General Physiological Principles Cell Physiology Functions of Cellular Membrane and Intracellular Structures Basic Principles of Physiological Regulations lecture from Physiology and Pathophysiology I 13. 9. 2022 M. Chalupová Physiology • science that describes how organisms FUNCTION and survive in continually changing environment • function can be described at various levels Basic Physiological Principles • living organism = open system with steady internal environment • HOMEOSTASIS – stable operating conditions in the internal environment – dynamic Cell Physiology CELL • the basic structural and functional unit of living organisms • the smallest unit of life that is classified as a living thing • consists of functional structures called CELL ORGANELLES Cell Structure Cell/Plasma Membrane • 2 primary building blocks include protein (about 60% of the membrane) and phospholipid (about 40%) • molecules of phospholipid form a phospholipid bilayer because the two ends of phospholipid molecules have very different characteristics – non-polar (hydrophobic) – polar (hydrophilic) Functions of Cell Membrane • supporting and retaining the cytoplasm • selective barrier • transport • communication (via receptors) • recognition Cell Organelles Membrane proteins Transport proteins • ion channels • carriers • ATP-ases Receptors • cell surface • (intracellular) Nucleus • replication and transfer of genetic information • RNA synthesis • regulation of cell differentiation and maturation Endoplasmic Reticulum SMOOTH ROUGH • surface is coated with ribosomes • mechanical support • synthesis (especially proteins by rough ER) • transport Golgi apparatus • modifying, sorting, and packaging of substances synthesized in the cell Function of ER and GA Lysosomes and Peroxisomes Lysosomes • contain acid hydrolase enzymes that break down waste materials and cellular debris Peroxisomes • the breakdown of very long chain fatty acids through beta-oxidation Mitochondria • generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy • contain own DNA Cytoskeleton • dynamic system of microfilaments, intermediate filaments, and microtubules determining the shape and internal architecture of cell and performing cell movement Receptors Ion channel linked receptors Receptors G protein-coupled receptors • Gs protein • Gi protein • Gp protein Receptors Receptors tyrosine kinases Receptors Intracellular receptors Cell Transport • provides necesarry communication between the cell and its environment • receptors • carriers • channels • pumps • exo- and endocytosis • transcellular transport • paracelullar transport Passive Transport Diffusion Facilitated diffusion • membrane carrier Ion channels • voltage-gated • ligand-gated • stress-activated Active Transport • the movement of a substance against its concentration gradient Active membrane transporters – pumps • primary active transport (ATP-ases) • secondary active transport – symport – antiport Cytosis – endocytosis – exocytosis Membrane and Action Potential Intercellular Communication Gap junctions Paracrine Autocrine Nervous Endocrine Neuroendocrine Cell Junctions Homeostasis and Adaptation • mechanisms consist of reducing the output or activity of any organ or system back to its normal range of functioning ADAPTATION • adjustement to the changed life conditions • selection press of the environment changes the frequency of genes performing basic life functions Feedback Negative feedback • mechanisms consist of reducing the output or activity of any organ or system back to its normal range of functioning Positive feedback • mechanisms are designed to accelerate or enhance the output created by a stimulus that has already been activated Negative Feedback Positive Feedback Feedback