Somatosenses Flashcards
cutaneous sensory info
different types of sense receptors, no need to know names of types of receptors Segregated sensory systems to the brain: - pressure - vibration - temperature - pain
kinesthesia sensory info
(actually in joints)
- position of limbs
- strength of movement
- direction of movement
touch
Touch is combination of vibration, pressure, and kinesthesia
First somatosensory pathway
Axons from receptors enter the spinal cord through the dorsal root of spinal nerves
- some cross immediately, some cross closer to brain, but all somatosensory info is contralaterally mediated
- to thalamus
- to primary sensory cortex
Second somatosensory pathway
2. Fine touch and kinesthesia ascend in dorsal columns of spinal cord, ipsilateral side > nuclei in medulla, cross to other side > ventral posterior nucleus in thalamus > primary somatosensory cortex > association somatosensory cortex
Third somatosensory pathway
- Pain and temperature, sensory input for reflexes
Synapse and cross immediately after entering spinal cord
> ascend in spinothalamic tract of spinal cord
> ventral posterior thalamus
> primary somatosensory cortex
> association somatosensory cortex
primary somatosensory cortex
post-central gyrus
somatotopically organized
Modules are arranged in columns
- each column responds to a different sub-modality of somato input from a certain area of the body
3 perceptual / behavioral effects of pain
- Sensory component (primary somatosensory cortex and assoc area)
- Immediate emotional response (ACC)
- Long-term emotional consequences of chronic pain (PFC)
These three mediated/processed by different brain mechanisms
Pain is conveyed over separate neural pathways, projects to areas of the brain others do not
Sensory aspect of pain
- mediated in primary and secondary somatosensory cortex
location of immediate emotional response to pain
(in particular aversiveness)
- mediated in the anterior cingulate cortex (ACC)
- ACC activated when s’s just heard words denoting pain, also when women saw partners experience pain
- ACC activation can be lowered with hypnosis, then pain is still felt but less aversion/unpleasantness
neural circuits in brain that produce analgesia
- periaqueductal gray receives input from frontal lobes, amygdala, and hypothalamus allowing for learning and emotions to affect responsiveness to pain
- medulla, too
- most release endogenous opioids
- electrical stim of the PAG or medulla produces analgesia (stimulator implants)
acupuncture and pain
produces endogenous opioid response that is blocked by naloxone
hypnosis and pain
- ACC activation can be lowered with hypnosis, then pain is still felt but less aversion/unpleasantness
- nalaxone does not block analgesia produced by hypnosis
- hypnosis produces analgesia in ACC rather than periaqueductal gray (PAG)
placebo effects
- Analgesia can be induced by placebo
- increases opioid activity in several areas of brain: dlPFC, ACC, insula, nucleus accumbens
- Placebo analgesia can be blocked by naloxone so effect occurs at periaqueductal gray
fMRI feedback / pain
with fMRI feedback, subjects can decrease activity in their ACC which raises their pain tolerance
