Lecture 41: Pain Flashcards
Pain is?
an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
4 components of pain?
Sensory - where the pain is actually felt and how it’s felt
Affective - mood and emotion
Autonomic - inc. HR, RR, BP sweat
Motor - withdrawal, immobilisation, vocalisation
Physiological response to pain?
- Increased HR, BP and RR
- increased blood sugar
- Decreased gastric mobility and BF to vsicera, kidney and skin
- pallor
- nausea
- Dilated pupils
- Diaphoresis (excessive sweating)
Pain thershold?
The point at which a stimulus is percieved as pain
affected by: personality, stress, anxiety, culture, exercise, previous experience, behavior, culture, mood, emotion etc.
Pain Tolerance?
Duration or intensity of pain that an individual will tolerate before initiation of overt pain response
Increased tolerance: Alcohol, medication, hypnosis, warmth, distractions, strong beliefs or faith
Decreased tolerance: Repeated exposure to pain, fatigue, anger, boredom, apprehnesion, sleep deprivation
Age variability with perception of pain?
Newborns: less sensitive to pain (or they lack the ability to verbalise it)
Children: lower pain thershld than adults
Adults: Pain threshold tends to increase with age (probably from peripheral neuropathies and increased thickness of the skin)
Analgesia, anaesthesia, hyperalgesia, allodynia paresthesia, causalgia, central pain?
Analgesia : Absence of pain in tresponse to normal painful stimulus
Anaesthesia: absence of ALL sensory modalities
Hyperalgesia: increased respose to a stimulus normally painful
Allodynia: pain due to stimulus normally NOT painful
Parasthesia: abnormal sensation of burning, numbness, tingling, itching
Causalgia: A syndrome of sustained burning pain and allodynia (after a traumatic nerve lesion)
Central pain: pain associated with a lesion of the CNS
Nociception, nociceptors and noxious stimulus?
Nociception:
- the sensory process of detecting tissue damage
Nociceptors:
- Free nerve endings
- Distributed throughout the body
- stimulated by noxious mechanical, thermal or chemical stimuli
Nocious Stimulus:
- one that is due to an event potentially or actually damaging to body tissue
Two types of primary afferents?
C Fibres:
- most nemerous (4:1)
- smaller diameter
- unmyelinated - slow conduction (0.5-2 m/s)
A-delta Fibres:
- medium diameter
- myelinated - fast conduction (4-30 m/s)
Primary Receptors and pain quality?
C fibres:
- Polymodal - respond to more than one type of noxious stimulus (mechanical, thermal and chemical)
- diffuse, dull, burning, ‘slow’ or secondary pain
A-delta fibres:
- Respond to noxious mechano-thermal stimuli over a certain intensity
- Well-localised, sharp, stinging, ‘fast’ or first pain
Transduction?
Sensory cells convert external painful stimuli >>> electrical signals (AP)
2nd Order neurons in DH?
- Nocioceptive specific (NS) - (rexed lamina I and II)
- activated ONLY by noxious stimuli
- A delta and C fibres
- Wide dynamic range (WDR)- (rexed lamina V)
- Activated by both noxious and innocuous
- cutaneous and/or visceral stimuli
- A delta, C and A beta fibres)
Where does perception of pain occur?
- The reticular system- Autonomic and motor response to pain
- The limbic system- Emotional and behavioral response
- Somatosensory cortex- Perception and interpretation of sensations
Pain dampening?
Down regulation of pain by:
- Segmental inhibition
- Descending inhibitory nerve system
Gate control theory? Three input variables?
Is based on the premise that a gate, located in the dorsal horn of the spinal cord, modulates the afferent nerve impulses
Implies that a non-painful stimulus can block the transmission of a noxious stimulus.
- A delta and C fibres open the gate
- A beta fibres carrying messages of light touch- close the gate
- Messages from the brain - open or close the gate