Pain and Nocioception Flashcards
What is pain?
Pain is an unpleasant sensory experience which may be associated with tissue damage
What is nociception?
Detecting and stimulation by noxious stimuli which cause tissue damage
What are the benefits of pain?
Avoid infection and harm, reduces our mobility to enable healing and be aware of our surroundings.
What is somatic pain?
Divided into superficial and deep pain.
What is superficial pain?
Pain in the skin which is highly localised.
What is deep pain?
Pain in the muscles, connective tissues, tendons or bones that is achy or sharp and localised.
What is visceral pain?
Pain in the organs which is poorly localised and vague.
What is acute pain?
Short term pain with an identifiable onset associated with pain and its function is to limit function as a warning for healing. It is associated with child birth and sports injuries.
What is chronic pain?
Pain with a duration over 3 months which is unpredictable and inconsistent severity even with treatment. There is no biological function and rest does not releive pain. This is associated with visceral pain, cancer pain and migraine.
How does nociception occur?
Detected by nociception down the primary afferent fibres to the odrsal root ganglion of the spinal cord to be transmitted via the dorsal horn to the brain.
What are nocioceptors?
Unspecialised nerve endings in the skin and tissues which respond to noxious stimuli. They are characterised by their axons and their receptor channels.
What are the types of nociceptors?
Mechanical, chemical, thermal, polymodal and silent nocioceptors
What is the mechanical nociceptor?
Responds to painful mechanical pressure on via the a-delta fibres.
What is the thermal nociceptor?
Transmits information about painful extreme temperature to the brain via the a-delta or c-fibres
What are the chemical nociceptors?
Transmits information about chemicals like irritants and food to the brain via the c fibres
What are polymodal nociceptors?
Detect thermal, mechanical and chemical noxious stimuli to the brain and have only c-fibres
What are sleeping/silent nociceptors?
Respond to inflammation following injury via c-fibres
How are nocicpetors characterised?
Based on their axon properties and receptor channels
What are the primary afferent fibres?
Axons/unspecialised nerve endings which respond to stimuli and classified by their diameter; a-alpha, a-beta, a-delta and c fibres
What are the A-alpha and A-beta fibres?
A-alpha has the largest diameter and highest conductivity and velocity and responds to propioception of skeletal muscle.
What are the A-beta fibres?
A-beta fibres have a large diameter with a fast conductivity to respond to non-painful mechanoreceptors in the skin
What are the Alpha-gamma and C fibres?
Alpha-gamma and C-fibres are afferent fibres of axons with a smallest diameter and a slow conductvity for nociception.
What are the a-delta fibres?
Axons/ unspecialised nerve endings with slow conductivity to respond to pain and temperature present in thermal nociceptors.
What are the C-fibres?
Axons/unspecialised nerve endings with the smallest diameter and slowest conductivity to respond to pain, temperature and itching. It is found in polymodal nociceptors, thermal nociceptors and silent nociceptors.
What is 1st pain?
Sharp localised pain in the skin with a fast onset and short duration driven by the a-delta fibres. Responsible for acute pain.
What is 2nd pain?
Dull/vague poorly localised pain with a slow onset and long duration driven by the c-fibres. Responsible for chronic pain.
What are first order somatosensory neurons?
Transduce information about the internal/external environment of the body to the spinal cord.
What are second order neurons?
Transduce information from the spinal cord to the thalamus
What are third order neurons?
Transduce information from the thalamus to the primary sensory cortex.
What are the Na+ channel nociceptors?
Na1.1, Na1.6, Na1.7, Na1.8