MCAT Psychological Social Foundations Flashcards: 6a Somatosensation Taste Smell

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This deck focuses on 6a Somatosensation Taste Smell, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Psychological Social Foundations.

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Flashcard 1: What receptor type detects skin stretch via Ruffini endings?

Answer: Mechanoreceptors (slow-adapting stretch receptors). Ruffini endings detect sustained skin deformation and stretching.

Flashcard 2: What is proprioception, and which receptors primarily support it?

Answer: Sense of body position; muscle spindles and Golgi tendon organs. Monitors joint angles and muscle tension for spatial awareness.

Flashcard 3: What is the primary function of mechanoreceptors in the skin?

Answer: Transduce mechanical stimuli (touch, pressure, vibration) into neural signals. Convert physical deformation into electrical signals for the nervous system.

Flashcard 4: What is the term for non-painful stimulus being perceived as painful, often after injury?

Answer: Allodynia. Central sensitization causes normally innocuous stimuli to hurt.

Flashcard 5: Which CNS structure is the primary relay for somatosensory signals to the cortex?

Answer: Thalamus. All somatosensory pathways synapse here before reaching cortex.

Flashcard 6: What are the five basic taste modalities tested on the MCAT?

Answer: Sweet, sour, salty, bitter, umami. Detected by specific taste receptor cells on tongue papillae.

Flashcard 7: What is the spinothalamic (anterolateral) pathway primarily responsible for?

Answer: Pain, temperature, and crude touch. Decussates at the spinal level and ascends to convey affective aspects of touch and nociceptive signals.

Flashcard 8: What is the spinothalamic (anterolateral) pathway primarily responsible for?

Answer: Pain, temperature, and crude touch. Crosses at spinal level to carry nociceptive/thermal signals.

Flashcard 9: What is the function of mechanoreceptors in somatosensation?

Answer: Transduce mechanical stimuli (touch, pressure, vibration, stretch). Convert physical deformation into electrical signals.

Flashcard 10: Which afferent fibers conduct slow, dull, aching pain?

Answer: C fibers. Unmyelinated fibers for persistent, diffuse pain signals.

Flashcard 11: What are the five basic taste qualities typically tested on the MCAT?

Answer: Sweet, sour, salty, bitter, and umami. Each mediated by specific receptors on taste bud cells.

Flashcard 12: Which pathway carries vibration, fine touch, and proprioception to the brain?

Answer: Dorsal column–medial lemniscus pathway. Crosses at medulla and ascends through medial lemniscus.

Flashcard 13: What receptor type detects potentially damaging stimuli and pain?

Answer: Nociceptors. Free nerve endings respond to extreme temperatures, chemicals, or mechanical damage to alert the body to harm.

Flashcard 14: What is two-point threshold (two-point discrimination) used to assess?

Answer: Tactile acuity; smallest distance sensed as two separate touches. Tests receptor density and cortical representation.

Flashcard 15: What cortical region is the primary somatosensory cortex (S1)?

Answer: Postcentral gyrus of the parietal lobe. Processes and integrates somatosensory information, with neurons organized in a topographic map of the body.

Flashcard 16: What does the somatosensory homunculus represent?

Answer: Cortical map where body parts with higher acuity have more area. Lips, hands, face have disproportionately large representation.

Flashcard 17: What is somatotopic organization in the somatosensory system?

Answer: Body regions map systematically onto S1 (sensory homunculus). Larger cortical areas for sensitive regions like lips/fingers.

Flashcard 18: What is transduction in olfaction based on at the receptor neuron level?

Answer: Odorant GPCRs activate Golf → cAMP-gated cation channels. G-protein cascade opens channels causing depolarization.

Flashcard 19: What are the five basic taste qualities typically tested on the MCAT?

Answer: Sweet, sour, salty, bitter, umami. Each activates specific taste receptor types on taste buds.

Flashcard 20: Which fiber type is most associated with slow, dull, aching pain transmission?

Answer: C fibers. Unmyelinated fibers conduct slowly, producing lingering pain.

Flashcard 21: What is the primary function of taste buds?

Answer: Chemoreception: transduce dissolved chemicals into neural signals. Taste cells bind specific molecules triggering depolarization.

Flashcard 22: What type of sensory receptor detects painful stimuli such as tissue damage?

Answer: Nociceptors. Free nerve endings activated by harmful mechanical, thermal, or chemical stimuli.

Flashcard 23: Which afferent fibers conduct fast, sharp pain?

Answer: A-delta fibers. Myelinated fibers for immediate, localized pain signals.

Flashcard 24: What is the primary reason flavor perception decreases during nasal congestion?

Answer: Reduced retronasal olfaction, not loss of taste receptor function. Flavor combines taste and smell; blocked nose prevents aroma detection.

Flashcard 25: Identify the CNS pathway that carries pain and temperature information to the brain.

Answer: Spinothalamic (anterolateral) pathway. Crosses at spinal cord level; carries nociceptive signals.

Flashcard 26: What receptor type detects light touch and vibration in the skin?

Answer: Mechanoreceptors. These receptors transduce mechanical stimuli into neural signals for tactile discrimination and vibration sensing.

Flashcard 27: Which cranial nerve carries taste from the posterior $\frac{1}{3}$ of the tongue?

Answer: Glossopharyngeal nerve (CN IX). Innervates circumvallate papillae, relaying signals from the back of the tongue to central gustatory pathways.

Flashcard 28: Which cranial nerve carries taste from the posterior $\frac{1}{3}$ of the tongue?

Answer: CN IX (glossopharyngeal nerve). Innervates circumvallate papillae and pharyngeal taste buds.

Flashcard 29: What cortical area is the primary somatosensory cortex, and where is it located?

Answer: Postcentral gyrus of the parietal lobe (S1). Receives thalamic input for conscious touch perception.

Flashcard 30: What term describes the topographic mapping of body regions onto the primary somatosensory cortex?

Answer: Somatotopic organization (sensory homunculus). Body parts mapped by sensitivity, not actual size.

Flashcard 31: Which taste modality is most closely associated with detection of amino acids such as glutamate?

Answer: Umami. Glutamate receptors detect savory protein flavors.

Flashcard 32: What is the term for smell molecules binding to receptors in the nasal cavity to create neural signals?

Answer: Olfactory transduction. Odorants bind to G-protein coupled receptors in olfactory epithelium.

Flashcard 33: What are the five basic taste modalities recognized in humans?

Answer: Sweet, sour, salty, bitter, umami. Each uses different receptors and signaling pathways.

Flashcard 34: What is somatosensation in the context of sensory processing?

Answer: Body-related sensation: touch, pressure, pain, temperature, proprioception. Encompasses all sensations from the body including internal awareness.

Flashcard 35: What are nociceptors?

Answer: Pain receptors that respond to tissue damage or potentially harmful stimuli. Free nerve endings that detect mechanical, thermal, or chemical damage.

Flashcard 36: Which cortical region contains the somatotopic map for touch and proprioception processing?

Answer: Primary somatosensory cortex (postcentral gyrus). Located in parietal lobe, organized by body part representation.

Flashcard 37: What is somatotopic organization in the somatosensory cortex?

Answer: Body surface is mapped onto S1 in an ordered layout. Adjacent cortical areas represent contiguous body parts, facilitating localized sensory perception.

Flashcard 38: What are the five basic taste qualities commonly tested on the MCAT?

Answer: Sweet, sour, salty, bitter, umami. Each uses distinct receptors/channels (e.g., T1R for sweet).

Flashcard 39: Which sensory modality has a pathway that can reach cortex without thalamic relay first?

Answer: Olfaction. Direct projections to piriform cortex and limbic structures.

Flashcard 40: What is two-point threshold (two-point discrimination) a measure of?

Answer: Tactile acuity; minimum distance to perceive two touches as distinct. Smaller distances indicate higher receptor density/sensitivity.

Flashcard 41: Which receptor type detects tissue damage and painful stimuli?

Answer: Nociceptors. Free nerve endings respond to harmful stimuli causing pain sensation.

Flashcard 42: Which mechanoreceptor is specialized for skin stretch and sustained pressure?

Answer: Ruffini ending. Slowly adapting receptor that responds to skin deformation.

Flashcard 43: What is the key distinction between fast pain and slow pain signaling?

Answer: Fast: $A\delta$ fibers; slow: C fibers. Myelinated vs unmyelinated fibers determine conduction speed.

Flashcard 44: What is the primary function of nociceptors?

Answer: Detect potentially damaging stimuli and signal pain. Free nerve endings that respond to tissue damage or threat.

Flashcard 45: Which olfactory brain structure receives input directly from receptor neurons?

Answer: Olfactory bulb. First processing center before signals reach higher brain areas.

Flashcard 46: Which cranial nerves carry taste information from the tongue to the brain?

Answer: CN VII, CN IX, and CN X. Facial (VII), glossopharyngeal (IX), and vagus (X) nerves.

Flashcard 47: What is the dorsal column–medial lemniscus pathway primarily responsible for?

Answer: Fine touch, vibration, and proprioception. Ascends ipsilaterally in the spinal cord, decussates in the medulla, and carries precise tactile and positional information to the thalamus.

Flashcard 48: Identify the CNS pathway that carries fine touch, vibration, and proprioception to the brain.

Answer: Dorsal column–medial lemniscus pathway. Crosses at medulla; carries discriminative touch sensations.

Flashcard 49: Which mechanoreceptor provides fine spatial detail such as edges and texture?

Answer: Merkel (tactile) disc. Slowly adapting receptor with small receptive fields for precision.

Flashcard 50: Which feature distinguishes olfaction from other senses in initial processing?

Answer: It bypasses the thalamus before reaching primary cortex. Direct connection to limbic system explains smell-memory link.

Flashcard 51: Which cranial nerve carries taste from the epiglottis and lower pharynx?

Answer: Vagus nerve (CN X). Minor taste contribution compared to CN VII and IX.

Flashcard 52: Which mechanoreceptor is specialized for edges, points, and fine spatial detail?

Answer: Merkel (tactile) disc. Slowly adapting receptor with small receptive fields for texture.

Flashcard 53: What is lateral inhibition in sensory systems?

Answer: Neighboring neurons inhibit each other to sharpen contrast and localization. Enhances perception by increasing signal-to-noise ratio at borders.

Flashcard 54: Identify the cranial nerve that carries taste from the anterior $\frac{2}{3}$ of the tongue.

Answer: Facial nerve (CN VII), via chorda tympani. Chorda tympani branch carries taste to brainstem nucleus.

Flashcard 55: Which skin receptor is most associated with detecting light touch and flutter?

Answer: Meissner corpuscles. Superficial, rapidly adapting receptors in dermal papillae.

Flashcard 56: What is the primary somatosensory cortex location for tactile processing?

Answer: Postcentral gyrus (S1) of the parietal lobe. Located behind central sulcus; receives thalamic sensory input.

Flashcard 57: Which taste modality is most closely associated with detecting toxins?

Answer: Bitter. Evolved to detect potentially harmful alkaloids in plants.

Flashcard 58: What is the gate control theory of pain?

Answer: Spinal gating modulates pain; touch input can inhibit pain signals. Non-painful input closes the 'gate' to pain signals.

Flashcard 59: What is the somatotopic map (sensory homunculus) in S1?

Answer: Ordered cortical map where adjacent body regions map to adjacent cortex. Body parts with more receptors get larger cortical representation.

Flashcard 60: Which thalamic nucleus is the main relay for body somatosensory input to cortex?

Answer: Ventral posterolateral (VPL) nucleus. Body sensations relay here before reaching somatosensory cortex.

Flashcard 61: Which cranial nerve carries taste from the posterior $\frac{1}{3}$ of the tongue?

Answer: Glossopharyngeal nerve (CN IX). Also carries general sensation from this tongue region.

Flashcard 62: Which taste modality is most strongly associated with detection of $\text{Na}^+$ salts?

Answer: Salty. Sodium ions pass through epithelial sodium channels (ENaC).

Flashcard 63: Which thalamic structure is the primary relay for somatosensory input to cortex?

Answer: Ventral posterior nucleus (VPL/VPM). Serves as a synaptic relay station, processing and forwarding somatosensory signals to the primary cortex.

Flashcard 64: What is somatosensation?

Answer: Sensation of touch, temperature, pain, and body position. Integrates multiple sensory inputs from the skin and body to perceive physical interactions with the environment.

Flashcard 65: What does the somatosensory homunculus represent?

Answer: Cortical body map with area proportional to receptor density. Hands and lips are disproportionately large due to sensitivity.

Flashcard 66: What are nociceptors?

Answer: Pain receptors that respond to tissue damage or potentially damaging stimuli. Free nerve endings that signal actual or potential tissue harm.

Flashcard 67: Which fiber type carries fast, sharp pain?

Answer: A-delta fibers. Myelinated fibers that transmit initial, localized pain.

Flashcard 68: What is proprioception?

Answer: Sense of body position and movement in space. Relies on muscle spindles and joint receptors for feedback.

Flashcard 69: What is proprioception?

Answer: Sense of body position and movement from muscles, tendons, and joints. Unconscious awareness crucial for coordinated movement.

Flashcard 70: Which cutaneous receptor is most associated with pressure edges and shape detection?

Answer: Merkel (tactile) disc. Slowly adapting receptor with small receptive fields for fine detail.

Flashcard 71: Which fiber type is faster and typically carries sharp, well-localized pain?

Answer: A-delta fibers. Myelinated fibers that transmit initial, sharp pain rapidly.

Flashcard 72: What is the two-point discrimination test primarily measuring in somatosensation?

Answer: Tactile acuity related to receptive field size and receptor density. Smaller fields and higher density improve spatial resolution.

Flashcard 73: What is the key anatomical feature that makes olfaction unique among senses on the MCAT?

Answer: It bypasses the thalamus for primary cortical processing. Direct projection to piriform cortex enables rapid processing.

Flashcard 74: Which sensory system uniquely bypasses the thalamus before reaching cortex?

Answer: Olfaction (smell). Projects directly to piriform cortex and limbic structures.

Flashcard 75: What does the somatosensory homunculus represent in primary somatosensory cortex?

Answer: Body map with cortical area proportional to sensory receptor density. Lips and hands have disproportionately large representation.

Flashcard 76: Which cortical region is the primary target for conscious touch processing?

Answer: Primary somatosensory cortex (postcentral gyrus). Located in parietal lobe; contains somatotopic map (homunculus).

Flashcard 77: What is the first brain structure that receives input from olfactory receptor neurons?

Answer: Olfactory bulb (via glomeruli). Synapses occur in spherical structures called glomeruli.

Flashcard 78: What is the key decussation location for the dorsal column–medial lemniscus pathway?

Answer: Medulla (after synapse in gracile/cuneate nuclei). Fibers cross after synapsing in nuclei gracilis and cuneatus.

Flashcard 79: What are the four primary cutaneous (skin) sensations classically described in MCAT psych?

Answer: Pressure, warmth, cold, pain. These four modalities represent distinct receptor types in skin.

Flashcard 80: What is the primary somatosensory cortex location that receives touch and proprioception input?

Answer: Postcentral gyrus of the parietal lobe (S1). S1 processes tactile and position information from the body.

Flashcard 81: What is olfaction, and what type of receptor detects odorants?

Answer: Smell; GPCR olfactory receptors on olfactory sensory neurons. Each receptor responds to specific odorant molecules.

Flashcard 82: What is proprioception?

Answer: Sense of body position and movement from muscles, tendons, and joints. Internal sensors provide awareness of body positioning without vision.

Flashcard 83: Identify the structure where olfactory receptor neuron axons synapse before reaching cortex.

Answer: Olfactory bulb (glomeruli with mitral/tufted cells). First relay station organizing odor information by type.

Flashcard 84: What are taste buds, and where are they located?

Answer: Clusters of gustatory receptor cells located mainly on tongue papillae. Each bud contains 50-100 cells that detect chemical stimuli.

Flashcard 85: Which skin mechanoreceptor detects high-frequency vibration and fine texture?

Answer: Pacinian corpuscles. Deep, rapidly adapting, detect vibrations 200-300 Hz.

Flashcard 86: What is the gate control theory of pain?

Answer: Spinal gating modulates pain transmission via competing input. Non-painful input can close the 'gate' to pain signals.

Flashcard 87: Which sensory system uniquely projects to cortex without first relaying through the thalamus?

Answer: Olfaction. Olfactory bulb projects directly to piriform cortex, bypassing thalamus.

Flashcard 88: What is the key idea of the gate control theory of pain?

Answer: Nonpainful input can inhibit pain transmission in the spinal cord. Explains why rubbing an injury reduces pain perception.

Flashcard 89: What term describes decreased pain perception during acute stress or injury?

Answer: Stress-induced analgesia. Endorphin release during stress reduces pain perception.

Flashcard 90: Which cranial nerve carries taste from the posterior $\frac{1}{3}$ of the tongue?

Answer: CN IX (glossopharyngeal nerve). Innervates circumvallate and foliate papillae.

Flashcard 91: Which taste modality is most associated with detecting amino acids such as glutamate?

Answer: Umami. Glutamate receptors detect savory protein taste.

Flashcard 92: Which mechanoreceptor is specialized for light touch and texture (fine detail)?

Answer: Meissner corpuscle. Rapidly adapting receptor in superficial skin layers.

Flashcard 93: What is the primary spinal pathway for fine touch, vibration, and proprioception?

Answer: Dorsal column–medial lemniscus pathway. Carries discriminative touch signals via medulla to contralateral cortex.

Flashcard 94: What is taste transduction for bitter stimuli primarily mediated by?

Answer: GPCR activation (often protective against toxins). T2R family receptors evolved to detect plant toxins.

Flashcard 95: What are the four major cutaneous mechanoreceptors and their primary stimulus types?

Answer: Meissner: light touch; Merkel: pressure; Pacinian: vibration; Ruffini: stretch. Each receptor specializes in detecting specific mechanical stimuli.

Flashcard 96: What is the key distinction between olfaction and other senses regarding thalamic relay?

Answer: Olfaction reaches cortex without an initial thalamic relay. Direct pathway from olfactory bulb to piriform cortex.

Flashcard 97: What receptor type primarily detects light touch and low-frequency vibration in glabrous skin?

Answer: Meissner corpuscles. Rapidly adapting receptors in superficial dermis detect gentle stimuli.

Flashcard 98: What is somatosensation?

Answer: Body sensations: touch, pressure, vibration, pain, temperature, proprioception. Encompasses all sensory modalities from skin, muscles, and joints.

Flashcard 99: Which two properties of a stimulus are encoded by action potentials?

Answer: Intensity by firing rate; location by which receptors/neurons are activated. Frequency encodes strength; spatial pattern encodes position.

Flashcard 100: What are the primary mechanoreceptors in glabrous (hairless) skin and their key stimulus types?

Answer: Meissner: light touch; Pacinian: vibration; Merkel: pressure; Ruffini: stretch. Four main mechanoreceptors detect different mechanical stimuli.