Nociception and Pain
• Pain → an unpleasant sensory and emotional experience associated with actual or potential tissue damage
described in terms of such damage
• 2 aspects of pain
o Sensory → where on/in the body have tissues been damaged
o Affective → how pain makes you feel
• Types of pain
o Inflammatory pain
▪ Arthritis, pancreatitis, burn
▪ Pathological events/tissue damage releases chemical mediators which sensitise either nerves in
the tissue or within the CNS
o Neuropathic pain
▪ Damage to/complete transection of a nerves gives rise to aberrant activity in the nerve itself or
in the parts of the spinal cord innervated by it. Abnormal activity leads to pain that is
uncontrollable
• How do we feel pain?
o Elements of the ‘pain pathway’
▪ Peripheral nociceptors
▪ Primary afferent neurones
▪ Intrinsic spinal dorsal horn neurones
▪ Ascending projection neurones
▪ Higher centre neurones
▪ Descending neurones
o Nociceptors
▪ Detect mechanical, thermal, chemical insult to tissue
▪ Examples; TRPV1 channel, ASIC channels, His receptors, bradykinin receptors
▪ Non-selective channel, associated with increase cellular activity
▪ Endogenous activators of channel include low pH, endocannabinoids
▪ Activator of TRPV1 is capsaicin which is found in Capsicum
o Peripheral nerves
▪ Transmission of info about tissue damage to the CNS
• 3 types
o A- large, myelinated, touch, innocuous info
o A - small, myelinated, pain
o C-fibers – small, unmyelinated, pain
o Spinal cord → innervation of dorsal horn
▪ Peripheral nerves have their cell bodies in the dorsal root ganglion, adjacent to and outside the
spinal cord
▪ Sensory neurones innervate target tissue and dorsal horn of spinal cord entering via dorsal root
▪ Different types of sensory neurone terminate in different parts of dorsal horn
▪ Pain processing requires formation of synapses between nociceptors and second order
neurones in spinal dorsal horn laminae I and II
o Ascending tract → get info to the brain
• Pain → an unpleasant sensory and emotional experience associated with actual or potential tissue damage
described in terms of such damage
• 2 aspects of pain
o Sensory → where on/in the body have tissues been damaged
o Affective → how pain makes you feel
• Types of pain
o Inflammatory pain
▪ Arthritis, pancreatitis, burn
▪ Pathological events/tissue damage releases chemical mediators which sensitise either nerves in
the tissue or within the CNS
o Neuropathic pain
▪ Damage to/complete transection of a nerves gives rise to aberrant activity in the nerve itself or
in the parts of the spinal cord innervated by it. Abnormal activity leads to pain that is
uncontrollable
• How do we feel pain?
o Elements of the ‘pain pathway’
▪ Peripheral nociceptors
▪ Primary afferent neurones
▪ Intrinsic spinal dorsal horn neurones
▪ Ascending projection neurones
▪ Higher centre neurones
▪ Descending neurones
o Nociceptors
▪ Detect mechanical, thermal, chemical insult to tissue
▪ Examples; TRPV1 channel, ASIC channels, His receptors, bradykinin receptors
▪ Non-selective channel, associated with increase cellular activity
▪ Endogenous activators of channel include low pH, endocannabinoids
▪ Activator of TRPV1 is capsaicin which is found in Capsicum
o Peripheral nerves
▪ Transmission of info about tissue damage to the CNS
• 3 types
o A- large, myelinated, touch, innocuous info
o A - small, myelinated, pain
o C-fibers – small, unmyelinated, pain
o Spinal cord → innervation of dorsal horn
▪ Peripheral nerves have their cell bodies in the dorsal root ganglion, adjacent to and outside the
spinal cord
▪ Sensory neurones innervate target tissue and dorsal horn of spinal cord entering via dorsal root
▪ Different types of sensory neurone terminate in different parts of dorsal horn
▪ Pain processing requires formation of synapses between nociceptors and second order
neurones in spinal dorsal horn laminae I and II
o Ascending tract → get info to the brain
