Basic Cellular Concepts John P. McDonough, CRNA, Ed.D., ARNP

Cellular Functions n Cells become specialized through differentiation. The 7 chief functions are: –movement –conductivity –metabolic absorption –secretion –excretion –respiration –reproduction

Structure & Function of Typical “eukaryotic” Cell n The 3 components: n Plasma membrane (plasmalemma) n Cytoplasm n Organelles

Organelles n Nucleous –surrounded by cytoplasm (not a cytoplasmic organelle) –largest membrane bound organelle –2 membrane “nuclear envelope” –nucleolus (houses DNA, histones, etc) –controls cell division and genetic information

Organelles (con’t) n Ribosomes n Endoplasmic reticulum n Golgi complex n Lysosomes n Perioxomes n Mitochondria n Cytoskeleton n Microtubules & Actin filaments

Cellular Receptors n Protein molecules capable of: –recognizing ligands –binding with ligands n Classified on basis of location and function n Receptors for drugs are found on the membrane, cytoplasm & nucleus n Membrane receptors are known for: –anesthetics, opiates, endorphins, enkephalins, etc.

Cell-To-Cell Communication n Endocrine n Paracrine n Autocrine n Synaptic

Cellular Intake & Output n Cells continually have “in & out” traffic n Passive transport (no life required) –diffusion –hydrostatic pressure –osmosis n Active transport –requires energy –requires receptors

Active Transport of Na + & K + n Found in virtually all mammalian cells n Na + moves in, K + moves out n Uses energy of ATP (60-70% total used) n Transporter is an enzyme –ATPase n Skeletal & cardiac muscle pumps Ca ++ also

Types of Tissues n Epithelial (simple & stratified) –covers most internal & external surfaces –attached to a basement membrane –surfaces differ according to location »smooth »microvilli »cilia

Types of Tissues (Con’t) n Connective –varies in structure & function –framework on which epithelial cells cluster –abundant extracellular matrix

Types of Tissues (Con’t) n Muscle –made up of myocytes –highly contractile –3 major types »skeletal (striated) »cardiac »smooth

Types of Tissues (Con’t) n Neural –receive & transmit electrical impulses –transmitted across synapses »nerve to nerve »nerve to muscle »transmission achieved with neurotransmitters »total number fixed at birth –all neurons have: »1 cell body, 1 axon, 1 or more dendrites

Cellular Adaptation n Atrophy –decrease in cell size –if enough cells  in size, so will organ –disuse atrophy –nutrition deprivation –atrophy due to  physiological stimulation

Cellular Adaptation n Hypertrophy –increase in cell size –heart & kidneys particularly responsive –associated with  in cell protein, not  in water –hypertrophy may be normal »muscle in exercise »uterus and mammary glands in pregnancy

Cellular Adaptation n Hyperplasia –  cell numbers from  cell division –normal (physiologic) »compensatory »hormonal –pathological »abnormal proliferation of normal cells »endometrium most common site »failure of growth control  malignant transformation

Cellular Adaptation n Dysplasia –“atypical hyperplasia” –abnormal changes in size, shape & organization –seen in epithelial cells of the cervix & resp tract –graded low  high –when inciting stimuli removed  reversible

Cellular Adaptation n Metaplasia –reversible replacement »one mature cell type by another –reversed if inducing stimuli removed –prolonged exposure  malignant transformation

Common Areas in Cellular Injury n ATP depletion n Oxygen derived free radicals n  cytosolic Ca ++ n Defects in membrane permeability

Cellular Injury n Adaptation n Reversible n Irreversible n Necrosis n Apoptosis

Cellular Injury n Hypoxic –ischemia Vs hypoxia n Chemical injury –lead, CO, ethanol, recreational drugs n Infectious n Immunologic & inflammatory n Injurious genetic factors

Cellular Injury n Nutritional imbalances n Injurious physical agents –thermal injury –Ionizing radiation –Illumination –Mechanical stress –Noise

Aging n Atrophy n Decreased function n Loss of cells (? Apoptosis) n Compensatory changes –hypertrophy, hyperplasia,  metaplasia  dysplasia  neoplasia