Introduction to Physiology, Homeostasis, Membrane Transport, and Capillary Exchange

Comprehensive vocabulary flashcards covering introductory human physiology, levels of body organization, homeostasis and control systems, capillary-interstitial fluid exchange, membrane transport mechanisms, and ion channels.

Physiology

The study of the functions of living things, focusing on how body processes occur in terms of cause-and-effect sequences of physical and chemical processes.

Anatomy

The study of the structure of the body, which is inseparable from physiology because physiological mechanisms depend on structural design.

Cell Differentiation

The developmental process by which unspecialized cells become specialized to carry out specific functions, creating about $200$ specialized cell types in the human body.

Basic Cell Functions

Fundamental life-sustaining processes performed by all cells, including obtaining nutrients and $\text{O}_2$, generating energy, eliminating waste, synthesizing structural/functional components, controlling material exchange, internal transport, responding to environmental signals, and reproducing (except nerve and muscle cells).

Muscle Tissue

A primary tissue type composed of cells specialized for contracting to generate tension and produce movement, divided into skeletal, cardiac, and smooth muscle.

Nervous Tissue

A primary tissue type consisting of cells specialized for initiating and transmitting electrical impulses that relay information for body communication, coordination, and control.

Epithelial Tissue

A primary tissue type consisting of cells specialized for exchanging materials between the cell and its environment, organized into protective epithelial sheets and secretory glands.

Exocrine Glands

Glands derived from epithelial tissue that maintain connecting ducts to secrete products to the outside of the body or into cavities opening to the exterior.

Endocrine Glands

Ductless glands derived from epithelial tissue that release their secretory products, known as hormones, internally into the blood.

Connective Tissue

A primary tissue type with relatively few cells dispersed in abundant extracellular material that connects, supports, and anchors body structures, including tendons, bone, and blood.

Organ

A functional structure composed of two or more primary tissue types integrated to perform specific body functions, such as the stomach.

Body System

A collection of related organs that perform complementary functions and interact to accomplish a common activity essential for body survival.

Homeostasis

A dynamic steady state of the constituents in the internal fluid environment ($\text{ECF}$) maintained within narrow limits compatible with cell survival.

Intracellular Fluid ($\text{ICF}$)

The fluid compartment collectively contained inside all body cells.

Extracellular Fluid ($\text{ECF}$)

The fluid outside body cells but inside the body, composed of plasma and interstitial fluid, which constitutes the internal environment.

Plasma

The liquid component of blood contained within blood vessels that circulates throughout the body to transport nutrients, gases, wastes, and hormones.

Interstitial Fluid ($\text{ISF}$)

The portion of extracellular fluid that directly surrounds and bathes individual tissue cells.

Homeostatic Control System

A functionally interconnected network of body components that operates to detect deviations, integrate information, and make adjustments to maintain a variable at a relatively constant optimal level.

Intrinsic Controls

Local homeostatic control mechanisms that are built into or inherent within an organ to regulate its own local activity.

Extrinsic Controls

Systemic regulatory mechanisms initiated outside an organ by the nervous and endocrine systems to coordinate multi-organ responses.

Sensor

The component of a homeostatic control system that monitors the magnitude of a controlled variable and detects deviations from normal.

Integrator

The control center that compares inputs from sensors against a set point and sends signals to direct compensatory responses.

Effector

The component of a homeostatic control system, such as a muscle or gland, commanded by the integrator to bring about a compensatory response.

Set Point

The desired optimal value or range at which a homeostatically controlled variable is maintained by a control system.

Negative Feedback

A primary homeostatic mechanism where a change in a controlled variable triggers a compensatory response that moves the variable in the direction opposite to its initial deviation.

Positive Feedback

A control mechanism in which the output enhances or amplifies an initial change, moving the controlled variable further in the direction of the initial change.

Feedforward Mechanisms

Regulatory control mechanisms that initiate physiological responses in anticipation of an impending change in a regulated variable.

Pathophysiology

The study of altered body function associated with disease states or severe disruptions in homeostasis.

Embryonic Stem Cells ($\text{ESCs}$)

Pluripotent, undifferentiated stem cells isolated from early embryos that can self-renew and give rise to any of the specialized cell types in the body.

Induced Pluripotent Stem Cells ($\text{iPSCs}$)

Adult specialized cells that have been genetically reprogrammed to revert to an embryonic-like pluripotent state.

Regenerative Medicine

An emerging medical field focused on repairing, replacing, or regenerating damaged cells, tissues, or organs using stem cells, scaffolds, or 3D organ printing.

Exercise Physiology

The study of functional changes that occur during a single session of exercise and the long-term physiological adaptations resulting from regular exercise training.

Diffusion

The passive movement of solute particles or gas molecules ($\text{O}_2$, $\text{CO}_2$) down a concentration or partial-pressure gradient from an area of higher concentration to lower concentration.

Filtration

The outward movement of water and small dissolved substances across capillary walls into the interstitium driven by hydrostatic and oncotic pressure differentials.

Reabsorption

The inward movement of water and dissolved fluid from the interstitial space back into capillaries, driven primarily by plasma oncotic pressure generated by proteins like albumin.

Bulk Flow

The collective, pressure-driven movement of water carrying dissolved small solutes together across capillary membranes.

Transcytosis

A transport process where select large molecules, such as small amounts of albumin and hormones, cross endothelial cells inside membrane-bound vesicles.

Starling Forces

The physical forces—capillary hydrostatic pressure ($P_c$), interstitial hydrostatic pressure ($P_i$), plasma oncotic pressure ($\pi_c$), and interstitial oncotic pressure ($\pi_i$)—that determine net fluid movement across capillary walls according to $J_v = K_f [(P_c - P_i) - \sigma(\pi_c - \pi_i)]$.

Lymphatic System

A network of vessels that drains excess filtered interstitial fluid and returned plasma proteins from tissues and empties them back into the venous blood.

Edema

The abnormal accumulation of excess fluid in interstitial spaces resulting when capillary filtration rate exceeds lymphatic drainage capacity.

Simple Diffusion

The unassisted passive transport of small lipid-soluble molecules, such as $\text{O}_2$, $\text{CO}_2$, and steroid hormones, directly through the phospholipid bilayer.

Facilitated Diffusion

Passive transport of substances down their electrochemical gradient across a membrane via specific transmembrane protein carriers or channels without direct usage of $\text{ATP}$.

Osmosis

The net diffusion of water across a selectively permeable membrane toward a region with a higher effective solute concentration.

Aquaporins

Water channel proteins embedded in cell membranes that facilitate rapid trans-membrane water movement.

Primary Active Transport

Energy-requiring transport across a membrane that directly hydrolyzes $\text{ATP}$ to pump solutes against their concentration or electrochemical gradient.

$$\text{Na}^+/\text{K}^+\text{-ATPase}$$

A primary active transport membrane pump that consumes one $\text{ATP}$ molecule to pump $3\,\text{Na}^+$ ions out of the cell and $2\,\text{K}^+$ ions into the cell.

Secondary Active Transport

A transport mechanism where solute movement against its gradient is powered by energy stored in an ion gradient (typically a $\text{Na}^+$ gradient) established by primary active transport.

Symport

A secondary active transport cotransport mechanism in which two different substances are moved across the membrane in the same direction, such as $\text{Na}^+\text{-glucose}$ cotransport.

Antiport

A secondary active transport countertransport mechanism in which two different substances are moved across the membrane in opposite directions, such as the $\text{Na}^+/\text{Ca}^{2+}$ exchanger.

Vesicular Transport

The active movement of large molecules or particulate matter across the plasma membrane inside membrane-enclosed vesicles, encompassing endocytosis and exocytosis.

Membrane Channels

Integral transmembrane proteins that form water-filled pores across the lipid bilayer, allowing rapid passive movement of selected ions or water down electrochemical gradients.

Selectivity Filter

A specialized structural region within a membrane channel pore that restricts ion passage based on ion size, electrical charge, and specific amino acid interactions.

Leaky Channels

Ion channels that remain continuously open under resting conditions, allowing continuous passive ion movement down electrochemical gradients to help establish the resting membrane potential.

Voltage-Gated Channels

Ion channels that open or close in response to alterations in the electrical potential difference (voltage) across the cell membrane.

Ligand-Gated Channels

Ion channels whose opening or closing is regulated by the binding of a specific chemical messenger (ligand) to internal or external receptor sites.

Mechanically Gated Channels

Ion channels that open or close in response to physical deformation of the cell membrane caused by stretch, pressure, vibration, or movement.