sensory receptors Flashcards
- Understand that mutations in genes that encode for proteins involved in phototransduction often lead to retinitis pigmentosa (Box B of Chapter 10 in Purves).
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Describe morphological features of sensory receptor
1) a receptive region, which may display a
morphological specialization associated with the absorption of a specific kind of physical energy; 2)Near the receptive region there is a region identifiable morphologically by being rich in mitochondria, presumably associated with the need for replacement of energy consumed in the transduction process. 3) soma. 4) axon. 5) a synaptic region, specialized to transmit information to the next cell in line. 1) a receptive region, which may display a
morphological specialization associated with the absorption of a specific kind of physical energy; 2)Near the receptive region there is a region identifiable morphologically by being rich in mitochondria, presumably associated with the need for replacement of energy consumed in the transduction process. 3) soma. 4) axon. 5) a synaptic region, specialized to transmit information to the next cell in line.
What is a transduction channel
A channel that detects some sort of sensory input and transforms that info into a change in neuronal polarization. NOT voltage gated channels
receptor potential
The interaction of a stimulus(light, heat, cold) with receptor proteins localized to the receptive region of sensory receptors elicits directly or indirectly a change in the membrane potential of the sensory receptor cell.
Examples of short sensory receptor cells
Rod photoreceptor cells and auditory hair cells
cell structure of short receptor cells vs long receptor cells
Short: does not have an axon. Long: has an axon
Describe receptor potential in short sensory receptor cells
The receptor potential spreads to the synaptic end of the cell by passive electrotonic transmission. Thus the receptor potential of a short cell very effectively alters the rate of transmitter release from that cell and so
regenerative action potentials are not necessary.The receptor potential spreads to the synaptic end of the cell by passive electrotonic transmission. Thus the receptor potential of a short cell very effectively alters the rate of transmitter release from that cell and so
regenerative action potentials are not necessary.
Examples of long sensory receptors
somatosensory receptor cell, skin mechanoreceptors
Describe receptor potential in long sensory receptor cells
must employ regenerative action potentials to carry
information from the receptive ending (e.g. in skin or muscle) to the synaptic release site (e.g., in the spinal cord or brain stem) because the receptor potential itself only affects a limited portion of the cell near the receptive ending.must employ regenerative action potentials to carry
information from the receptive ending (e.g. in skin or muscle) to the synaptic release site (e.g., in the spinal cord or brain stem) because the receptor potential itself only affects a limited portion of the cell near the receptive ending.
Neurotransmitter for most sensory receptor cells
glutamate
Describe depolarizing receptor potentials
Stimulus causes increase in nonspecific cation conductance in the receptive area membrane. This conductance increase causes the membrane potential to move toward 0 mV.The cation conductance increase, and hence the depolarization, increases in a graded fashion with the intensity of the stimulus.
example of depolarizing sensory receptors
Muscle mechanoreceptors: dorsal root ganglion neurons extend sensory endings into muscle spindles. These sensory endings have mechanosensitive cation channels that open in response to stretch, depolarizing the cell
Describe hyperpolarizing receptor potentials
Sensory receptors have resting potentials btw 0mV and -70mV. Stimulus causes cation channels in receptive area to close, hyperpolarizing the cell.
example of hyperpolarizing sensory receptors
rod photoreceptor - 1. light stimulation of 1-cis-retinal bound to rhodopsin receptor in optic disc causes change of conformation to 1-trans-retinal which further changes rhodopsin to metarhodopsin which activates G protein transducin. 2. cGMP phosphodiesterase (PDE) is activated. 3. PDE hydrolyzes cGMP reducing its concentration. 4. cGMP gated- cation channels close. 5. hyperpolarization and the synaptic end does not release neurotransmitter anymore
Unique feature of photoreceptors
The photoreceptor does not fire action potentials. Rather, the hyperpolarization is transmitted to the synaptic end by electrotonic transmission