Lecture 9 - Vision (Part 1) Flashcards
What is sensation?
Sensation is when cells in the nervous system detect stimuli from the environment (like light, sound, or heat) and convert these signals into changes in the cell’s membrane potential, leading to the release of neurotransmitters.
What is perception?
Perception is the conscious experience and interpretation of the sensory information the brain receives from signals detected by sensory cells.
How do sensation and perception differ in terms of processing sensory information?
Sensation refers to the initial detection and conversion of environmental stimuli into neural signals, while perception involves the conscious experience and interpretation of those signals in the brain.
Why is perception considered a “conscious experience” while sensation is not?
Perception is considered a conscious experience because it involves the brain’s interpretation of sensory signals, which allows us to consciously recognize and make sense of stimuli. Sensation is the basic detection of stimuli and does not involve conscious awareness.
If someone touches a hot surface and quickly withdraws their hand, which process (sensation or perception) is responsible for the initial detection of heat?
Sensation is responsible for the initial detection of heat, as sensory cells in the skin detect the temperature change and trigger a response.
Imagine you hear a faint sound while studying. Which process occurs first: sensation or perception?
Sensation occurs first, as your auditory cells detect the sound. Perception follows when your brain interprets the sound and you become consciously aware of it.
How would you describe the relationship between sensation and perception in everyday experiences?
Sensation and perception work together to help us interpret the world; sensation detects stimuli, and perception interprets these signals, allowing us to respond meaningfully.
What are sensory neurons?
Sensory neurons are special cells designed to detect specific types of physical stimuli from the environment.
What types of stimuli do sensory neurons detect?
Sensory neurons detect molecules, physical pressure, temperature, pH, and electromagnetic radiation (light).
How do sensory neurons contribute to the sense of smell and taste?
Sensory neurons detect specific molecules related to smells and tastes, enabling us to experience these sensations.
What types of physical stimuli do sensory neurons related to touch and balance detect?
Sensory neurons detect physical pressure, including sensations like touch, stretch, vibration, acceleration, gravity, and balance.
What types of temperature sensations can sensory neurons respond to?
Sensory neurons can respond to heat, cold, and sensations of pain related to temperature.
How do sensory neurons sense pH, and what sensations does this contribute to?
Sensory neurons, such as chemoreceptors and nociceptors, detect pH levels to sense whether a substance is acidic or alkaline. This allows us to experience sensations like the sour taste of lemons, pain from acidic substances, and suffocation due to carbon dioxide buildup, which makes the blood more acidic. These neurons help us perceive changes in acidity or alkalinity.
What is the role of sensory neurons in vision?
Sensory neurons detect electromagnetic radiation (light), which is essential for the sense of vision.
Can you name an additional sense that some animals possess that humans do not?
Some animals can detect electrical fields, magnetic fields, humidity, and water pressure, which are additional senses beyond those in humans.
If a person feels a sharp pain when touching a hot surface, which type of sensory neuron is primarily involved?
Nociceptors, which detect harmful stimuli such as heat and pressure, are primarily involved in sensing the pain. Thermoreceptors also detect the temperature, while mechanoreceptors might contribute to the touch sensation, depending on the pressure involved.
What is sensory transduction?
Sensory transduction is the process by which specialized receptors in sensory neurons convert external stimuli (like light, sound, or pressure) into changes in the receptor’s membrane potential, which are then processed as electrical signals by the brain.
How do sensory neurons differ in terms of structure?
Sensory neurons can vary in shape and size; some do not have axons or generate action potentials, yet they all release neurotransmitters.
What role do specialized receptors play in sensory transduction?
In vision, photoreceptors in the retina, specifically rods and cones, contain specialized opsin proteins that detect light. When light hits these opsins, it causes a change in their structure, triggering a signaling cascade. This leads to the opening and closing of ion channels in the photoreceptor membrane, changing its membrane potential. This process, called sensory transduction, converts light into electrical signals that are transmitted to the brain for visual processing.
How do sensory neurons without action potentials release neurotransmitters?
Sensory neurons without action potentials release neurotransmitters in a graded manner, where the amount released is proportional to the degree of depolarization of their membrane potential.
What happens to neurotransmitter release as the membrane potential of a sensory neuron changes?
As the membrane potential of a sensory neuron depolarizes more, it releases a greater amount of neurotransmitter.
If a sensory neuron detects a very bright light, how might sensory transduction occur in this case?
In the visual system, when the sensory neuron (the photoreceptor) detects bright light, it causes a significant hyperpolarization of the photoreceptor. This hyperpolarization leads to a greater decrease in neurotransmitter release compared to dim light. The reduction in neurotransmitter release helps signal to the brain that more light is present, and the intensity of the light is communicated based on how much the release decreases. So, with bright light, the photoreceptor releases even less neurotransmitter to indicate the higher intensity of the light.
Why is it important that sensory neurons can vary in shape and size?
The variation in shape and size allows different sensory neurons to effectively detect and respond to a wide range of sensory stimuli, ensuring that the nervous system can process diverse environmental information.
What are photoreceptor cells?
Photoreceptor cells are sensory neurons responsible for vision that convert electromagnetic energy from visible light into changes in membrane potential, influencing neurotransmitter release.
How do photoreceptor cells differ from typical neurons in terms of action potentials?
Photoreceptor cells do not have action potentials; they respond to light by changing their membrane potential and regulating neurotransmitter release.
What are opsins?
Opsins are light-sensitive proteins in the retina’s rods and cones that detect light. When opsins bind to retinal, they change shape, triggering a change in membrane potential and starting the process of converting light into electrical signals sent to the brain to form visual images.
What is the function of retinal in photoreceptors?
Retinal is a small molecule made from vitamin A that absorbs light and attaches to opsins, enabling photoreceptors to detect light.
What is the role of opsins in the process of vision?
Opsins are light-sensitive proteins in the photoreceptor cells of the retina. When retinal binds to an opsin and undergoes a shape change in response to light, it activates a signaling cascade known as the phototransduction pathway, which ultimately converts light into electrical signals for the brain to interpret as vision.
How does the binding of light to retinal affect opsins?
When light is absorbed by retinal, it changes shape, which activates opsins and initiates the signal transduction pathway for vision.
In a dimly lit room, how do photoreceptor cells help you see?
In a dimly lit room, photoreceptor cells (rods) are sensitive to low light levels. They undergo changes in membrane potential when exposed to light, leading to a decrease in neurotransmitter release. This signals the brain and allows you to perceive the image, even in low-light conditions.
If someone is colorblind, how might their photoreceptor cells be affected?
In colorblind individuals, specific opsins or retinal molecules may be absent or dysfunctional, impairing their ability to detect certain wavelengths of light, leading to color vision deficiencies.
What happens when retinal absorbs light?
When retinal absorbs light, it changes shape and activates the opsin protein.
What is opsin and what kind of receptor is it?
Opsin is a metabotropic receptor protein that is activated when retinal absorbs light.
What role does the G-protein signaling cascade play in photoreception?
It activates opsin, which triggers a cascade leading to the closure of ion channels, hyperpolarization of photoreceptor cells, and reduced neurotransmitter release, transmitting visual information to the brain.
How does the shape change of retinal affect photoreceptor function?
The shape change of retinal activates opsin, initiating a signaling cascade that alters the photoreceptor’s membrane potential and neurotransmitter release.
What is the outcome of the G-protein signaling cascade in photoreceptors?
The G-protein signaling cascade in photoreceptors leads to the closure of ion channels, specifically sodium channels, causing hyperpolarization of the photoreceptor’s membrane. This reduces the release of neurotransmitter glutamate, which affects the signal transmitted to the next neuron in the visual pathway.
If a person experiences a defect in their photoreceptor cells, how might this affect their ability to perceive light?
A defect in photoreceptor cells may disrupt the normal function of retinal and opsin, impairing the signaling cascade and leading to reduced sensitivity or inability to detect light.
Describe a scenario in which a person is unable to see well in low-light conditions. Which processes might be impaired?
If a person struggles to see in low-light conditions, it could be due to impaired function of the rods in their retina, which are responsible for low-light vision. This impairment could involve dysfunctional opsin proteins (such as rhodopsin) or retinal molecules that prevent the proper conversion of light into neural signals, hindering the ability to see in dim light.
What are photoreceptor cells?
Photoreceptor cells are specialized cells in the retina that detect light and convert it into neural signals for vision.
What are the four types of photoreceptor cells involved in conscious vision?
The four types of photoreceptor cells are red cone cells, green cone cells, blue cone cells, and rod cells.
