Somatosensation-Touch Flashcards
where does somatic sensation originate from?
the activity of afferent nerve fibres whose peripheral processes ramify within the skin
where do cell bodies of afferent fibres reside?
in the dorsal root ganglia
where do the dorsal root ganglia lie?
alongside the spinal cord and brain stem in the PNS
what is sensory transduction?
the process of converting the energy of a stimulus into an electrical signal so our brain can understand it
what is the AP firing rate proportional to?
the magnitude of the stimulus
what are the 2 types of afferent nerves?
free nerve endings (pain)
encapsulated endings (non painful sensation)
what are encapsulated endings surrounded by?
specialized receptor cells-> mechanoreceptors
what are discriminative (fine touch) mechanoreceptors?
Meissners corpuscles
Pacinians corpuscles
Ruffini organs
Merkel disks
what are free nerve endings for?
crude touch, temp, pain
what are common properties of mechanoreceptors?
1:transduction (if there is an adequate stimulus -> depolarization occurs)
2:no spontaneous activity (APs only produced when adequate stimulus is present)
what are the distinct functional properties of mechanoreceptors?
1: axon diameter
2:receptive field size
3:temporal dynamics of response
4:quality of somatic stimulation
what does axon diameter determine?
conduction speed
what is the receptive field size?
the area of skin surface over which stimulation results in a significant rate of action potentials
what is the functional property of the receptive field size?
it allows your brain to determine the location of the stimulus
does every sensory neuron have a receptive field?
yes. its the region of the skin that influences that neuron
what does size of the receptive field depend on?
how widespread the branching of its terminals are
what is the con of a large receptive field?
can’t give accurate information about where the stimulus is within this field
what is the pro of a small receptive field?
more precise information about location of stimulus
what is spatial acuity?
ability to distinguish different points on the skin
what is spatial acuity dependent on?
innervation density (how many receptors in an area)
receptive field size of the receptor
what is temporal dynamics of response?
some afferents fire rapidly; others generate sustained charge
are Merkel disks and Ruffini organs slow or rapidly adapting?
slow (static)
are meissner and pacinian corpuscles slow or rapidly adapting?
rapidly (dynamic)
what is quality of somatic stimulation?
respond to mechanical change vs temperature change
using the braille example, what does the merkel,meissner, pacinian, and Ruffini mechanoreceptors detect?
Merkel- details
meissner- coarser representation
pacinian and Ruffini- no detail but rather tracking of finger movement and position
which direction is the post central gyrus organized?
medial to lateral
what is the amount of brain devoted to a body part related to?
tactile acuity
