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Questions and Answers
What type of sensory receptor is responsible for detecting pain?
What type of sensory receptor is responsible for detecting pain?
Which cranial nerve is associated with the sense of hearing and balance?
Which cranial nerve is associated with the sense of hearing and balance?
Which type of sensory receptor would respond to changes in temperature?
Which type of sensory receptor would respond to changes in temperature?
What is the role of sensory receptors in relation to action potentials?
What is the role of sensory receptors in relation to action potentials?
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Which of the following is NOT a type of mechanoreceptor?
Which of the following is NOT a type of mechanoreceptor?
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What defines a sensory receptor as a transducer?
What defines a sensory receptor as a transducer?
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Which cranial nerves are involved in the sense of taste?
Which cranial nerves are involved in the sense of taste?
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What do proprioceptors primarily provide information about?
What do proprioceptors primarily provide information about?
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What characteristic distinguishes mechanoreceptors that respond to light touch from those that detect deep pressure?
What characteristic distinguishes mechanoreceptors that respond to light touch from those that detect deep pressure?
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What occurs when the generator potential (GP) is sufficiently large?
What occurs when the generator potential (GP) is sufficiently large?
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Which statement best describes the comparison between generator potentials (GP) and action potentials (AP)?
Which statement best describes the comparison between generator potentials (GP) and action potentials (AP)?
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What type of adaptation do mechanoreceptors that detect vibrations and touch exhibit?
What type of adaptation do mechanoreceptors that detect vibrations and touch exhibit?
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What role do voltage-gated Na+ channels play in generating an action potential?
What role do voltage-gated Na+ channels play in generating an action potential?
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What is the function of the first node of Ranvier in myelinated sensory axons?
What is the function of the first node of Ranvier in myelinated sensory axons?
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What is the primary mechanism responsible for the generation of graded potentials (GP) in sensory receptors?
What is the primary mechanism responsible for the generation of graded potentials (GP) in sensory receptors?
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Which sensory receptors are the most sensitive to stretching and torque?
Which sensory receptors are the most sensitive to stretching and torque?
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In somatosensory mechanoreceptors, what type of channels are primarily involved in the generation of graded potentials?
In somatosensory mechanoreceptors, what type of channels are primarily involved in the generation of graded potentials?
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Which distinguishing feature does not apply to generator potentials?
Which distinguishing feature does not apply to generator potentials?
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What is the net result of ion movement through non-selective channels in somatosensory mechanoreceptors?
What is the net result of ion movement through non-selective channels in somatosensory mechanoreceptors?
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What coding strategy involves an increased frequency of action potentials in response to higher stimulus intensity?
What coding strategy involves an increased frequency of action potentials in response to higher stimulus intensity?
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How does population coding represent increased stimulus intensity?
How does population coding represent increased stimulus intensity?
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What type of receptors utilizes separate cells or G-protein-coupled mechanisms to influence channels indirectly?
What type of receptors utilizes separate cells or G-protein-coupled mechanisms to influence channels indirectly?
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Which of the following statements about somatosensory mechanoreceptors is FALSE?
Which of the following statements about somatosensory mechanoreceptors is FALSE?
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In the context of stimulus coding, which representation is NOT typically associated with intensity?
In the context of stimulus coding, which representation is NOT typically associated with intensity?
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What happens to action potential frequency along the afferent neuron when stimulus strength increases?
What happens to action potential frequency along the afferent neuron when stimulus strength increases?
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Which type of receptors adapt slowly or not at all, continuously relaying information to the CNS?
Which type of receptors adapt slowly or not at all, continuously relaying information to the CNS?
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What do we call the process where increased stimulus strength leads to greater neurotransmitter release from afferent terminals?
What do we call the process where increased stimulus strength leads to greater neurotransmitter release from afferent terminals?
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What is an example of a tonic receptor?
What is an example of a tonic receptor?
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Which of the following statements correctly describes phasic receptors?
Which of the following statements correctly describes phasic receptors?
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What role does receptor adaptation play in sensory processing?
What role does receptor adaptation play in sensory processing?
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How does the CNS utilize the information from sensory receptors?
How does the CNS utilize the information from sensory receptors?
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Which of the following phenomena is referred to as population coding?
Which of the following phenomena is referred to as population coding?
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Study Notes
Principles of Sensory Physiology
- Sensory physiology studies how the nervous system detects and interprets stimuli.
- This lecture covers defining sensory receptors, identifying types, understanding signal transduction to the CNS, and receptor adaptation.
Objectives
- Define a sensory receptor.
- Identify and classify sensory receptors.
- Explain how sensory receptors relay signals to the CNS, including how intensities are coded.
- Describe two types of receptor adaptation.
Special and General Senses
- Special senses are carried by cranial nerves:
- Olfaction (smell) – Cranial Nerve I
- Vision – Cranial Nerve II
- Taste – Cranial Nerves VII and IX
- Hearing and balance (equilibrium) – Cranial Nerve VIII
- General (somatosensory) senses are detected from all body parts (and head) via:
- Cranial Nerve V (trigeminal)
- Spinal nerves (except C1)
Sensory Receptors
- Sensory receptors are transducers; they convert one form of energy into another (action potentials).
- They detect various stimuli.
- Includes:
- Photoreceptors (light): rods and cones in the retina.
- Thermoreceptors (temperature changes): central (hypothalamus) and peripheral (skin).
- Nociceptors (pain).
- Mechanoreceptors (mechanical stimuli):
- Exteroceptors (external stimuli, e.g., touch receptors).
- Proprioceptors (body position, e.g., muscle spindles).
Mechanoreceptors: Tactile
- Subtypes and characteristics:
- Meissner corpuscles (light touch, rapid adaptation).
- Pacinian corpuscles (deep pressure, rapid adaptation).
- Ruffini endings (stretch, slow adaptation).
- Merkel disks (touch, slow adaptation).
Receptor and Generator Potentials
- Sensory receptor membranes must depolarize to threshold to trigger action potentials.
- Generator potential (GP) is a depolarization of the receptive sensory axon, caused by stimuli. (Hyperpolarization can also occur in some specialized receptors).
- Activating stimulus produces large enough GP to reach threshold and generate action potentials (APs).
- In myelinated fibers, APs start at the first node of Ranvier.
GP vs. EPSP/AP
- Generator potential (GP) is similar to EPSP in:
- Graded amplitude.
- No refractory period.
- Not actively propagated.
- GP differs from AP in:
- All or none response
- Refractory period allowing rapid firing.
- Actively propagated along the axon.
Mechanisms of GP
- Somatosensory mechanoreceptors: effect of mechanical stimuli on stretch-sensitive channels allowing both sodium and potassium to pass, which leads to greater driving force for Na+.
- Nociceptors, photoreceptors, and chemoreceptors: separate cells or G-protein-coupled mechanisms influencing channels indirectly.
Receptor Potential Types
- Receptor potential in specialized afferent ending (example): stimulus opens stimulus-sensitive channels allowing sodium entry which produces receptor potential.
- Local current flow depolarises adjacent region opening voltage-gated Na+ channels creating action potential.
- Receptor potential in Separate Cell Ending (example): stimulus opens stimulus-sensitive channels causing sodium entry that makes receptor potential.
- Local current flow opens voltage-gated calcium channels
- Calcium entry triggers neurotransmitter release.
- Neurotransmitter binding to receptor channels allows sodium entry triggering action potential.
Coding Stimulus Intensity
- Two strategies for coding intensity:
- Frequency coding: higher intensity, faster frequency of action potentials (not linear).
- Population coding: increased stimulus intensity recruits more receptors.
Receptor Adaptation
- Tonic receptors: slow or no adaptation, continuing to signal sustained stimuli. (Example: muscle stretch receptors).
- Phasic receptors: rapid adaptation, stopping signals to maintained stimuli. (Example: tactile receptors).
Speed of Stimulus Adaptation
- Tonic Receptors: slow to adapt, continue firing and sending information.
- Phasic Receptors: rapidly adapt to continuing stimuli; signals stop during the presence of stimulus.
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Description
Test your knowledge on sensory receptors, including their types, functions, and the related cranial nerves. This quiz covers topics such as pain detection, mechanoreceptors, and the role of adaptation in sensory responses. Challenge yourself to understand the complexities of how our body perceives stimuli.
