Somatosensory Flashcards
Somatosensory system
-Used by the brain to understand the bodys sensations and movements
Somatosensory senses
- Discriminitive touch
- Deep touch
- Itch and tickle
- Pain
- Cold and warmth
- Position and movement
Cutaneous senses
-External (exogenous) touch, pain, temperature
Organic senses
-Internal (endogenous) stimuli from internal organs etc.
Cutaneous receptors
-Nerve endings (afferent neurones)
Movement of sensory information
-Information from the PNS is sent to the CNS via the spinal nerves in the body then the cranial nerves in the head to be processed in the somatosensory cortex
Detecting tactile stimuli
- Large amounts of pressure or vibration causes dendrites to signal reeptors to open ion channels allowing an action potential to be fired along the axon to the dorsal root or cranial nerve ganglia
Pathways from receptors to the left hemisphere
- Dorsal column L - precise movement and fine touch
- Spinothalamic R - pain/temperature
- to medulla to midbrain to somatosensory
Somatosensory representation changes with practice
-Violinist: Right somatosensory cortex (SSC) for four fingers of left hand enlarged
Tactile agnosie
-Damage to somatosensory association cortex causes inability to recognise objects by touch (E.C. though pinecone was bruch etc.)
Pain receptors (Noiceptors)
- Free nerve ending receptors (pain sensitisation)
- High threshold receptors (intense pressures)
- TRPV1 receptors (extreme heat, acid and capsaicin)
- Receptors sensitive to inflammation from chemicals
Pain axons
- Little - no myelin transmits dull pain relatively slow (0.5-30m/s) vs motor response (35-120m/s)
- Thinly myelinated axon conveys sharp pain quickly
Pain neurotrsnsmitters
- Released into spinal cord
- Glutamate: mild pain
- Substance P and glutamate: stronger pain
Lack of substacnce P in mice
-React to severe injury as if it was a mild injury
Emotional pain fMRI
-FMRi found that activity is seen in the somatosensory cortex when participant is given an electric shock. When a loved one receives, and electric shock activity is seen in the cingulate cortex (Empathy)
Emotional pain hypnosis
-Half of participants were hypnotized; those hypnotizes were told they would put their hand in an ice bucket, and they wouldn’t feel anything. The hypnotized group showed less intensity in the cingulate cortex than the non-hypnotized group.
Emotional pain as a basic need
-Infants feel emotional pain when separated from their caregiver, and caregivers experience emotional pain to drive them to care for infants, suggesting this pain is evolutionary necessary and the first basic need.
Relieving emotional pain
-Paracetamol and Tylenol can relieve physical and emotional pain
Dangers of insensitivity to pain
-People with a gene that inactivates pain axons suffer repeated injuries
Endogenous vs exogenous
- Naturally occurring
- From outside the body
Opiods and endorphins
- Opioids bind to the receptors in peri-aqueductal gray area of the midbrain to block release of substance P to mute the messages after pain is alerted
- Endorphins (bodies opiate) released during sex which can decrease pain
Gate control of pain
-Spinal cord receives messages from pain receptors and touch receptors e.g. rubbing stubbed toe closes gate for pain
Placebo
-Placebo drugs work on emotional pain by releasing endogenous opiates
Capsaicin
-Releases substance P faster than it can be resynthesized inhibiting pain messages or damaging pain receptors (pain relief)
