Ascending Sensory Systems

Question 1

Where is the spinal cord larger in diameter?

Answer 1

Cervical and lumbar regions

Question 2

Where dose cervical nerve 1 exit?

Answer 2

Above the atlas

Question 3

Where does cervical nerve 8 exit?

Answer 3

Between C7 and T1 as there is no C8

Question 4

Where do spinal nerves below C8 exit?

Answer 4

Beneath their corresponding vertebrae

Question 5

What is gray matter made of?

Answer 5

Neuronal cell bodies including secondary sensory neurons, interneurons and motor neurons

Question 6

Substantia gelatinosa? What and where

Answer 6

a distinct region of grey matter that caps the dorsal horn and appears to be involved inthe transmission of pain information. It is present at all levels of the spinal cord.

Question 7

Clarke’s nucleus? What and where

Answer 7

an important relay nucleus for the trasmission of information to the cerebellum. It is present at T1-L2/3

Question 8

Intermediolateral cell column? What and where

Answer 8

It contains the preganglionic sympathetic neurons of the autonomic nervous system and is present at levels T1-L2/3 of the spinal cord.

Question 9

Sacral parasympathetic nucleus? What and where

Answer 9

contains preganglionic parasympathetic to pelvic viscera and is present at levels S2-S4

Question 10

Accessory nucleus? What and where

Answer 10

It cnotians motor nurons that project to the trapezius and sternoleidomastoid muscles. Extends from the medulla to C5 of the spinal cord

Question 11

Phrenic nucleus? What and where

Answer 11

It contains motor neurons that control the diaphragm and is present at levels C3-C5 of the spinal cord

Question 12

What are the primary neurons for the long ascending pathways of the spinal cord?

Answer 12

Dorsal root ganglion

Question 13

Generally, which cells are the ones which decussate in the spinal cord/medulla?

Answer 13

Second-order neurons

Question 14

Where is the third order neuron in relaying sensory information located?

Answer 14

The thalamus. The axons of these teriary neurons project to the somatosensory area of the cerebral cortex

Question 15

Posterior Column-Medial Lemniscal System (Dorsal Column Pathway)-Origin and Destination

Answer 15

Fasciculus gracilis and fasciulus cuneatus are two tracts in the posterior/dorsal columns. They originate from primary sensory neurons with cell bodies located in the dorsal root ganglia. Peripheral processes conduct information received from the cutaneous join and muscle receptors. The central processes fo th drg cells enter the cord via the dorsal roots and course to the posterior funiculus. Primary large-diamter myelinated fibers, Aalpha and Abeta

Question 16

Posterior Column-Medial Lemniscal System (Dorsal Column Pathway)-Modalities Carried

Answer 16

Touch, deep pressure, sense of position of joints, temporal and spatial discrimination, vibratory-sense

Question 17

Posterior Column-Medial Lemniscal System (Dorsal Column Pathway)-Somatotopic Organization

Answer 17

Dorsal roots are comprised of fibers which derive from the same somite as the corresponding segment of the spinal cord. Cutaneous area supplied by fibers from a single dorsal root and its ganglion is called a dermatome. Somatotopic organization of fibers is medial to lateral, sacral to cervical

Question 18

Fasciculus gracilis is composed of dorsal root fibers from?

Answer 18

Sacra, lumbar and lower 6 thoracic levels

Question 19

Fasciculus cuneatus is composed of fibers from?

Answer 19

Upper six thoracic levels and cervical levels

Question 20

Posterior Column-Medial Lemniscal System (Dorsal Column Pathway) - Route through spinal cord

Answer 20

These tracts do not cross in the spinal cord (remain ipsilateral to point of origin). A lesion of the posterior column would result in loss of sensation on the same side as the lesion. It decussates at the pyramids of the medulla.

Question 21

Spinothalamic Tract - Orgin and Destination

Answer 21

The spinothalamic tract originates in the grey matter of the spinal cord and ascends the neuroaxis to terminate in the thalamus.

Question 22

Spinothalamic Tract-Modalities

Answer 22

The STT carries info on pain and temp from sacral through cervical spinal levels. Pain and temp info is transmitted from periphery to spinal cord via processes of drg. Pain and temp info originates from small diameter axons. Myelinated-Adelta, unmyelinated-C fibers. Soon after entering the spinal cord, fibers or axons of the primary sensory neuronal cel bodies located in the drg synapse with secondary neurons in the gray matter. The STT consists of fibers which originate from the secondary neuronal cells located in the dorsal horn of the spinal cord. The tract is formed by fibers from the secondary cells that cross the midline in the anterior/ventral white commissure and course to the lateral funiculus.

Question 23

What are the primary sensory neurons in the STT?

Answer 23

DRG

Question 24

Spinothalamic Tract-Somatotopic Organization

Answer 24

Most inferior fibers entering the cord are sacral fibers. These synapse and begin to form the tract. More superior fibers enter the cord, they synapse and axons of the secondary cells course to the lateral funiculus. They layer so that sacral fibers have the most lateral position and cervical fibers have more medial positions.

Question 25

Spinothalamic Tract-Course through spinal cord

Answer 25

The fibers of the econdary cell cross the midline obliquely over 2-3 segments. Crossing occurs bilaterally in the anterior white commissure. Therefore, tract is contralateral to point of entry.

Question 26

Spinocerebellar Tract-Origin and Destination

Answer 26

There are two (anterior and posterior). Both tracts convey info of tension in muscles and orientation of joints to the cerebellum from receptors located in muscles, tendons and joints. Information goes to the cerebellum via these pathways originates from the ipsilateral side of the body.

Question 27

Spinocerebellar Tract-Modalities -Posterior Tract

Answer 27

Proprioception, especially in lower limbs. The posterior tract conveys info from individual extremity muscles. .

Question 28

Spinocerebellar Tract-Modalities;Anterior Tract

Answer 28

Proprioception. The Anterior tract conveys info from the entire extremity

Question 29

Spinocerebellar Tract-Somatotopic Org-Posterior

Answer 29

The secondary cells for the posterior tract are located in Clark’s nucleus which is found in the cord between T1 and L2/3. Processes of primary cells in DRG entering cord at these levels synapse on cells in Clark’s nucleus and form the ipsilateral tract.
Above T1-central processes travel to the posterior columns to reach the accessory cuneate nucleus in the medulla. After synapsing the fibers form the cuneocerebellar tract and project to the cerebellum.

Question 30

Fibers from the posterior spinocerebellar tract and cuneocerebellar tract travel to the cerebellum via what?

Answer 30

The inferior cerebellar peduncle

Question 31

Anterior spinocerebellar tract-Somatotopic Organization

Answer 31

Central processes of the DRG cells synapse on cells in the grey matter of the cord, cross to the opposite side and ascend the neuroaxis. In the midbrain, the fibers cross again to enter the cerebellum and terminate ipsilateral to the point of origin.

Question 32

Fibers from the anterior spinocrebellar tract travel to the cerebellum via what?

Answer 32

The superior cerebellar peduncle.

Question 33

What is suspended sensory loss?

Answer 33

Bilateral loss of pain and temperature involving several dermatomes. Results from damage to the spinaothalamic tract crossing in the ventral white commisure. Characteristic of lesions involving the central area of the spinal cord.

Question 34

What is the Romberg sign?

Answer 34

If a patient has damaged posterior columns, closing their eyes will cause a fall.