Study "hubs lecture 23 - sensory receptors", a flashcard deck on FORKSAI.
Define the three general types of sensation as described in neurophysiology.
The three general types of sensation are somatic, visceral, and special senses. Somatic senses perceive physical aspects like touch and temperature, often specific in location. Visceral senses monitor internal organs, providing a generalized sense of well-being, and are difficult to pinpoint. Special senses are detected by highly specialized organs, such as vision, smell, and taste.
Distinguish between tonic and phasic receptors, providing an example for each.
Tonic receptors are slow-adapting and continually active, reflecting a background level of stimulation, with their action potential frequency changing with stimulus intensity. An example is proprioceptors. Phasic receptors are fast-adapting, normally silent, and send action potentials only when a stimulus changes, stopping quickly thereafter. Temperature receptors are a good example.
How does sensory transduction convert a sensory stimulus into an action potential?
Sensory transduction is the process of converting a sensory stimulus into an action potential. This typically involves a stimulus deforming a receptor membrane, which opens specific gated ion channels. The influx of ions, such as Na+, depolarizes the membrane, and if the threshold is reached, an action potential is fired and propagated to the brain.
Explain the function and features of thermoreceptors in sensory perception.
Thermoreceptors are nerve endings equipped with temperature-gated ion channels. They respond to different temperatures and changes in temperature, functioning as phasic (fast-adapting) receptors. When stimulated, temperature-gated Na+ channels open, allowing Na+ to enter and depolarize the membrane, leading to an action potential if the threshold is met.
Describe how chemoreceptors contribute to sensory perception, including their adaptability.
Chemoreceptors are specialized receptor cells with chemically-gated ion channels that translate changes in chemical concentration into action potentials. They can be fast or slow-adapting depending on the specific chemical and location. Examples include receptors for oxygen, CO2, and acid, which are crucial for monitoring internal body chemistry.
What are mechanoreceptors, and what types of sensations do they detect?
Mechanoreceptors are nerve endings with mechanically-gated ion channels that respond to physical forces distorting the plasma membrane. They detect tactile sensations (light touch, pressure, texture), proprioception (body position and movement from muscle, tendon, and joint stretch), and baroreception (pressure/stretch in vessels and visceral tubes).
Explain the role of nociceptors in the body and their typical adaptability.
Nociceptors are nerve endings that respond to noxious (harmful or painful) stimuli, typically caused by tissue damage. They possess temperature-gated, chemically-gated, or mechanically-gated ion channels that react to extreme stimuli. Nociceptors tend to be tonic (slow-adapting), providing sustained signals about ongoing tissue damage, though some can be phasic.
How does the brain interpret the intensity of a sensory stimulus?
The brain interprets the intensity of a sensory stimulus based on two main factors: the frequency of action potentials arriving from afferent neurons and the number of neurons activated. A higher frequency of action potentials and the activation of more sensory neurons indicate a more intense sensation, while fewer action potentials suggest a milder stimulus.
Define a receptive field and explain how its size and density affect sensory perception.
A receptive field is the area of skin with receptive endings for a single sensory neuron. The size and density of receptive fields significantly affect discriminatory touch and the ability to localize a stimulus. Small, densely packed receptive fields provide greater sensitivity and more accurate localization, whereas large, widely spaced fields offer less sensitivity and localization accuracy.
How do receptive fields relate to the somatotopic map in the primary somatosensory cortex?
The size and density of receptive fields directly influence their representation in the somatotopic map of the primary somatosensory cortex. Areas with smaller, more densely packed receptive fields (e.g., fingers, lips) have a larger representation in the brain, indicating higher sensitivity and more neurons involved. Conversely, areas with larger, widely spaced receptive fields (e.g., torso, limbs) have less brain representation due to fewer neurons.