The Spinal Cord and Periphery

Question 1

afferent/sensory fibres travel through the _____ horn of the spinal cord

Answer 1

dorsal

Question 2

efferent/motor fibres travel through the _____ horn of the spinal cord

Answer 2

ventral

Question 3

which horn is anterior

Answer 3

ventral

Question 4

3 columns of white matter

Answer 4

posterior, lateral and anterior

Question 5

ascending pathways are (sensory/motor)

Answer 5

sensory

Question 6

3 most important spinal tracts

Answer 6

1. corticospinal/pyramidal
2. posterior/dorsal
3. lateral spinothalamic

Question 7

corticospinal carries…

Answer 7

motor impulses from motor cortex to skeletal muscles (hence cortico –> spinal)

Question 8

posterior column carries…

Answer 8

sensory - touch, localisation, vibration, proprioception

Question 9

lateral spinothalamic carries…

Answer 9

pain and temperature

Question 10

where does the corticospinal tract cross over to the contralateral side (mostly)

Answer 10

decussation of medulla pyramids

Question 11

course of corticospinal

Answer 11

1. from primary motor cortex down through the corticospinal tract till the medulla where it crosses sides at the decussation of pyramids.
   Travels down spinal cord till synapses with 2nd neuron in ventral horn
2. leaves through ventral root at same spinal level as synapse

Question 12

what is a cranial nerve nucleus

Answer 12

an area of grey matter in the brainstem associated with one or more cranial nerves (i.e. where some cranial nerves make synapses)

Question 13

how many neurons in the two ascending pathways

Answer 13

3.

Question 14

ascending 1st order neuron

Answer 14

comes in from periphery and enters spinal cord through dorsal horn
crosses at point of entry to spinal cord or at nucleus in medulla

Question 15

location of ascending 1st order neuron cell body

Answer 15

dorsal root ganglion

Question 16

lateral spinothalamic 1st order neuron enter through the dorsal root and synapses with the 2nd order in the …

Answer 16

dorsal horn of spinal cord at level of entry

Question 17

posterior column 1st order neuron

Answer 17

enters through dorsal root and travels up the column. Synapses with the 2nd neuron in a nucleus of the lower part of the medulla (before decussation)

Question 18

lateral spinothalamic 2nd order neuron

Answer 18

synapses with 1st neuron in dorsal horn at level of entry.
Then crosses the spinal cord to the lateral spinothalamic tract.
It then travels up the spinal cord in this tract to the thalamus where it synapses with 3rd neuron

Question 19

posterior column 2nd order neuron

Answer 19

synapses with 1st neuron in medulla nucleus.
Crosses medulla into a new tract called medial lemniscus.
Travels up to thalamus to synapse with 3rd neuron

Question 20

lateral spinothalamic and posterior 3rd neuron

Answer 20

synapses with 2nd in thalamus.

Travel through internal capsule to post-central gyrus in parietal lobe

Question 21

tract that posterior column 2nd order neuron crosses into

Answer 21

medial lemniscus

Question 22

lobe of pre-central gyrus

Answer 22

frontal

Question 23

a medullary lesion below the level of decussation on the left side will effect which tracts and functions

Answer 23

lateral spinothalamic - pain and temp from the right side
posterior - other sensory from the left side
corticospinal - motor to the left side

Question 24

a lesion below the level of lateral spinothalamic decussation on the left side effects which tracts and functions

Answer 24

all three tracts on the left side - all sensory and motor to that side

Question 25

what are the two types of reflex

Answer 25

stretch and flexor

Question 26

process of a stretch reflex response

Answer 26

tendon stretched --> sensory muscle fibres (intrafusal) stimulated --> sensory neuron activated --> synapses with motor on same level back to original muscle --> muscle contracts --> second axon travels through cord to synapse with interneuron onto a motor neuron for anagonist muscle --> muscle relaxes

Question 27

process of a flexor reflex response with it's crossed extensor reflex

Answer 27

pain stimulus --> pain neuron activated --> synapses with an interneuron in spinal cord --> one synapses to motor response on pain side to flex and withdraw, other to the contralateral limb motor for support

Question 28

purpose of flexor response

Answer 28

to protect from pain

Question 29

purpose of stretch reflex

Answer 29

control muscle tone and posture

Question 30

which part of the stretch reflex is monsynaptic

Answer 30

reflex arc from the muscle's sensory to motor neuron. only 2 neurons, hence monosynapse

Question 31

what part of the stretch reflex in polysynaptic

Answer 31

the reflex arc to the antagonist muscle. there is an interneuron between the sensory input and motor response

Question 32

what makes a flexor reflex polysynaptic

Answer 32

sensory input from pain synapses with an interneuron in spinal cord with synapses onto motor for the pain limb and contralateral limb

Question 33

where does the lower motor neuron go

Answer 33

from the ventral horn of the spinal cord and out through the ventral root

Question 34

where does the upper motor neuron go

Answer 34

from primary motor cortex down through thalamus and brainstem. Crosses over at decussation. and travels down spinal cord till 2nd neuron at level of exit

Question 35

effect of UMN lesion on reflexes

Answer 35

exaggerated

Question 36

which motor neuron mediates refelxes

Answer 36

LMN

Question 37

which motor neuron lesion increases tone

Answer 37

UMN

Question 38

summarise the effects of LMN and UMN lesions on reflexes, tone and paralysis

Answer 38

LMN lesion - reduced/absent reflexes - loss of tone - paralysis on side of lesion UMN lesion - exaggerated reflexes - increased tone - paralysis on same side when below level of decussation

Question 39

lateral spinothalamic tract in the middle of the spinal cord on the left side is carrying what sensory information

Answer 39

pain and temperature from right side of body

Question 40

posterior column in middle of spinal cord on the left side is carrying what information

Answer 40

sensory other than pain and temp from the left side of the body

Question 41

what brain area is the primary motor cortex (aka precentral gyrus)

Answer 41

area 4

Question 42

what brain area is the primary sensory cortex in (post-central gyrus)

Answer 42

area 3, 1, 2