NSC Touch and Pain

exam 2

Graded potentials (EPSP)

Receptor cells

Intensity of a stimulus

Coding

Single neurons

Same cell fires at different rate. The faster the rate the more intense.

Multiple neurons

Brain counts number of neurons firing. The more neurons the more intense.

Different neurons

certain neurons respond to certain intensities (specialists)

Detects touch and pain

Somatosensory system

Touch systems

4 : pain and touch (outer) Vibration and stretch (deep in skin)

Touch receptors

5 : Free nerve endings (pain), meissner’s corpuscle and Merkel’s disc (touch), Pacinian corpuscle (vibration), Ruffini’s ending (stretch)

Cold and heat receptors

CMR1 and TRPV1/ TRPV 2

spice receptor

TRPV1

activates C fibers via TRVP 1, neurotoxic, lowers BP fights diabetes and lowers weight

Capsaicin

slow, small and unmyelinated (aching pain)

C fibers

fast, large and myelinated (sharp pain)

A delta fibers

goes on forever as long as touched (no decline in number of APs)

Tonic receptors

Short lived attention getting mechanism, decreases in frequency

Phasic receptors

Part of the world every single sensory neuron responds to

Receptive field

Differs in size and shape, smaller = more neurons = more precise

Receptive field

spine —> thalamus —> sensory cortex for touch processing

Spinothalamic system

touch/ vibration processing

Dorsal column

Pain/ temperature processing

Spinothalamic system

map of where each body part is processed in the brain (hands have the most space). reorganizes after amputation

Homunculus

Pain pathway

Spinal cord processing → pain processing → motor response mechanism

Cognitive pain perception system

learned behavior (men don’t cry), frontal cortex

Motivational pain perception

emotion linked, anterior cingulate cortex

how is the ACC activated

as someone touches something hot, somatosensory cortex turns on, when heat becomes painful ACC is turned on and increases in activity.

Sensory pain perception

Pain analysis, somatosensory cortex

Pain pathway in terms of chemicals

free nerve endings recognize chemicals in the blood stream (serotonin and prostaglandins) which triggers an EPSP and the release of substance P

pain neurotransmitter

Substance P

Proprioception tells you where your muscles. Patient loses ability to move his muscles when he closes his eyes or whenever the lights are off.

Lost proprioception

inherited loss off function in Na+ channels leading to loss of feeling

Congenital insensitivity

Man on fire syndrome (too sensitive)

Congenital hypersensitivity

continues and grows, high in younger women, remodels spinal cord and overactive somatosensory cortex. Substance P uptake remodels cell and GABA inhibitory becomes excitatory

Chronic pain.

histamine release, pain migrates and swelling. somatosensory cortex inappropriately activates sympathetic nervous system

RSD

hypersensitivity to touch (stimulus avoiders and seekers)

SID

wrong brain connections. Stimulus in one modality leads to a sensation in another

Synesthesis

too many connections

Psychedelic hyper connectivity

brain fires differently, goes away over time. Limb is not present but pain is still felt

Phantom limb pain