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Questions and Answers
Which type of receptor is responsible for detecting high-frequency vibrations?
Which type of receptor is responsible for detecting high-frequency vibrations?
Which of these receptors are specifically responsible for detecting skin stretching and pressure?
Which of these receptors are specifically responsible for detecting skin stretching and pressure?
Which type of receptor is most closely associated with the sensation of touch and low-frequency vibrations?
Which type of receptor is most closely associated with the sensation of touch and low-frequency vibrations?
Which of these receptors exhibit a rapid adaptation rate?
Which of these receptors exhibit a rapid adaptation rate?
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Which type of receptor is responsible for detecting muscle tension?
Which type of receptor is responsible for detecting muscle tension?
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Which type of receptor is responsible for detecting warmth or cold?
Which type of receptor is responsible for detecting warmth or cold?
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Which of these is NOT a type of tactile receptor?
Which of these is NOT a type of tactile receptor?
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Which of the following is NOT a characteristic of Ruffini corpuscles?
Which of the following is NOT a characteristic of Ruffini corpuscles?
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Which of these is a type of proprioceptor?
Which of these is a type of proprioceptor?
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Which type of touch receptor is responsible for detecting pressure?
Which type of touch receptor is responsible for detecting pressure?
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Which type of touch receptor is responsible for detecting lower-frequency vibrations?
Which type of touch receptor is responsible for detecting lower-frequency vibrations?
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What is the main function of Merkel cells?
What is the main function of Merkel cells?
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Where are Pacinian corpuscles NOT found?
Where are Pacinian corpuscles NOT found?
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Which of the following is NOT a known trigger for itch?
Which of the following is NOT a known trigger for itch?
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Which of the following chemicals is known to stimulate itch?
Which of the following chemicals is known to stimulate itch?
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Which of these best describes the relationship between Meissner corpuscles and Pacinian corpuscles?
Which of these best describes the relationship between Meissner corpuscles and Pacinian corpuscles?
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What type of sensory information does the anterolateral or spinothalamic pathway carry?
What type of sensory information does the anterolateral or spinothalamic pathway carry?
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Where do first-order neurons of the spinothalamic pathway synapse with second-order neurons?
Where do first-order neurons of the spinothalamic pathway synapse with second-order neurons?
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Which tract carries pain and temperature sensations in the spinothalamic pathway?
Which tract carries pain and temperature sensations in the spinothalamic pathway?
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Where do third-order neurons of the spinothalamic pathway project?
Where do third-order neurons of the spinothalamic pathway project?
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What type of sensory information does the trigeminothalamic pathway carry?
What type of sensory information does the trigeminothalamic pathway carry?
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Where are the cell bodies of first-order neurons in the trigeminothalamic pathway located?
Where are the cell bodies of first-order neurons in the trigeminothalamic pathway located?
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Whichcranial nerve is involved in the trigeminothalamic pathway?
Whichcranial nerve is involved in the trigeminothalamic pathway?
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Where do some first-order neurons of the trigeminothalamic pathway synapse with second-order neurons?
Where do some first-order neurons of the trigeminothalamic pathway synapse with second-order neurons?
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How does proprioception differ from kinesthesia?
How does proprioception differ from kinesthesia?
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What is the main function of muscle spindles?
What is the main function of muscle spindles?
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Which of the following statements accurately describes proprioceptive adaptation?
Which of the following statements accurately describes proprioceptive adaptation?
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What is the role of proprioceptors in weight discrimination?
What is the role of proprioceptors in weight discrimination?
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Which part of the brain processes proprioceptive information consciously?
Which part of the brain processes proprioceptive information consciously?
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What kind of muscle fibers are found within muscle spindles?
What kind of muscle fibers are found within muscle spindles?
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Where are tendon organs located?
Where are tendon organs located?
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Which of the following best describes the function of the spinocerebellar pathways?
Which of the following best describes the function of the spinocerebellar pathways?
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What is the primary role of the ventral posterior nucleus of the thalamus in the trigeminothalamic pathway?
What is the primary role of the ventral posterior nucleus of the thalamus in the trigeminothalamic pathway?
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Which of the following is NOT a sensory modality carried by the trigeminothalamic tract?
Which of the following is NOT a sensory modality carried by the trigeminothalamic tract?
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Which cranial nerve conveys impulses for most somatic sensations from the left side of the face into the pons?
Which cranial nerve conveys impulses for most somatic sensations from the left side of the face into the pons?
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What is the main consequence of damage to the posterior column of the spinal cord?
What is the main consequence of damage to the posterior column of the spinal cord?
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How does the homunculus illustrate the organization of the primary somatosensory area?
How does the homunculus illustrate the organization of the primary somatosensory area?
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What is meant by the term ‘plasticity’ in the context of the primary somatosensory area?
What is meant by the term ‘plasticity’ in the context of the primary somatosensory area?
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Which of the following best describes the relationship between the trigeminothalamic tract and the spinocerebellar tracts?
Which of the following best describes the relationship between the trigeminothalamic tract and the spinocerebellar tracts?
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Which of the following sensations are NOT carried by the posterior column-medial lemniscus pathway?
Which of the following sensations are NOT carried by the posterior column-medial lemniscus pathway?
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Where do the axons of second-order neurons in the posterior column-medial lemniscus pathway cross to the opposite side of the brain?
Where do the axons of second-order neurons in the posterior column-medial lemniscus pathway cross to the opposite side of the brain?
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What is the name of the structure in the thalamus that receives input from the medial lemniscus?
What is the name of the structure in the thalamus that receives input from the medial lemniscus?
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Which of the following is NOT a component of the posterior column-medial lemniscus pathway?
Which of the following is NOT a component of the posterior column-medial lemniscus pathway?
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What is the function of the gracile fasciculus?
What is the function of the gracile fasciculus?
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Flashcards
Posterior Column
Posterior Column
A part of the spinal cord consisting of the gracile and cuneate fasciculi.
Gracile Fasciculus
Gracile Fasciculus
Part of the posterior column carrying impulses from lower body regions.
Cuneate Fasciculus
Cuneate Fasciculus
Part of the posterior column transmitting impulses from upper body regions.
Medial Lemniscus
Medial Lemniscus
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Thalamus Connection
Thalamus Connection
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Meissner's Corpuscles
Meissner's Corpuscles
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Hair Root Plexuses
Hair Root Plexuses
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Type I Cutaneous Mechanoreceptors
Type I Cutaneous Mechanoreceptors
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Type II Cutaneous Mechanoreceptors
Type II Cutaneous Mechanoreceptors
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Pacinian Corpuscles
Pacinian Corpuscles
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Nociceptors
Nociceptors
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Muscle Spindles
Muscle Spindles
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Tendon Organs
Tendon Organs
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Trigeminothalamic pathway
Trigeminothalamic pathway
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First order neurons
First order neurons
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Second order neurons
Second order neurons
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Ventral posterior nucleus of the thalamus
Ventral posterior nucleus of the thalamus
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Primary somatosensory area
Primary somatosensory area
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Homunculus
Homunculus
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Spinocerebellar pathways
Spinocerebellar pathways
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Neurosyphilis
Neurosyphilis
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Proprioception
Proprioception
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Kinesthesia
Kinesthesia
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Proprioceptors
Proprioceptors
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Joint Kinesthetic Receptors
Joint Kinesthetic Receptors
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Weight Discrimination
Weight Discrimination
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Cerebellum vs. Cerebral Cortex
Cerebellum vs. Cerebral Cortex
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Anterolateral Pathways
Anterolateral Pathways
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Lateral Spinothalamic Tract
Lateral Spinothalamic Tract
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Anterior Spinothalamic Tract
Anterior Spinothalamic Tract
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Trigeminal Ganglia
Trigeminal Ganglia
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Second-order Neurons in Pons
Second-order Neurons in Pons
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Pressure Sensation
Pressure Sensation
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Vibration Sensation
Vibration Sensation
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Itch Mechanism
Itch Mechanism
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Bradykinin and Histamine
Bradykinin and Histamine
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Study Notes
Receptor Types and Structures
- Tactile receptors (touch, pressure, vibration, itch, tickle): Meissner corpuscles (rapid adaptation), hair root plexuses (rapid adaptation), Type I cutaneous mechanoreceptors (tactile discs) (slow adaptation), Type II cutaneous mechanoreceptors (Ruffini corpuscles) (slow adaptation), Lamellated (Pacinian) corpuscles (rapid adaptation)
- Thermoreceptors (warmth and cold): Free nerve endings (initial rapid, then slow adaptation)
- Nociceptors (pain): Free nerve endings (slow adaptation)
- Proprioceptors (muscle length and tension, joint position and movement): Muscle spindles (slow adaptation), tendon organs (slow adaptation), joint kinesthetic receptors (rapid adaptation)
Tactile Sensations
- Tactile sensations include touch, pressure, and vibration, plus itch and tickle.
- Differences in these sensations arise from activation of multiple receptor types and multiple stimuli from different receptors.
Touch
- Crude touch—the ability to perceive something has touched the skin, without being able to determine specific location, shape, or texture.
- Discriminative touch—provides specific information like exact location, shape, size, and texture of the stimulus, is carried along separate pathways.
Touch (Rapidly Adapting Receptors)
- Corpuscles of touch (Meissner’s corpuscles)—located in dermis of glabrous (hairless) skin. Abundant in fingertips, hands, eyelids, tongue tip, lips, nipples, soles, clitoris, and penis tip. Each corpuscle has egg-shaped collection of dendrites.
- Hair root plexuses—located in hairy skin; consist of free nerve endings wrapped around hair follicles. Detect movement on skin surface that disturbs hairs (e.g., bug landing).
Touch (Slowly Adapting Receptors)
- Type I cutaneous mechanoreceptors (Merkel discs)—sausage-shaped flattened free nerve endings that make contact with Merkel cells in the stratum basale. Function in touch and pressure. Most abundant in fingertips, hands, lips, and external genitalia
Touch (Type II Receptors)
- Type II cutaneous mechanoreceptors (Ruffini corpuscles)—encapsulated receptors. Found deep in dermis and in ligaments and tendons. Abundant in hands, especially fingers and soles. Respond to stretching of skin, and also helps to detect pressure
Pressure
- Pressure is a sustained sensation over a large area.
- Type I and Type II cutaneous mechanoreceptors contribute to pressure sensation.
Vibration
- Sensations of vibration result from repetitive stimulation of tactile receptors.
- Meissner corpuscles detect lower frequency vibrations. Pacinian corpuscles detect higher frequency vibrations.
- Lamellar corpuscles (Pacinian) are distributed throughout the body in dermis, and subcutaneous tissue, muscles, tendons, and around joints, mammary glands, external genitalia, pancreas and urinary bladder.
Itch and Tickle
- Itch is thought to involve mechanical, temperature, or chemical stimuli (e.g., bradykinin and histamine).
- Itch is not fully understood.
- Tickle is thought to involve free nerve endings, and is not fully understood.
Phantom Limb Sensations
- Patients with an amputated limb may experience sensations as if the limb were still present.
- An older explanation suggests the cerebral cortex interprets as coming from the phantom limb.
- Neurons in the brain that previously received signals re-organizes (plasticity), and now sensations elsewhere in the body create a phantom sensation from the former limb.
Thermal Sensations
- Cold receptors—located in stratum basale of epidermis; attached to medium-diameter myelinated A fibers, and few unmyelinated C fibers. Activated by temperatures between 10° and 35°C (50–95°F).
- Warm receptors—located in dermis; attached to small-diameter, unmyelinated C fibers. Activated by temperatures between 30° and 45°C (86–113°F). Respond rapidly at first, but generate low-frequency impulses. Pain is produced below 10°C and above 45°C.
Pain Sensations
- Free nerve endings, activated by intense thermal, mechanical, or chemical stimuli, present in virtually all body tissues, except the brain.
- Tissue irritation or injury releases chemicals (e.g., prostaglandins, substance P, kinins, potassium ions) that stimulate nociceptors.
- Pain may persist even after the initial stimulus is removed, because pain-mediating chemicals linger.
- Conditions such as excessive distention, prolonged contractions, muscle spasms, and ischemia can elicit pain.
Pain Sensations (Fast Pain)
- Occurs rapidly (0.1 second) after stimuli, felt as acute, sharp, or pricking pain
- Felt in the skin, propagate along medium-diameter, myelinated A fibers.
Pain Sensations (Slow Pain)
- Begins more slowly and increases in intensity, felt as burning, aching, or throbbing pain,
- Occurs in both the skin and internal organs. Propagates along small-diameter, unmyelinated C fibers.
Pain Sensations (Visceral Pain)
- Unlike somatic pain, usually felt in or just under the skin that overlies the stimulated organ.
- Can be caused by localized damage (e.g., cutting intestines) or diffuse stimulation (e.g., distension of a bile duct from a gallstone, or distension of the ureter from a kidney stone)
- Can be referred, meaning felt in a surface area far from the stimulated organ
Pain Threshold vs. Pain Tolerance
- Pain threshold—the minimum stimulus intensity required to elicit a pain response.
- Pain tolerance—the maximum amount of pain an individual can endure. Vary widely between individuals and is not well-understood.
Drugs for Pain
- Analgesics block prostaglandin and thromboxane formation, which stimulate nociceptors.
- Local anesthetics block voltage-gated sodium channels in the axons of first-order pain neurons.
- Opiates alter pain perception in the brain, but pain may still be perceived differently.
Proprioception
- Proprioception is the awareness of the position, location, and movement of one's body parts, without having to look.
- Kinesthesia is the perception of body movements
Proprioceptors
- Embedded in muscles, tendons, and joints, helping to understand the degree of muscle contraction, tension on tendons, and joint position.
Muscle Spindle
- Located in skeletal muscles, monitors changes in muscle length, participates in stretch reflex.
- Consists of slowly adapting sensory nerve endings
- Surrounded by extrafusal fibers, which are controlled by alpha motor neurons.
Golgi Tendon Organ (GTO)
- Located at the junction of tendons and muscles, detects changes in muscle tension or excessive tension
- Generates nerve impulses that go to the CNS, providing information about muscle tension changes
- Helps to inhibit muscle contraction, relieves excessive tension
Joint Kinesthetic Receptors
- Located within and around the articular capsules of synovial joints.
Somatic Sensory Pathways
- Relay information about somatic receptors to the primary somatosensory area in cerebral cortex and cerebellum.
- Usually made up of first-order, second-order, and third-order neurons.
Somatic Sensory Pathways (First-Order Neurons)
- Conduct impulses from somatic receptors to the CNS (brainstem or spinal cord).
Somatic Sensory Pathways (Second-Order Neurons)
- Conduct impulses from CNS to thalamus—crosses over to the opposite side of the body in the brainstem or spinal cord before ascending to the thalamus—Sensory info from one side of body reaches the contralateral half of the thalamus
Somatic Sensory Pathways (Third-Order Neurons)
- Conduct impulses from the thalamus to the primary somatosensory area in the cortex, (post-central Gyrus in parietal lobe)
Somatic Sensory Pathways (Posterior Column-Medial Lemniscus Pathway)
- Conducts impulses for touch, pressure, vibration, and conscious proprioception from upper limbs, trunk, neck, and posterior head
- Impulses travel up the spinal cord cuneate fasiculus to the cuneate nuclei
- Impulses from lower limbs and trunk go up the gracile fasiculus to the gracile nuclei
Somatic Sensory Pathways (Anterolateral Pathways)
- Mainly carries pain, temperature, crude touch, tickle, and itch sensations.
- Impulses poorly localised on these pathways.
Somatic Sensory Pathways (Trigeminothalamic Pathways)
- Pathway for most somatic sensation (tactile, thermal, pain, and proprioception) from the face, nasal cavity, oral cavity, and teeth that ascends to cerebral cortex
- Consists of 3-neuron sets.
Somatic Sensory Pathways (Spinocerebellar Pathways)
- Major proprioceptive impulses from the trunk and limbs to the ipsilateral cerebellum
- Critical for posture, balance, and smooth movement
Primary Somatosensory Area
- Located in the postcentral gyri of the parietal lobes.
- Receives signals from the opposite side of the body.
- The degree of sensitivity is proportional to the number of sensory receptors in a given area.
Syphilis
- Bacterial infection (Treponema pallidum)
- Late stage neurosyphilis: progressive spinal cord degeneration.
- Posterior column damage: loss of conscious proprioception, results in gait disturbances.
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Description
Test your knowledge on the various types of sensory receptors responsible for detecting touch, pressure, temperature, and vibrations. This quiz covers key concepts such as proprioceptors and the characteristics of different tactile receptors. Challenge yourself and enhance your understanding of sensory physiology!