Lecture 13 Flashcards
Sensation
collecting data about what is going on in the external world
perception
is about making sense of the data/sensations
how many senses are there
vision- color, motion, shape
touch- pain, temperature, pressure
small- pheromones
taste
sensory transduction
receptor cells convert (transduce) energy/ information from the external environment into a code the brain can understand (action potentials)
how do you code continuous stimulus intensity using only all or none action potentials
rate code- high firing rate is large strong stimulus, low firing rate is small weak stimulus
range fractionation
using a different neuron for different intensities
low threshold neuron, medium threshold neuron (and low), high threshold neuron (and low and medium)
labeled lines
an action potential coming in on a particular axon means a specific sensation
specific kinds of info enter the brain via specific nerve pathways (visual info via optic nerve)
temporal pattern codes
some stimuli can be identified by the pattern of firing, by a given neuron, or across many neurons
principles for touch
reception
transduction
transmission, analysis, integration
pain receptors, touch, vibration, stretch
skin receptors
free nerve endings (pain, temp) merkels disc meissners corpuscle hair follicle receptor (touch) pacinian corpuscle ruffinis endings
pacinian corpuscle
detect vibration and pressure
large, vague borders, fast adapting (only respond to start and stop stimuli)
nerve embedded in onion layers
outside axon is myelinated
how pacinian corpuscle sends info
- stretching axon results in opening sodium channels to come in
- goes along axon to ganglion dorsal root where cell bodies are into dorsal side of spinal cord up into brain
- if potential is large enough AP is generated, only feel vibration if action potential is generated
meissner’s corpuscle
small sharp borders, fast adapting, deep touch
merkels disc
small, sharp borders, slow adapting (continues to monitor persistent continuous stimuli) deep touch
ruffini’s ending
large vague borders, slow adapting, stretch
when is slow adapting useful and when is fast adapting useful
slow adapting is useful for continued sensation or touch or shape
fast adapting is useful for sensing change in shape or touch (something moving for example)
sensory peripheral nerve path
spinal cord to brain stem to thalamus to primary sensory cortex areas to non primary sensory cortical areas such as hippocampus, amygdala, prefrontal cortex
sensory cranial nerve pathway
brain stem to thalamus to primary sensory cortex areas to non primary sensory cortical areas such as hippocampus, amygdala, prefrontal cortex
what is the location of the nervous system where quality of feeling is generated
somatosensory cortex
pain caused by
activation of receptors on free nerve endings
transient receptor potential (TRP) ion channels are key
TRPV1-R
activated by capsaicin and by low heat. hot peppers and hot stove signal pain in the same way
pain steps
1- damaged cells release substances that excite free nerve endings that function as nociceptors
2- action potentials generated in periphery can reflexively excite blood vessels and other cells to produce inflammation
3- information enters through dorsal root and synapses on neurons in the dorsal horn
4- pain fibers release glutamate as a transmitter and substance p (excites local cells for swelling and local blood flow) as a neuromodulator in the spinal cord
5- the dorsal horn cells then send information across the midline and up to the thalamus and substance p onto cells that make histamine for inflammatory response
perception of pain depends on
individual
current emotional and motivational state
cognitive factors
context
phantom limbs
perception of missing limb is common
stump (nerve activation) and spinal cord (cross talk)
resembles pre-amputation pain which suggest pain memories become entrenched
axon potential still in brain from axons who used to handle it
what does mirror box therapy suggest
phantom pain is associated with brain mechanisms of body image
