PSYC 372 Unit 2 Study Guide: Sensory Systems, Motor Control, and Biological Rhythms

Comprehensive practice flashcards for Unit 2 covering visual system anatomy, auditory and somatosensory mechanisms, motor pathways, and circadian sleep rhythms.

What are the primary functions of the cornea, pupil, iris, and lens in the eye?

The cornea is a protective outer membrane that lets light enter; the pupil is the center aperture that admits light into the inner eye to reach the retina; the iris is the colored tissue regulating pupil size and light entry; the lens is a disk-like inner eye structure that focuses light onto the retina.

What are the three structural layers of the retina from back to front?

Photoreceptive layer (back/posterior), Bipolar cell layer (middle), and Ganglion cell layer (front/anterior).

How do the fovea and retinal periphery differ in receptor composition and visual function?

The fovea is the central retinal area containing cones that enables acute, detailed vision; the periphery lies outside the fovea, consists primarily of rods, and detects movement across a wider visual field.

In what order does light travel through and activate the layers of the retina?

Light hits the posterior eye to activate the photoreceptive layer first and travels anteriorly: Photoreceptors $\rightarrow$ Bipolar Cells $\rightarrow$ Ganglion Cells.

What are the key functional differences and ratio between rods and cones?

Cones mediate color vision and are active in bright light within a small visual field mainly at the fovea; rods mediate low-light vision and motion detection in faint light, outnumbering cones $20\text{ to }1$.

What are the three types of retinal ganglion cells and their visual functions?

Parvocellular cells (fine detail and color, located in or near the fovea), Magnocellular cells (movement and broad outlines, distributed throughout the retina), and Koniocellular cells (varied functions, distributed throughout the retina).

Which three theories account for the mechanisms of color vision?

Trichromatic Theory, Opponent-Process Theory, and Retinex Theory.

What is the pathway of visual information from the retina to the optic nerve?

Photoreceptors (rods and cones) $\rightarrow$ Bipolar cells $\rightarrow$ Ganglion cells $\rightarrow$ Optic nerve.

What are the respective visual functions of cortical regions V1, V2, V4, V5, and MST?

V1 performs first-stage processing from the LGN; V2 processes information further with larger, specialized receptive fields; V4 (ventral stream) identifies objects, shapes, and color; V5 (dorsal stream) processes motion, speed, and spatial location; MST processes visual expansion, contraction, rotation, and head movements.

What are the distinct receptive field properties of simple, complex, and end-stopped (hypercomplex) cells in V1?

Simple cells are line detectors with fixed excitatory ("ON") and inhibitory ("OFF") zones; complex cells detect motion and light orientation without fixed zones; end-stopped/hypercomplex cells are angle detectors that respond to bar-shaped patterns to locate object boundaries.

What distinct visual functions and cortical regions characterize the ventral and dorsal visual streams?

The ventral stream ("what" pathway in the inferior temporal cortex) identifies and recognizes objects and shapes; the dorsal stream ("where" pathway in the posterior parietal cortex) processes motion, speed, and spatial localization.

What are saccades, and how do they alter cortical neural activity?

Saccades are rapid voluntary eye movements between fixation points; neural activity and blood flow in the visual cortex decrease $75\text{ milliseconds}$ before and during the movement.

What are the neuroanatomical causes and symptoms of visual agnosia, prosopagnosia, and motion blindness?

Visual agnosia (inability to recognize objects) results from temporal cortex pattern pathway damage; prosopagnosia (inability to recognize faces) results from fusiform gyrus damage; motion blindness (inability to detect movement speed or direction) results from area MT damage.

What physical sound wave properties define amplitude, frequency, and timbre?

Amplitude is the sound wave intensity; frequency is the number of compressions or cycles per unit of sound; timbre is the tone quality or complexity.

What is the anatomical structure and auditory function of the pinna?

The pinna is the external flesh and cartilage on each side of the head that alters sound reflection into the middle ear to aid sound localization.

What are the functions of the tympanic membrane, oval window, cochlea, and hair cells?

The tympanic membrane vibrates at incoming sound frequencies; the oval window transmits mechanical waves into cochlear fluid; the cochlea houses three fluid-filled canals (scala vestibuli, scala media, scala tympani); hair cells on the basilar membrane transduce fluid waves into neuronal signals.

How do Place Theory and Frequency Theory explain pitch perception?

Place theory posits that hair cells along specific regions of the basilar membrane respond only to specific frequencies; Frequency theory posits that the basilar membrane vibrates synchronously with incoming sound, eliciting action potentials at that same frequency.

What two auditory cues enable sound localization?

Interaural intensity difference (loudness disparity between ears) and interaural time difference (arrival time disparity between ears).

How do conductive hearing loss and sensorineural (nerve) hearing loss differ in pathology?

Conductive hearing loss results from outer or middle ear physical blockages (infections, tumors, disease) preventing sound waves from reaching the cochlea; sensorineural hearing loss stems from damage to the cochlea, hair cells, or auditory nerve (due to genetics, tumors, or disorders).

What are the stimulus specialties and adaptation rates of the four somatosensory receptors?

Pacinian corpuscles detect pressure and high-frequency vibration (rapidly adapting); Meissner corpuscles detect skin movement and low-frequency vibration (rapidly adapting); Merkel disks detect static light touch (slow adapting); Ruffini endings detect skin stretch (slow adapting).

What pathway carries somatosensory and pain signals to the cortex, and what neurotransmitters mediate mild versus strong pain?

Signals travel: Spinal cord $\rightarrow$ Medulla $\rightarrow$ Thalamus $\rightarrow$ Somatosensory cortex. Mild pain releases glutamate; strong pain releases glutamate alongside several neuropeptides.

How do transduction mechanisms operate across the different basic taste modalities?

Salty taste allows $Na^+$ influx to depolarize the membrane; sour taste detects acids that open $Na^+$ and $Ca^+$ channels; sweet, bitter, and umami tastes trigger G-protein-coupled receptors that mobilize intracellular second messengers.

What are the functional distinctions among smooth, skeletal (striated), and cardiac muscle tissues?

Smooth muscle mediates involuntary internal pushing (digestive tract, blood vessels); skeletal/striated muscle directs voluntary movement of the body relative to the environment; cardiac muscle forms heart tissue and exhibits blended properties of both.

How does acetylcholine operate at the neuromuscular junction?

Acetylcholine is released from motor neuron axons onto muscle fibers, acting as an EPSP that opens $Na^+$ channels to initiate muscle contraction.

What are the two primary muscle proprioceptors and what specific changes do they sense?

Muscle spindles detect muscle stretch and evoke a compensatory contraction; Golgi tendon organs detect increases in muscle contraction tension.

What defines a ballistic movement?

A ballistic movement is a reflex or motor action that cannot be modified or altered once initiated.

What is a central pattern generator (CPG)?

A neural circuit in the spinal cord and brainstem that generates rhythmic patterns of motor output (e.g., walking or running) in the absence of sensory feedback.

How do the premotor, supplementary motor, and prefrontal cortices contribute to motor preparation?

The premotor cortex plans movements using body position and posture data; the supplementary motor area coordinates complex sequential movements in precise order; the prefrontal cortex evaluates probable movement outcomes and inhibits impulses.

How do the lateral and medial corticospinal tracts differ in control and anatomical routing?

The lateral tract directs lateral peripheral muscles (hands, feet) via M1, midbrain red nucleus, medulla, and cord; the medial tract directs axial muscles (neck, trunk) via M1, midbrain, vestibular nucleus, medulla, and cord for balance and posture.

What is a readiness potential and what does it indicate regarding conscious motor intent?

A readiness potential is motor cortex activity preceding the subjective decision to make a voluntary movement, indicating that cortical preparation initiates before conscious awareness occurs.

How do parallel fibers and Purkinje cells interact to regulate motor output?

Parallel fibers excite Purkinje cells, which send inhibitory outputs to cerebellar and vestibular nuclei; these nuclei signal the midbrain and thalamus to modulate primary motor cortex (M1) firing.

How do the direct and indirect basal ganglia pathways modulate motor output via the thalamus?

The direct pathway facilitates movement by inhibiting the globus pallidus to disinhibit (excite) the thalamus; the indirect pathway suppresses competing movements by exciting the globus pallidus to inhibit thalamocortical drive.

How do circadian rhythms differ from circannual rhythms?

Circadian rhythms are endogenous biological processes recurring on a $24\text{-hour}$ cycle (e.g., core body temperature, hormone release); circannual rhythms are internal cycles operating on a yearly timeline (e.g., seasonal migration, hibernation).

What is the suprachiasmatic nucleus (SCN) and where is it located?

The SCN is the master circadian pacemaker controlling sleep and temperature rhythms; it is located in the hypothalamus and operates genetically and independently of adjacent neural structures.

Why does eastward travel produce more disruptive jet lag than westward travel?

Eastward travel requires a circadian "phase-advance" (accommodating a shorter day), which is biologically harder than the "phase-delay" (accommodating an extended day) required by westward travel.

How does the retinohypothalamic path reset the suprachiasmatic nucleus?

It transmits signals from specialized retinal ganglion cells containing melanopsin, which depolarize directly in response to long-lasting ambient light without requiring rod or cone input.

How does the pineal gland influence the sleep-wake cycle under SCN regulation?

The SCN controls the pineal gland (an endocrine gland posterior to the thalamus), regulating its secretion of melatonin, a hormone that promotes sleepiness.

What frequencies and features define alpha waves, theta waves, K-complexes, and sleep spindles?

Alpha waves are $8\text{--}13\text{ Hz}$ (relaxed state); theta waves are $3\text{--}8\text{ Hz}$; K-complexes are sharp waves reflecting transient neural inhibition; sleep spindles are $12\text{--}14\text{ Hz}$ bursts lasting at least half a second.

How does REM sleep differ electrophysiologically from deep NREM slow-wave sleep?

REM sleep exhibits desynchronized, rapid brain wave activity resembling waking consciousness accompanied by rapid eye movements, whereas deep NREM sleep features synchronized, slow, high-amplitude delta waves.

What symptoms define periodic limb movement disorder and REM behavior disorder?

Periodic limb movement disorder involves repeated involuntary leg twitches during sleep; REM behavior disorder entails vigorous, dream-enacting physical movements during REM episodes due to absent motor inhibition.