Lecture #14 Flashcards
what are the two main parts of the sensory system?
thalamus and the somatosensory cortex
what is the somatosensory cortex responsible for?
the elaboration of the sensory inputs
describe pseudopolar unipolar neurons:
ex: in the finger there are the terminal regions of these cells whereas the cell bodies are in the dorsal route ganglia which are flanking the spinal cord → cytoplasmic bundles are directly connected to the axons allowing the electrical signal arising from the periphery to travel to the spinal cord
what is one way you can activate some areas of the thalamus allowing the brain to discriminate the position of incoming stimuli?
some of the long axons cross the midline and some of them cannot
what type of signal is created by mechanoreceptors?
located in the periphery and enter in contact with the stimulations - an analogical signal is transformed into an electrical signal formed by trains of action potentials
the signal then traces to pseudo-polar cells up to the dorsal nuclei of the spinal cord and to the thalamus
what is the second relias important in?
contacts the somatosensory cortex and is involved in the elaboration of information
helps to build a representation of the external environment
which of the two original philosophical theories about how the brain creates images is probably more correct?
Kant - the brain has an innate ability to elaborate images
how to mechanoreceptors in the skin work?
specialized cells under the skin that can sense a variation in pressure and transform this input in trains of action potentials that propagate it to the dorsal root ganglia
what do the specific mechanoreceptors in muscles, tendons, and joints sense?
proprioreception: to understand the position of a limb or allow you to move it in a specific way
why are the cells n charge of perception called pseudo polar?
they are directly connected to a structure very similar to an axon → signals travel directly from the periphery to the spinal cord
according to Webb, what does the difference between two stimuli depend on?
the intensity of the strength = there is a linear relationship
ΔS=k x S
what formula is used today for the difference in two stimuli?
I=k x (S-S(0))^n
n depends on the sensory pathway involved (pressure = 1 for example)
what is the sensory threshold?
under a certain intensity, a subject cannot sense a sound - if this threshold starts to drift to the right then there is an issue with the hearing system
what is reaction time elicited by?
strong stimuli that are shorter than the ones elicited by weak stimuli
describe a parallel analysis:
try to find a blue cross among red crosses → if you increase the number of items in a picture or if you reduce the number of items you need to look for, the reaction time does not change because in this case the brain is doing a parallel search