Somatosensory Pathways I

Front 1

What are the three long tracts for innervation of your body?

Back 1

Corticospinal, PCML, ALS

Front 2

What is the corticospinal tract for?

Back 2

voluntary motor, descends from brain to body

Front 3

What is the function of the PCML?

Back 3

sensory of fine touch and proprioception, ascends from body to the somatosensory cortex in the brain

Front 4

What is the function of the ALS?

Back 4

sensory of pain and temperature that ascends from the body to the somatosensory cortex in the brain

Front 5

What is the analogous system for the face of the corticospinal tract?

Back 5

corticobulbar tract, motor descends from brain to face (axon bundles as the cranial nerves rather than spinal nerves)

Front 6

What does the Posterior-Column Medial Lemniscal pathway do?

Back 6

mediates fine discriminative touch and vibration sense and proprioception

Front 7

What type of axons are the primary afferent fibers of the PCML?

Back 7

A-alpha
A-beta
large diameter and heavily myelinated
these are very fast synaptic transmission fibers

Front 8

Where is the primary neuronal cell body found in the PCML system?

Back 8

Dorsal root ganglia (DRG)
A pseudounipolar neuron with primary process in contact with peripheral receptor and its secondary process carrying sensory information into the spinal cord

Front 9

What are the three tracts that originate in the anterolateral system?

Back 9

spinothalamic tract
spinoreticular tract
spinomesencephalic tract

Front 10

What is the function of the spinothalamic tract?

Back 10

perception of pain, temperature, and crude touch

Front 11

What is the function of the spinoreticular tract?

Back 11

arousal aspect of pain

Front 12

The __________ tract has the function of descending pain modulation.

Back 12

Spinomesencephalic tract
a more complicated system because behavioral responses to pain are more relevent to survival

Front 13

What type of fibers are present in the ALS system?

Back 13

A-delta & C fibers
these are small, unmyelinated and very slow synaptic transmission

Front 14

The primary neuronal cell body of the ALS is found in the ______.

Back 14

DRG

Front 15

________ is a peripheral region innervated by sensory fibers from a single nerve root

Back 15

dermatome

Front 16

True or False
Each spinal nerve has a sensory component and a motor component.

Back 16

True
the large and smal diameter fibers of the PCML & ALS bring sensory information into the CNS
the lower motor neuron component of the corticospinal tract carries motor information out of the CNS

Front 17

T/F
A decussation is when neuronal cell bodies cross the midline of the CNS

Back 17

False
A decussation is when the axons cros the midline to the opposite side of the CNS

Front 18

Each long tract in the body has a specific site of decussation. A lesion interrupting the tracts below the site of decussation will yield ____________ deficits.

Back 18

IPSILATERAL

Front 19

A lesion interrupting the tracts above the site of decussation of a long tract will yield __________ deficits.

Back 19

CONTRALATERAL

Front 20

The ______ brings sensations of fine touch, vibration sense, and proprioception from peripheral receptors in the skin and muscle into the spinal cord.

Back 20

ALS's A-alpha fibers and C-fibers

Front 21

Where does the PCML's fibers enter the spinal cord?

Back 21

Medial dorsal root entry zone

Front 22

Where do the primary axons of the primary cell bodies go once they have entered the spinal cord?

Back 22

1. most immediately ascend in the posterior columns
2. second collaterals into the central gray matter to synapse on interneurons and lower motor neurons to mediate deep tendon reflexes

Front 23

What controls deep motor reflexes from the PCML system?

Back 23

primary afferent fibers send collaterals to synapse on interneurons that mediate deep tendon reflexes and gate control of pain sensation

Front 24

What are the spinal cord columns of axons?

Back 24

posterior, lateral, and meidal columns/funiculi

Front 25

What are the spinal cord cell columns/neurons?

Back 25

dorsal horn: sensory
ventral horn: motor

Front 26

The Gracile fasciculus is found in what part of the spinal cord?

Back 26

it is found the entire length of the spinal cord
It is most medial and found predominately in S5-T7

Front 27

The Cuneate fasciculus would be found where?

Back 27

In the spinal cord starting at T6-C1 and it is the most lateral column in the posterior columns

Front 28

In the PCML where do first order axons synapse on 2nd order neurons?

Back 28

1. Gracile nucleus
2. Cuneate nucleus
in the caudal medulla

Front 29

Once the PCML has synapsed where do the axons of the 2nd order neurons travel?

Back 29

Gracile and Cuneat nuclei axons immediately DECUSSATE forming the internal arcuate fibers which coalesce to ascend in the axonal bundle called the medial lemniscus

Front 30

T/F
The medial lemniscus does not maintain somatotropic organization

Back 30

False
It does maintain somatotropic organization

Front 31

What part of the bodies signals are sent to the posterior portion of the medial lemniscus?

Back 31

The upper body

Front 32

What part of the bodies signals are sent to the anterior portion of the medial lemniscus?

Back 32

the lower body

Front 33

True or False
Lesions above the Medial Lemniscus in the PCML will produce a loss of sensation of fine touch and proprioception on half of the body CONTRALATERAL to the site of the lesion.

Back 33

TRUE

Front 34

Where do the second order axons of the medial lemniscus ascend to?

Back 34

second order axons ascend from medulla to pons to midbrain to the VPL nucleus of the thalamus

Front 35

How does the medial lemniscus of the PCML change position as it ascends through the brainstem?

Back 35

It maintains its relative somatotropic organization as it ascends through the brainstem, but changes its position from medial to lateral and from standing up to laying down

Front 36

In the PCML system what do second order axons synapse on and where?

Back 36

second order axons of the medial lemniscus synapse on third order neurons that make up the ventral posterior lateral nucleus of the thalamus

Front 37

The __________ projection from VPL to primary somatosensory cortex

Back 37

Thalamocortical

Front 38

Where are the axons of the VPL found as they ascend to the primary somatosensory cortex?

Back 38

The axons arising from the VPL travel in a bundle that is found on the medial porition of the posterior limb of the internal capsule

Front 39

The primary somatorsensory cortex is where ________ is found.

Back 39

fourth order neurons of the PCML are found in somatosensory cortex

Front 40

What layer of the cortex do the thalamic projections synapse in?

Back 40

Layer IV

Front 41

What areas of the primary somatosensory cortex does information from mechanoreceptors get processed in?

Back 41

Areas 3a and 2
this information is coming from joints and muscles (MSO, GTO)

Front 42

_________ information is precessed in areas 3b and 1 of the primary somatosensory cortex.

Back 42

information from cutaneous receptors that is important in superficial touch and includes texture discrimination

Front 43

What is necessary for higher order sensory processing?

Back 43

Corticocortical projections are necessary this gives meaning and context of the sensation

Front 44

Where do the corticocortical association neurons project to?

Back 44

corticocortical association neurons of the primary somatosensory cortex project ipsilateral cortical areas including higher order somatosensory cortex

Front 45

Where do the callosal neurons project to?

Back 45

callosal neurons project to contralateral somatosensory association cortex via the corpus callosum

Front 46

T/F
Primary somatosensory cortex is extensively interconnected with adjacent motor cortex

Back 46

True

Front 47

Where does higher order sensory processing occur for the PCML?

Back 47

in the association cortex in the parietal lobe

Front 48

What are the parts of the cortex responsible for higher order sensory processing?

Back 48

1. Unimodal association cortex: integrates information from a single sensory system
--Posterior parietal cortex (BA 5&7) integrates somatosensory information
2. Heteromodal association cortex: integrates sensory information from multiple sensory systems to create a visual spatial gestalt out of all our seperate sensory experiences

Front 49

Where is the secondary somatosensory cortex of the parietal operculum associated with?

Back 49

It is the lips of the cortex bordering the superior regions of the lateral fissure

Front 50

What can cause left-side hemineglect syndrome?

Back 50

lesions of the parietal association cortex in nondominant hemisphere can cause this

Front 51

An individual is unable to pay attention to/perceive sensation from the contralateral side of the body, and or unable to process visual and sensory information obtained by the contralateral side of the body. What syndrome do they have?

Back 51

Hemineglect syndrome

Front 52

What is the blood supply to the posterior columns of the spinal cord?

Back 52

2 posterior spinal arteries that arise from PICA

Front 53

The PARAMEDIAN branches of the VERTEBRAL artery and the anterior spinal artery supply what in the brainstem to do with the PCML?

Back 53

Medulla
-medial lemniscus

Front 54

____ ________ ___ __ _______ _______ supplies the meidal lemniscus in the pons

Back 54

paramedian branches of the basilar artery

Front 55

_____ _______ _______ is the blod supply for the medial lemniscus in the midbrain

Back 55

Posterior Cerebral Artery (PCA)

Front 56

________ & __________ arteries are the supply for the VPL of the thalamus.

Back 56

thalamogeniculate & thalamoperforator arteries (small branches of PCA)

Front 57

What is the blood supply for PLIC ?

Back 57

the anterior choridal artery a small branch of the internal carotid supplies PLIC

Front 58

What is the blood supply for the primary somatosensory cortex?

Back 58

ACA: medial
MCA: lateral

Front 59

What vascular zone is the PCML present in the spinal cord?

Back 59

posterior spinal arteries

Front 60

What vascular zone is the PCML present in medulla?

Back 60

medial vascular zone

Front 61

What vascular zone is the PCML present in the pons?

Back 61

medial vascular zone

Front 62

What vascular zone is the PCML present in the midbrain?

Back 62

lateral vascular zone

Front 63

What arteries supply the medial vascular zone of the midbrain?

Back 63

paramedian branches of the basilar artery

Front 64

What arteries supply the lateral vascular zone of the midbrain?

Back 64

Proximal PCA

Front 65

What arteries supply the dorsal vascular zone od the midbrain?

Back 65

SCA and proximal PCA

Front 66

What two vascular zones are present in the pons?

Back 66

medial vascular zone
dorsolaterla vascular zone

Front 67

The ________ supplies the medial vascular zone of the pons.

Back 67

Basilar artery (paramedian branches)

Front 68

AICA and basilar arteries circumferential branches supply this part of the pons?

Back 68

Dorsolateral vascular zone

Front 69

The vertebral artery and PICA supply this part of the medulla.

Back 69

Dorsolaterla vascular zone

Front 70

The VERTEBRAL artery is responsible for supplying this part of the medulla.

Back 70

Lateral vascular zone

Front 71

The medial vascular zone which includes the medial lemniscus is and the posterior columns is supplied by these arteries.

Back 71

Vertebral artery and anterior spinal artery