B7.016 Spinal Cord and Long Pathways

Question 1

how are neurons organized?

Answer 1

functional pathways or systems
composed of multi-neuron chains
transmit info from one part of the nervous system to another
facilitated by synaptic transmission

Question 2

afferent

Answer 2

toward CNS

Question 3

efferent

Answer 3

away from CNS

Question 4

ascending

Answer 4

information from lower to higher levels

Question 5

descending

Answer 5

information from higher to lower levels

Question 6

corticospinal pathway

Answer 6

voluntary motor

Question 7

dorsal column / medial lemniscus

Answer 7

sensory touch

Question 8

anterolateral / spinothalamic

Answer 8

pain

Question 9

tract

Answer 9

bundle of axons in the CNS (also fasciculus, lemniscus)

name of the tract often tells source and termination of axons

Question 10

decussate

Answer 10

cross from one side of the brain to the other

Question 11

somatotropy

Answer 11

adjacent structures in the body are represented by adjacent neurons in the CNS; contributes to regional specialization

Question 12

organization of the dorsal column

Answer 12

sacral region most medial

cervical region most lateral

Question 13

organization of the ventral column

Answer 13

sacral region most lateral
CS
ALS
cervical region most medial

Question 14

relative lengths of spinal cords and vertebral column

Answer 14

spinal cord is much shorter

Question 15

stain for cell bodies of neurons

Answer 15

Nissl Stain

gray matter stains darker because cell bodies congregate there

Question 16

dorsal

Answer 16

sensory

Question 17

ventral

Answer 17

motor

Question 18

nucleus

Answer 18

group of cell bodies within the CNS

Question 19

substantia gelatinosa

Answer 19

area within dorsal horn with pain neuron synapses

contains many cell bodies, but very few axons (appears white with myelin staining)

Question 20

white matter staining

Answer 20

stains dark when myelin stain is used

many axons run through the white matter

Question 21

describe the structure of the corticospinal system

Answer 21

2 neuron pathway carrying information from the motor cortex to striated muscles
responsible for voluntary motor control

Question 22

2 neurons in the corticospinal system

Answer 22

1. cortical motoneuron = upper motoneuron

2. alpha motoneuron = lower motoneuron

Question 23

upper motoneuron

Answer 23

in motor cortex (precentral gyrus)

axons terminate with monosynaptic connections on alpha motoneurons (within ventral horn of spinal cord)

Question 24

lower motoneuron

Answer 24

in ventral horn of spinal cord

axon projects through ventral root to striated muscle

Question 25

describe the decussation of the corticospinal pathways

Answer 25

pyramidal decussation | occurs at the cervicomedullary junction (caudal end of medulla)

Question 26

give a brief overview of the course of the corticospinal pathway

Answer 26

1. precentral gyrus (motor cortex) 2. posterior limb of internal capsule 3. pyramidal decussation @ caudal end of medulla 4. lateral corticospinal tract 5. synapse in anterior horn of level of LMN 6. LMN leaves through anterior root and travels to target muscle

Question 27

what happens when you damage neurons in the corticospinal pathway

Answer 27

loss of voluntary motor control of the body | -paralysis

Question 28

UMN damage

Answer 28

spastic paralysis | tone present

Question 29

LMN damage

Answer 29

flaccid paralysis | limp muscle

Question 30

relationship between deficit and site of lesion in corticospinal

Answer 30

1. rostral to the decussation = contralateral 2. caudal to the decussation = ipsilateral 3. in spinal cord = caudal to lesion

Question 31

overview of somatosensory pathways

Answer 31

``` information from periphery enters the spinal cord and ascends to the cortex 2 pathways: 1. dorsal column / medial lemniscus -fine touch -proprioception -vibration 2. ALS/ spinothalamic -pain and temperature -crude touch ```

Question 32

dorsal root divisions

Answer 32

medial division = large fibers, DC/ML | lateral division = small fibers, ALS

Question 33

characterize the DC/ML system

Answer 33

``` sensory modalities: -vibration -proprioception -discriminative touch large diameter, myelinated fibers rapidly conducting high fidelity system ```

Question 34

characterize the ALS/spinothalamic system

Answer 34

``` sensory modalities: -pain -temperature small diameter myelinated and unmyelinated fibers slowly conducting ```

Question 35

discuss the structure of the DC/ML pathway

Answer 35

three neurons ascending pathway carries fine touch, proprioception, and vibration information to the somatosensory cortex (postcentral gyrus)

Question 36

anatomy of the primary DC/ML pathways

Answer 36

cell body of primary neuron located in dorsal root ganglion (DRG) peripheral (distal) process innervated skin, joint or muscle central process terminates in the medulla in either the -nucleus cuneatus (arm) -nucleus gracilis (leg) together, these are called the dorsal column nuclei DRG axons form the dorsal columns in the spinal cord -gracile fasiculus (medial, legs) -cuneate fasiculus (lateral, arms)

Question 37

where is the site of decussation in the DC/ML pathway

Answer 37

medulla

Question 38

anatomy of the secondary DC/ML pathways

Answer 38

axons of neurons in the dorsal column nuclei decussate in the medulla and ascend to the thalamus (this bundle of axons is called the medial lemniscus)

Question 39

anatomy of the tertiary DC/ML pathways

Answer 39

axons in the medial lemniscus synapse in the ventral posterolateral (VPL)nucleus in the thalamus VPL neurons send their axons to synapse in the primary somatosensory cortex

Question 40

nature of deficit when you damage the DC/ML pathway

Answer 40

loss of touch, vibration, proprioception from specific regions

Question 41

relationship between deficit and site of lesion in DC/ML

Answer 41

1. rostral to the decussation = contralateral 2. caudal to the decussation = ipsilateral 3. in spinal cord = ipsilateral body surface, involving dermatomes at and below the level of the lesion

Question 42

discuss the structure of the ALS/ spinothalamic pathway

Answer 42

three neurons ascending pathways carries pain and temp info to the somatosensory cortex (postcentral gyrus)

Question 43

anatomy of primary ALS/ spinothalamic pathway

Answer 43

cell body of primary neuron located in dorsal root ganglion (DRG) peripheral (distal) process of the DRG neuron innervates skin central (proximal) process of DRG enters the spinal cord, ascends a level or two, and then synapses in the dorsal horn of the spinal cord (substantia gelatinosa)

Question 44

anatomy of secondary ALS/ spinothalamic pathway

Answer 44

axons of the dorsal horn neurons decussate in the anterior white commissure ascend to the thalamus in the spinothalamic tract, also called anterolateral pathway

Question 45

anatomy of tertiary ALS/ spinothalamic pathway

Answer 45

axons in the spinothalamic tract synapse in the ventral posterolateral (VPL) nucleus in the thalamus VPL neurons send their axons to synapse in the primary somatosensory cortex

Question 46

nature of deficit when you damage the ALS/ spinothalamic pathway

Answer 46

loss of pain and temperature sensation from specific regions of the body

Question 47

relationship between deficit and site of lesion in ALS/ spinothalamic pathways

Answer 47

1. rostral to the decussation = contralateral 2. caudal to the decussation = ipsilateral 3. in spinal cord = contralateral body surface, involving dermatomes at and below the level of the lesion

Question 48

which spinal cord level has the most white matter

Answer 48

cervical/ thoracic

Question 49

which spinal cord level has the most gray matter

Answer 49

sacral / lumbar

Question 50

SNS pathways from the spinal cord

Answer 50

thoracolumbar

Question 51

PNS pathways from the spinal cord

Answer 51

craniosacral