APSY 214: Sleep, Hormones, Homeostasis, and Sensory Processes

Vocabulary flashcards covering sleep stages, circadian rhythms, neuroendocrinology, homeostasis, hunger mechanisms, and sensory systems across lectures 7 through 11.

Biological Rhythms

Regular and predictable biological fluctuations in a living organism that are controlled by an internal biological clock across various time courses ranging from hourly to yearly.

Circadian Rhythm

A biological rhythm operating on a $24\text{-hour}$ cycle that regulates key physiological processes including hormone levels, cognitive performance, digestion, immune system function, and the sleep-wake cycle.

Suprachiasmatic Nucleus (SCN)

A nucleus located within the hypothalamus that serves as the primary internal biological clock regulating endogenous circadian rhythms.

Melatonin & Cortisol

Hormones involved in endogenous circadian control; melatonin is produced by the pineal gland to promote sleepiness and is inhibited by light, whereas cortisol is produced via the hypothalamus to regulate stress, alertness, and wakefulness.

Zeitgeber

An external environmental cue or "time-giver", such as the daily light-dark cycle, used by organisms to synchronize internal biological rhythms with the environment.

Free-Running Circadian Rhythms

Circadian rhythms that occur when an organism operates strictly under endogenous control without resetting or synchronizing to external zeitgebers.

Human Sleep Measurement (EEG, EOG, EMG)

Quantitative physiological measures used to evaluate sleep: Electroencephalogram (EEG) measures brain waves, Electrooculogram (EOG) measures eye movements, and Electromyogram (EMG) measures muscle tension.

Sleep Spindles & K Complexes

Key EEG features of Stage $2$ NREM sleep; sleep spindles are activity bursts peaking around $15\,\text{Hz}$ involved in memory consolidation, while K complexes aid in sensory processing.

Extended Metabolic Depression (EMD)

A physiological state of minimal physical and metabolic activity, which includes hibernation (during cold periods), aestivation (during hot or dry periods), brumation (in reptiles during winter), and torpor.

Parasomnias

A category of sleep disorders characterized by abnormal behaviors, movements, or physiological events during sleep or transitional states between waking and sleeping.

Narcolepsy

A sleep disorder characterized by excessive daytime sleepiness and abrupt sleep attacks during waking hours, often associated with GABA dysfunction or loss of orexin neurons, and accompanied by sleep paralysis, hypnagogic hallucinations, and cataplexy.

Endocrine System

A complex network of glands and organs throughout the body that synthesizes and releases chemical messengers called hormones into the bloodstream to mediate physiological responses.

Protein vs. Steroid Hormone Receptors

Protein hormone receptors sit on the outer cell membrane surface and activate secondary messenger systems via G-protein pathways, whereas steroid hormone receptors float inside the cell, bind the hormone, cross into the nucleus, and directly alter DNA expression.

Berthold's Foundational Experiment

A landmark study demonstrating that transplanted or reimplanted testes revascularize in the abdomen and release a secretory blood-borne product (testosterone) into the bloodstream to drive male physiological and behavioral development.

Organizational-Activational Hypothesis

The theory that steroid hormones permanently organize neural circuits during critical early developmental periods, enabling those same hormones to activate or inhibit specific behaviors in adulthood.

Sex Determining Protein (SDP)

A protein encoded by the SRY gene on the Y chromosome that directs the differentiation of immature, undifferentiated primitive gonads into testes.

Müllerian & Wolffian Ducts

Embryonic duct systems in which the Müllerian duct develops into female sexual organs (degrading in males due to Müllerian-inhibiting factor) and the Wolffian duct develops into male internal sexual organs (promoted by testosterone).

Alpha-Fetoprotein

A developmental protein that binds circulating estrogen in the bloodstream, preventing it from crossing the blood-brain barrier and shielding the female fetus brain from estrogen-induced masculinization.

Sexually Dimorphic Nuclei (SDN-POA & AVPV)

Sexually dimorphic brain structures: the Medial Preoptic Area / Sexually Dimorphic Nucleus (SDN-POA) is larger in males and mediates male sexual behavior, whereas the Anteroventral Periventricular Nucleus (AVPV) is larger in females and regulates ovulation.

Homeostasis & Set-Point Theory

Homeostasis is the active physiological maintenance of internal stability around a set point; Set-Point Theory posits that the body adjusts metabolic and behavioral processes to resist deviations from this baseline.

Glucostatic Theory & Short-Term Energy Storage

The model proposing that hunger is regulated by blood glucose levels; short-term excess glucose is stored in the liver as glycogen and broken back down into glucose when circulating levels drop.

Lipostatic Theory & Long-Term Energy Storage

The model proposing that hunger is triggered by decreases in long-term stored body fat; energy is stored as triglycerides in adipose cells, which liberate free fatty acids as fuel for non-neural peripheral tissues.

Hormonal Control of Hunger (Ghrelin, CCK, Leptin)

Peptide and hormone signals controlling feeding: ghrelin is secreted by an empty stomach to signal hunger, stomach wall stretching and cholecystokinin (CCK) send short-term satiety signals via the vagus nerve, and leptin is released by adipose cells to signal long-term fat accumulation.

Hypothalamic Feeding Centers (LH & PVN)

Arcuate nucleus subregions in the hypothalamus that regulate eating: one set of arcuate neurons activates the Lateral Hypothalamus (LH) to trigger hunger and food seeking before meals, while another set activates the Paraventricular Nucleus (PVN) to signal satiety after meals.

Signal Transduction

The physiological process by which specialized sensory receptor cells convert environmental stimuli into electrical neural signals that can be processed and interpreted by the central nervous system.

Retina & Fovea

Structures of the ocular visual system: the retina is the light-sensitive neural tissue layer lining the back of the eye containing photoreceptors, and the fovea is the central focal region densely packed with cones for high-acuity photopic vision.

Cones vs. Rods

The two primary photoreceptor types: Cones mediate high-acuity photopic color vision with low convergence onto individual ganglion cells; Rods mediate low-light scotopic peripheral vision with high convergence onto ganglion cells.

Trichromatic Cone Photoreceptors

The three subtypes of visual cone photoreceptors tuned to specific spectral wavelengths: Blue cones (Short / S wavelengths), Green cones (Medium / M wavelengths), and Red cones (Long / L wavelengths).

Visual Receptive Fields

Concentric center-surround spatial areas that trigger ganglion cell firing; On-Center ganglion cells activate when light hits the center, whereas Off-Center ganglion cells activate when light hits the surround region.

Primary Visual Pathway

The principal neural pathway for visual processing running from the retina along the optic nerve, partially decussating at the optic chiasm, synapsing in the Lateral Geniculate Nucleus (LGN) of the thalamus, and terminating in the Primary Visual Cortex (V1).

Dorsal & Ventral Visual Streams

Cortical streams for secondary visual processing: the Dorsal ("Where") stream processes object movement and spatial location, while the Ventral ("What") stream processes object identification, form, and color.

Prosopagnosia & Optic Ataxia

Stream-specific visual disorders: Prosopagnosia (face blindness) results from damage to the Ventral stream, whereas Optic Ataxia (inability to guide motor interaction with visually presented objects) results from damage to the parietal portion of the Dorsal stream.

Auditory Ossicles

Three tiny bones located within the middle ear—the Malleus (hammer), Incus (anvil), and Stapes (stirrup)—that mechanically amplify and transmit sound vibrations from the tympanic membrane to the oval window.

Primary Auditory Pathway

The main neural pathway for sound processing, traveling from hair cells in the cochlea via the auditory nerve to the Cochlear Nucleus in the medulla, Inferior Colliculus, Medial Geniculate Nucleus (MGN) of the thalamus, and Primary Auditory Cortex.

Vestibular System

The inner ear sensory system responsible for balance and spatial orientation, comprising three fluid-filled Semicircular Canals (detecting rotational movement) and the Utricle and Saccule (detecting horizontal and vertical linear movements via otoconia).

Somatosensory Mechanoreceptors

Specialized cutaneous receptors that transduce touch and mechanical pressure, comprising Merkel's Disks, Meissner's Corpuscles, Ruffini Endings, and Pacinian Corpuscles.

Taste Receptor Cells

Receptors housed within taste buds on the tongue that transduce tastants for five distinct taste modalities: salty ($\text{Na}^+$ ions), sour ($\text{H}^+$ ions), sweet, bitter, and umami (glutamate).

Olfactory System Pathway

The non-thalamic sensory pathway for smell, in which odorants bind to cilia on olfactory receptor neurons, projecting to glomeruli and mitral cells in the olfactory bulb, and passing via the olfactory tract directly to the Primary Olfactory Cortex, Orbitofrontal Cortex, Amygdala, and Hippocampus.