L5 T1 Sensory pathways

Question 1

Ascending pathways are made up of what three orders of neurons?

Answer 1

Primary sensory, secondary, and tertiary.

Question 2

Where do primary sensory neurons enter the spinal cord?

Answer 2

Dorsal roots of spinal (cranial) nerves

Question 3

Where are the cell bodies of primary sensory neurons located?

Answer 3

dorsal root ganglia

Question 4

With what do the primary sensory neurons synapse in the spinal cord?

Answer 4

Secondary neurons

Question 5

Where do the primary sensory neurons originated from?

Answer 5

peripheral receptors such as Merkel’s discs.

Question 6

Where do secondary neurons originate?

Answer 6

Spinal cord gray matter

Question 7

Secondary neurons make up ______ in spinal cord and brainstem.

Answer 7

tracts

Question 8

Do secondary neurons travel through the spinal cord in myelinated or unmyelinated columns?

Answer 8

myelinated

Question 9

True/False: Secondary neurons do not decussate.

Answer 9

False. Secondary neurons DO decussate.

Question 10

Where, and with what do secondary neurons synapse

Answer 10

thalamus; tertiary neurons

Question 11

Tertiary neurons travel from thalamus, through what, to what?

Answer 11

Through the internal capsule to the primary sensory cortex.

Question 12

What location to the tertiary neurons terminate?

Answer 12

Somatosensory cortex

Question 13

What is the internal capsule in which tertiary neurons travel?

Answer 13

Myelinated pathway between thalamus and some of the basal nuclei

Question 14

What two ascending pathways are used for conscious perception?

Answer 14

Spinothalamic system (divided into lateral spinothalamic tract and anterior spinothalamic tract), and medial lemniscal system.

Question 15

What are the four ascending pathways for unconscious perception?

Answer 15

Spinocerebellar, spino-olivary, spinotectal, and spinoreticular

Question 16

Where do all of the ascending pathways for unconscious perception originate?

Answer 16

Spinal cord, and go to different parts of the brainstem

Question 17

What does the lateral spinothalamic tract carry?

Answer 17

Pain and temperature

Question 18

Primary fibers ascend or descend how many spinal cord segments before synapsing with secondary fibers in the lateral tract?

Answer 18

1-2

Question 19

What type of axons make up the lateral spinothalamic tract traveling in the lateral column of the spinal cord?

Answer 19

secondary axons

Question 20

Secondary fibers that are joined in the brainstem by fibers of trigeminothalamic tract carry what?

Answer 20

pain and temperature from the face and teeth

Question 21

What is the function of secondary collaterals projecting to the reticular formation?

Answer 21

Stimulate wakefulness and consciousness

Question 22

Where do tertiary fibers synapse?

Answer 22

postcentral gyrus

Question 23

From what do the tertiary fibers form?

Answer 23

part of the internal capsule

Question 24

Anterior spinothalamic tract neurons carry what sensation?

Answer 24

Crude/light touch, pressure, tickle, and itch

Question 25

Primary neurons of the anterior spinothalamic tract ascend how many spinal cord segments before they synapse with secondary neurons?

Answer 25

8-10

Question 26

In reference to anterior spinothalamic tract secondary fibers, where do they decussate?

Answer 26

anterior gray or white commissures

Question 27

The dorsal column-medial lemniscal pathway systems carries sensations for what?

Answer 27

two-point sensation (fine touch), pressure and vibration.

Question 28

What is two point discrimination?

Answer 28

refers to the ability to distinguish two separate points as close as two millimeters apart.

Question 29

Lemniscal primary fibers ascend.....and synapse with.....

Answer 29

ascend the entire length of the spinal cord; synapse with the secondary neurons in medulla.

Question 30

Where do fibers of the fasciculus gracilis synapse? what to they carry?

Answer 30

they synapse in the nucleus gracilis and convey sensations from below midthoracic level.

Question 31

Where do fibers of the fasciculus cutaneous synapse? what to they carry?

Answer 31

they synapse in the nucleus cutaneous and convey sensations from above the midthoracic level.

Question 32

What neurons decussate?

Answer 32

Secondary

Question 33

The primary somatosensory area is made up of which Brodmann's areas?

Answer 33

1, 2, and 3

Question 34

The somatosensory association area is made up of which Brodmann's areas?

Answer 34

5 and 7

Question 35

Somatosensory area II receives signals from:

Answer 35

- brainstem, transmitted upward from both sides of the body - secondarily from somatosensory area I - other sensory areas of the body, including visual and auditory

Question 36

True/False: Projections from somatosensory area I are required for function of somatosensory area II.

Answer 36

True

Question 37

True/False: Removal of somatosensory II has no apparent effect on the response of neurons in somatosensory area I.

Answer 37

True

Question 38

What is the function of layers I and II (the superficial layers) of the somatosensory cortex?

Answer 38

receive input signals from lower brain centers

Question 39

What is the function of layers II and III of the somatosensory cortex?

Answer 39

Send information through the corpus callosum to opposite hemisphere.

Question 40

What is the function of layers V and VI (deepest layers) of the somatosensory cortex?

Answer 40

- large neurons in layer V project to distant areas such as basal nuclei, brainstem, and spinal cord. - axons from layer VI project to thalamus

Question 41

What is the function of layer IV of the somatosensory cortex?

Answer 41

receives incoming sensory signals

Question 42

What is lateral inhibition?

Answer 42

It is important in blocking the lateral spread of excitatory signals, thereby increasing the degree of contrast in the cerebral cortex. It helps to sharpen the incoming signal.

Question 43

Where does lateral inhibition occur?

Answer 43

at each synaptic level - dorsal column nuclei - ventrobasal nuclei of thalamus - somatosensory cortex

Question 44

Pain receptors are made of what?

Answer 44

free nerve endings

Question 45

What are the characteristics of fast pain?

Answer 45

- felt quickly (0.1 seconds) after stimuli - not felt in most deeper tissues - generally elicited by mechanical and thermal stimuli - typically carried by Adelta fibers

Question 46

Where do pain fibers typically terminate?

Answer 46

in the lamina I of the dorsal horns of the spinal cord.

Question 47

What are the characteristics of slow pain?

Answer 47

- begins approx. 1 second after stimulus is applied and increases over several seconds - described as aching, slow burning, throbbing, nauseous, and chronic - can be elicited by mechanical, thermal, and chemical stimuli.

Question 48

Fast pain is typically carried by what?

Answer 48

by A-delta fibers

Question 49

Slow pain is typically carried by what?

Answer 49

by C type fibers

Question 50

Where do slow pain fibers typically terminate?

Answer 50

in layers II and III of the dorsal horns of the spinal cord.

Question 51

What tract does pain travel through?

Answer 51

anterolateral tracts

Question 52

Primary pain fibers synapse where with secondary fibers?

Answer 52

in the dorsal horns of the spinal cord

Question 53

Once the primary pain fibers synapse with the secondary fibers, the secondary fibers immediately ________ and make their way up the ___________ pathways.

Answer 53

decussate; anterolateral

Question 54

Fast pain fibers make up what tract and synapse and terminate in the ventrobasal nuclei of the thalamus?

Answer 54

neospinothalamic

Question 55

Slow pain fibers make up what tract?

Answer 55

paleospinthalamic

Question 56

The A-delta fibers of the fast-pain path use which neurotransmitter?

Answer 56

glutamate

Question 57

Type C pain fibers use what two neurotransmitters?

Answer 57

glutamate - acts instantaneously | Substance P - released more slowly

Question 58

Pain travels through what tract?

Answer 58

anterolateral

Question 59

What are the components of the analgesia system?

Answer 59

- periaquaductal gray and periventricular regions of brainstem and third ventricle - raphe magnus nucleus and reticular nuclei in medulla - pain inhibitory complex in dorsal horns of spinal cord

Question 60

What are the three receptors that discriminate thermal gradations?

Answer 60

cold, warmth, pain

Question 61

Warmth nerve endings are mainly transmitted by what type of fiber?

Answer 61

C type fibers

Question 62

Cold receptors are 3-10 times as numerous as warm nerve receptors and are what type of fiber?

Answer 62

small type A-delta myelinated endings

Question 63

True/False: Thermal signals are not transmitted in pathways parallel to those for pain signals.

Answer 63

False; thermal signals ARE transmitted in pathways parallel to those for pain signals

Question 64

When does referred pain occur?

Answer 64

occurs when visceral pain fibers are stimulated and stimulate some of the pain fibers that conduct pain signals from the skin.

Question 65

When does severe referred pain occur?

Answer 65

Severe pain results when there is diffuse stimulation of pain nerve endings throughout the viscera (as opposed to highly localized types of damage to the viscera).

Question 66

All visceral pain from the thoracic and abdominal cavities is transmitted via what type of pain fiber?

Answer 66

type C pain fibers

Question 67

__________ are the result of pain referred to the surface of the head from deep head structures.

Answer 67

Headaches