Sensory Receptors and Phototransduction

Flashcards covering key terms and concepts related to sensory receptors and the phototransduction pathway.

Transduction

The process by which a sensory receptor cell converts a stimulus into a change in membrane potential.

Photoreceptors

Sensory receptors in the retina that detect light; include rods and cones.

Rods

Photoreceptor cells that are highly sensitive to light and responsible for vision in low-light conditions.

Cones

Photoreceptor cells that allow for color vision and function best in bright light.

Chemoreceptors

Sensory receptor cells that respond to chemical stimuli, such as taste and smell.

Mechanoreceptors

Receptor cells that detect mechanical pressure or distortion; involved in hearing and proprioception.

Phototransduction pathway

The sequence of events in photoreceptor cells that converts light stimuli into electrical signals.

Retinal

A pigment derived from vitamin A that changes conformation when it absorbs light, crucial for vision.

Opsin

A G protein-coupled receptor that, when activated by retinal, initiates the phototransduction cascade.

cGMP

Cyclic guanosine monophosphate, a second messenger that regulates ion channels in photoreceptor cells.

Hyperpolarization

A change in membrane potential that makes the inside of the cell more negative; occurs in photoreceptors in response to light.

Glutamate release

The release of a neurotransmitter from presynaptic terminals that communicates signal changes to bipolar cells.

Dark current

The influx of sodium ions in photoreceptors in the absence of light, resulting in a relatively depolarized state.

Bipolar cells

Interneurons that connect photoreceptor cells to ganglion cells and process visual information.

Vestibular apparatus

Inner ear structures that contribute to the sense of balance and spatial orientation.

Calcium ions in phototransduction

Ions that play a crucial role in signal transduction and neurotransmitter release in photoreceptor cells.

Transduction

The process by which a sensory receptor cell converts a stimulus into a change in membrane potential.

Photoreceptors

Sensory receptors in the retina that detect light; include rods and cones.

Rods

Photoreceptor cells that are highly sensitive to light and responsible for vision in low-light conditions.

Cones

Photoreceptor cells that allow for color vision and function best in bright light.

Chemoreceptors

Sensory receptor cells that respond to chemical stimuli, such as taste and smell.

Mechanoreceptors

Receptor cells that detect mechanical pressure or distortion; involved in hearing and proprioception.

Phototransduction pathway

The sequence of events in photoreceptor cells that converts light stimuli into electrical signals.

Retinal

A pigment derived from vitamin A that changes conformation when it absorbs light, crucial for vision.

Opsin

A G protein-coupled receptor that, when activated by retinal, initiates the phototransduction cascade.

cGMP

Cyclic guanosine monophosphate, a second messenger that regulates ion channels in photoreceptor cells.

Hyperpolarization

A change in membrane potential that makes the inside of the cell more negative; occurs in photoreceptors in response to light.

Glutamate release

The release of a neurotransmitter from presynaptic terminals that communicates signal changes to bipolar cells.

Dark current

The influx of sodium ions in photoreceptors in the absence of light, resulting in a relatively depolarized state.

Bipolar cells

Interneurons that connect photoreceptor cells to ganglion cells and process visual information.

Vestibular apparatus

Inner ear structures that contribute to the sense of balance and spatial orientation.

Calcium ions in phototransduction

Ions that play a crucial role in signal transduction and neurotransmitter release in photoreceptor cells.

Mechanotransduction channel (SAC)

A stretch-activated ion channel tethered to both the extracellular matrix (ECM) and the cytoskeleton, crucial for mechanoreception.

Tether model of mechanotransduction

A mechanism where movement of the extracellular matrix relative to the cytoskeleton pulls open the tethered mechanotransduction channel (SAC), initiating a signal.

Sweet tastant (T1R2/T1R3) model

A chemoreception pathway where a sweet tastant binds to a metabotropic receptor (T1R2/T1R3), initiating a G protein cascade that leads to calcium release and membrane depolarization, signaling sweetness.

T1R2/T1R3 receptor

A specific G protein-coupled metabotropic receptor complex on taste cells that binds sweet tastants, crucial for initiating the transduction pathway for sweetness perception.

Metabotropic receptor (in taste)

A type of receptor, like T1R2/T1R3, that, when bound by a ligand (e.g., sweet tastant), activates an intracellular signaling cascade, often involving G proteins and second messengers.

Role of G protein in sweet taste

Upon sweet tastant binding to the T1R2/T1R3 receptor, the associated G protein dissociates and activates an enzyme, leading to subsequent steps in the signaling cascade.

Secondary messenger (sweet taste)

A molecule produced after enzyme activation in the sweet taste pathway; it opens calcium ion channels in the endoplasmic reticulum (ER), increasing intracellular \text{[Ca}^{2+}\text{]} .

Calcium ions in sweet taste transduction

Released from the ER in response to a secondary messenger, an increased cytoplasmic \text{[Ca}^{2+}\text{]} concentration then opens sodium ion channels, leading to membrane depolarization.

Depolarization in sweet taste

The influx of sodium ions, triggered by increased cytoplasmic \text{[Ca}^{2+}\text{]} , causes the taste cell membrane to depolarize, generating an electrical signal perceived as sweetness.

Effect of sodium channel blockage on sweet taste

Blocking sodium ion channels prevents the influx of \text{Na}^{+}\text{]} ions necessary for membrane depolarization, thereby decreasing the ability to taste sweet things.

Transduction

The process by which a sensory receptor cell converts a stimulus into a change in membrane potential.

Photoreceptors

Sensory receptors in the retina that detect light; include rods and cones.

Rods

Photoreceptor cells that are highly sensitive to light and responsible for vision in low-light conditions.

Cones

Photoreceptor cells that allow for color vision and function best in bright light.

Chemoreceptors

Sensory receptor cells that respond to chemical stimuli, such as taste and smell.

Mechanoreceptors

Receptor cells that detect mechanical pressure or distortion; involved in hearing and proprioception.

Phototransduction pathway

The sequence of events in photoreceptor cells that converts light stimuli into electrical signals.

Retinal

A pigment derived from vitamin A that exists as 11-cis-retinal in the dark and changes to all-trans-retinal upon light absorption, initiating vision.

Opsin

A G protein-coupled receptor associated with transducin, activated by the conformational change of retinal to initiate the phototransduction cascade.

cGMP

Cyclic guanosine monophosphate, a second messenger that regulates ion channels in photoreceptor cells.

Hyperpolarization

A change in membrane potential that makes the inside of the cell more negative; occurs in photoreceptors in response to light.

Glutamate release

The release of a neurotransmitter from presynaptic terminals that communicates signal changes to bipolar cells.

Dark current

The influx of sodium ions in photoreceptors in the absence of light, resulting in a relatively depolarized state.

Bipolar cells

Interneurons that connect photoreceptor cells to ganglion cells and process visual information.

Vestibular apparatus

Inner ear structures that contribute to the sense of balance and spatial orientation.

Calcium ions in phototransduction

Ions that play a crucial role in signal transduction and neurotransmitter release in photoreceptor cells.

Mechanotransduction channel (SAC)

A stretch-activated ion channel tethered to both the extracellular matrix (ECM) and the cytoskeleton, crucial for mechanoreception.

Tether model of mechanotransduction

A mechanism where movement of the extracellular matrix relative to the cytoskeleton pulls open the tethered mechanotransduction channel (SAC), initiating a signal.

Sweet tastant (T1R2/T1R3) model

A chemoreception pathway where a sweet tastant binds to a metabotropic receptor (T1R2/T1R3), initiating a G protein cascade that leads to calcium release and membrane depolarization, signaling sweetness.

T1R2/T1R3 receptor

A specific G protein-coupled metabotropic receptor complex on taste cells that binds sweet tastants, crucial for initiating the transduction pathway for sweetness perception.

Metabotropic receptor (in taste)

A type of receptor, like T1R2/T1R3, that, when bound by a ligand (e.g., sweet tastant), activates an intracellular signaling cascade, often involving G proteins and second messengers.

Role of G protein in sweet taste

Upon sweet tastant binding to the T1R2/T1R3 receptor, the associated G protein dissociates and activates an enzyme, leading to subsequent steps in the signaling cascade.

Secondary messenger (sweet taste)

A molecule produced after enzyme activation in the sweet taste pathway; it opens calcium ion channels in the endoplasmic reticulum (ER), increasing intracellular \text{[Ca}^{2+}\text{]} .

Calcium ions in sweet taste transduction

Released from the ER in response to a secondary messenger, an increased cytoplasmic \text{[Ca}^{2+}\text{]} concentration then opens sodium ion channels, leading to membrane depolarization.

Depolarization in sweet taste

The influx of sodium ions, triggered by increased cytoplasmic \text{[Ca}^{2+}\text{]} , causes the taste cell membrane to depolarize, generating an electrical signal perceived as sweetness.

Effect of sodium channel blockage on sweet taste

Blocking sodium ion channels prevents the influx of \text{Na}^{+}\text{]} ions necessary for membrane depolarization, thereby decreasing the ability to taste sweet things.

Photopigments

Light-sensitive molecules in photoreceptors, composed of a Retinal chromophore and an Opsin protein.

11-cis-retinal

The inactive, bent conformation of retinal found in the dark, bound to opsin.

all-trans-retinal

The active, straightened conformation of retinal formed after absorbing light, which causes it to dissociate from opsin and activate it.

Transducin

The G protein associated with opsin, which is activated by light-induced conformational changes in opsin.

Activation of Opsin by light

Light causes 11-cis-retinal to isomerize to all-trans-retinal, inducing a conformational change in opsin that activates it and initiates the phototransduction cascade.

Transduction

The process by which a sensory receptor cell converts a stimulus into a change in membrane potential.

Photoreceptors

Sensory receptors in the retina that detect light; include rods and cones.

Rods

Photoreceptor cells that are highly sensitive to light and responsible for vision in low-light conditions.

Cones

Photoreceptor cells that allow for color vision and function best in bright light.

Chemoreceptors

Sensory receptor cells that respond to chemical stimuli, such as taste and smell.

Mechanoreceptors

Receptor cells that detect mechanical pressure or distortion; involved in hearing and proprioception.

Phototransduction pathway

The sequence of events in photoreceptor cells that converts light stimuli into electrical signals.

Retinal

A pigment derived from vitamin A that exists as 11-cis-retinal in the dark and changes to all-trans-retinal upon light absorption, initiating vision.

Opsin

A G protein-coupled receptor associated with transducin, activated by the conformational change of retinal to initiate the phototransduction cascade.

cGMP

Cyclic guanosine monophosphate, a second messenger that regulates ion channels in photoreceptor cells.

Hyperpolarization

A change in membrane potential that makes the inside of the cell more negative; occurs in photoreceptors in response to light.

Glutamate release

The release of a neurotransmitter from presynaptic terminals that communicates signal changes to bipolar cells.

Dark current

The influx of sodium ions in photoreceptors in the absence of light, resulting in a relatively depolarized state.

Bipolar cells

Interneurons that connect photoreceptor cells to ganglion cells and process visual information.

Vestibular apparatus

Inner ear structures that contribute to the sense of balance and spatial orientation.

Calcium ions in phototransduction

Ions that play a crucial role in signal transduction and neurotransmitter release in photoreceptor cells.

Mechanotransduction channel (SAC)

A stretch-activated ion channel tethered to both the extracellular matrix (ECM) and the cytoskeleton, crucial for mechanoreception.

Tether model of mechanotransduction

A mechanism where movement of the extracellular matrix relative to the cytoskeleton pulls open the tethered mechanotransduction channel (SAC), initiating a signal.

Sweet tastant (T1R2/T1R3) model

A chemoreception pathway where a sweet tastant binds to a metabotropic receptor (T1R2/T1R3), initiating a G protein cascade that leads to calcium release and membrane depolarization, signaling sweetness.

T1R2/T1R3 receptor

A specific G protein-coupled metabotropic receptor complex on taste cells that binds sweet tastants, crucial for initiating the transduction pathway for sweetness perception.

Metabotropic receptor (in taste)

A type of receptor, like T1R2/T1R3, that, when bound by a ligand (e.g., sweet tastant), activates an intracellular signaling cascade, often involving G proteins and second messengers.

Role of G protein in sweet taste

Upon sweet tastant binding to the T1R2/T1R3 receptor, the associated G protein dissociates and activates an enzyme, leading to subsequent steps in the signaling cascade.

Secondary messenger (sweet taste)

A molecule produced after enzyme activation in the sweet taste pathway; it opens calcium ion channels in the endoplasmic reticulum (ER), increasing intracellular \text{[Ca}^{2+}\text{]} .

Calcium ions in sweet taste transduction

Released from the ER in response to a secondary messenger, an increased cytoplasmic \text{[Ca}^{2+}\text{]} concentration then opens sodium ion channels, leading to membrane depolarization.

Depolarization in sweet taste

The influx of sodium ions, triggered by increased cytoplasmic \text{[Ca}^{2+}\text{]} , causes the taste cell membrane to depolarize, generating an electrical signal perceived as sweetness.

Effect of sodium channel blockage on sweet taste

Blocking sodium ion channels prevents the influx of \text{Na}^{+}\text{]} ions necessary for membrane depolarization, thereby decreasing the ability to taste sweet things.

Photopigments

Light-sensitive molecules in photoreceptors, composed of a Retinal chromophore and an Opsin protein.