Pain Receptor 1 Lecture 1 | The University Of Western Ontario

University:
The University Of Western Ontario
Course:
Pathology 3500B | Human Pathology
Academic year:

2023
Views:

329

Pages:

4
Author:

Kyuwon J.

● Nociceptors ○ Sensory receptors are used for detecting signals ■ Damaged + potentially damaged stimuli ■ Triggers a sense of pain ○ Free nerve endings ■ No specialized structures in the body ■ Skin, joints, muscles A) Free nerve ending ● Bare nerve endings in sensory neurons ● In skin, cornea, mucosa + connective tissues ● Pain detection ● Temperature changes ● Aδ fibers ○ Sharp + fast pains ● C fibers ○ Dull slow pain ● The peripheral process will detect the stimulus ○ Cell body of dorsal root ganglion ○ The central process then goes to the dorsal horn B) Encapsulated Nerve ending ● Connective tissues capsular ● Modifies nerve response ● touch, pressure, vibration ● Aδ fibers ● Different from Free nerve endings in response to stimuli C) Receptor cell in Synapse to Sensory Neurons ● Separate sensory cells ○ Detection of stimulus ● Releases neurotransmitter in sensory neuron ○ Peripheral process ● Simulus is activated in the receptor cell ○ The receptor cell gets depolarized ■ Transmitter binds on sensory neurons = generation of action potentials ● C is separate receptor cell compared to A, and B ○ Passes signals to neurons D) Unipolar Sensory Neurons ● Peripheral process is extended in receptor sites ● Central process enters through CNS ● Cell body is seen in the dorsal root ● General organization on somatic sensory ● Allow action potential to go directly to central process ○ Does not pass cell body ○ Used for pain signalling Pathway ● Peripheral activation ○ Mechanical thermal, chemical damage => activation of nociceptors ■ Skin, muscles ,joints ○ Nociceptors => noxious stimulus to electrical signals ■ Potential generations ■ Aδ fibers ● Myelinated fast pain response ■ C fibers ● Unmyelinated, slow dull pain response ○ Action potential travels through primary afferents to DRG ■ Cell body resides in DRG ■ Central process in neuron => dorsal root => dorsal horn (spinal cord) ○ Synapse with second order neurons ■ Laminae 1,2,5 of dorsal horn ● Cross Over ○ Second oder neurons axon crosses ■ Contralateral sides = anterior white commissure ■ Pain in one side processed in the opposite side of the brain (opposite hemisphere) Decussation Pain fibers cross to the opposite side of the spinal cord early in the pathway Spinothalamic tract Carries pain and temperature signals upward to the brain Thalamus Acts as a central sensory relay station Somatosensory Cortex Enables conscious perception and localization of pain Insular Cortex & ACC Adds emotional and subjective dimensions to the pain experience ● Ascending pathway ○ Second order neurons ascends in anterolateral system ■ Lateral spinothalamic tract ● Pain + temperature ■ Anterior spinothalamic tract ● Touch + pressure