Functional Organization of the Human Body.pdf.pdf

Medical Physiology Functional Organization of the Human Body ‫اﻻﺳﺗﺎذ اﻟﻣﺳﺎﻋد اﻟدﻛﺗور ﺳرﺣﺎن راﺷد اﻟزﯾﺎدي‬ ١٤٤٢/٠٥/١٨  ‫ ﺳرﺣﺎن راﺷد اﻟزﯾﺎدي‬.‫د‬.‫م‬.‫أ‬...

Medical Physiology Functional Organization of the Human Body ‫اﻻﺳﺗﺎذ اﻟﻣﺳﺎﻋد اﻟدﻛﺗور ﺳرﺣﺎن راﺷد اﻟزﯾﺎدي‬ ١٤٤٢/٠٥/١٨  ‫ ﺳرﺣﺎن راﺷد اﻟزﯾﺎدي‬.‫د‬.‫م‬.‫أ‬ ‫اﺳﺗﺎذ اﻟﻣﺎدة‬ ‫ﻓﺳﻠﺟﺔ ﻧظري – اﻟﻣرﺣﻠﺔ اﻟﺛﺎﻧﯾﺔ – اﻟﻣﺣﺎﺿرة اﻻوﻟﻰ‬ Functional Organization of the Human Body Human Physiology In human physiology, we attempt to explain the specific characteristics and mechanisms of the human body that make it a living being. Cells as the Living Units of the Body The basic living unit of the body is the cell. Each organ is an aggregate of many different cells held together by intercellular supporting structures. Each type of cell is specially adapted to perform one or a few particular functions. For instance, the red blood cells, numbering 25 trillion in each human being, transport oxygen from the lungs to the tissues. “Homeostatic” Mechanisms of the Major Functional Systems Homeostasis The term homeostasis is used by physiologists to mean maintenance of nearly constant conditions in the internal environment. Essentially all organs and tissues of the body perform functions that help maintain these relatively constant conditions. For instance, the lungs provide oxygen to the extracellular fluid to replenish the oxygen used by the cells, the kidneys maintain constant ion concentrations, and the gastrointestinal system provides nutrients. ١  ‫ ﺳرﺣﺎن راﺷد اﻟزﯾﺎدي‬.‫د‬.‫م‬.‫أ‬ ‫اﺳﺗﺎذ اﻟﻣﺎدة‬ ‫ﻓﺳﻠﺟﺔ ﻧظري – اﻟﻣرﺣﻠﺔ اﻟﺛﺎﻧﯾﺔ – اﻟﻣﺣﺎﺿرة اﻻوﻟﻰ‬ Specialized Cells of the Human Body Here are some of the different types of specialized cells within the human body.  Nerve Cells: Also called Neurons, these cells are in the nervous system and function to process and transmit information (it is hypothesized). They are the core components of the brain, spinal cord and peripheral nerves. They use chemical and electrical synapses to relay signals throughout the body.  Epithelial cells: Functions of epithelial cells include secretion, absorption, protection, transcellular transport, sensation detection, and selective permeability.  Exocrine cells: These cells secrete products through ducts, such as mucus, sweat, or digestive enzymes. The products of these cells go directly to the target organ through the ducts. For example, the bile from the gall bladder is carried directly into the duodenum via the bile duct.  Endocrine cells: These cells are similar to exocrine cells, but secrete their products directly into the bloodstream instead of through a duct.  Blood Cells: The most common types of blood cells are: o red blood cells (erythrocytes). The main function of red blood cells is to collect oxygen in the lungs and deliver it through the blood to the body tissues. o various types of white blood cells (leukocytes). They are produced in the bone marrow and help the body to fight infectious disease and foreign objects in the immune system. Cellular Organization Cell Membranes The boundary of the cell, sometimes called the plasma membrane, separates internal metabolic events from the external environment and controls the movement of materials into and out of the cell. The plasma membrane is a double phospholipid membrane, or a lipid bilayer, with the nonpolar hydrophobic tails pointing toward the inside of the membrane and the polar hydrophilic heads forming the inner and outer surfaces of the membrane. ٢  ‫ ﺳرﺣﺎن راﺷد اﻟزﯾﺎدي‬.‫د‬.‫م‬.‫أ‬ ‫اﺳﺗﺎذ اﻟﻣﺎدة‬ ‫ﻓﺳﻠﺟﺔ ﻧظري – اﻟﻣرﺣﻠﺔ اﻟﺛﺎﻧﯾﺔ – اﻟﻣﺣﺎﺿرة اﻻوﻟﻰ‬ Protein and Cholesterol Proteins and cholesterol molecules are scattered throughout the flexible phospholipid membrane There are a variety of membrane proteins that serve various functions:  Channel proteins: Proteins that provide passageways through the membranes for certain hydrophilic or water-soluble substances such as polar and charged molecules.  Transport proteins: Proteins that spend energy (ATP) to transfer materials across the membrane  Recognition proteins: Proteins that distinguish the identity of neighboring cells  Adhesion proteins: Proteins that attach cells to neighboring cells or provide anchors for the internal filaments and tubules that give stability to the cell.  Receptor proteins: Proteins that initiate specific cell responses once hormones or other trigger molecules bind to them.  Electron transfer proteins: Proteins that are involved in moving electrons from one molecule to another during chemical reactions. ٣  ‫ ﺳرﺣﺎن راﺷد اﻟزﯾﺎدي‬.‫د‬.‫م‬.‫أ‬ ‫اﺳﺗﺎذ اﻟﻣﺎدة‬ ‫ﻓﺳﻠﺟﺔ ﻧظري – اﻟﻣرﺣﻠﺔ اﻟﺛﺎﻧﯾﺔ – اﻟﻣﺣﺎﺿرة اﻻوﻟﻰ‬ Transport Across the Cell Membrane 1. Passive transport describes the movement of substances down a concentration gradient and does not require energy use. 1.1.Bulk flow is the collective movement of substances in the same direction in response to a force, such as pressure. Blood moving through a vessel is an example of bulk flow. 1.2.Simple diffusion, or diffusion, is the net movement of substances from an area of higher concentration to an area of lower concentration. 1.3.Facilitated diffusion is the diffusion of solutes through channel proteins in the plasma membrane. Water can pass freely through the plasma membrane without the aid of specialized proteins (though facilitated by aquaporins). 1.4.Osmosis is the diffusion of water molecules across a selectively permeable membrane. 1.5.Dialysis is the diffusion of solutes across a selectively permeable membrane. 2. Active Transport Across the Cell Membrane Active transport is the movement of solutes against a gradient and requires the expenditure of energy, usually in the form of ATP. Active transport is achieved through one of these two mechanisms: 1. Protein Pumps Transport proteins in the plasma membrane transfer solutes such as small ions (Na+ , K+ , Cl- , H+ ), amino acids, and monosaccharides 2. Vesicular Transport Vesicles or other bodies in the cytoplasm move macromolecules or large particles across the plasma membrane. Types of vesicular transport include: 1. Exocytosis, which describes the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell. This process is common when a cell produces substances for export. 2. Endocytosis, which describes the capture of a substance outside the cell when the plasma membrane merges to engulf it. The substance subsequently enters the cytoplasm enclosed in a vesicle. There are three kinds of endocytosis: 3.1.Phagocytosis or cellular eating, occurs when the dissolved materials enter the cell. The plasma membrane engulfs the solid material, forming a phagocytic vesicle. 3.2.Pinocytosis or cellular drinking occurs when the plasma membrane folds inward to form a channel allowing dissolved substances to enter the cell. ٤  ‫ ﺳرﺣﺎن راﺷد اﻟزﯾﺎدي‬.‫د‬.‫م‬.‫أ‬ ‫اﺳﺗﺎذ اﻟﻣﺎدة‬ ‫ﻓﺳﻠﺟﺔ ﻧظري – اﻟﻣرﺣﻠﺔ اﻟﺛﺎﻧﯾﺔ – اﻟﻣﺣﺎﺿرة اﻻوﻟﻰ‬ 3.3.Receptor-mediated endocytosis occurs when specific molecules in the fluid surrounding the cell bind to specialized receptors in the plasma membrane. Cell components  Cytoplasm The gel-like material within the cell membrane is referred to as the cytoplasm. It is a fluid matrix, the cytosol, which consists of 80% to 90% water, salts, organic molecules and many enzymes that catalyze reactions, along with dissolved substances such as proteins and nutrients  Cytoskeleton Threadlike proteins that make up the cytoskeleton continually reconstruct to adapt to the cell's constantly changing needs. It helps cells maintain their shape and allows cells and their contents to move.  Microtubules Microtubules function as the framework along which organelles and vesicles move within a cell. They are the thickest of the cytoskeleton structures. They are long hollow cylinders, composed of protein subunits, called tubulin  Microfilaments Microfilaments provide mechanical support for the cell, determine the cell shape, and in some cases enable cell movements. They have an arrow-like appearance ٥  ‫ ﺳرﺣﺎن راﺷد اﻟزﯾﺎدي‬.‫د‬.‫م‬.‫أ‬ ‫اﺳﺗﺎذ اﻟﻣﺎدة‬ ‫ﻓﺳﻠﺟﺔ ﻧظري – اﻟﻣرﺣﻠﺔ اﻟﺛﺎﻧﯾﺔ – اﻟﻣﺣﺎﺿرة اﻻوﻟﻰ‬ Organelles Organelles are bodies embedded in the cytoplasm that serve to physically separate the various metabolic activities that occur within cells. The organelles are each like separate little factories, each organelle is responsible for producing a certain product that is used elsewhere in the cell or body.  Nucleus Controls the cell; houses the genetic material (DNA). The nucleus is the largest of the cells organelles. Cells can have more than one nucleus or lack a nucleus all together. Skeletal muscle cells contain more than one nucleus whereas red blood cells do not contain a nucleus at all.  Chromosomes A rough sketch of a chromosome. Inside each cell nucleus are chromosomes. Chromosomes are made up of chromatin, which is made up of protein and deoxyribonucleic acid strands. Deoxyribonucleic acid is DNA  Centrioles are rod like structures composed of 9 bundles which contain three microtubules each. Centrioles are very important in cellular division.  Ribosomes Ribosomes play an active role in the complex process of protein synthesis, where they serve as the structures that facilitate the joining of amino acids. Each ribosome is composed of a large and small subunit which are made up of ribosomal proteins and ribosomal RNAs  Mitochondria Mitochondria are the organelles that function as the cell "powerhouse", generating ATP, the universal form of energy used by all cells. It converts food nutrients such as glucose, to a fuel (ATP) that the cells of the body can use.  Endoplasmic Reticulum Endoplasmic means "within the plasm" and reticulum means "network". A complex three dimensional internal membrane system of flattened sheets, sacs and tubes, that play an important role in making proteins and shuttling cellular products; also involved in metabolisms of fats, and the production of various materials.  Golgi Apparatus "Packages" cellular products in sacs called vesicles so that the products can cross the cell membrane and exit the cell. The Golgi apparatus is the central delivery system for the cell. They function to modify and package proteins and lipids into vesicles  Vacuoles Spaces in the cytoplasm that sometimes serve to carry materials to the cell membrane for discharge to the outside of the cell  Lysosomes Lysosomes are sac-like compartments that contain a number of powerful degradative enzyme  Peroxisomes Organelles in which oxygen is used to oxidize substances, breaking down lipids and detoxifying certain chemicals. ٦  ‫ ﺳرﺣﺎن راﺷد اﻟزﯾﺎدي‬.‫د‬.‫م‬.‫أ‬ ‫اﺳﺗﺎذ اﻟﻣﺎدة‬ ‫ﻓﺳﻠﺟﺔ ﻧظري – اﻟﻣرﺣﻠﺔ اﻟﺛﺎﻧﯾﺔ – اﻟﻣﺣﺎﺿرة اﻻوﻟﻰ‬ Cell Junctions The plasma membranes of adjacent cells are usually separated by extracellular fluids that allow transport of nutrients and wastes to and from the bloodstream. In certain tissues, however, the membranes of adjacent cells may join and form a junction. Three kinds of cell junctions are recognized: 1. Desmosomes are protein attachments between adjacent cells. 2. Tight junctions are tightly stitched seams between cells. The junction completely encircles each cell, preventing the movement of material between the cell. 3. Gap junctions are narrow tunnels that directly connect the cytoplasm of two neighbouring cells, consisting of proteins called connexons. These proteins allow only the passage of ions and small molecules. ٧  ‫ ﺳرﺣﺎن راﺷد اﻟزﯾﺎدي‬.‫د‬.‫م‬.‫أ‬ ‫اﺳﺗﺎذ اﻟﻣﺎدة‬ ‫ﻓﺳﻠﺟﺔ ﻧظري – اﻟﻣرﺣﻠﺔ اﻟﺛﺎﻧﯾﺔ – اﻟﻣﺣﺎﺿرة اﻻوﻟﻰ‬ Cell Metabolism Cell metabolism is the total energy released and consumed by a cell. Metabolism describes all of the chemical reactions that are happening in the body. 1. Catabolism: The energy releasing process in which a chemical or food is used (broken down) by degradation or decomposition, into smaller pieces. 2. Anabolism: Anabolism is just the opposite of catabolism. In this portion of metabolism, the cell consumes energy to produce larger molecules via smaller ones. Energy Rich Molecules Adenosine Triphosphate (ATP) ATP is the currency of the cell. When the cell needs to use energy such as when it needs to move substances across the cell membrane via the active transport system, it "pays" with molecules of ATP. The total quantity of ATP in the human body at any one time is about 0.1 Mole. The energy used by human cells requires the hydrolysis of 200 to 300 moles of ATP daily. This means that each ATP molecule is recycled 2000 to 3000 times during a single day. ATP cannot be stored, hence its consumption must closely follow its synthesis. On a per-hour basis, 1 kilogram of ATP is created, processed and then recycled in the body. Looking at it another way, a single cell uses about 10 million ATP molecules per second to meet its metabolic needs, and recycles all of its ATP molecules about every 20-30 seconds. Flavin Adenine Dinucleotide (FAD) When two hydrogen atoms are bonded, FAD is reduced to FADH2 and is turned into an energy-carrying molecule. FAD accommodates two equivalents of Hydrogen; both the hydride and the proton ions. This is used by organisms to carry out energy requiring processes Nicotinamide Adenine Dinucleotide (NADH) Nicotinamide adenine dinucleotide (NAD+ ) and nicotinamide adenine dinucleotide phosphate (NADP) are two important cofactors found in cells ٨