The Cellular Level Of Organization PDF

Physiology (140501221) 3 Credit Hours Dr. Raed Halalsheh  References  Text book ▪ Principles of anatomy and physiology, 13th Ed., by Tortora and Derrickson, 2011.  Support reading ▪ Textbook of Medical Physiology, 10th Ed., by Guyton, 2000. ▪ Human Physiolog...

Physiology (140501221) 3 Credit Hours Dr. Raed Halalsheh  References  Text book ▪ Principles of anatomy and physiology, 13th Ed., by Tortora and Derrickson, 2011.  Support reading ▪ Textbook of Medical Physiology, 10th Ed., by Guyton, 2000. ▪ Human Physiology, the mechanisms of body function, 10th Ed., by Vander et al., 2004.  Introduction to Physiology  The Cellular Level of Organization  Parts of a Cell  The cell can be divided into three principal parts for ease of study. 1. Plasma (cell) membrane 2. Cytoplasm ▪ Cytosol ▪ Organelles (except for the nucleus) 3. Nucleus  The Plasma Membrane  The plasma membrane is a flexible, sturdy barrier that surrounds and contains the cytoplasm of the cell.  The fluid mosaic model: The membrane consists of proteins in a sea of lipids. Lipid Bilayer of the Cell Membrane  The lipid bilayer is the basic framework of the plasma membrane and is made up of ▪ Two back-to-back layers of phospholipid (75%) molecules. ▪ Cholesterol (20%) and glycolipids (5%) scattered among a double row of phospholipid molecules.  Membrane Proteins Proteins that stretch across the entire bilayer and project on both sides of the membrane are termed transmembrane proteins.  Glycocalyx  Glycocalyx is an extensive sugary coat facing the extracellular fluid, composed of: ▪ Glycolipids ▪ Glycoproteins  The glycocalyx acts like a molecular signature that ▪ enables cells to recognize one another (e.g. white blood cells). ▪ enables cells to adhere to one another in some tissue. ▪ protects cells from being digested by enzymes in the extracellular fluid. Functions of Membrane Proteins Functions of Membrane Proteins  Formation of Channel ▪ passageway to allow specific substance to pass through.  Transporter Proteins ▪ bind a specific substance, change their shape & move it across membrane.  Receptor Proteins ▪ cellular recognition site -- bind to substance  Act as Enzyme ▪ speed up reactions  Linker ▪ anchor proteins in cell membrane or to other cells ▪ allow cell movement ▪ cell shape & structure  Cell Identity Marker ▪ allow cell to recognize other similar cells.  Membrane Permeability  Plasma membranes are selectively permeable.  The lipid bilayer portion of the membrane is permeable to small, nonpolar, uncharged molecules but impermeable to ions and charged or polar molecules.  The membrane is also permeable to water.  Aquaporins, transmembrane proteins that function as water channels.  Transmembrane proteins that act as channels or transporters increase the permeability of the membrane to molecules that cannot cross the lipid bilayer.  Macromolecules are unable to pass through the plasma membrane except by vesicular transport. Gradients Across Membrane  Concentration gradient  Electrical gradient Transport Across The Plasma Membrane Transport Across The Plasma Membrane  Active Transport  Active transport is an energy- requiring process that moves solutes such as ions, amino acids, and monosaccharides against a concentration gradient.  In primary active transport, energy derived from ATP changes the shape of a transporter protein, which pumps a substance across a plasma membrane against its concentration gradient.  Primary Active Transport  The most prevalent primary active transport mechanism is the sodium/potassium ion pump. ▪ requires 40% of cellular ATP. ▪ all cells have 1000s of them. ▪ maintains low concentration of Na+ and a high concentration of K+ in the cytosol. ▪ operates continually.  Secondary Active Transport  In secondary active transport, the energy stored in the form of a sodium or hydrogen ion concentration gradient is used to drive other substances against their own concentration gradients.  Plasma membranes contain several antiporters and symporters powered by the sodium ion gradient. Antiporters symporters carry two carry two substances substances across the across the membrane membrane in opposite in the same directions direction. Osmosis  Osmosis  Osmotic pressure of a solution is proportional to the concentration of the solute particles that cannot cross the membrane. Tonicity  Clinical Application:  Cystic fibrosis is caused by a defective gene that produces an abnormal chloride ion transporter. The disease affects the respiratory, digestive, urinary, and reproductive systems.  Digitalis slows the sodium ion-calcium ion antiporters, allowing more calcium to stay inside heart muscle cells, which increases the force of their contraction and thus strengthens the heartbeat.  Transport in Vesicles  Materials can also enter or leave the cell through vesicle transport.  A vesicle is a small membranous sac formed by budding off from an existing membrane.  Endocytosis = bringing something into cell ▪ phagocytosis = cell eating (e.g. macrophages) ▪ pinocytosis = cell drinking  Exocytosis = release something from cell Vesicles form inside cell, fuse to cell membrane Release their contents (e.g. digestive enzymes, hormones, neurotransmitters or waste products) replace cell membrane lost by endocytosis Plan of Human Body 24  External & Internal Environments ▪ Interior of body separated from external environment by a layer of epithelial tissue ▪ Exchange between blood and external environment  Lungs  Gastrointestinal tract  Kidneys ▪ Lumens of respiratory, gastrointestinal, & urinary systems are part of external environment 25  Body Fluids ❑ Mostly water 26  The Internal Environment ❑ The interior of body, the environment of cells inside the body ❑ Internal environment = fluid surrounding cells The ECF is the internal environment 27  What is in the ECF?  Ions  O2  Nutrients (glucose, f.a, a.a)  Waste products (CO2, garbage) 28  Fluid Compartments  60% of body weight Extracellular fluid Intracellular fluid (ECF) (ICF) ( 1/3) ( 2/3) 20% of body weight 40% of body weight Plasma Interstitial fluid Transcellular fluid 25% of ECF 75% of ECF 5% of body wt 15% of body wt CSF Intraocular Pleural Peritoneal Pericardial Synovial Digestive secretions 29  Homeostasis Body cells are surrounded by watery internal environment through which life-sustaining exchanges are made Extracellular fluid (ECF) – Fluid environment in which the cells live (fluid outside the cells) – Two components Plasma, interstitial fluid Intracellular fluid (ICF) – Fluid contained within all body cells  Homeostasis  = State of constancy of conditions within the body  = Maintaining a dynamic steady state of the internal environment  “Essential for cell survival” 31  Factors Homeostatically Regulated 1. Concentration of nutrient molecules 2. Concentration of gases in blood (O2 and CO2 3. Concentration of waste products 4. pH of blood plasma 5. Concentration of water, salt, and other electrolytes 6. Volume of body fluids and vascular pressure 7. Body Temperature 32  The Human Body Systems Contribute to Homeostasis ✓ circulatory - transports materials (e.g., nutrients, gases) ✓ digestive - breaks dietary food into small nutrient molecules ✓ respiratory - obtains oxygen and eliminates carbon dioxide ✓ urinary - removes and eliminates wastes from the plasma ✓ skeletal - provides support and protection for soft tissues ✓ muscular - moves the bones ✓ integumentary - serves as an outer protective barrier ✓ immune - defends against foreign invaders ✓ nervous - controls and coordinates activities rapidly ✓ endocrine - regulates activities that require duration ✓ reproductive - ??? perpetuation of the species 33 Role of Body Systems in Homeostasis  Homeostatic Control Systems In order to maintain homeostasis, control system must be able to: Detect deviations from normal in the internal environment that need to be held within narrow limits. - Integrate this information with other relevant information. - Make appropriate adjustments in order to restore factor to its desired value.  Homeostatic Control Systems Control systems are grouped into two classes – Intrinsic (within) controls Local controls that are inherent in an organ Example exercising skeletal muscle consumes more oxygen leading to fall in oxygen concentration in the skeletal muscle (local). This local decrease in oxygen acts directly on smooth muscle of blood vessels of skeletal muscle causing dilatation of theses blood vessels ( more blood flow means more oxygen supply and thus maintain oxygen level in exercising skeletal muscle. – Extrinsic (outside) controls Regulatory mechanisms initiated outside an organ Accomplished by nervous and endocrine systems Example: when blood pressure falls, the nervous system acts on heart (increases heart rate and contractility) and on blood vessels (vasoconstriction). Both effects can increase blood pressure to normal.  Homeostatic Control Systems Feedback Refers to responses made after change has been detected. Types of feedback systems Negative Positive  Homeostatic Control Systems (cont) Negative Feedback ▪ Change in a condition leads to a response which counteracts that change (opposes an initial change)  Change →  Response →  Change →  Response ▪ Most common type of response 38  Homeostatic Control Systems Negative feedback system – Primary type of homeostatic control – Opposes initial change – Components Sensor – Monitors magnitude of a controlled variable Control center – Compares sensor’s input with a set point Effector – Makes a response to produce a desired effect Maintaining constant body temperature by negative feedback mechanism  Negative Feedback Exposure to cold Normal Body Temperature ↓ Body Temperature + ↑ Body Brain Temperature + Shivering + 41  Negative Feedback Exposure to heat ↑ Body Temperature Normal Body Temperature rat+ Brain ↓ Body Temperature + Sweating + 42  Negative Feedback (Contol of glucose in plasma Glucose Intake ↑ Blood Glucose - + Pancreas Cellular Uptake of Glucose + Insulin + 43  Homeostatic Control Systems  Positive feedback system ▪ Amplifies an initial change. ▪ Do not occur as often as negative feedback system. ▪ Example  Uterine contractions become increasingly stronger until the birth of the baby  Useful positive feedback Childbirth : Uterine contraction pushes head to stretch cervix muscle→ signals through the uterine muscle, causing even more contraction. This action is repeated until the baby is born. Positive feed back mechanism of blood clotting  Homeostatic Control Systems  Intrinsic (local) - inherent in an organ  Extrinsic (body-wide) - outside the organ to alter the activity of the organ 1. Nervous system 2. Endocrine system 47 Positive Feedback 48  Disruption in Homeostasis can lead to illness and death Pathophysiology the abnormal functioning of the body during disease 49