NSCI 0817: Brain Matters - Comprehensive Sensory, Endocrine, and Behavioral Neuroscience

A comprehensive vocabulary flashcard set covering vision, hearing, emotional and reward processing, the endocrine and autonomic systems, and theories of motivation and homeostasis based on NSCI 0817 lecture slides.

Phototransduction

The biochemical process within photoreceptors (rods and cones) where light absorption triggers a signaling cascade that turns photon energy into traditional electrical nervous system signals, causing the cells to shut off their default release of glutamate.

Cornea

The clear outer surface of the eye that provides most of the optical power to focus incoming light onto the retina, which can be corrected for refractive errors using glasses or contacts.

Iris

The colored, circular structure of the eye containing contractile muscles that regulate the size of the pupil in response to ambient lighting conditions.

Lens (Crystalline Lens)

The transparent, flexible structure behind the pupil that changes its curvature to dynamically adjust optical focus when viewing objects at near or far distances.

Fovea

The specialized central depression of the retina responsible for sharp central vision, packed exclusively with cone photoreceptors and completely lacking rods.

Optic Disk

The anatomical location where retinal ganglion cell axons exit the eye to form the optic nerve; because it contains no photoreceptors, it creates a physiological blind spot that the brain fills in.

Bipolar Cells

Interneurons in the retina possessing two distinct processes—a dendritic end and an axonal end—that relay signals vertically from photoreceptors to retinal ganglion cells.

Retinal Ganglion Cells

The output neurons of the retina that generate action potentials and transmit visual information to the brain along their axons, which form the optic nerve.

Troxler Effect

A visual phenomenon identified in 1804 in which unchanging stimuli in the peripheral visual field gradually disappear from conscious perception due to sensory adaptation, reappearing as soon as a saccade moves the eyes.

Dorsal Stream ("Where" Pathway)

The visual pathway projecting into the parietal cortex specialized for detecting spatial location and motion; damage or breakdown in this pathway can produce akinetopsia.

Ventral Stream ("What" Pathway)

The visual pathway extending into the inferior temporal cortex that processes object identity and form; lesions in this pathway can lead to prosopagnosia.

Akinetopsia

A rare neuropsychological condition characterized by motion blindness, in which an individual cannot perceive motion fluidly, resulting from dysfunction in the dorsal visual pathway.

Prosopagnosia

A neurological impairment commonly called face blindness, characterized by an inability to identify familiar faces despite intact low-level vision, resulting from damage along the ventral "what" pathway.

Pinna

The external cartilaginous portion of the outer ear that collects ambient sound waves and funnels them directly into the external auditory canal.

Tympanic Membrane

The thin sheet of tissue, commonly referred to as the eardrum, separating the outer and middle ear that vibrates mechanically when struck by acoustic air pressure waves.

Ossicles

The trio of tiny bones in the middle ear consisting of the malleus, incus, and stapes, which amplify vibrational energy from the tympanic membrane and transmit it to the cochlear oval window.

Oval Window

The membrane-covered boundary on the cochlea contacted by the stapes footplate, where sound vibrations are transduced from airborne waves into fluid pressure waves.

Round Window

A membrane-sealed opening on the cochlea that flexes outward to relieve fluid displacement generated by sound wave propagation within the inner ear.

Basilar Membrane

A flexible membrane along the cochlea that vibrates differentially based on frequency, with the narrow, stiff base responding to high frequencies (up to $16{,}000\,\text{Hz}$) and the wide, flexible apex responding to low frequencies ($25\,\text{Hz}$ to $500\,\text{Hz}$).

Organ of Corti

The specialized sensory epithelial structure within the cochlear duct resting upon the basilar membrane that houses inner and outer hair cells, supporting cells, and overlying tectorial membrane.

Hair Cells (Auditory)

Specialized sensory mechanoreceptors in the inner ear whose stereocilia bend during fluid motion, causing depolarization via potassium entry and subsequent glutamate release to activate cochlear nerve fibers.

Superior Olivary Nuclei

A pair of brainstem nuclei located in the pons that receive bilateral synaptic inputs from the cochlear nuclei and play a critical role in localizing sound in space.

Inferior Colliculus

The principal midbrain auditory structure that receives ascending auditory projections from the brainstem and coordinates instinctual orienting responses to sound stimuli.

Tonotopic Organization

The systematic spatial arrangement of frequency representation preserved from the cochlea up to the primary auditory cortex, where low frequencies map to the apex-corresponding region and high frequencies map to the base-corresponding region.

Cochlear Implant

A surgically implanted neuroprosthetic device with an electrode array threaded into the cochlea that directly provides electrical stimulation to the auditory nerve fibers in individuals with damaged hair cells.

Sexual Dimorphism (Human Brain)

The concept that brains exhibit two distinct male and female structural forms; extensive meta-analyses demonstrate that while adult male brains average $11\%$ larger in volume, sex/gender explains only approximately $1\%$ of structural variance independent of size, disproving categorical sexual dimorphism.

HPA Axis

The hypothalamic-pituitary-adrenal neuroendocrine circuit in which the hypothalamus secretes CRH, triggering the anterior pituitary to release ACTH, which stimulates the adrenal cortex to release cortisol during the slow, long-term stress response.

Mu ($\mu$) Opioid Receptor

A receptor class within the endogenous analgesic system that can block incoming pain signals, produce euphoria, and suppress respiration when activated by endogenous endorphins or exogenous morphine.

Anandamide

A naturally occurring endogenous cannabinoid neurotransmitter produced within the body that binds to and activates cannabinoid receptors in the endocannabinoid system.

Tetrahydrocannabinol (THC)

An exogenous phytocannabinoid compound from the cannabis plant that acts as a direct agonist at CB1 receptors in the central nervous system and CB2 receptors in peripheral tissues.

Cannabidiol (CBD)

A non-intoxicating exogenous chemical constituent of cannabis that does not directly fit or bind CB1 or CB2 receptors, but produces powerful indirect physiological and anti-inflammatory effects.

Mesolimbic Dopamine Pathway

The primary reward circuit in the brain, originating from dopaminergic neurons in the ventral tegmental area (VTA) that project forward to the nucleus accumbens, stimulated by natural reinforcers and drugs of abuse.

Limbic System

An interconnected group of brain structures—including the hippocampus, amygdala, fornix, mammillary body, cingulate cortex, septum, and hypothalamus—mediating emotional processing, motivation, and memory.

Urbach-Wiethe Disease

A rare genetic disorder involving a mutation in an extracellular matrix protein gene that leads to calcium deposits in blood vessels and bilateral amygdala destruction, depriving patients (such as Patient SM) of the ability to experience or recognize fear.

Ventromedial Prefrontal Cortex

A cortical region involved in suppressing and regulating emotions; damage to this area (as historically observed in Phineas Gage) produces flat affect and inappropriate social conduct.

Tropic Hormones

Hormones produced and secreted by the anterior pituitary into circulation that target other endocrine glands to regulate their hormonal production and release.

Adenohypophysis

The anterior lobe of the pituitary gland, composed of glandular tissue that secretes tropic hormones in response to hypothalamic releasing and inhibiting factors delivered via portal vessels.

Neurohypophysis

The posterior lobe of the pituitary gland, composed of nervous tissue where hypothalamic neurosecretory axons terminate to release hormones directly into systemic circulation.

Afferent Nerves

Peripheral nerve fibers that carry sensory information inward toward the central nervous system.

Efferent Nerves

Peripheral motor nerve fibers that conduct regulatory impulses outward away from the central nervous system toward muscles and target glands.

Sympathetic Nervous System

The thoracolumbar branch of the autonomic nervous system responsible for accelerating bodily resources during "fight or flight" scenarios, promoting adrenaline release, tachycardia, and pupil dilation.

Parasympathetic Nervous System

The craniosacral division of the autonomic nervous system responsible for "rest and digest" physiological states, stimulating digestive functions and slowing heart rate.

Motivation

The set of internal factors ("to set in motion") that initiate, sustain, and direct goal-oriented behaviors essential for survival, frequently organized around the "four Fs": feeding, fleeing, fighting, and fornicating.

Homeostasis

The dynamic physiological process by which internal stability is actively maintained around specific set points despite changing external circumstances.

Inverted-U Model of Performance

The performance paradigm demonstrating that optimal behavioral execution occurs at intermediate arousal levels, whereas insufficient or excessive arousal impairs functioning.

Instinct Theory

A motivational theory asserting that behaviors are propelled by innate, preprogrammed, and unlearned behavioral routines present across all members of a species.

Drive Theory

A theory of motivation proposing that deviations from homeostatic balance create internal physiological needs and drive states that compel behaviors designed to restore equilibrium.

Incentive Theory

A motivational framework stating that human actions are drawn and directed by external incentives or secondary reinforcers, such as grades, academic praise, or monetary compensation.

Arousal Theory

A model stating that individuals are motivated to behave in ways that maintain an optimal level of physiological arousal and sensation, modulated centrally by dopamine signaling.

Thermoregulation

The negative-feedback homeostatic control of core body temperature, activating sweating and cutaneous vasodilation when body temperature increases, and shivering and vasoconstriction when body temperature drops.