Physiology Of The Spinal Cord

Question 1

Sensation?

Answer 1

Detection by receptors

Question 2

Perception?

Answer 2

Interpretation by spinal cord and brain circuits

Question 3

If you want high spatial resolution then…

Answer 3

Low convergence such as cones and bipolar cells in retina

Question 4

If you want to detect weak signals then?

Answer 4

High convergence is needed e.g road and bipolar cells

Question 5

High divergence example?

Answer 5

Vestibulo ocular reflex

Question 6

Touch pressure and vibration are detected by?

Answer 6

Merkels cells ruffini end organ and Pacinian corpuscles,

Which are A Beta wide diameter and fast

Question 7

Bare nerve ending for touc are?

Answer 7

Medium diameter and speed, a delta

Question 8

Pain bare nerve endings are?

Answer 8

A delta medium diameter and C fibres slow and thin diameter

Question 9

Meissners corpuscles detect?

Answer 9

Shear force

Question 10

Merkel disks detect?

Answer 10

Contact

Question 11

Ruffini’s corpuscle detect?

Answer 11

Tension, folding

Question 12

Pacinian detect?

Answer 12

Deep pressure, vibration

Question 13

Free nerve endings detect?

Answer 13

Pricking

Question 14

Two pint discrimination?

Answer 14

Higher the density of mechanoreceptors the smaller the distance at which 2 tactile stimuli can be discriminated

Question 15

Where is the density of mechanoreceptors greater?

Answer 15

Hand and face, so greater spatial resolution

Question 16

Each column contains?

Answer 16

Larger alpha neuron (thick axon and high conductance velocity)

Smaller gamma (thin axon and low conductance velocity)

Question 17

Destruction of a single ventra root will cause?

Answer 17

Paresis not paralysis

Question 18

Proprioception sensory organs?

Answer 18

Muscle spindles- negative feedback regulation of muscle length

Golgi tendon organs- -ve feedback regulation of muscle tension

Question 19

polysynaptic reflex pathway?

Answer 19

Stimulation of cutaneous pain receptors in the foot leads to activation of spinal cord local circuits that withdraw (flex) the stimulated extremity and extend the other extremity to provide compensatory support.

Question 20

Anterior cord syndrome?

Answer 20

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).

But: Tactile discrimination and vibratory and proprioceptive sensations are preserved because the posterior (dorsal) white columns on both sides are undamaged

Question 21

Brown – Séquard or cord hemisection syndrome?

Answer 21

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.

Question 22

Complete cord transection syndrome.

Answer 22

Complete loss of sensation and voluntary movement below the level of the lesion.
Bilateral lower motor neuron paralysis and muscular atrophy in the segment of the lesion.
Bilateral spastic paralysis below the level of the 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)