Neuroscience 3-1 Ascending Pathways Overview Amanda C. Conta Steencken

Question 1

Name the four somatosensory circuits.

Answer 1

1. Dorsal Column-Medial Leminiscal System
2. Anterolateral (spinothalamic) System
3. Spinocerebellar system
4. Trigeminal system

Question 2

Anterolateral system carries what kind of information?

Answer 2

Protopathic sense from trunk and limbs

Question 3

Dorsal Column-Medial Lemniscal System carries what kind of information?

Answer 3

Epicritic sense from trunk and limbs

Question 4

What does protopathic mean?

Answer 4

Pain and temperature, and crude touch, nocioception

Question 5

What does epicritic mean?

Answer 5

Mechanosensation

Question 6

What does mechanosensation include?

Answer 6

Vibration, position, 2-point discrimination, simple touch

Question 7

Where can you find the gracile and cuneate nuclei?

Answer 7

Medulla

Question 8

Where do fibers from the dorsal column-medial lemniscal system decussate?

Answer 8

At the level of the medulla

Question 9

What’s the pathway for vibration/light touch?

Answer 9

Skin –> DRG –> posterior (dorsal) columns –> primary sensory neuron –> sensory decussation in internal arcuate fibers –> Posterior (dorsal) column nuclei (cuneate/gracile) –> secondary sensory neuron (medial lemniscus) –> thalamus (ventral posterior lateral nucleus)

Question 10

Where do mechanoreceptors from the lower body synapse?

Answer 10

The gracile nucleus in the caudal medulla

Question 11

Where do mechanoreceptors from the upper body synapse?

Answer 11

The cuneate nucleus in the caudal medulla

Question 12

Where do the mechanoreceptor neurons decussate?

Answer 12

In the caudal medulla, in the internal arcuate fibers, AFTER entering their respective dorsal column nuclei

Question 13

Where do the anterolateral neurons decussate?

Answer 13

At the level of the spinal cord

Question 14

What do anterolateral and dorsal column medial lemniscal systems have in common?

Answer 14

They both project from the thalamus to the primary somatosensory cortex.

Question 15

What are the three things we are to associate with the spinocerebellar tract?

Answer 15

Ipsilateral
Proprioception
Cerebellum

Question 16

What information does the trigeminal system carry?

Answer 16

All sensory information from the head and neck:

• -epicritic
• -protopathic
• -proprioceptive

Question 17

The thalamus surrounds what ventricle?

Answer 17

3rd

Question 18

Name this structure: relay center of the brain, conveying sensory and motor information to/from the cerebral cortex.

Answer 18

Thalamus

Question 19

Sensory circuits are also known as __1__ circuits, while, motor circuits are also known as __2__ circuits.

Answer 19

1. Ascending

2. Descending

Question 20

Why are the descending tracts called the pyramidal system? Is this direct or indirect motor system?

Answer 20

Because the motor axons pass through the medullary pyramids, this is an example of direct cortical motor control

Question 21

If the motor axons don’t go through the medullary pyramids, where do they go? Is this direct or indirect motor system?

Answer 21

They are extra-pyramidal, they are thus part of the brainstem-spinal system. This is an indirect motor system.

Question 22

The pyramidal system includes what direct tracts?

Answer 22

Corticospinal tract (lateral and ventral)
Corticobulbar tract

Question 23

The brainstem-spinal system includes what indirect tracts?

Answer 23

Rubrospinal tract
Tectospinal
Reticulospinal
Vestibulospinal

Question 24

What is the function of the lateral corticospinal tract?

Answer 24

Controls voluntary, fine, motor movements of distal/appendicular musculature

Question 25

Where do the lateral corticospinal tract neurons synapse?

Answer 25

Within the spinal gray matter

Question 26

What is the pattern of decussation in the lateral corticospinal tract?

Answer 26

85% of axons cross in the caudal medulla, called the "pyramidal decussation"

Question 27

If the motor axons do not decussate in the caudal medulla, what happens to them and what do they become?

Answer 27

15% of the descending motor axons do not cross the midline; they descend in the anterior ventral white matter of the spinal cord as the anterior corticospinal tract

Question 28

Cortical control of the hypoglossal nucleus is predominantly:

Answer 28

Controlateral

Question 29

The facial nerve synapses in the motor nucleus of CN 7. Where do the lower nerves go?

Answer 29

The lower nerves primarily innervate the controlateral facial muscles (muscles of expression), and both the contralateral and ipsilateral upper face (forehead)

Question 30

Name the 5 main upper motor neuron lesion signs:

Answer 30

1. Hypperreflexia 2. Hypertonia 3. Positive Babinski 4. No muscle atrophy 5. No fasciculations

Question 31

Name the 5 main lower motor neuron lesion signs:

Answer 31

1. Hyporeflexia 2. No Babinski 3. Muscle atrophy 4. Fasiculations 5. Hypotonia

Question 32

Axons of upper motor neurons project to:

Answer 32

another motor neuron in the brainstem or spinal cord

Question 33

Axons of lower motor neurons project to:

Answer 33

muscles

Question 34

From CN VIII to cochlear nucleus you can have __1__ hearing loss. After cochlear nuclei and second order neurons there is __2__. Therefore hearing loss can be __3__.

Answer 34

1. unilateral 2. crossing over, and bilateral hearing 3. not be obvious

Question 35

Where do the auditory neurons synapse of the vestibulocochlear nerve synapse? After that, how do the nerves proceed?

Answer 35

Dorsal and Ventral Cochlear Nuclei, proceeding ipsilaterally

Question 36

2nd order neurons leave the cochlear nuclei and synapse:

Answer 36

Assorted pontine nuclei, bilaterally

Question 37

What is the lateral lemniscus?

Answer 37

Neurons conveying auditory information from the pontine regions form the lateral lemniscus

Question 38

Where does the lateral lemniscus terminate?

Answer 38

Inferior Colliculus

Question 39

Axons from the inferior colliculus pass to the __1__ bilaterally in the __2__.

Answer 39

1. Medial Geniculate Nucleus | 2. Brachium of the inferior colliculus

Question 40

MGN axons project to primary auditory cortex called __1__ via the auditory radiations.

Answer 40

Heschel's gyrus

Question 41

The auditory radiations are also known as:

Answer 41

Sublenticular portion of the internal capsule

Question 42

Name the ways you can achieve total bilateral hearing loss.

Answer 42

1. Damage to both vestibulocochlear nerves 2. Damage both cochlear nuclei 3. Lesions to both sides of the auditory pathway 4. Damage to Both auditory cortices 5. Damage to BOTH MGN 6. Damage to both auditory radiations.

Question 43

After the dorsal and ventral cochlear nuclei, all auditory information is:

Answer 43

bilateral

Question 44

Wernicke's area includes the:

Answer 44

1. supramarginal gyrus | 2. planum temporale

Question 45

Deafness in one ear can only be caused by:

Answer 45

1. damage to the vestibulocochlear nerve | 2. damage to the cochlear nuclei

Question 46

Each visual field is "seen" by the ___ visual cortex.

Answer 46

contralateral

Question 47

Axons carrying information destined for V1 of the primary visual cortex synapse where?

Answer 47

In the LGN

Question 48

Second order neurons project from the LGN to where?

Answer 48

They become the optical radiations and travel to V1.

Question 49

Explain what happens in the optic radiations.

Answer 49

1. Information from the upper half of the VF travels in the TEMPORAL lobe bundle - lower banks of the calcarine sulcus in the lingual gyrus 2. Information in the lower half of the VF travels in the PARIETAL lobe bundle - upper banks of the calcarine sulcus in the cuneate gyrus

Question 50

A right homonymous hemianopia is caused by a lesion where?

Answer 50

In the left optic tract

Question 51

A left homonymous quadrantanopia is caused by a lesion where?

Answer 51

Upper or lower optic radiations on the right side

Question 52

A right homonymous hemianopia with central sparing is caused by a lesion where?

Answer 52

Occipital lobe optic radiations