injury and pain perception

types of sensory receptors

mechanoreceptors, chemoreceptors, thermoreceptors, photoreceptors, nociceptors

mechanoreceptors

sensitive to compression, bending, stretching of cells

stimulated by mechanical deformation of cell membrane

types of cutaneous receptors

- pacinian corpuscles: vibration
- meissner's corpuscles: light touch
- merkel's discs: heavy pressure
- ruffini endings: stretch

location of mechanoreceptors

mostly in skin; also in muscles, tendons, joints, blood vessels, hair follicles

chemoreceptors

sensitive to smell, taste, O2, CO2, pH

assist in regulating HR and breathing in cardiovascular system

photoreceptors

sensitive to light

rods in the retina of eye

responsible for vision in low light environments and achromatic vision (seeing shapes)

cones in the retina of the eye

responsible for vision in high light environments and color vision

thermoreceptors

respond to temperature changes

______ is where information for warm stimuli travel on.

unmyelinated C - fibers

______ is where information for cold stimuli travel on.

thinly myelinated A-sigma fibers and C-fibers

nociceptors

respond to extreme mechanical, chemical, or thermal stimuli (pain)

what do injured tissues release to stimulate pain fibers?

chemicals --> bradykinin, histamine, prostaglandin

types of ascending sensory pathway tracts

spinocerebellar tract, spinothalamic tract (anterolateral), dorsal column-medial lemniscus (DCML)

spinocerebellar tract

unconscious proprioception (resting muscle tension/stretch)

spinothalamic tract (anterolateral)

pain, temperature, crude touch, pressure

dorsal column-medial lemniscus (DCML)

fine touch, vibration, two-point discrimination, conscious proprioception (raising arm when eyes closed)

ascending pain pathway

multiple processing centers at level of brain to help us determine our reaction after

types of nociceptive pain

fast pain and slow pain

nociceptive fast pain

travels on myelinated A-sigma fibers at 30m/sec

sharp, localized, stabbing

pain perceived with injury

nociceptive slow pain

travels on unmyelinated C-fibers at 2m/sec

longer lasting, dull, diffuse feeling

burning

referred pain

perception of pain on familiar cutaneous areas in response to painful stimuli applied to unfamiliar viscera

always a structure innervated at the same spinal cord level

how long does acute pain last?

lasting > 3 months (less than 3 months)

what can cause acute pain?

a noxious stimulus or illness

how would you describe acute pain?

brief, localized
typically subsides after injury/illness subsides

how long does chronic pain last?

lasting longer than 3-6 months

what can cause chronic pain?

long standing pain

lower intensity pain

pain not from stimulus, but from tissue

what can chronic pain do?

long standing pain can create changes in the brain

neuropathic pain

damage traced to peripheral nerves or to parts of the CNS (spinal cord and brain)

long standing pain can create change within the brain (central sensitization)

what do you feel when experiencing neuropathic pain?

shooting, stabbing, burning

symptoms of neuropathic pain

hyperalgesia, allodynia

hyperalgesia

increased pain from stimulus that normally provokes pain

decreased nociceptive threshold, pain spreads to neighboring, non-injured areas (increased pain sensitivity)

allodynia

pain from stimulus that does not normally provoke pain

body's natural ways of reducing pain is through …

endogenous opioids (enkephalins, dynorphins, endorphin)

opiate receptors location

both sides of synapse between nociceptive neurons and dorsal horn interneurons in spinal cord

opiates function at the spinal cord level

decrease number of neurotransmitters released by nociceptors

blocks perception of pain

descending pain pathways from brain

control neuron release of serotonin onto dorsal horn interneurons, which release enkephalin, inhibiting transmission of pain from periphery to brain

gate control theory of pain: spinal gating

spinal cord acts as the gate that allows pain to travel to brain (specifically at dorsal horn)

pain

the physical feeling caused by disease, injury or something that hurts the body

mental or emotional suffering

someone or something that causes trouble or makes you feel annoyed or angry

influences of pain perception

beliefs, knowledge, social context, life events, stress, threat

neuroplasticity

changes in neural pathways and synapses due to changes in behavior, environment, neural processes, and from bodily injury

changes in brain structure are based on learning