending fibres that leave the dorsal column nuclei are called ____ _____ fibres

A

The ascending fibres that leave the dorsal column nuclei are called INTERNAL ARCUATE fibres

19
Q

The fibre tract that ascends contralaterally towards the thalamus is called the _____ _______

A

The fibre tract that ascends contralaterally towards the thalamus is called the medial lemniscus

19
Q

The thalamic nucleus where the information from the DCML pathway is relayed is the __________ nucleus

A

The thalamic nucleus where the information from the DCML pathway is relayed is the ventroposterolateral (VPL) nucleus

19
Q

The _____ ____ is the tract that conveys sensory information from the sensory thalamus to the primary somatosensory cortex

The primary somatosensory cortex is located in the _______ gyrus

A

The internal capsule is the tract that conveys sensory information from the sensory thalamus to the primary somatosensory cortex

The primary somatosensory cortex is located in the postcentral gyrus

20
Q

The trigeminal nucleus is the medullar relay of the pathway (2nd order neuron), but where are the cell bodies of the 1st order neuron

A

the cell bodies of the trigeminal nerve are found in the trigeminal (Gasserian) ganglion which is the equivalent of a dorsal root ganglion

21
Q

What is the cortical proximity principle

A

cortical proximity principle: if a limb was amputated, it was believed that the area devoted to that limb shrunk and the area devoted to surrounding parts of the body would expand

in amputation or congenital malformation of an arm: neighbouring areas in the somatosensory cortex would overtake the deprived hand region
= this is considered maladaptive, causing the emergence of phantom limb pain, a percept of pain ascribed to the missing hand

22
Q

what regions of the body have the highest density of touch receptors

A

hands, lips and tongue have the highest density of touch receptors

as a general rule areas of skin w highest density of touch + proprioceptive receptors occuoy largest areas of the cortical map (HOMUNCULI)

23
Q

what do we mean by homunculi (or homunculus) of brain

A

The sensory homunculus is a map along the cerebral cortex of where each part of the body is processed. The sensations occur all along the body. The impulses from the body will be sent into the spinal cord and eventually back to the brain to be processed. While the trigeminal nerve carries the face’s sensations.

24
Q

what is stereognosis

A

the tactile ability to perceive the form of solid objects

25
Q

which kind of accessory is used to test the sense of touch

A

a piece of cotton wool

26
Q

Which sensory pathways convey the senses below?
* joint position sense + vibration
* temperature (warmth)
* discriminative touch
* temperature (cold)
* crude touch
* pricking pain

A
  • joint position sense + vibration = Dorsal column medial lemniscus pathway
  • temperature (warmth)= anterior spinothalamic tract
  • discriminative touch= dorsal column medial lemniscus pathway
  • temperature (cold)= lateral spinothalamic tract
  • crude touch= anterior spinothalamic touch
  • pricking pain= lateral spinothalamic touch
27
Q

what is sensory ataxia

A

sensory ataxia= inability to balance when visual input is removed

28
Q

what nerve fibres transmit
1) fast pain
2) slow pain

A

Aδ=fast fibres (sharp pain= short but v unbearable, localised) transmitted by posterior spinothalamic tract
C= slow pain (dull pain= long lasting + bearable but burning,itchy, hard to localise) transmitted by anterior spinothalamic (polysynaptic tract)

Aδ fibres have smaller + more numerous cutaneous receptive fields than C fibres. Allows accurate location of painful stimulus

n.b. pain perception occurs when the sensation is interpreted, as such by the brain and this involves various forebrain regions

29
Q

in dorsal horn Aβ fibres (touch + vibration) terminate in ____ laminae _____

Afferent fibres from Aδ and C fibres terminate in ______ laminae ______ these are specific for pain

Aδ fibres also terminate in laminae III + V

A

in dorsal horn Aβ fibres (touch + vibration) terminate in deep laminae (III-V)

Afferent fibres from Aδ and C fibres terminate in **superficial laminae (I+ II) **these are specific for pain

Aδ fibres also terminate in laminae III + V

30
Q

What are WDR neurons + where are they found

A

laminae IV + VI contain multireceptive wide dynamic range (WDR) neurons aka convergent neurons, these WDR neurons:
* are involved in transmission + processing of nociception (pain) but also in the modulation of incoming info (gate control of pain)
* respond to noxious + non-noxious stimuli
* posses broad receptive fields

31
Q

Cell in lamina I (projection neurons) + projections arising from lamina II project across the midline (decussate) in spinal cord + ascend in the contralateral anterolateral part of the cord as the __________ or the _________

A

Cell in lamina I (projection neurons) + projections arising from lamina II project across the midline (decussate) in spinal cord + ascend in the contralateral anterolateral part of the cord as the lateral spinothalamic tract (Aδ fibres) or the anterior spinothalamic tract (C fibres)

32
Q

What are pyramidal tracts and give an example of one u need to know

A

Pyramidal tracts – These tracts originate in the cerebral cortex, carrying motor fibres to the spinal cord and brain stem. They are responsible for the voluntary control of the musculature of the body and face.
The pyramidal tracts derive their name from the medullary pyramids of the medulla oblongata, which they pass through.

* **Corticospinal tract**  ( from cortex to spinal cord  ) = carries motor signals from the primary motor cortex in the brain, down the spinal cord, to the muscles of the trunk and limbs. Thus, this tract is involved in the voluntary movement of muscles of the body.)
33
Q

unilateral meaning

A

affecting one side only (e.g. unilateral lesion is a lesion affecting one side only)

34
Q

What do we know about referred pain? Know common examples : cardiac ischemia, inflamed appendix

A

pain is usually referred to a structure that developed from the same embryonic segment or dermatome as the structure in which the pain originates

cardiac ischemia: PAIN FROM T1-T4 dermatomes pain sensation can occur in the upper chest as a restricted feeling, or as an ache in the left shoulder, arm or even hand

inflamed appendix: pain felt in T10 dermatome arround umbilicus

ruptured spleen indication: upper back pain, especially between your shoulder blades (Kehr’s sign)

colon/ kidney issues: Lower back pain or flank pain

35
Q

What is the thalamic relay for the anterior spinothalamic tract?

A

intralaminar (IL) nuclei of the thalamus

36
Q

An anterior cord syndrome results in bilateral loss of what 3 sensations? What 2 sensations are preserved below level of lesion

A

an anterior cord syndrome results in bilateral loss of motor function, temperature and pain.

fine touch/discriminative touch and conscious proprioception is preserved below the level of lesion

37
Q

a complete/transverse cord lesion of the spinal cord results in bilateral loss of _______ and ______ functions

A

a complete/transverse cord lesion of the spinal cord results in bilateral loss of motor and sensory functions

38
Q

what kind of ipsilateral and contralateral loss does Brown-Sequard syndrome aka partial cord/hemicord lesion result in

A

Brown-Sequard:
results in ipsilateral loss of motor function, conscious proprioception and fine touch
it also results in contralateral loss of pain and temperature

Brain + Behaviour (14 decks)

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