L18- Physiology of the Spinal Cord Flashcards Preview

Theme 1: Fundamental Neuroscience and the Brain > L18- Physiology of the Spinal Cord > Flashcards

Flashcards in L18- Physiology of the Spinal Cord Deck (16)
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1
Q

Physiological functions of the spinal cord:

A

Initial processing of somatosensory input by the CNS

Final processing of motor output by the CNS

2
Q

What is sensation?

A

Detection by receptors

3
Q

What is perception?

A

Interpretation by spinal cord and brain circuits

4
Q

Mechanoreceptors

A

Detect touch, pressure, vibration
A-beta fibre type

wide diameter= fast conduction velocity

examples include- Pacinian corpuscle, Ruffini end corpuscles, Merkell cells

5
Q

Bare nerve ending for pain

A

Fast pricking pain
-A-delta fibres
medium diameter=medium cv

slow burning pain, itch
-C-fibres (unmyelinated)
thin diameter=slow cv

6
Q

Cutaneous Mechanosensory Receptors

A

Meissner’s corpuscle- shear forces/light touch

Merkel disk-contact

Ruffini’s corpuscle-tension, folding and stretching

7
Q

LMN

A

Final common path for all signals from the CNS to skeletal muscles
Longitudinal organised columns (alpha and gamma)

8
Q

Alpha and gamma axons

longitudinal organised columns

A

Alpha - larger, thick axon, high conductance velocity

Gamma- smaller, thin axon, low conductance velocity

Organised in columns- supplies a muscle or group of functionally similar muscles

9
Q

Paresis

  • define
  • how can it be caused?
A

muscular weakness

caused by Destruction of a single ventral root or a single spinal nerve

10
Q

Proprioceptive sensory organs [2]

A

Muscle spindles – negative feedback regulation of muscle length due to passive strength

Golgi tendon organs – negative feedback regulation of muscle tension due to contraction

11
Q

Stretch reflex circuit

A

Monosynaptic pathway

  1. Muscle spindle: initiates the reflex. (sensory receptor)
  2. Stretch increases la afferent activity
    - this increases alpha motor neuron activity =contraction of the same muscle.
  3. Stretch reflex
    - negative feedback loop
    - regulate muscle length via descending pathways
12
Q

Anterior cord syndrome

A

Bilateral lower motor neuron paralysis and muscular atrophy in the segment of the lesion (due to damage to lower motor neurons).

Bilateral spastic paralysis below the level of the lesion (due to loss of anterior descending tracts).

Bilateral loss of pain, temperature and light touch sensations below the level of the lesion (due to loss of anterior and lateral spinothalamic tracts).

Tactile discrimination and
vibratory and proprioceptive sensations intact

13
Q

Brown-Sequard/ cord hemisection syndrome

A

Ipsilateral lower motor neuron paralysis and muscular atrophy in the segment of the lesion (due to damage to lower motor neurons).

Ipsilateral spastic paralysis below the level of the lesion (due to loss of anterior descending tracts).

Ipsilateral band of cutaneous anesthesia in the segment of the lesion (due to loss of dorsal root).
Ipsilateral loss of tactile discrimination and of vibratory and proprioceptive sensations below the level of the lesion (due to loss of ascending tracts in the dorsal white column on the side of the lesion).

Contralateral loss of pain, temperature and light touch (due to loss of crossed lateral spinothalamic tracts on the side of the lesion).

Discriminative touch pathways travelling in the ascending tracts in the contralateral dorsal white column remain intact.

14
Q

Complete cord transection syndrome

A

Complete loss of sensation and voluntary movement below level of lesion.

Bilateral lower motor neuron paralysis and muscular atrophy in the segment of the lesion.

Bilateral spastic paralysis below level of lesion (due to loss of descending tracts).

Bilateral loss of all sensations below the level of the lesion (due to loss of ascending tracts).

Bladder and bowel functions no longer under voluntary control (due to loss of descending autonomic fibres)

15
Q

Flexion reflex

-give example

A

Polysynaptic pathway

  1. Stimulation of cutaneous pain receptors in the foot
  2. Activation of spinal cord local circuits
  3. flexion at stimulated extremity and extension at other extremity to provide support.
16
Q

Somatotopic organization of LMN

-location of MN innervating axial musculature and distal musculature

A

axial musculature (i.e., postural trunk muscles) are located most medially

distal musculature (in hands) are located more laterally