CNS/Sensory IV

Question 1

Pain is detected by […]

Answer 1

Nociceptors

Question 2

Nociceptors open in response to […]

Answer 2

Mechanical deformation, excessive temperature, or chemicals

Question 3

Are pain afferents highly modulated or minimally modulated?

Answer 3

Highly modulated.

Question 4

What are visceral pain receptors?

Answer 4

They are pain receptors inside your organs that are activated by inflammation.

Question 5

When nociceptors are activated, they lead to the release of […] in the […]

Answer 5

Substance P, spinal cord

Question 6

What is the function of substance P?

Answer 6

It is a neurotransmitter, so it activates second order neurons that send the pain signal up to the brain.

Question 7

Nociceptors are enhanced by the release of […]

Answer 7

Substance P

Question 8

What are the two ways in which nociceptors are enhanced?

Answer 8

1. Enhancement of surrounding nociceptors by injured tissue and afferent feedback onto mast cells
2. Dilation of nearby blood vessels

Question 9

Explain how enhancement of surrounding nociceptors by injured tissue works.

Answer 9

When substance P is released, mast cells are prompted to release histamine. The cells around the injury become more susceptible to injury, and when they burst, they release bradykinin, 5-HT, and Prostaglandin. This creates a feedback loop that increases the sensitivity of the injury and continues the release of histamine and the other substances.

Question 10

Explain how enhancement of nociceptors by dilation of nearby blood vessels works.

Answer 10

The dilation of blood vessels causes swelling, which further enhances injury due to a simple somatosensory stimulation.

Question 11

What is the purpose of somatosensory enhancement?

Answer 11

To tell you not to use the injured part of your body until healing has occurred.

Question 12

Nociceptor enhancement is a […] mechanism called […]

Answer 12

Bottom-up, hyperalgesia

Question 13

What are the 2 pathways that carry somatosensory information?

Answer 13

Dorsal columns and anterolateral pathway

Question 14

What type of stimulus do the dorsal columns and anterolateral pathways transport?

Answer 14

Dorsal columns: touch and proprioception
Anterolateral: temperature and pain

Question 15

Describe the 4 steps of the travel of a signal up the dorsal columns pathway.

Answer 15

1.Signal travels along spinal nerve and enters spinal cord via dorsal root ganglion.
2. Signal travels along dorsal columns on ipsilateral side and reaches medulla in midbrain.
3. Signal crosses at midline and travels up (via medial lemniscus) to thalamas on contralateral side.
4. Signal continues on to the somatosensory cortex.

Question 16

Describe the 4 steps of travel of a signal up the anterolateral pathway.

Answer 16

1. The signal travels along the spinal nerve and enters spinal cord through dorsal root ganglion then dorsal horn.
2. Travels to contralateral side of spinal cord and then goes up via the anterolateral column.
3. The signal travels up and branches into the reticular formation and goes up into the thalamus.
4. The signal travels on to the somatosensory cortex.

Question 17

If there is a lesion on the dorsal root, what part of the nervous system will it affect?

Answer 17

It will lead to ipsilateral loss of sensation at the level of the lesion.

Question 18

If there is a lesion on the spinal cord itself, what part of the nervous system will it affect?

Answer 18

It will lead to ipsilateral loss of sensation at and below the level of the lesion.

Question 19

If someone has loss of touch and proprioception starting at the left hand and proceeding down to the toes, all else being normal, where is their lesion?

Answer 19

Touch and proprioception = dorsal column pathway
Left hand = left cervical nerves
At and below = injury to dorsal columns
Answer: left cervical dorsal columns

Question 20

If someone has bilateral loss of touch and proprioception from the bellybutton down to the toes, all else being normal, where is their lesion?

Answer 20

Touch and proprioception = dorsal columns pathay
Bilateral = injury at the enter
Bellybutton = lower thoracic
At and below = injury to dorsal columns
Answer: both dorsal columns at lower thoracic

Question 21

If someone has bilateral loss of pain and temperature in a thin strip at the level of the lower chest, all else being normal, where is their lesion?

Answer 21

Pain and temperature = anterolateral
Thin strip = injury to dorsal root
Lower chest = thoracic
Bilateral = both sides injured
Answer: lesion must be at the center of the grey matter (to block off signals from either side only at that level)

Question 22

If someone has loss of touch and proprioception on their entire left side from the belly button down, loss of temperature and pain on their entire right side from the bellow button down, and loss of touch and temperature/pain along a thin strip on their left side, where are their lesions?

Answer 22

Loss of temperature and pain on right side: lesion on left anterolateral column
Loss of touch and proprioception on left side: lesion on left dorsal column
Loss of both along thin strip on left side: lesion on left dorsal root

Question 23

What is a somatotopic map?

Answer 23

It is a map depicting how somatosensory information is organized in the brain depending on what part of the body the signal is coming from. The size of the body part on the map represents the acuity of the area.

Question 24

Put the following body parts in order on a somatotopic map: genitals, face, tongue, hands, legs, back, arms, feet

Answer 24

Heading towards the midline: tongue, face, hands, arms, back, legs, feet, genitals

Question 25

What body parts occupy the most space on a somatotopic map? What does this say about their acuity?

Answer 25

Hands and head. This means that they have the highest acuity (and thus most sensitivity)

Question 26

What is referred pain? Give an example

Answer 26

It is when the brain incorrectly assigns pain to the skin when a pain signal is actually coming from somewhere else (usually the inside of the body). For example, when someone is having a heart attack, they experience pain in their left arm.

Question 27

Explain the cause of referred pain.

Answer 27

Visceral and somatic pain afferents commonly synapse on the same neurons in the spinal cord. So, when a signal arrives at the synapse, the brain might assign the pain to the skin, where you will feel pain, instead of to the correct place.

Question 28

The regulation of nociceptive information is called [...] and is a [...] process

Answer 28

Analgesia, top-down (descending)

Question 29

Where does analgesia take place?

Answer 29

It gets activated as pain travels up through the midbrain, and then travels down and takes action at the synapse in the spinal code, affecting the second order neuron.

Question 30

Analgesia is a form of [...]

Answer 30

Presynaptic inhibition

Question 31

In analgesia, the descending pathways release [...]

Answer 31

Opiate neurotransmitters

Question 32

What is the effect of opiate neurotransmitters released during analgesia?

Answer 32

They stop the release of substance P in the spinal cord, thus reducing pain.

Question 33

Give an example of a pain-reduction drug and where it takes action.

Answer 33

Morphine. Its site of action is the opiate neurotransmitter receptors that are used in analgesia.

Question 34

If someone feels pain on the left side of their neck without reason, what is the likely source of the pain?

Answer 34

Lung and diaphragm

Question 35

If someone feels pain on the right side of their neck without reason, what is the likely source of the pain?

Answer 35

Liver and gallbladder

Question 36

If someone feels pain on the left side of their chest without reason, what is the likely source of the pain?

Answer 36

Heart

Question 37

If someone feels pain on the right side of their ribcage without reason, what is the likely source of the pain?

Answer 37

Liver and gallbladder

Question 38

If someone feels pain on the sides of their hips, what is the likely source of the pain?

Answer 38

Kidney

Question 39

If someone feels pain on the lower right side of their body, what is the likely source of the pain?

Answer 39

Appendix

Question 40

If someone feels pain around the private parts or butt, what is the likely source of the pain?

Answer 40

Urinary bladder

Question 41

If someone feels pain at the center of their chest or back, what is the likely source of the pain?

Answer 41

Stomach