spinal cord

Question 1

spinal cord sections

Answer 1

grey matter medially containing cell bodies and rami, white matter laterally containing tracts

Question 2

pattern of grey and white matter

Answer 2

grey matter is butterfly shape; white matter fills rest

Question 3

define dermatome and what innervates it; trunk vs limbs

Answer 3

area of skin innervated by one single pair of spinal nerves or spinal segment; posterior root; trunk is segmental as in strips, limbs are not as simple as when limbs grow and rotate, segmental organisation becomes less organised

Question 4

define myotome and what innervates it

Answer 4

muscles innervated by one single pair of spinal nerves or spinal segment; anterior root

Question 5

cross section of spinal cord: pathway of posterior and anterior horns

Answer 5

2 posterior (dorsal) and 2 anterior (ventral) horns of grey matter -> posterior and anterior rootlets -> posterior (sensory) and anterior (motor) root -> spinal (sensory) ganglion following posterior (sensory) root -> join together to form mixed spinal nerve -> posterior ramus (branch supplying muscle and skin at back) and anterior ramus (everything else)

Question 6

what ligament anchors spinal cord to dura mater

Answer 6

denticulate ligament

Question 7

cross section of spinal cord: white matter from posterior median sulcus to anterior median fissure

Answer 7

posterior median sulcus (divides posterior surface into two halves) -> posterior column -> posterolateral sulcus (entry point of posterior - sensory - root) -> lateral column -> anterolateral sulcus (exit point for anterior - motor - root) -> anterior column -> anterior median fissure (divides anterior surface into two halves)

Question 8

cross section of spinal cord: grey matter: main pathway 1: discriminative touch and proprioception sensory neurones pathway

Answer 8

sensory fibres enter dorsal horn and travel in dorsal columns without synapsing in posterior horn

Question 9

cross section of spinal cord: grey matter: main pathway 2: pain and temperature sensory neurones pathway

Answer 9

fibers enter dorsal horn, may travel up or down 1-2 segments in posterolateral fasciculus (Lissauer tract), then synapse in nucleus proprius of dorsal horn (dorsal root ganglion); fibers then cross midline in anterior commissure and travel in spinothalamic tract

Question 10

cross section of spinal cord: grey matter: location and function of substantia gelatinosa

Answer 10

lamina II of grey matter: first modulation for pain and temperature just before dorsal horn

Question 11

cross section of spinal cord: grey matter: main pathway 3: motor neurones pathway and other contents

Answer 11

a-motor neurones located in anterior horn; exit spinal cord and travel to target muscles; interneurone circuits in anterior horn filter descending motor information and are part of localised reflex circuits

Question 12

7 major tracts of spinal cord from dorsal medial laterally to anterior medial

Answer 12

anterior white commisure, fasciculus gracilis, fasciculus cuneatus, spinocerebellar tract, lateral corticospinal tracts, spinothalamic tracts, anterior corticospinal tract

Question 13

function of anterior white commisure

Answer 13

pain and temperature fibers cross; anterior corticospinal tract fibers cross

Question 14

function of fasciculus gracilis

Answer 14

sensory (fine touch, vibration, proprioception) from ipsilateral lower limb

Question 15

function of fasciculus cuneatus

Answer 15

sensory (fine touch, vibration, proprioception) from ipsilateral upper limb

Question 16

function of spinocerebellar tract

Answer 16

proprioception from limbs to cerebellum

Question 17

function of lateral corticospinal tracts

Answer 17

motor from brain to ipsilateral anterior horn (mostly limb musculature; main voluntary movement pathway)

Question 18

function of spinothalamic tracts

Answer 18

pain and temperature from contralateral side of body

Question 19

function of anterior corticospinal tract

Answer 19

motor from brain to ipsi- and contralateral anterior horn (mostly axial musculature)

Question 20

corticospinal tract constituents

Answer 20

cerebral cortex gyrus -> descending motor fibers -> 15% [anterior corticospinal tract -> motor nuclei; trunk] or 85% [decussation of lateral corticospinal tract -> lateral corticospinal tract; arms and legs]

Question 21

main sensory pathways: pair of dorsal column pathways - fasciculus gracilis and fasciculus cuneatus: discrimative touch, vibration, prociception from upper and lower limbs

Answer 21

primary sensory neurone -> dorsal root ganglion -> spinal cord -> posterior column medial lemniscus system -> synapse onto medulla to secondary sensory neurone then crosses -> pons -> midbrain -> synapses onto thalamus -> third sensory neurone to cortex

Question 22

main sensory pathways: pair of spinothalamic tract: pain and temperature

Answer 22

primary sensory neurone -> dorsal root ganglion -> enters and synapses onto spinal cord via Lissauer tract -> secondary sensory neurone crosses in spinal cord -> anterolateral system to medulla then pons then midbrain -> synapses onto thalamus -> third sensory neurone to cortex

Question 23

reflex pathways: patellar tendon jerk reflex and painful stimulus e.g. plug on floor reflex

Answer 23

sensory muscles stretch -> signal back to spinal cord -> motor response to muscle -> muscle contracts; also synapse into brain to bring in responses and sense pain; reflexes can get bigger if stroke and smaller if peripheral nerve lesion; response to same limb, different limb, core etc. to remove stimulus, maintain stability etc.

Question 24

in thoracolumbar segments, size of grey matter and what ANS branch does the lateral horn consist of

Answer 24

grey matter small, lateral horn (site of motor neurones: intermediate horn between dorsal and ventral) sympathetic visceomotor

Question 25

in sacral segments, size of grey matter and what ANS branch does the lateral horn consist of

Answer 25

grey matter big, lateral horn (site of motor neurones: intermediate horn between dorsal and ventral) parasympathetic visceromotor

Question 26

parasympathetic outflow segments

Answer 26

brainstem cranial nerves III, VII, IX, X; S2-S4

Question 27

sympathetic outflow segments

Answer 27

T1-L2

Question 28

directions in neuroanatomy

Answer 28

superior = rostral, inferior = caudal, posterior = dorsal, anterior = ventral

Question 29

define root

Answer 29

contains nerve fibres of only one type (motor or sensory)

Question 30

define ramus

Answer 30

contains mixture of motor and sensory nerve fibres