sensory physiology- general principals Flashcards
what are the types of sensory receptors?
Mechanoreceptors
Thermoreceptors
Photoreceptors
Chemoreceptors
Nociceptors
Physical (direct) transduction:
Interaction of stimulus with membrane protein opens ion channel
examples of direct/physical transduction
somatosensory, vestibular, auditory, taste
Molecular transduction:
molecular interaction of stimulus with membrane protein
e.g. G-protein
examples of molecular transduction
vision, taste, olfaction
what are the steps that occur during “direct” transduction in the taste system?
- Na+ enters through “ENaCs”
(epithelial Na+ channels) - Action potentials lead to Ca++ entry
- Release of ATP as neurotransmitter
what taste utilizes molecular transduction?
sweet, amino acids, bitter
what are the steps involved in molecular (g-protein coupled) transduction of taste?
(give the example for “sweet” tastes)
1.Sugars bind to receptor coupled to G-protein
- Release of intracellular Ca++ activates TRPm5 channel
(Transient Receptor Potential) - Depolarization leads to action potentials &
release of neurotransmitter ATP
which molecule is the “key” in the pathway for sensing sweetness?
TRPm5 channel
transient receptor potential channel
TRP channels are Cation ion channel that can pass _______ with a large variety of activating mechanisms
calcium ions
Ca2+
what are some examples of activating mechanisms for TRP channels?
Intracellular Ca++ temperature chemicals sound light pH and osmolarity mechanical
how can the nervous system code for the intensity of a stimulus?
A) increase stimulus intensity
B) increase receptor potential
C) increase the number of action potentials
T/F: the threshold value is a known, quantifiable number for a neuron
False- it is not a precise value, its a statistical concept
defined as the stimulus intensity detected on 50% of trials
the ________ Can be affected by psychological, neurological, or pharmacological factors
threshold
what are the common stimulus attributes coded by sensory systems?
A) Modality & quality (what?)
B) intensity (how much?)
C) location (where?)
D) duration (when?)
the _________ is what a receptor (or neuron) is sensitive to
receptive field
T/F: in a single neuron, location and intensity can be confounded (confused)
true
how does our body prevent the confounding of location and intensity?
Across neuron coding
use multiple neurons to identify location
how is olfactory quality determined?
Comparing activity across olfactory fibers
what is lateral inhibition?
the capacity of an excited neuron to reduce the activity of its neighbors
-vital for determining the location of a stimulus
what type of inhibition occurs when a hyperpolarized axon terminal leads to less Ca++ entry and less neurotransmitter release
Presynaptic inhibition
what occurs during postsynaptic inhibition?
EPSPs and IPSPs interact: spatial & temporal summation
describe the sensory pathway for the auditory system:
start at the hair cell
- Hair cells (receptor cells) in cochlea (inner ear)
- Innervation by CN VIII nerve
- CN VIII nerve synapses in cochlear nuclei
- Ascending sensory pathway to cortex
- Efferent pathway from superior olivary nuclei
T/F: Superior olivary nucleus has descending
Pathway to auditory receptor cell
true
