Neurophysiology 2: Somatosensation And Ascending Tracts (Lecture 76)

Question 1

What are somatosensory receptors for?

Answer 1

General senses are relatively simple in structure and physiology

Question 2

What do somatosensory receptors consist of?

Answer 2

Primary afferent neuron

(May or may not be encapsulated)

Question 3

What are four examples of somatosensory receptors?

Answer 3

Thermoreceptors, nociceptors, mechanoreceptors, Proprioceptors

Question 4

Once a primary afferent neuron fires, where does the signal go?

Answer 4

Up the nerve fiber of the primary afferent neuron Or the nucleus of the trigeminal nerve for structures of the head

Question 5

Out of the sensory functions, which one has the largest fibers? Smallest?

Answer 5

Largest fibers: Proprioceptors
Smallest fibers: pain, temperature, itch

Question 6

Do larger or smaller fibers have faster conduction velocity?

Answer 6

Larger fibers= faster
smaller fibers = slower

Question 7

What are the functions of the spinal cord?

Answer 7

Conduction-afferent and efferent (structural and functional link between brain and body)
Neural integration
Reflexes

Question 8

What is contained in the grey matter of the spinal cord?

Answer 8

Neuronal cell bodies

Question 9

What does the dorsal horn house?

Answer 9

Axons of sensory neurons and cell bodies of interneurons

Question 10

What does the ventral horn house?

Answer 10

Cell bodies of somatic motor neurons

Question 11

What does the lateral horn house?

Answer 11

Cell bodies of autonomic motor neurons

Only present T1-L3

Question 12

What does gray commissure of the spinal cord contain?

Answer 12

Contains unmyleinated axons connecting left and right gray matter

Question 13

What does the white matter within the spinal cord contain?

Answer 13

Myelinated axons

Question 14

What is contained within the myelinated axons of the white matter of the spinal cord?

Answer 14

Columns or funiculi
Tracts or fasciculi

Question 15

Describe the conscious somatosensory projection pathway

Answer 15

First-order neuron
-from body, enter the spinal chord via dorsal root
-from head, enter via cranial nerve (trigeminal)
Second order neuron
-projects from the CNS cranially
-decussation to contralateral side
-end in thalamus
Third order neuron
-thalamus to primary somatosensory cortex of cerebrum

Question 16

What is the fasciculus cuneatus?

Answer 16

Fiber bundle that carries tactile and proprioceptive information from cranial trunk and thoracic limb

Question 17

What is the fasciculus gracilis?

Answer 17

Fiber bundle that carries tactile and proprioceptive information I from caudal trunk and pelvic limbs

Question 18

What do the fasciculus cuneatus and gracilis both detect?

Answer 18

Conscious proprioception , touch, pressure, vibration

Question 19

In subconscious proprioception, at least ______ neuron pathways leading to the ______ cerebellum .

Answer 19

2

Ipsilateral

Question 20

What does the spinocerebellar tract do?

Answer 20

Relays unconscious proprioceptive information from the caudal trunk and pelvic limbs

Question 21

What does the spinocuneocerebellar (cuneocerebellar) tract do?

Answer 21

Relays unconscious proprioceptive information from the cranial trunk and thoracic limbs

Question 22

What type of pathways are nocicpetive pathways?

Answer 22

Complex, multisynpatic, ipsilateral and contralateral pathways

Question 23

What is the clinical significance of nocicpetive pathways?

Answer 23

Loss of nocicpetion is a poor prognostic indicator

Question 24

What two tracts are associated with nociceptive pathways ?

Answer 24

Spinothalamic tract
Spinocervicothalamic tract

Question 25

What do viscerosensory afferent (GVA) travel with?

Answer 25

ANS fibers

Question 26

What tract do viscerosensory afferent (GVA) travel?

Answer 26

Spinothalmic tract

Ascend to cerebrum for conscious perception

Question 27

What is referred pain?

Answer 27

Many somatic and visceral sensory neurons send signals via the same ascending tracts within spinal cords. Somatosensory cortex is unable to determine true source

Ex: heart attack

Question 28

What fibers make of viscerosensory afferent (GVA)?

Answer 28

A delta and C fibers