Somatosensation, Taste, and Smell (6A) - MCAT Psychological and Social Foundations
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What is the primary somatosensory cortex, and where is it located?
What is the primary somatosensory cortex, and where is it located?
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Postcentral gyrus of parietal lobe; processes somatic sensory input. Located behind central sulcus; receives touch/pressure signals.
Postcentral gyrus of parietal lobe; processes somatic sensory input. Located behind central sulcus; receives touch/pressure signals.
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Which sensory system uniquely bypasses the thalamus before reaching cortex?
Which sensory system uniquely bypasses the thalamus before reaching cortex?
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Olfaction (smell). Projects directly to piriform cortex and limbic structures.
Olfaction (smell). Projects directly to piriform cortex and limbic structures.
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What is the first brain structure that receives input from olfactory receptor neurons?
What is the first brain structure that receives input from olfactory receptor neurons?
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Olfactory bulb (via glomeruli). Synapses occur in spherical structures called glomeruli.
Olfactory bulb (via glomeruli). Synapses occur in spherical structures called glomeruli.
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What is olfaction, and what type of receptor detects odorants?
What is olfaction, and what type of receptor detects odorants?
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Smell; GPCR olfactory receptors on olfactory sensory neurons. Each receptor responds to specific odorant molecules.
Smell; GPCR olfactory receptors on olfactory sensory neurons. Each receptor responds to specific odorant molecules.
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What are the five basic taste qualities commonly tested on the MCAT?
What are the five basic taste qualities commonly tested on the MCAT?
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Sweet, sour, salty, bitter, umami. Each uses different receptors and transduction mechanisms.
Sweet, sour, salty, bitter, umami. Each uses different receptors and transduction mechanisms.
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Which receptors detect sustained pressure and fine spatial detail (edges, texture)?
Which receptors detect sustained pressure and fine spatial detail (edges, texture)?
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Merkel (tactile) discs. Slowly adapting receptors crucial for reading Braille.
Merkel (tactile) discs. Slowly adapting receptors crucial for reading Braille.
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Which afferent fibers conduct fast, sharp pain?
Which afferent fibers conduct fast, sharp pain?
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A-delta fibers. Myelinated fibers for immediate, localized pain signals.
A-delta fibers. Myelinated fibers for immediate, localized pain signals.
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Which afferent fibers conduct slow, dull, aching pain?
Which afferent fibers conduct slow, dull, aching pain?
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C fibers. Unmyelinated fibers for persistent, diffuse pain signals.
C fibers. Unmyelinated fibers for persistent, diffuse pain signals.
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What is proprioception?
What is proprioception?
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Sense of body position and movement from muscles, tendons, and joints. Unconscious awareness crucial for coordinated movement.
Sense of body position and movement from muscles, tendons, and joints. Unconscious awareness crucial for coordinated movement.
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What is taste transduction for sour stimuli primarily mediated by?
What is taste transduction for sour stimuli primarily mediated by?
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H+ (acid) effects on ion channels causing depolarization. Protons block K+ channels and activate other channels.
H+ (acid) effects on ion channels causing depolarization. Protons block K+ channels and activate other channels.
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What does the somatotopic map (sensory homunculus) represent?
What does the somatotopic map (sensory homunculus) represent?
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Body regions mapped to adjacent cortical areas by input location. Larger cortical areas for more sensitive body parts (lips, hands).
Body regions mapped to adjacent cortical areas by input location. Larger cortical areas for more sensitive body parts (lips, hands).
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Which receptors detect light touch and low-frequency vibration in glabrous skin?
Which receptors detect light touch and low-frequency vibration in glabrous skin?
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Meissner corpuscles. Rapidly adapting receptors in hairless skin areas.
Meissner corpuscles. Rapidly adapting receptors in hairless skin areas.
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Which receptors detect deep pressure and high-frequency vibration?
Which receptors detect deep pressure and high-frequency vibration?
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Pacinian corpuscles. Deep, onion-shaped receptors that rapidly adapt to pressure changes.
Pacinian corpuscles. Deep, onion-shaped receptors that rapidly adapt to pressure changes.
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What is taste transduction for salty stimuli primarily mediated by?
What is taste transduction for salty stimuli primarily mediated by?
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Na+ influx through ion channels (depolarization). ENaC channels allow sodium entry, triggering depolarization.
Na+ influx through ion channels (depolarization). ENaC channels allow sodium entry, triggering depolarization.
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What is the function of Golgi tendon organs in proprioception?
What is the function of Golgi tendon organs in proprioception?
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Detect muscle tension (force) in tendons. Prevent muscle damage by signaling excessive force.
Detect muscle tension (force) in tendons. Prevent muscle damage by signaling excessive force.
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What is the function of muscle spindles in proprioception?
What is the function of muscle spindles in proprioception?
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Detect muscle length and rate of stretch. Intrafusal fibers signal changes in muscle length.
Detect muscle length and rate of stretch. Intrafusal fibers signal changes in muscle length.
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Which cutaneous receptors are most associated with skin stretch and hand shape?
Which cutaneous receptors are most associated with skin stretch and hand shape?
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Ruffini endings. Slowly adapting receptors that signal joint position.
Ruffini endings. Slowly adapting receptors that signal joint position.
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What are nociceptors?
What are nociceptors?
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Pain receptors that respond to tissue damage or potentially damaging stimuli. Free nerve endings that signal actual or potential tissue harm.
Pain receptors that respond to tissue damage or potentially damaging stimuli. Free nerve endings that signal actual or potential tissue harm.
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Which pathway primarily carries fine touch, vibration, and proprioception?
Which pathway primarily carries fine touch, vibration, and proprioception?
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Dorsal column–medial lemniscus pathway. Ascends ipsilaterally, crosses at medulla.
Dorsal column–medial lemniscus pathway. Ascends ipsilaterally, crosses at medulla.
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What are the five basic taste modalities tested on the MCAT?
What are the five basic taste modalities tested on the MCAT?
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Sweet, salty, sour, bitter, umami. Each detected by specific receptor types on taste buds.
Sweet, salty, sour, bitter, umami. Each detected by specific receptor types on taste buds.
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Which cranial nerves carry taste from the anterior $\frac{2}{3}$ of the tongue?
Which cranial nerves carry taste from the anterior $\frac{2}{3}$ of the tongue?
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CN VII (facial nerve; chorda tympani). Chorda tympani branch innervates fungiform papillae.
CN VII (facial nerve; chorda tympani). Chorda tympani branch innervates fungiform papillae.
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Which cranial nerve carries taste from the posterior $\frac{1}{3}$ of the tongue?
Which cranial nerve carries taste from the posterior $\frac{1}{3}$ of the tongue?
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CN IX (glossopharyngeal nerve). Innervates circumvallate and foliate papillae.
CN IX (glossopharyngeal nerve). Innervates circumvallate and foliate papillae.
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Which cranial nerve carries olfactory information from the nasal cavity?
Which cranial nerve carries olfactory information from the nasal cavity?
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Cranial nerve I (olfactory nerve). Synapses directly in olfactory bulb before cortical processing.
Cranial nerve I (olfactory nerve). Synapses directly in olfactory bulb before cortical processing.
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What is the olfactory receptor neuron type and where is it located?
What is the olfactory receptor neuron type and where is it located?
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Bipolar neurons in the olfactory epithelium. Only neurons that directly contact external environment.
Bipolar neurons in the olfactory epithelium. Only neurons that directly contact external environment.
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Which spinal tract primarily carries pain and temperature to the brain?
Which spinal tract primarily carries pain and temperature to the brain?
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Spinothalamic tract (anterolateral system). Crosses at spinal level and ascends contralaterally.
Spinothalamic tract (anterolateral system). Crosses at spinal level and ascends contralaterally.
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What is somatosensation?
What is somatosensation?
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Body senses: touch, pressure, pain, temperature, proprioception. Encompasses all sensory modalities from skin, muscles, and joints.
Body senses: touch, pressure, pain, temperature, proprioception. Encompasses all sensory modalities from skin, muscles, and joints.
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What is the primary somatosensory cortex (S1) location?
What is the primary somatosensory cortex (S1) location?
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Postcentral gyrus of the parietal lobe. Located behind the central sulcus, receives sensory input from the body.
Postcentral gyrus of the parietal lobe. Located behind the central sulcus, receives sensory input from the body.
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What does the somatosensory homunculus represent in S1?
What does the somatosensory homunculus represent in S1?
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Cortical area proportional to sensory receptor density. Body parts with more receptors get larger cortical representation.
Cortical area proportional to sensory receptor density. Body parts with more receptors get larger cortical representation.
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Which mechanoreceptor detects light touch and low-frequency vibration?
Which mechanoreceptor detects light touch and low-frequency vibration?
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Meissner corpuscle. Superficial, rapidly adapting receptor in glabrous skin.
Meissner corpuscle. Superficial, rapidly adapting receptor in glabrous skin.
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Which mechanoreceptor detects deep pressure and high-frequency vibration?
Which mechanoreceptor detects deep pressure and high-frequency vibration?
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Pacinian corpuscle. Deep, rapidly adapting receptor sensitive to vibration.
Pacinian corpuscle. Deep, rapidly adapting receptor sensitive to vibration.
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