hubs lecture 23 - sensory receptors flashcards

All 20 cards

1. Card 1

   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.

2. Card 2

   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.

3. Card 3

   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.

4. Card 4

   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.

5. Card 5

   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.

6. Card 6

   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).

7. Card 7

   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.

8. Card 8

   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.

9. Card 9

   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.

10. Card 10

    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.

11. Card 11

    What is the primary difference between afferent and efferent signals in the nervous system?

    Afferent signals are sensory signals sent to the central nervous system (CNS) to provide information about the environment and body homeostasis. Efferent signals, on the other hand, are instructions sent from the CNS to the rest of the body after this information has been processed, typically leading to a motor or glandular response.

12. Card 12

    Why are visceral senses often difficult to pinpoint a precise location?

    Visceral senses monitor internal organs and are often difficult to pinpoint precisely because they tend to be generalized senses of well-being or discomfort rather than specific localized sensations. This is due to the nature of their receptive fields and the way their signals are processed in the central nervous system, often leading to a diffuse perception.

13. Card 13

    Explain the process of stimulus transduction using the example of touching something with your finger.

    When you touch something with your finger, a mechanoreceptor in the skin gets squished. This physical deformation of the membrane opens mechanically-gated Na+ channels, allowing Na+ to enter and depolarize the membrane. If the depolarization reaches the threshold, action potentials are sent to the brain, making you aware of the touch.

14. Card 14

    What is the benefit of adaptation in sensory receptors, particularly for phasic receptors?

    The benefit of adaptation, especially for phasic (fast-adapting) receptors, is to prevent the nervous system from being overwhelmed by constant, unchanging stimuli. By becoming silent quickly after a change, these receptors highlight new or changing stimuli, allowing the brain to focus on relevant information and ignore static background noise, conserving neural resources.

15. Card 15

    Why are proprioceptors considered tonic (slow-adapting) receptors?

    Proprioceptors are considered tonic (slow-adapting) receptors because they continually monitor and provide information about body position and movement. They remain active to reflect the background level of stimulation, and their action potential frequency changes only when the stimulus intensity (e.g., muscle stretch or joint position) changes, allowing for constant awareness of limb position.

16. Card 16

    How do light touch receptors differ from proprioceptors in terms of their adaptation?

    Light touch receptors are typically phasic (fast-adapting), meaning they respond to the onset or change of a light touch stimulus and then quickly cease firing, adapting to the constant pressure. Proprioceptors, however, are tonic (slow-adapting), continuously providing information about body position and movement, reflecting ongoing stretch or tension in muscles, tendons, and joints.

17. Card 17

    What types of ion channels are involved in the transduction of temperature stimuli by thermoreceptors?

    Thermoreceptors utilize temperature-gated Na+ channels for the transduction of temperature stimuli. When exposed to appropriate temperature changes, these channels open, allowing Na+ to enter the cell. This influx of positive ions causes depolarization of the membrane, which, if sufficient, leads to the generation and propagation of an action potential to the brain.

18. Card 18

    Why do areas like the hands, fingers, and lips have more accurate localization of sensation?

    Areas like the hands, fingers, and lips have more accurate localization of sensation because they possess small and densely packed receptive fields. This arrangement means that a smaller area of skin is covered by each sensory neuron, leading to better two-point discrimination and a more precise representation in the somatosensory cortex of the brain.

19. Card 19

    What is the significance of the statement that 'No APs = no sensation' in the context of stimulus intensity?

    The statement 'No APs = no sensation' highlights that the generation of action potentials is fundamental for sensory perception. If a stimulus is too weak to reach the threshold for action potential generation in afferent neurons, no signal is transmitted to the brain, and therefore, no sensation is perceived, regardless of the physical presence of the stimulus.

20. Card 20

    In the context of sensory receptors, what does 'deformation' refer to, and which receptor type is primarily associated with it?

    In the context of sensory receptors, 'deformation' refers to the physical distortion or change in shape of the plasma membrane of a nerve ending. Mechanoreceptors are primarily associated with deformation, as they respond to physical forces like pressure, stretch, or touch that physically alter their membrane, leading to the opening of mechanically-gated ion channels.

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