Lecture 1 Flashcards
(29 cards)
Functions of pain
- Warning
- Support of healing process
Acute vs. Chronic pain
- Persists longer than 6 months
- Lost its warning function
- Occurs even in the absence of noxious stimuli
- Occurs even after successful healing
Pain is
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. - ISAP (international association for the study of pain)
Sensory and affective component:
- How intense, what quality?
- How unpleasant, annoying, distressing?
What are the multiple response levels of pain?
- Brain
- Reflexes
- Facial expressions
- VNS (vegetative nervous system)
- Report
What is nociception?
- Processing and transmission of signals detected by nociceptors
- Sensory basis for adaptive protective behavior
What are nociceptors?
- Specific sensors with high sensory threshold, only excited by stimulation which is tissue-damaging or threat of tissue damage.
- Free-ending nerve fibres (Aδ- and C-fibers)
- Mostly polymodal
How are nociceptors polymodal?
They respond to:
- Thermal
- Mechanical
- And chemical stimulation
What is not pain?
Activity induced in the nociceptor and nociceptive pathways by a noxious stimulus is not pain.
How is pain described?
- It is always a psychological phenomenon
- It is highly subjective
Nociception vs Pain
Nociception: detection and processing of noxic (harmful) stimuli by highly specialized part of the somatosensory system (nociceptive system)
Pain: conscious experience of this perception, emerging from cognitive and emotional evaluation of the information gathered through the nociceptive system
What is the nociceptive system?
Somatosensory system
What is the prevalence of pain in Europe?
- 19% of the European population
What are the most common places where people experience chronic pain?
- Back
- Lower back
- Knee
- Head
- Leg
- Joints
- Shoulder
- Neck
- Hip
- Hand
- Upper back
What are the most common causes of pain?
- Arthritis/osteoarthritis
- Hemiated/deteriorating diacs
- Traumatic injury
- Rheumatoid arthitis
- Migraine headache
- Fracture/detoriation of spine
- Nerve damage
- Cartilage damage
- Whiplash
- Surgery
What are the phases of nociceptive pain?
- Transduction
- Conduction
- Transmission
- Perception
- Modulation
In slides:
Trauma > signal > pain
Painful event is detected by nociceptors, transmitted along nerves to the spinal cord and from there to the brain.
What are nociceptors (neurobiologically)?
- Specialized neurons which respond to intense, noxious stimuli
- Found in every tissue of the human body (skin, muscles, inner oorgans, bones)
- Polymodal (react to thermal, chemical, mechanical stimulation)
What are the stations of nociceptive signaling?
- Nociceptor
- Peripheral Nerve
- Spinal Cord
- Brain
What are the ascending pathways?
- Afferent nociceptive information enters the brain from the spinal cord.
- Afferent spinal pathways include the spino-thalamic, and the spino-amygdaloid pathways.
- Nociceptive information from the thalamus is projected to the insula, anterior cingulate cortex (ACC), primary somatosensory cortex (S1) and secondary somatosensory cortex (S2).
- Nociceptive information from the amygdala (AMY) is projected via the Prefrontal Cortex (PFC), and from there to the basal ganglia (BG).
What is the lateral pain system?
Lateral nuclei of the thalamus, S1, S2 > sensory/discriminatory component of pain
What is the medial pain system?
Medial nuclei of the thalamus, (anterior) cingulate cortex (ACC), prefrontal cortex (PFC) > affective-motivational pain component
What does the insula do?
Integrates sensory and affective pain components, crucial for the representation of body (integrity)
What is the pain-matrix?
- Lateral pain system
- Medial pain system
- Insula
What is the descending pain modulatory system?
The ascending pain signals can be modulatted (i.e. enhanced or inhibited) via descending pathways:
- Descending input from the anterior cingulate cortex (ACC) to the prefrontal cortex (PFC) and ten to the periaqueductal gray (PAG)
- Descending input from the insula via the amygdala to the PAG
- Descending pathway from the PAG through the rostroventral medulla (RVM) to the dorsal horn of the spinal cord influences nociceptive afferent transmission
What are experimental pain paradigms?
- Electrical stimulation
- Thermal stimulation (e.g. thermode laser, cold pressor test)
- Mechenical stimulation (e.g., pressure pain)
- Chemical stimulation: capsaicin, NaCl-injection
- Ischemic stimulation: arresting blood flow with a tourniquet
