MCAT Psychological Social Foundations Flashcards: 6a Sensory Receptors Neural Pathways

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This deck focuses on 6a Sensory Receptors Neural Pathways, 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: Which cortical lobe contains primary auditory cortex (A1)?

Answer: Temporal lobe. Superior temporal gyrus processes sound and auditory information.

Flashcard 2: Which thalamic nucleus relays most visual information to primary visual cortex (V1)?

Answer: Lateral geniculate nucleus (LGN). Six-layered structure organizing visual info from optic tract.

Flashcard 3: Which law states that the JND is a constant fraction of the initial stimulus intensity?

Answer: Webers law. States that $\Delta I/I = k$ (constant ratio of change to initial intensity).

Flashcard 4: Which theory explains pitch coding by frequency of auditory nerve firing for lower frequencies?

Answer: Frequency theory. Nerve firing rate matches sound wave frequency up to ~1000 Hz.

Flashcard 5: Which somatosensory pathway carries pain and temperature to cortex?

Answer: Spinothalamic (anterolateral) pathway. Crosses at spinal level; relays through VPL thalamus.

Flashcard 6: What is the term for the minimum stimulus intensity that is detected $50\%$ of the time?

Answer: Absolute threshold. The weakest stimulus detected half the time.

Flashcard 7: What is the name of the sensory receptor type that detects mechanical pressure or vibration?

Answer: Mechanoreceptor. Responds to physical deformation from touch, pressure, or stretch.

Flashcard 8: What is a sensory receptor in terms of transduction and the type of stimulus it detects?

Answer: A specialized cell that transduces a specific stimulus into neural signals. Receptors are specialized for one stimulus type and convert it to action potentials.

Flashcard 9: Which thalamic nucleus relays auditory information to primary auditory cortex?

Answer: Medial geniculate nucleus (MGN). Processes tonotopic information from inferior colliculus.

Flashcard 10: Which retinal cells carry output from the retina to the optic nerve?

Answer: Ganglion cells. Their axons form the optic nerve.

Flashcard 11: What is the difference between tonic and phasic sensory receptors?

Answer: Tonic: sustained firing; phasic: rapid adaptation to constant stimuli. Tonic receptors signal continuously; phasic receptors signal changes only.

Flashcard 12: What type of receptor primarily transduces pressure, vibration, and stretch?

Answer: Mechanoreceptors. These detect mechanical deformation of tissue.

Flashcard 13: What is the primary role of the medial geniculate nucleus (MGN)?

Answer: Thalamic relay from auditory pathways to auditory cortex. Processes auditory signals before cortical projection.

Flashcard 14: Which spinal pathway primarily carries pain and temperature information to the brain?

Answer: Spinothalamic tract (anterolateral system). Crosses at spinal level and ascends contralaterally.

Flashcard 15: What thalamic nucleus is the primary relay for somatosensory input from the face?

Answer: Ventral posteromedial nucleus (VPM). Relays touch/proprioception from face via trigeminal nerve.

Flashcard 16: What thalamic nucleus is the primary relay for somatosensory input from the body (not face)?

Answer: Ventral posterolateral nucleus (VPL). Relays touch/proprioception from body below neck to cortex.

Flashcard 17: Which receptor type primarily detects temperature changes at the skin surface?

Answer: Thermoreceptors. Contain ion channels that open/close in response to temperature changes.

Flashcard 18: What is the primary cortical area that receives auditory input relayed by the MGN?

Answer: Primary auditory cortex in the superior temporal gyrus. Heschl's gyrus processes frequency and temporal sound patterns.

Flashcard 19: Which thalamic nucleus relays somatosensory information to the primary somatosensory cortex?

Answer: Ventral posterior nucleus (VPL/VPM). VPL processes body; VPM processes face sensations.

Flashcard 20: Which thalamic nucleus relays visual information to the primary visual cortex?

Answer: Lateral geniculate nucleus (LGN). Part of thalamus that processes visual information.

Flashcard 21: What does Weber's law state about the just noticeable difference (JND)?

Answer: JND is a constant fraction of baseline intensity: $\frac{\Delta I}{I}=k$. The ratio of change to baseline remains constant across intensities.

Flashcard 22: Which thalamic nucleus relays visual information to primary visual cortex?

Answer: Lateral geniculate nucleus (LGN). LGN processes visual signals before sending to occipital lobe.

Flashcard 23: Which pathway carries fine touch, vibration, and proprioception to the thalamus?

Answer: Dorsal column–medial lemniscus pathway. Crosses at medulla; precise touch and position sense.

Flashcard 24: What is the general pathway name for sensory signals traveling to the CNS?

Answer: Afferent pathway. Carries sensory information toward the brain.

Flashcard 25: Which retinal photoreceptor supports color vision and high visual acuity?

Answer: Cones. These photoreceptors have pigments for red, green, or blue light, enabling color perception and detail in bright conditions.

Flashcard 26: Which thalamic nucleus relays somatosensory information to primary somatosensory cortex?

Answer: Ventral posterior nucleus (VPL/VPM). VPL receives body info; VPM receives face/head info.

Flashcard 27: Which somatosensory receptors detect light touch and flutter in glabrous skin?

Answer: Meissner corpuscles. Rapidly adapting mechanoreceptors in hairless skin areas like fingertips.

Flashcard 28: Which sensory modality reaches cortex without first synapsing in the thalamus?

Answer: Olfaction (smell). Smell signals go directly to olfactory cortex, bypassing thalamus.

Flashcard 29: Which receptor type detects temperature changes (hot or cold)?

Answer: Thermoreceptors. Free nerve endings that respond to temperature; separate cold and warm receptors.

Flashcard 30: What is the main somatosensory pathway for pain and temperature?

Answer: Spinothalamic (anterolateral) pathway. Crosses spinal cord to carry nociceptive and thermal signals.

Flashcard 31: What does Weber's law state about the just-noticeable difference relative to stimulus intensity?

Answer: JND is a constant proportion of baseline intensity. Weber found that JND = k × I, where k is constant and I is baseline intensity.

Flashcard 32: Which thalamic nucleus relays visual information from the retina to primary visual cortex?

Answer: Lateral geniculate nucleus (LGN). Part of the visual pathway from eye to occipital lobe.

Flashcard 33: Identify the receptor type that detects mechanical deformation (pressure, vibration, stretch).

Answer: Mechanoreceptors. Respond to physical forces like touch, hearing, and proprioception.

Flashcard 34: Which sensory modality bypasses the thalamus on its initial route to cortex?

Answer: Olfaction (smell). Olfactory signals project directly to cortex without thalamic relay.

Flashcard 35: Which cortical lobe contains the primary somatosensory cortex (postcentral gyrus)?

Answer: Parietal lobe. Postcentral gyrus processes touch, pressure, temperature, and proprioception.

Flashcard 36: Which pathway carries pain and temperature information from body to thalamus?

Answer: Spinothalamic tract (anterolateral system). Crosses at spinal level; slow, poorly localized pain.

Flashcard 37: Which inner ear structure contains hair cells that transduce sound vibrations?

Answer: Organ of Corti (in the cochlea). Hair cells here bend with fluid waves from sound, converting vibrations into neural impulses.

Flashcard 38: What is the retinal region where the optic nerve exits and no photoreceptors are present?

Answer: Optic disc (blind spot). Where ganglion cell axons exit retina, creating a blind spot.

Flashcard 39: What is the difference between an afferent neuron and an efferent neuron?

Answer: Afferent: to CNS; efferent: from CNS to effectors. Afferent carries sensory info inward; efferent carries motor commands outward.

Flashcard 40: Which visual photoreceptor mediates high acuity and color vision in bright light?

Answer: Cones. Concentrated in fovea for detailed central vision.

Flashcard 41: Which retinal photoreceptor is specialized for color vision and high acuity?

Answer: Cones. Three types (S, M, L) contain photopsins for red, green, and blue wavelengths.

Flashcard 42: Identify the receptor type that detects temperature changes in the skin and body.

Answer: Thermoreceptors. Separate receptors for cold and warm sensations.

Flashcard 43: What is tonotopic organization in the cochlea?

Answer: Base codes high frequency; apex codes low frequency. Frequency mapping along cochlear length enables pitch discrimination.

Flashcard 44: Identify the correct mapping: which sensory modality primarily uses chemoreceptors?

Answer: Olfaction and gustation. Smell and taste rely on chemical binding to receptors, unlike mechanical or light-based senses.

Flashcard 45: What is the difference between an afferent neuron and an efferent neuron?

Answer: Afferent: to CNS; efferent: from CNS to muscles/glands. Afferent carries sensory info inward; efferent carries motor commands outward.

Flashcard 46: Which receptor type primarily detects tissue damage or noxious stimuli?

Answer: Nociceptors. Pain receptors respond to potentially harmful stimuli.

Flashcard 47: Identify the receptor type that detects tissue damage and is associated with pain perception.

Answer: Nociceptors. Free nerve endings that signal potential or actual tissue harm.

Flashcard 48: Which sensory receptor type responds primarily to light (photons) in the retina?

Answer: Photoreceptors. Light-sensitive cells containing photopigments.

Flashcard 49: What is the absolute threshold in psychophysics?

Answer: Minimum stimulus detected $50\%$ of the time. The weakest intensity that can be perceived half the time.

Flashcard 50: Which somatosensory receptors detect temperature and pain (noxious stimuli)?

Answer: Free nerve endings (thermoreceptors and nociceptors). Unmyelinated nerve endings that respond to extreme temperatures and tissue damage.

Flashcard 51: What is the difference between adequate stimulus and threshold stimulus for a receptor?

Answer: Adequate: preferred modality; threshold: minimum intensity to detect. Adequate is the optimal stimulus type; threshold is the weakest detectable intensity.

Flashcard 52: What is the function of nociceptors in somatosensation?

Answer: Detect potentially damaging stimuli and signal pain. They respond to tissue damage or extreme temperatures/pressures.

Flashcard 53: Identify the vestibular system function most directly tested on the MCAT.

Answer: Balance and spatial orientation (head position and motion). Inner ear organs detect head movements and maintain equilibrium.

Flashcard 54: Which retinal photoreceptors are most sensitive in dim light and support night vision?

Answer: Rods. Contain rhodopsin, highly sensitive to light but provide no color information.

Flashcard 55: What is lateral inhibition in sensory systems?

Answer: Neighboring neurons inhibit each other to sharpen contrast. Enhances edges and boundaries in sensory perception.

Flashcard 56: Which thalamic nucleus relays auditory information to the primary auditory cortex?

Answer: Medial geniculate nucleus (MGN). Part of thalamus that processes auditory information.

Flashcard 57: What is the correct neural pathway for vision from retina to cortex?

Answer: Retina  optic nerve  LGN (thalamus)  V1 (occipital). Visual signals relay through lateral geniculate nucleus before reaching primary visual cortex.

Flashcard 58: What is the key functional difference between the fovea and the optic disc?

Answer: Fovea: highest acuity; Optic disc: blind spot (no photoreceptors). Fovea has only cones for sharp vision; optic disc lacks receptors entirely.

Flashcard 59: Which option best describes contralateral sensory processing in the somatosensory system?

Answer: Each hemisphere primarily represents sensation from the opposite side of the body. Due to decussation of ascending sensory pathways.

Flashcard 60: What is adequate stimulus, and what does it predict about receptor sensitivity?

Answer: Preferred stimulus type; receptor is most sensitive to that modality. Each receptor type responds best to its specific stimulus modality.

Flashcard 61: Which retinal cells send action potentials through the optic nerve to the brain?

Answer: Retinal ganglion cells. Only ganglion cells generate action potentials in the retina.

Flashcard 62: Identify the correct order of the visual pathway from retina to cortex.

Answer: Retina → optic nerve → optic chiasm → LGN → optic radiations → V1. Visual signals cross at chiasm before reaching thalamus and cortex.

Flashcard 63: What is a sensory receptor in terms of stimulus transduction into neural signals?

Answer: A cell/ending that transduces stimuli into action potentials. Converts physical/chemical stimuli into electrical signals for nervous system processing.

Flashcard 64: Which cranial nerve carries olfactory information from nasal epithelium to the brain?

Answer: Olfactory nerve (CN I). Only cranial nerve that bypasses thalamus, going directly to cortex.

Flashcard 65: What is the key distinction between rods and cones in the retina regarding function?

Answer: Rods: dim light; cones: color and acuity. Rods for scotopic vision; cones for photopic and color vision.

Flashcard 66: Which receptor type primarily detects mechanical deformation (touch, vibration, stretch)?

Answer: Mechanoreceptors. These respond to pressure, vibration, and stretch in skin and organs.

Flashcard 67: What is the correct order of the auditory pathway from cochlea to cortex?

Answer: Cochlea → brainstem → inferior colliculus → MGN → A1. Sound ascends through brainstem nuclei and thalamus to temporal cortex.

Flashcard 68: Identify the structure where nasal retinal fibers cross to the opposite hemisphere in vision.

Answer: Optic chiasm. X-shaped crossing where nasal fibers decussate for binocular vision.

Flashcard 69: What is the functional distinction between afferent and efferent neurons in neural pathways?

Answer: Afferent: sensory to CNS; efferent: motor from CNS to effectors. Afferent = arriving at CNS; efferent = exiting CNS (remember SAME: Sensory-Afferent).

Flashcard 70: Which visual field is processed by the left primary visual cortex (V1)?

Answer: Right visual field. Contralateral processing: left V1 receives right visual field.

Flashcard 71: What is the difference between tonic and phasic receptors?

Answer: Tonic: sustained firing; phasic: rapid adaptation, onset/offset firing. Tonic detect sustained stimuli; phasic detect changes.

Flashcard 72: Which thalamic nucleus relays auditory information to auditory cortex?

Answer: MGN (medial geniculate nucleus). Sound information relays through this thalamic nucleus.

Flashcard 73: Which receptor type detects stretch, vibration, pressure, and body position (proprioception)?

Answer: Mechanoreceptors. Respond to mechanical deformation of tissue.

Flashcard 74: What are the four primary types of sensory receptors by stimulus modality?

Answer: Mechanoreceptors, chemoreceptors, photoreceptors, thermoreceptors. Classified by the type of physical stimulus they detect.

Flashcard 75: Identify the visual photoreceptor that mediates high-acuity color vision in bright light.

Answer: Cones. Three cone types (S, M, L) enable trichromatic vision in photopic conditions.

Flashcard 76: What are the four main sensory receptor types by stimulus modality?

Answer: Mechanoreceptors, chemoreceptors, photoreceptors, thermoreceptors. These four types classify receptors by the stimulus they detect.

Flashcard 77: Which thalamic nucleus relays visual information from the optic tract to primary visual cortex?

Answer: Lateral geniculate nucleus (LGN). Six-layered structure organizing visual signals before cortical processing.

Flashcard 78: What is the fovea, and what is its major contribution to vision?

Answer: Cone-dense retinal region for highest visual acuity. High cone density enables sharp central vision for detailed tasks.

Flashcard 79: What is the retinal location where the optic nerve exits and no photoreceptors are present?

Answer: Optic disc (blind spot). Where ganglion cell axons converge to form the optic nerve; creates blind spot.

Flashcard 80: Which thalamic nucleus relays visual information from the optic tract to primary visual cortex?

Answer: Lateral geniculate nucleus (LGN). Thalamic relay station for visual processing.

Flashcard 81: What is the optic disc, and what key visual consequence does it produce?

Answer: Exit of optic nerve; creates the blind spot. Axons bundle here to form the optic nerve, leaving no photoreceptors and thus a gap in the visual field.

Flashcard 82: Which thalamic nucleus is the primary relay for auditory information to auditory cortex?

Answer: Medial geniculate nucleus (MGN). Thalamic relay station for hearing before reaching A1.

Flashcard 83: What is the correct neural pathway order for audition from cochlea to primary auditory cortex?

Answer: Cochlea → CN VIII → thalamus (MGN) → auditory cortex (temporal lobe). CN VIII carries signals from inner ear; MGN relays to superior temporal gyrus.

Flashcard 84: What is the primary visual pathway from retina to primary visual cortex?

Answer: Retina → optic nerve → LGN → optic radiation → V1. Visual signals relay through thalamus (LGN) before reaching occipital cortex.

Flashcard 85: What thalamic nucleus relays somatosensory information from the body to cortex?

Answer: VPL (ventral posterolateral) nucleus. Body sensations below neck relay through this thalamic nucleus.

Flashcard 86: Which thalamic nucleus relays visual information to primary visual cortex?

Answer: LGN (lateral geniculate nucleus). Visual information relays through this thalamic nucleus.

Flashcard 87: What is the difference between an afferent neuron and an efferent neuron?

Answer: Afferent: to CNS; efferent: from CNS to muscles or glands. Afferent carries sensory info in; efferent carries motor commands out.

Flashcard 88: What is a receptive field for a sensory neuron?

Answer: Region of sensory space that alters that neuron's firing. Stimulation here excites or inhibits the neuron's response.

Flashcard 89: Which sensory pathway primarily carries fine touch, vibration, and proprioception: dorsal column or spinothalamic?

Answer: Dorsal column–medial lemniscus pathway. Crosses at medulla; fast, precise tactile and position sense.

Flashcard 90: What is the name of the sensory receptor type that detects body position and movement?

Answer: Proprioceptor. Located in muscles and joints to sense body position in space.

Flashcard 91: What type of receptor primarily transduces chemicals for taste and smell?

Answer: Chemoreceptors. These detect chemical molecules in gustatory and olfactory systems.

Flashcard 92: Which receptor type detects tissue damage and signals pain?

Answer: Nociceptors. Specialized free nerve endings detecting harmful stimuli.

Flashcard 93: What is the adequate stimulus for a sensory receptor?

Answer: The stimulus type the receptor is most sensitive to. Each receptor type evolved to detect specific stimulus forms.

Flashcard 94: Which cranial nerve carries olfactory information to the brain?

Answer: Olfactory nerve (CN I). Only sensory nerve that bypasses thalamus, projecting directly to limbic structures.

Flashcard 95: Which sensory pathway primarily carries pain and temperature to the brain: dorsal column or spinothalamic?

Answer: Spinothalamic tract. Crosses at spinal level; slower, less precise than dorsal column.

Flashcard 96: Which cortical area is the primary visual cortex that receives LGN input?

Answer: Occipital lobe (V1, striate cortex). Located in occipital lobe; processes basic visual features like edges and orientation.

Flashcard 97: What is a nociceptor?

Answer: A pain receptor that detects actual or potential tissue damage. Specialized free nerve endings that signal harmful stimuli.

Flashcard 98: What are photoreceptors, and where are they located?

Answer: Rods and cones in the retina. Light-sensitive cells containing photopigments that initiate vision.

Flashcard 99: What type of sensory receptor detects mechanical deformation such as touch, pressure, or vibration?

Answer: Mechanoreceptor. Responds to physical forces like bending or stretching.

Flashcard 100: What is the main somatosensory pathway for fine touch and proprioception?

Answer: Dorsal column–medial lemniscus pathway. Carries discriminative touch via brainstem nuclei to thalamus.