Biopsychology: Comprehensive Review of Neuroanatomy, Cellular Mechanisms, and Sensory Systems

Flashcards covering biopsychology fundamentals: nervous system divisions, cellular neurobiology, electrophysiology, neuroanatomy, cranial nerves, visual system pathways, and dissectible structures.

Biopsychology

A division of behavioral neuroscience that studies the physiological and biological mechanisms of the nervous system and investigates how they directly relate to behavior, frequently utilizing non-human animal models.

Central Nervous System (CNS)

The major division of the nervous system located entirely within the skull and vertebral canal—encompassing the brain, spinal cord, and retina—responsible for coordinating the physiological activity of the entire body.

Peripheral Nervous System (PNS)

The division of the nervous system residing outside the skull and spine that connects the central nervous system to the body's limbs, skin, sensory receptors, and internal viscera.

Somatic Nervous System (SNS)

The subdivision of the PNS involved in processing external sensory information and governing voluntary motor commands to skeletal muscles.

Autonomic Nervous System (ANS)

The subdivision of the PNS that regulates internal sensations and coordinates involuntary, automated physiological responses, such as cardiac contractions, digestion, and vascular constriction.

Sympathetic Nervous System

The 'fight or flight' branch of the ANS that mobilizes bodily energy during threatening or high-demand situations by dilating pupils, accelerating heart rate, inhibiting digestion, and relaxing pulmonary airways.

Parasympathetic Nervous System

The 'rest and digest' division of the ANS that supports energy conservation, relaxation, and recovery by constricting pupils and airways, slowing heart rate, and stimulating digestive functions.

Afferent Nerves

Sensory nerve fibers that carry incoming impulses from skin, sensory organs, skeletal muscles, and viscera inward toward the central nervous system ('A' for accepted or arriving signals).

Efferent Nerves

Motor nerve fibers that carry outgoing control commands from the central nervous system outward to peripheral effectors, including skeletal muscles and visceral organs ('E' for exiting signals).

Neuron

The fundamental signaling unit of the nervous system (numbering approximately $86\text{ billion}$ in the human brain) specialized for receiving, integrating, and transmitting electrochemical information across neural circuits.

Glial Cells

Non-neuronal support cells of the nervous system that provide physical scaffolding, nutritional maintenance, metabolic waste clearance, chemical insulation, and developmental guidance for neurons.

Dendrites

Branch-like projections extending from the neuronal soma that receive biochemical inputs and electrical signals from presynaptic axon terminals.

Axon Hillock

The conical transition region connecting the soma to the axon where incoming postsynaptic graded potentials (EPSPs and IPSPs) summate to initiate an action potential.

Myelin Sheath

A lipid-rich insulating bilayer wrapped around axons that prevents ion leakage and dramatically accelerates the velocity of action potential propagation.

Nodes of Ranvier

Unmyelinated gaps of approximately $1\,\mu m$ along an axon, containing high concentrations of voltage-gated ion channels and pumps that enable saltatory nerve conduction.

Multipolar Neuron

A structural class of neuron possessing a single soma, multiple branching dendrites, and a single axon; characteristic of motor neurons and most CNS interneurons.

Bipolar Neuron

A neuron with a central cell body from which two distinct processes emerge: one dendrite and one axon; found in specialized sensory structures such as the retina, inner ear, and olfactory mucosa.

Pseudounipolar Neuron

A sensory neuron whose soma gives rise to a single bifurcating axon that splits into peripheral and central branches (with no traditional dendrites), commonly located in the dorsal root ganglia.

Astrocytes

Star-shaped CNS glial cells with extensive processes that encase capillaries to establish the selective blood-brain barrier (BBB), regulate active cerebral blood flow, and clear chemical waste.

Microglia

The resident immune cells of the central nervous system that clear cellular debris via phagocytosis, mediate neuroinflammatory responses to injury, and release neurotrophic growth factors.

Oligodendrocytes

Myelin-producing glial cells restricted to the central nervous system, capable of extending multiple cytoplasmic processes to insulate segments on several different axons simultaneously.

Schwann Cells

Myelinating glial cells restricted to the peripheral nervous system that wrap around a single axonal segment and provide structural guidance scaffolding during peripheral axon regeneration.

Resting Membrane Potential

The stable electrical voltage difference across a resting neuronal membrane, typically measured at $-70\,mV$, established by differential ion concentrations and resting membrane permeability.

Threshold of Excitation

The critical membrane depolarization level (approximately $-55\,mV$) required to open voltage-gated $Na^+$ channels and trigger an all-or-nothing action potential.

Absolute Refractory Period

The phase during and immediately following an action potential's peak ($\sim +40\,mV$) in which voltage-gated $Na^+$ channels are inactivated, rendering the membrane completely incapable of generating another action potential.

Relative Refractory Period

The interval during action potential repolarization and after-hyperpolarization when $K^+$ channels remain open; an action potential can only be elicited by a stimulus stronger than normal threshold intensity.

Sodium-Potassium Pump

An ATP-driven transport protein that restores baseline transmembrane ionic gradients by actively pumping $3\,Na^+$ ions out of the neuron in exchange for $2\,K^+$ ions imported.

Excitatory Postsynaptic Potential (EPSP)

A graded, decremental depolarization of the postsynaptic membrane, typically produced by the opening of ligand-gated sodium channels, increasing the probability that an action potential will fire.

Inhibitory Postsynaptic Potential (IPSP)

A graded, decremental hyperpolarization of the postsynaptic membrane caused by $K^+$ efflux or $Cl^-$ influx, serving as an active brake that decreases the probability of an action potential.

Temporal Summation

The integration of postsynaptic potentials generated by rapid, high-frequency stimulation from a single presynaptic neuron over a short duration of time.

Spatial Summation

The additive integration of multiple postsynaptic potentials originating simultaneously from physically distinct synaptic terminals across a neuron's dendritic arbor.

Exocytosis

The process by which action potentials depolarize the presynaptic terminal to open voltage-gated $Ca^{2+}$ channels, triggering vesicular fusion and the rapid release of neurotransmitters into the synaptic cleft.

Ionotropic Receptor

A ligand-gated transmembrane protein channel that directly and rapidly (often in less than $1\,ms$) opens an ion pore upon neurotransmitter binding to produce fast, brief postsynaptic potentials.

Metabotropic Receptor

A G-protein coupled receptor (GPCR) that, upon ligand binding, dissociates an intracellular G-protein subunit to initiate a secondary messenger cascade (such as cAMP), producing slower ($30\,ms+$) but long-lasting neural effects.

Transporter Receptors

Presynaptic membrane proteins responsible for reuptake, moving released neurotransmitters out of the synaptic cleft back into the presynaptic terminal to terminate synaptic signaling.

Autoreceptors

Presynaptic receptors sensitive to the neuron's own released neurotransmitter that act as negative feedback sensors to suppress further transmitter synthesis and exocytosis.

Glutamate

The primary excitatory neurotransmitter of the vertebrate central nervous system, responsible for opening cation channels to induce depolarizing EPSPs.

GABA (Gamma-Aminobutyric Acid)

The principal inhibitory neurotransmitter of the brain, mediating hyperpolarizing IPSPs to regulate overall neural excitability.

Acetylcholine (ACh)

A neurotransmitter essential for somatic muscle contraction at neuromuscular junctions, parasympathetic autonomic function, and learning and memory circuits within the hippocampus.

Dopamine

A monoamine neurotransmitter operating within the nigrostriatal pathway for movement coordination and the mesolimbic pathway for reward, motivation, and reinforcement learning.

Serotonin

A neurotransmitter critical for the regulation of mood, sleep, and emotional stability; represents the primary therapeutic target of selective serotonin reuptake inhibitors (SSRIs).

Dura Mater

The tough, fibrous, outermost meningeal layer that adheres to the skull interior, anchoring the brain and preventing excessive movement that could rupture cerebral vasculature.

Arachnoid Mater

The web-like intermediate layer of the meninges that cushions the central nervous system and encloses the subarachnoid space containing cerebrospinal fluid (CSF) and major arteries.

Pia Mater

The delicate, vascularized innermost meningeal membrane that closely adheres to the contours, sulci, and gyri of the brain and spinal cord, separating neural tissue from CSF.

Coronal Cut

A vertical dissection cut parallel to the face (lateral left to right) that divides the brain into anterior (rostral) and posterior (caudal) sections, highlighting medial versus lateral relationships.

Midsagittal Cut

A vertical dissection plane passing directly through the medial longitudinal fissure along the midline, dividing the brain into symmetrical left and right hemispheres.

Horizontal Cut

A dissection cut oriented parallel to the dorsal surface of the brain that divides neural structures into superior (upper) and inferior (lower) halves.

Medial Longitudinal Fissure

The deep sagittal groove that runs along the midline of the telencephalon to anatomically separate the left and right cerebral hemispheres.

Frontal Lobe

The anterior-most cerebral lobe housing the prefrontal cortex (responsible for executive functions, planning, and personality) and the primary motor cortex (precentral gyrus, controlling fine movement).

Parietal Lobe

The cerebral lobe situated posterior to the central sulcus containing the postcentral gyrus (primary somatosensory cortex) that processes touch, pain, spatial orientation, and numerical information.

Temporal Lobe

The lateral cortical lobe positioned ventral to the frontal and parietal lobes that processes audition (primary auditory cortex), complex visual identification (fusiform gyrus), and memory via medial structures.

Occipital Lobe

The caudal-most cerebral lobe housing the primary visual cortex (striate cortex/V1); unilateral damage produces cortical blindness in the contralateral visual field.

Thalamus

An egg-shaped diencephalic gray matter relay hub located inferior to the third ventricle that processes and routes incoming sensory information (except olfaction) to designated neocortical regions.

Hypothalamus

A ventral diencephalic structure situated below the thalamus that regulates the autonomic nervous system and endocrine output via the pituitary gland to control survival drives ('the 4 F's').

Optic Chiasm

The X-shaped decussation point on the ventral brain surface where axons originating from the nasal hemiretina cross over to the contralateral hemisphere, ensuring opposite-field visual processing.

Superior Colliculus

Paired visual tectal swellings on the dorsal midbrain that coordinate reflexive eye movements, pupillary orientation, and tracking in response to visual stimuli.

Inferior Colliculus

Paired auditory tectal swellings located immediately caudal to the superior colliculi that process auditory localization cues and auditory reflex reactions.

Cerebral Peduncles

Substantial white matter bundles situated on the ventral tegmentum of the midbrain carrying descending motor system projections from the cerebral cortex to the brainstem and spinal cord.

Cerebellum

The highly folded metencephalic structure ('mini brain') located dorsal to the pons that refines motor coordination, accuracy, aim, timing, and balance without directly initiating movement.

Pons

A prominent metencephalic bulge ventral to the cerebellum that serves as an information conduit between cerebrum, cerebellum, and spinal cord, while participating in respiratory control.

Medulla

The myelencephalic component of the brainstem continuous with the spinal cord that contains vital autonomic reflex centers governing heart rate, blood pressure, and respiration.

Olfactory Nerve (CN I)

A purely sensory cranial nerve appearing as flaps over the olfactory bulbs, responsible for conveying olfactory (smell) sensations from the nasal mucosa into the telencephalon.

Optic Nerve (CN II)

A purely sensory cranial nerve composed of myelinated retinal ganglion cell axons entering the anterior portion of the optic chiasm to transmit visual data to the brain.

Oculomotor Nerve (CN III)

A motor cranial nerve exiting the ventral midbrain alongside the cerebral peduncles that coordinates extraocular muscle contractions, pupil constriction, and lens accommodation.

Trochlear Nerve (CN IV)

A thin motor cranial nerve emerging laterally from the midbrain that innervates the superior oblique extraocular muscle to control downward and outward eye movements.

Trigeminal Nerve (CN V)

A large mixed cranial nerve appearing as tooth-like fibers on the lateral pons, mediating facial sensations of touch, temperature, and pain (sensory) while controlling the muscles of chewing (motor).

Abducens Nerve (CN VI)

A motor cranial nerve emerging at the pontomedullary junction that innervates the lateral rectus muscle to control lateral, side-to-side eye abduction (and the nictitating membrane in sheep).

Facial Nerve (CN VII)

A mixed cranial nerve responsible for gustatory sensation on the anterior $2/3$ of the tongue and somatic motor innervation to muscles producing facial expressions.

Vestibulocochlear Nerve (CN VIII)

A sensory cranial nerve transmitting acoustic input from the cochlea (hearing) and balance equilibrium information from the vestibular apparatus to the brainstem.

Glossopharyngeal Nerve (CN IX)

A mixed cranial nerve mediating taste sensation from the posterior $1/3$ of the tongue and providing motor control to the muscles of the throat and tongue during swallowing.

Vagus Nerve (CN X)

The 'wandering' mixed cranial nerve that carries visceral touch sensations from internal organs and delivers primary parasympathetic efferent regulation to the heart, lungs, and gastrointestinal tract.

Spinal Accessory Nerve (CN XI)

A motor cranial nerve running along the lateral cervical spinal cord and medulla that innervates the trapezius and sternocleidomastoid muscles to mediate head and shoulder movements.

Hypoglossal Nerve (CN XII)

A motor cranial nerve emerging from the ventral medulla that controls intrinsic and extrinsic tongue musculature to support articulation, mastication, and swallowing.

Cornea

The transparent, convex anterior covering of the eye that provides primary optical refractive power and allows light to enter the ocular anterior chamber.

Lens

The transparent, flexible disc positioned posterior to the pupil that changes shape via ciliary muscle accommodation to precisely refract and focus images of near or distant objects onto the retina.

Retina

The multi-layered neuroepithelial tissue lining the posterior eye where photoreceptive cells convert absorbed photons into neurochemical signals through visual sensory transduction.

Choroid

A highly vascularized, heavily pigmented black tissue layer situated between the retina and sclera that provides metabolic nourishment to the retina and absorbs stray light.

Tapetum Lucidum

An iridescent, reflective blue-green membrane located behind the retina in sheep and nocturnal animals (absent in humans) that reflects unabsorbed light back across photoreceptors to enhance vision in low light.

Nictitating Membrane

A protective 'third eyelid' found in sheep and other quadrupeds (lacking in humans), innervated by the abducens nerve to provide corneoconjunctival moisture and defense.

Cones

Color-sensitive photoreceptor cells concentrated heavily within the retinal fovea (numbering $\sim 6\text{ million}$ in humans) that function in photopic (bright) illumination to provide high spatial acuity.

Rods

Highly sensitive photoreceptors concentrated in the peripheral retina (numbering $\sim 120\text{ million}$ in humans, outnumbering cones $20:1$) specialized for scotopic vision and movement detection without color discrimination.

Blind Spot

The specific region on the retina where ganglion cell axons gather to form the optic nerve (optic disc), lacking photoreceptors and producing an absence of light sensitivity.

Parvocellular Cells (P Cells)

Retinal ganglion cells characterized by small cell bodies and compact receptive fields, located primarily in the fovea, that exhibit high chromatic sensitivity and process fine visual details.

Magnocellular Cells (M Cells)

Retinal ganglion cells with large somas and broad receptive fields distributed throughout the retina, specialized for tracking visual movement and processing broad spatial forms without color sensitivity.

Lateral Geniculate Nucleus (LGN)

The primary sensory nucleus within the dorsal thalamus that receives segregated retinal inputs via the optic tract and projects optic radiations to area V1 of the occipital cortex.

Primary Visual Cortex (Area V1)

The striate cortex located in the occipital pole that executes the initial cortical processing of visual stimuli, detecting spatial frequency, edge contours, and orientation.

Ventral Stream

The 'what' visual pathway projecting from V1 to the inferior temporal cortex and V4, specialized for identifying complex forms, object identity, and color constancy.

Dorsal Stream

The 'where' visual pathway projecting from V1 to the posterior parietal cortex and MT/V5, specialized for processing motion, spatial orientation, and coordinating movement relative to visual targets.

Color Constancy

The cortical ability—mediated by area V4—to perceive consistent surface colors despite extensive fluctuations in environmental illumination and wavelength composition.

Visual Agnosia

The inability to identify or recognize objects visually despite preserved primary visual sensation, typically caused by lesions along the ventral stream in the inferior temporal cortex.

Prosopagnosia

A visual deficit characterized by the inability to recognize familiar human faces, resulting from structural damage to the fusiform gyrus of the inferior temporal cortex.

Blindsight

A paradoxical phenomenon resulting from V1 lesions where patients lack conscious visual perception yet demonstrate accurate above-chance responses to the location and movement of visual targets.

Corpus Callosum

The largest cerebral commissure, consisting of a broad white matter tract bridging the two cerebral hemispheres to enable interhemispheric transfer of neural information.

Fornix

A prominent C-shaped white matter tract of the limbic system located inferior to the lateral ventricles that connects the hippocampus to the mammillary bodies and contralateral hippocampus to support memory consolidation.

Arbor Vitae

The distinctive tree-like branching architecture of white matter inside the cerebellum that carries afferent and efferent impulses to and from the cerebellar cortex.

Cingulate Gyrus

A major limbic gyrus situated immediately superior to the corpus callosum; its anterior segment mediates emotional regulation, impulse control, and empathy, while its posterior segment supports spatial and episodic memory.

Pineal Gland

A dorsal diencephalic neuroendocrine gland situated caudal to the thalamus, regulated by the suprachiasmatic nucleus (SCN) of the hypothalamus to synthesize and secrete melatonin for circadian sleep-wake regulation.

Corona Radiata

A radiating, fan-like array of subcortical white matter fibers that conveys bidirectional axonal projections between the cerebral cortex and the internal capsule.

Septum Pellucidum

A thin, vertical midline sheet of nervous tissue separating the frontal horns of the left and right lateral ventricles, visible only in anterior coronal brain cuts.

Basal Ganglia

A subcortical collection of interconnected gray matter nuclei (including caudate, putamen, and globus pallidus) governing voluntary motor initiation, procedural motor learning, and habit execution.