Chapter 11

Question 1

Sores on feet

Answer 1

Lack of blood means that neurons cannot transmit sensation. Lose protective sensation (free nerve endings that detect pain)

Question 2

Rout of somatosensation

Answer 2

Has a peripheral part that starts in the body and a central part that goes to the spinal cord and in the head (in and up)

3 places

• Conscious awareness (able to classify hurt, where we are in space (cerebral cortex))
• Cerebellum- automatic correction of posture and movement (not conscious awareness)
• Limbi lobe and hypothalamus (emotional and autonomic areas at the base of the brain) no conscious awareness (stub toe and react out of emotion).

Question 3

pathways to brain

Answer 3

Conscious relay (cerebral cortex)

• Divergent (many locations in brainstem and cerebrum, conscious and nonconscious)
• Nonconscious relay (cerebellum)

Question 4

High fidelity pathways

Answer 4

A high degree of body map organization (somatotopic=body layout). the amount of brain devoted to a part of the body is proportional to the density of sensory receptors in that body part.
-foot in longitudinal fissure and face and arm in the lateral parietal lobe (MCA)

Question 5

Low fidelity pathways

Answer 5

Low degree of body map organization/localization.
-the spino-emotional pathway is a low fidelity pathway. When it arrives at the limbic lobe you don’t really know where you are hurt but you know you are hurt and mad as heck. generate broad autonomic and emotional responses.

Question 6

Neurons in the pathway

Answer 6

Interneurons can be interspersed anywhere in the synaptic connections. (signals can be turned up or down, or spread or gathered in the synapse pathway.

Question 7

Somatosensation routing

Answer 7

Conscious relay implies there will be a handoff.
(modalities such as touch, proprioception, pain, and temp)

-routing through the spinal cord- sensory and pain signals start in the skin/body. when they get to the spinal cord they go to the dorsal columns (conscious touch and proprioception). In the spinal cord, pain sensation come to the anterolateral (front side= conscious pain and temp), once they get to the brain stem they fade to the back.

Question 8

Discriminative touch/conscious proprioception pathway

Answer 8

Dorsal column/ medial lemniscus pathway- place where the pathway ascends the spinal cord/brainstem (where you would find the axons of this pathway)

-3 neuron pathway (3rd neuron ends up in the cerebral cortex)
1st order- Sensory receptors to caudal medulla. From skin, up the spinal cord to the brainstem (peripheral)
2nd order- Caudal medulla to thalamus (cross). Crosses the street to the other side of the brain and then goes up all the way to the thalamus (thalamus is the routing station for things going to the cerebral cortex).
3rd order- thalamus to cerebral cortex (post-central gyrus) of the parietal lobe.

Walk through:
feel pressure on arm. Pseudounipolar peripheral axon turns into pseudo central axon, goes up the dorsal column to the caudal medulla where it crosses and starts to ascend through the brain stem until it gets to the thalamus where it synapses again, third neuron goes from thalamus to the cerebral cortex.

1st order neuron has 3 branches.
1-to the spinal cord up the dorsal column
2-cerebellar branch
3-stays in the spinal cord and is part of a spinal reflex loop

Question 9

Primary and secondary sensory cortex

Answer 9

primary sensory cortex- senses the sensation and hands off the message to the secondary sensory cortex- makes meaning of the sensation

feel it and make sense of what it is.

Question 10

discriminative pain and temp pathway

Answer 10

1st- starts at a free nerve ending (high threshold) starts in the body and sends its central axon into the dorsal horn of the spinal cord (synapses in the dorsal horn) (dorsal horn is gray because it has cells of pain pathway)
2nd- as soon as it synapses it immediately crosses the midline at the same level of the synapse and rises up the anterolateral columns all the way to the thalamus. Once it gets to the brainstem it fades posterior.
3rd- starts in the thalamus and goes to the cerebral cortex (post central gyrus)

Spinothalamic pathway- start and stop of second neuron in the pathway. also called the lateral pain system=takes position in anterolateral position.

1st order neuron= A-delta fiber

walk through:
sensation from arm, peripheral axon bypasses pseudo cell body to the dorsal horn, synapses at dorsal horn and crosses midline, rises up through the spinal cord and brain stem (eventually fades to the back once it gets to the brainstem) to the thalamus, 3rd order synapses and goes up to the cerebral cortex/postcentral gyrus.

ascends the spinal cord in the anterolateral column

Question 11

pathway of pain and touch

Answer 11

Touch and pain get separated in their pathway for a period of time. Due to the separation there can be a difference in sensory loss in the spinal cord depending on the injury. Both finish on other side of nervous system.

A-delta- incoming A-delta fibers will split into several branches above and below where it comes in at.

Question 12

Divergent pathways

Answer 12

end in a whole bunch of different places.

2 or 3 neuron pathways (can have either) if only 2 then it doesn’t go to the cerebral cortex, if 3 then at least part of the pathway goes to the cerebral cortex.

Spinoreticular (2)- starts in the spinal cord, ends in the reticular formation (a loose cluster of cells up and down the brainstem)

Spinomesencephalic (2)- starts in the spinal card, ends in the midbrain.

Spino-emotional (3)- starts in the spinal cord, ends in the limbic lobe and the cerebral cortex (divergent pathway of emotional and autonomic factors)

1st order- is a class C fiber- smallest diameter and least myelinated (higher threshold=takes mote of a stimulus to depolarize. (slow pain=dull, aching pain)

Part of pain system- it is dangerous to us so it sends pathways to a whole bunch of different places.

Question 13

Spinoreticular (2)

Answer 13

One peripheral pain neuron splits as it gets to the dorsal horn (where it diverges into 3 different pathways going to 3 different places). teal- 2nd order crosses midline and rises up to the reticular formation (reticulates/ governs our level of arousal).

Question 14

Spinomesencephalic

Answer 14

Terminates in the midbrain- in area of the midbrain that helps turn your head to the location of the pain, it also activates some neurons that project from the brainstem back down to the spinal cord to shut off the pain pathway (governor that limits the amount of pain that is allowed so the pain doesn’t get so strong that it disables us).

periaqueductal gray-red triangle- cells that send axons back down the spinal cord to turn off pain and help us not get overloaded by the pain

Question 15

Spino-emotional (3)

Answer 15

crosses midline and goes up the anterolateral column and can go to the emotion part of the thalamus and goes to the limbic lobe (emotional part of the brain) and to the autonomic part of the brain (hypothalamus). autonomic system alerted that there is a threat to homeostasis.

Question 16

Peripheral sensitization

Answer 16

any injury to the body can result in sensitization of the peripheral neurons (sensitization of free nerve endings) have a lower threshold for action potentials (to be slightly depolarized and easier to activate)

Sunburn example

Question 17

Neurotransmitter of first synapse

Answer 17

Spinothalamic pathway= glutamate (fast acting-get message quick to tell where and how much I have been hurt)

Divergent pathways=Substance P- message doesn’t come fast and discrete, it comes slow and long lasting

Question 18

Clinical perspectives on pain

Answer 18

Fast- (superficial and or “sharp”) pain. alerts us to injury and helps us to avoid it and move away from it. (I know where it is, I can describe it, I can get away from it)

Slow- deep, dull pain (settle down, rest and recover) pain has already happened.

Problems-

1) when pain severely limits function (A-delta pain causes stiffness)
2) pain lasts beyond the time we expect the injury to heal

Question 19

Referred pain

Answer 19

heart attack- left arm hurts, left chest hurts (we believe that all of our visceral organs have peripheral pain receptors that go to the spinal cord and converge with neurons of somatic (nonvisceral body)

Heart also sends afferents into the spinal cord and converge with same gold spinothalamic neurons as the arm pain (all life arm pain is associated with the gold neuron) when gold neuron is activated by the heart we still associate pain with arm pain.
Referred pain is the brain getting fooled by our lived experiences.

All peripheral organs converge with neurons of visceral organs as well.

Question 20

Sensory-Discriminative aspects

Answer 20

-spinothalamic pathway- Through the spinal thalamic pathway (conscious- where was I, how was I hurt, what caused the hurt, can I get away from it)

Question 21

Motivational-Affective aspects

Answer 21

-Spino-emotional, Spinoreticular pathways- can pr0duce unconscious changes in our mood, emotion, change in our want to (drive). When we are hurt we want to hunker down and not do anything (what makes us alert to the pain first)

Question 22

Cognitive-Evaluative aspects

Answer 22

Monitors the pain experience and thinks about it. Evaluates what is the significance of the pain experience in my life. (I hurt my back, I cant work, I cant pay my bills, I cant buy food or shelter for family) what does the pain mean in my life and how well can I deal with it.

Question 23

Antinociception-

Answer 23

Anything we can do to distract from or turn down the perception of pain.

Question 24

Pronociception-

Answer 24

Increasing the perception of pain. 2 things:

1) wither let the pain signals come in more easily
2) or turn up the volume and increase the signal coming in. Encourage it to come in. especially powerful wen motivational affective piece is active.

If I believe that something has hurt me and is bad/I want to always be alert to that sensation. From top down, the pain pathway can let that signal come in more easily.

Place where the signal can be turned up, down, spread, or gathered=the synapse

Question 25

Gate theory

Answer 25

one opportunity to modify the strength of the pain signal. Close the gate, pain signals don’t get through, open the gate and the signals do get through. we have some capacity both physically and pharmacologically to close the gate.

Question 26

Counterirritant theory

Answer 26

Tissue damage is an irritant (causes depolarizing of free nerve ending) when we rub it where it hurts it is a counter irritant, a way that we can synoptically close the gate to the transmission of the pain. Activate an inhibitory interneuron and close the synaptic gate in the dorsal horn. A beta stimulation from the rubbing can turn off the C signals in the pain pathway.

Question 27

states of Dorsal horn processing:

Answer 27

Normal- free nerve ending depolarizes and passes the signal (action potential) from a damaging stimulus.

Suppressed- It can not pass action potentials as easily. we suppress the pain synapse when we rub it where it hurts so we can temporarily suppress the synapse by rubbing it where it hurts. Some pharmacologic pain medication can also suppress a synapse and make it difficult for signals to pass through.

Sensitized (temporary and neuropathic)- easier to pass the pain message across the pain synapse. Temporarily release more neurotransmitter at the presynaptic terminal.

Reorganized (persistent and neuropathic)- Synapse can be reorganized (long term potentiation) postsynaptic membrane grows spines and concentrates receptors so it is easier to pass the signal through. much easier for signals to get passed in the pain pathway.

Neuropathic= conditions where the nerve itself is sick and there is not normal communication in this pathway.

Question 28

Sites of antinociception: Periphery

Answer 28

Free nerve endings (pain receptors). Anything that we can do to reduce depolarization of pain receptors will reduce patients pain. (anything that reduces inflammation, takes away histamines and the free nerve endings don’t get depolarized) (mechanical stiffness that is depolarizing free nerve endings, reduce mechanical stiffness and we can reduce the pain signaling from the mechanical stiffness (stretch muscles, mobilizing the join))

Heat, cold, massage, mobilizing joint, stretch a muscle,

Question 29

Sites of antinociception: Dorsal horn

Answer 29

Where there is a synapse and where we can turn it down at the synapse (we can rub it where it hurts at level 2) not the best therapy.

TENS units- electrically depolarizes A-beta will tend to close the gate

mechanoreceptors that are out in the body and so moving in itself can close the gate in the dorsal horn for A-betas (mvmt is pain reducing to a certain degree).

Question 30

Sites of antinociception: Midbrain descending

Answer 30

Spinomesinthelialic- turn on neuron in periaqueductal gray, turn signal.

Somewhat naturally active, some of the pain medications do activate the descending system (antipain meds activate midbrain back down the spinal cord system and turning off the pain signal).

Rephespinal and ceruleospinal are the descending spinal pain pathways.

there are ways to think this pathway into action.

Question 31

Sites of antinociception: Hormonal

Answer 31

Pituitary level (autonomic nervous system)- dump chemicals into the blood for body wide distribution (not much direct control over this level, spontaneously active to some degree)

Some pain medications tend to turn on this distribution.

Distributes endogenous opiates=made inside us (powerful pain relievers and can go to every place in the body like the dorsal horn and shut off the pain there. Or they can turn on the midbrain system).

2 possibilities:
runners high-endorphins in the blood stream

-turn on the system just a little bit (pain meds can turn it on, maybe aerobic activity can turn it on, and one mode of the TENS unit (strong low rate-feels like a little punch can turn on the endogenous opioid system) outlasts the stimulation by 3 ot 4 hours (promotes turn it on, get the pain reduction, turn it off, and do exercise).

Question 32

Sites of antinociception: Amygdala and cortex

Answer 32

Amygdala- part of the subcortical emotion circuitry (primal brain- survival brain) it evaluates everything in terms of its threat level (if it determines yes it immobilizes us appropriately).

Cortex- part of cognitive evaluative piece that evaluates what is the consequence of this pain for me.

We have direct effect on periphery and level 5, we can also affect the midbrain as well.

Cerebral cortex has nociception pathways back down the spinal cord that can turn down the pain pathway at the dorsal horn. We can think our way to less pain (complicated)

HUGS MAKE IT BETTER-because we know it is going to be okay and feel comforted.

Question 33

Sites of antinociception:

Answer 33

I- Periphery
II- Dorsal Horn
III- Midbrain descending
IV-Hormonal
V- Amygdala & Cortex

Question 34

Pronociception

Answer 34

Top down has a powerful effect of antinociception but it can also let pain in if it turns off or the top down can actually amplify the pain signals, it can open the gate and has two ways it can work (antinociception or pronociception). thoughts can amplify pain or create it with no physical stimulus.

Anything that lowers the threshold for free nerve endings can produce disproportionate amounts of pain.

Question 35

Chronic pain

Answer 35

pain that extends beyond the time expected for normal tissue healing.

Nociceptive- continuing pain stimulus
-pain neurons functioning normally
(continually depolarizing free nerve endings)

Neuropathic- no continuing pain stimulus
-pain neurons typically NOT functioning normally.

Question 36

causes of acute pain

Answer 36

-threat of or actual tissue damage

Question 37

causes of chronic pain

Answer 37

continuing tissue damage

• environmental factors
• sensitization of nociceptive pathway neurons
• dysfunction of endogenous pain control system.