Neurophysiology of Pain

_________: a $ that is damaging or threatens damage to normal tissues (ex: stubbing a toe, placing a hand on a stove, spraining an ankle)

Noxious stimulus

________: specialized receptors that send danger signals to the brain

Nocicepters

________: high-threshold receptors within the periphery that pick up noxious stimuli

Nociceptors (just another definition for these)

True or false there are different types of nociceptors that respond to different noxious $ (chemical, thermal, mechanical)

TRUE

Which ascending pathway carries the information about a noxious stimulus into the spinal cord/CNS?

Spinothalamic tract (part of the anterolateral system)

Spinothalamic tract: 1st order neuron

Dorsal root ganglion (where the cell bodies of the nociceptors are located)

Spinothalamic tract: 2nd order neuron

Posterior horn/column (where noxious signals enter the spinal cord)

Spinothalamic tract: region in the spinal cord where the 2nd order neuron crosses to the other side

Anterior white commissure

As the message continues towards the brain, it will pass through which structures on its way to the 3rd order neuron?

Medulla, pons, midbrain (starts relatively anterior --> moves relatively posterior, almost becoming one with the DCML)

What is the name for the region in the spinal cord that acts as a "gate keeper" or "bouncer" to help modulate whether a noxious $ gets to progress up to the brain?

Posterior horn (location of the 2nd order neuron -- approximately within the substantia gelatinosa)

In persistent pain, what happens to the bouncer?

It can die out --> hypersensitivity

If the 2nd order neuron (in posterior horn) is the bouncer, what is the noxious stimulus?

The drunk frat boy (or girl)

If the 2nd order neuron (in the posterior horn) is the bouncer, what is the brain?

The night club the drunk frat boy (or girl) is trying to get into

Spinothalamic tract: 3rd order neuron located

Ventral posterolateral (VPL) nucleus of thalamus

Which regions of the brain does the 3rd order neuron project to as part of the "lateral pain system"?

Primary and secondary somatosensory cortices (serve as ways to determine where the "danger" is coming from)

True or false: there is such thing as pain signals

FALSE!!

True or false: pain is an output of the brain

TRUE!!

True or false: the homunculus is plastic, meaning we can change it to make sensitivity lower or greater to noxious $

TRUE!!

Which pain system adds meaning to a danger pathway?

Medial pain system

Which structures are involved in the medial pain system?

Anterior cingulate cortex, hypothalamus, hippocampus, amygdala, and prefrontal cortex

Inputs to body-self neuromatrix come from which 3 domains?

1. Cognitive-related brain areas (memories of past experience, attention, meaning, anxiety)

2. Sensory signaling systems (cutaneous, visceral, MSK)

3. Emotion-related brain areas (limbic system and associated homeostatic/stress mechanisms)

Overall, the body-self neuromatrix is comprised of ________ (S), ________ (A), and _________ (C)

Sensory, affective, cognitive

Outputs of the body-self matrix to brain areas produce which 3 domains?

1. Pain perception (sensory, affective, and cognitive dimensions)

2. Action programs (voluntary and involuntary patterns)

3. Stress-regulation programs (cortisol, norepinephrine, and endorphin levels; immune system)

___________: relay center and initial processing of nociceptive sensory info before distribution to cerebral cortex

Ventral posterolateral (and ventral posteroinferior and ventral medial) nucleus of thalamus

__________: sensory discriminative processing -- intensity, localization, and character of pain

Primary (S1) and secondary (2) somatosensory cortex

_________: consciousness, self-awareness and homeostatic emotions such as hunger and sensory perception of pain

Insula

_________: EMOTION and subjective pain experience; attention allocation, decision making, impulse control

Anterior cingulate cortex

_________: memory modulation, reward and emotional responses, FEAR AND ANXIETY

Amygdala

________: episodic (short-term) memory, consolidation of memory, emotion and learning (reinforces pain memories)

Hippocampus

________: maintains homeostasis and connects to endocrine system; modulates response to stress (influences pain experience)

Hypothalamus

__________: behavior, decision making, emotion regulation, processing of risk and fear

Pre-frontal cortex

_________: motor responses

Cerebellum

_________: autonomic function, behavior responses, controls descending pain modulation

Periaqueductal grey

________: motivation, reward and reinforcement of learning; role in addiction

Nucleus accumbens

True or false: persistent pain can be reversed

TRUE!!