Cell Physiology and Communication

Flashcards covering cell physiology, homeostasis, membrane structure, transport mechanisms, and cellular communication based on Lecture 1.

Physiology

The integrative science that illustrates how organ systems coordinate to maintain life in a constantly changing environment; the study of function.

Anatomy

The study of form, which physiology reflects.

Homeostasis

The ability to maintain a relatively stable internal environment despite changes in the external environment.

Sensor (receptor)

A component of a homeostatic control system that monitors the environment, responds to changes (stimuli), and sends input to the control center.

Control Center (integrating center)

A component of a homeostatic control system that analyzes input, determines the set point and required response, and sends output info to the effector.

Effector

A component of a homeostatic control system that acts on output information and provides a response.

Intracrine

Homeostatic mechanisms at the intracellular level, such as biochemical reactions or enzyme modifications within the cell.

Intrinsic Control (Local Control)

Autoregulation within a tissue (autocrine or paracrine) that involves short distance control of adjacent cells without requiring the nervous or endocrine systems.

Extrinsic Control (Reflex Control)

A control system located outside the organ or tissue being influenced, requiring the nervous or endocrine systems and involving feedback loops.

Negative Feedback Control

A mechanism where the response shifts the variable in the opposite direction to correct it back to the baseline or desired value.

Positive Feedback Control

A mechanism where the response causes the variable to continue increasing or decreasing away from the intended value in a vicious cycle until the stimulus is removed.

Cytology

The scientific study of cells.

Cytoplasm

The area within the cell containing organelles, cytoskeleton, inclusions, and the cytosol (intracellular fluid).

Intracellular Fluid (ICF)

Fluid inside the cell comprising $40\%$ of body weight and $2/3$ of total body water; it contains large amounts of potassium, magnesium, and phosphate ions.

Extracellular Fluid (ECF)

Fluid outside of cells comprising $20\%$ of body weight and $1/3$ of total body water; it contains large amounts of $Na^+$, $Cl^-$, and bicarbonate ions.

Bicarbonate Buffer System

The system used in the blood to maintain pH between $7.35-7.45$.

Amphipathic

Molecules, like phospholipids, that contain both hydrophilic and hydrophobic parts.

Cholesterol

A membrane lipid ($20\%$) that holds phospholipids still and can stiffen the membrane.

Glycolipids

Phospholipids with short carbohydrate chains on the extracellular face, making up $5\%$ of membrane lipids.

Transmembrane Proteins

Proteins that pass completely through the membrane, with hydrophilic regions contacting fluid and hydrophobic regions passing through the lipids.

Ligand-gated channels

Channel proteins that open or close in response to chemical messengers.

Voltage-gated channels

Channel proteins that respond to changes in electrical charge.

Mechanically gated channels

Channel proteins that respond to physical stress on the cell.

Occluding (Tight) Junctions

Cell adhesion molecules that interconnect adjacent cells and seal gaps between epithelial cells to serve a barrier function.

Communicating (Gap) Junctions

Channel proteins that allow passage of ions or molecules directly between neighboring cells.

Desmosomes

Anchoring junctions where filaments of the cytoskeleton anchor cells to each other.

Osmosis

The net flow of water through a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.

Osmolarity

The osmotic concentration expressed as the quantity of nonpermeating solutes per liter of solution; blood plasma is typically $300\,mOsm/L$.

Tonicity

The ability of a surrounding solution to affect fluid volume and pressure in a cell based on nonpermeating solute concentration.

Hypotonic solution

A solution with a lower concentration of nonpermeating solutes than ICF, causing cells to absorb water and potentially lyse.

Hypertonic solution

A solution with a higher concentration of nonpermeating solutes than ICF, causing cells to lose water and crenate (shrivel).

Filtration

The movement of substances through a membrane from an area of high pressure to low pressure along a hydrostatic gradient.

Uniport

A carrier protein that moves only one type of solute, such as a calcium pump.

Symport (Cotransport)

A carrier protein that moves two or more solutes simultaneously in the same direction, such as sodium-glucose transporters.

Antiport (Countertransport)

A carrier protein that moves two or more solutes in opposite directions, such as the sodium-potassium pump.

Facilitated Diffusion

A passive, carrier-mediated transport mechanism that moves solutes down their concentration gradient without consuming ATP.

Primary Active Transport

Carrier-mediated transport that moves solute against its concentration gradient using ATP directly, such as the sodium-potassium pump.

Secondary Active Transport

Carrier-mediated transport that uses the concentration gradient of one molecule to move another molecule against its gradient, using ATP indirectly.

Phagocytosis

A form of endocytosis where the cell uses pseudopods to engulf and destroy large particles.

Pinocytosis

A form of endocytosis where the cell takes in droplets of ECF containing molecules useful to the cell.

Neurotransmitters

Primary chemical messengers of the nervous system released from axon terminals into the synaptic cleft to bind to target cell receptors.

Hormones

Primary chemical messengers of the endocrine system secreted into the ECF and transported via the bloodstream throughout the body.

Secondary Messenger Molecules

Intracellular signaling molecules, such as cAMP, cGMP, or inositol triphosphate, released internally in response to primary messengers binding to surface receptors.