Sensory Systems, Ingestive Behavior, and Sleep Reviewer

Comprehensive vocabulary flashcards covering the key terms, biological mechanisms, neural structures, and clinical disorders outlined in Units V, VI, and VII (Sensory Systems, Ingestive Behavior, and Sleep).

Somatosensory system

The sensory network responsible for conscious bodily sensations, including touch, pressure, pain, temperature, and awareness of body position, with receptors located in the skin, muscles, joints, and connective tissues.

Stereognosis

The ability to recognize and identify an object through touch alone, without seeing it.

Nociception

The detection and neural processing of potentially harmful stimuli that contribute to the experience of pain.

Kinesthetic awareness

Awareness of the movement and position of body parts without needing to see them.

Exteroceptive system

The somatosensory system division that detects mechanical, thermal, and nociceptive stimuli applied to the outside of the body, especially the skin.

Proprioceptive system

The sensory system that monitors the position and movement of the body through receptors located in muscles, joints, and organs involved in balance.

Interoceptive system

The sensory system that provides information regarding the internal condition of the body, such as temperature, blood pressure, respiration, and hunger.

Pacinian corpuscles

Large, onion-like cutaneous receptors located deep in the skin that adapt rapidly and respond strongly to vibration and sudden pressure changes.

Merkel's disks

Slowly adapting cutaneous touch receptors that respond to sustained pressure, skin indentation, and fine surface details.

Ruffini endings

Slowly adapting sensory endings located in the skin that respond to skin stretch and sustained deformation.

Cortical magnification

The principle that body regions requiring fine sensory discrimination, such as the hands, lips, and tongue, receive a disproportionately large area of representation in the somatosensory cortex.

Neuroplasticity

The nervous system's capacity to reorganize and change in response to experience, learning, environmental demands, or altered sensory input.

Innervation ratio

The relationship between the number of muscle fibers supplied by a single motor neuron, where a lower ratio enables finer motor control.

Neuromuscular junction

The synapse formed between a motor neuron and a muscle fiber where acetylcholine is released to initiate muscle contraction.

Muscle spindle

A sensory receptor oriented parallel to ordinary muscle fibers that detects and responds to muscle stretch and changes in muscle length.

Golgi tendon organ

A sensory receptor located in tendons, arranged in series with muscle fibers, that detects muscle tension and force, acting as a brake against excessively vigorous contractions.

Central pattern generators (CPGs)

Neural circuits, particularly in the spinal cord, that produce rhythmic, alternating motor output patterns without requiring constant sensory input.

Hyperalgesia

An increased sensitivity to pain, causing a stimulus that is normally painful to produce an unusually intense pain response.

Paresthesia

An abnormal spontaneous skin sensation, such as tingling, warmth, coldness, or 'pins and needles,' experienced without an obvious external stimulus.

Phantom limb

The persistent sensation that an amputated or missing body part is still present, which can include perceptions of position, movement, or pain.

Absolute threshold

The minimum physical intensity of a stimulus that can be detected approximately $50\%$ of the time under specified conditions.

Difference threshold

The smallest detectable difference between two stimuli, also referred to as the just noticeable difference.

Accommodation

The adjustment of the shape of the lens by the ciliary muscles to focus incoming light on objects at varying distances.

Young–Helmholtz trichromatic theory

The theory proposing that color vision begins with three distinct types of cones that are differentially sensitive to short, medium, and long wavelengths of light.

Opponent-process theory

The theory that post-receptor visual processing involves opposing pairs of color responses: red versus green, blue versus yellow, and light versus dark.

Timbre

The unique quality or texture of a sound that allows a listener to distinguish different sound sources having identical pitch and loudness.

Prosody

The rhythm, stress, and intonation patterns of speech that convey meaning and emotional context.

Place theory

The pitch perception theory asserting that sound frequency is represented by the specific location of maximum vibration along the cochlear basilar membrane.

Volley principle

The auditory principle stating that groups of neurons alternate firing to represent sound frequencies up to approximately $4{,}000\,\text{Hz}$ that exceed the firing rate of any single neuron.

Pheromones

Chemical signals released by an organism that influence the physiology or behavior of other individuals of the same species.

Anosmia

The complete absence or loss of the sense of smell, either general or specific to particular odors.

Cephalic phase

The preparatory phase of energy metabolism triggered by the sight, smell, taste, or thought of food, characterized by high insulin and low glucagon levels.

Absorptive phase

The phase of energy metabolism during which absorbed nutrients meet the body's immediate energy needs or are stored, marked by high insulin and low glucagon levels.

Fasting phase

The metabolic period when unabsorbed energy from a previous meal is depleted and the body draws upon stored fuels, characterized by high glucagon and low insulin levels.

Insulin

A pancreatic hormone that facilitates glucose utilization and the storage of glycogen in liver and muscle, fats in adipose tissue, and amino acids as proteins.

Glucagon

A pancreatic hormone that promotes the mobilization of stored energy reserves into the bloodstream, primarily triggering glucose release from the liver.

Set-point assumption

The hypothesis that hunger is triggered by an energy deficit and that eating proceeds until energy reserves return to a biologically determined homeostatic baseline.

Positive-incentive perspective

The view that eating is primarily motivated by the anticipated pleasure, reward value, or appeal of food rather than solely by an internal energy deficit.

Sensory-specific satiety

The progressive decline in the pleasantness and consumption of a specific food being consumed, while different or novel foods remain appealing.

Lateral hypothalamus (LH)

A hypothalamic region historically described as the feeding center whose lesion leads to aphagia (failure to eat).

Ventromedial hypothalamus (VMH)

A hypothalamic region historically viewed as the satiety center whose lesion causes hyperphagia and substantial body weight gain.

Ghrelin

A hormone released predominantly by the stomach that stimulates appetite and signals hunger before meal times.

Leptin

A peptide hormone produced by adipose tissue that provides long-term negative feedback to the brain regarding total body fat reserves, suppressing food intake.

Neuropeptide Y (NPY)

A hypothalamic peptide neurotransmitter that strongly stimulates feeding behavior, reduces metabolism, and promotes fat deposition.

Cholecystokinin (CCK)

A gastrointestinal hormone released by the small intestine in response to food ingestion that induces satiety and suppresses eating.

Hyperphagia

An excessive, abnormally persistent sensation of hunger and drive to consume food, characteristic of Prader-Willi syndrome and VMH damage.

Osmotic thirst

Thirst triggered by an elevated concentration of solutes in the extracellular fluid, drawing water out of cells and leading to cellular dehydration.

Hypovolemic thirst

Thirst elicited by a reduction in total extracellular fluid volume or blood volume and pressure, such as through heavy sweating or blood loss.

Circumventricular organs (CVOs)

Specialized brain structures with an incomplete blood-brain barrier that detect circulating blood solutes and hormones involved in fluid homeostasis.

Antidiuretic hormone (ADH)

A hormone secreted by the posterior pituitary that promotes water reabsorption in the kidneys, decreasing urinary output (also called vasopressin).

Renin–angiotensin–aldosterone system (RAAS)

A hormone pathway activated by low blood volume or pressure that synthesizes angiotensin II and aldosterone to stimulate thirst and conserve sodium and fluid.

Circadian rhythm

An endogenous biological rhythm running on an approximate $24\text{-hour}$ cycle that governs sleep-wake states, body temperature, and endocrine activity.

Suprachiasmatic nucleus (SCN)

The master circadian pacemaker located in the hypothalamus above the optic chiasm that synchronizes internal rhythms to external day-night cycles.

Zeitgeber

An external environmental cue, such as light, activity routines, or regular meal times, that entrains and synchronizes an organism's circadian pacemaker.

Polysomnography

A multi-parametric diagnostic sleep recording procedure that simultaneously measures EEG (brain activity), EOG (eye movements), and EMG (muscle tone).

Hypnagogic state

A dreamlike transitional state of consciousness occurring between wakefulness and the onset of sleep.

Sleep spindles

Brief, rhythmic bursts of brain wave activity appearing on an EEG that characterize Stage 2 non-REM sleep.

K-complexes

Large, distinctive sharp biphasic waveforms observed on an EEG during Stage 2 non-REM sleep that occur spontaneously or in response to external stimuli.

Delta waves

High-amplitude, slow brain waves characteristic of deep non-REM slow-wave sleep.

REM sleep

A sleep stage defined by rapid eye movements, desynchronized cortical EEG activity, vivid dreaming, and a profound suppression of skeletal muscle tone.

REM atonia

The temporary paralysis or profound loss of skeletal muscle tone during REM sleep that prevents the physical enactment of dream experiences.

Activation-synthesis theory

Hobson's dream theory positing that dreaming represents the forebrain's attempt to synthesize and make sense of random neural activation generated by the brainstem during REM sleep.

Reticular Activating System (RAS)

A network of brainstem and forebrain pathways that regulates cortical arousal, vigilance, and the maintenance of wakefulness.

Obstructive sleep apnea (OSA)

A sleep-related breathing disorder characterized by repetitive collapse and narrowing of the upper airway during sleep despite continuing respiratory effort.

Central sleep apnea (CSA)

A sleep-related breathing disorder resulting from a transient cessation of the brainstem respiratory drive, leading to an absence of respiratory effort.

Cataplexy

A sudden, brief loss of skeletal muscle tone triggered by strong emotion while the individual remains fully conscious, pathognomonic for narcolepsy type 1.

REM sleep behavior disorder (RBD)

A parasomnia involving the loss of normal REM muscle atonia, allowing individuals to physically act out their dreams through motor behaviors.

Restless legs syndrome (RLS)

A sensorimotor disorder characterized by an uncomfortable crawling sensation and an irresistible urge to move the legs, primarily occurring during evening rest or inactivity.