Lecture 1 - Cells and Body Organization (2023).pdf
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Chapter 3 The Cellular Level of Organization Lecture Presentation by LeeDr. A...
Chapter 3 The Cellular Level of Organization Lecture Presentation by LeeDr. AnnLeo Lee Frederick [email protected] University of Texas at Arlington Martini FH, Nath JL and Bartholomew EF (2015). Fundamentals of Anatomy and Physiology (10th ed.). Pearson, ISBN 10:0-321-73553-6. © 2015 Pearson Education, Inc. An Introduction to Cells Learning Outcomes 3-1 List the functions of the plasma membrane and the structural features that enable it to perform those functions. 3-2 Briefly describe the organelles of a typical cell, and indicate the specific functions of each. 3-3 Explain the functions of the cell nucleus and discuss the nature and importance of the genetic code. 3-4 Summarize the role of DNA in protein synthesis, cell structure, and cell function. 3-5 Understand the basic features of cell division, including mitosis and meiosis, and explain their significance. 2 Outline An introduction to human cells Structure of a typical mammalian cell Subcellular organelles Plasma membrane Protein synthesis (including gene expression) Cell division Mitosis, Meiosis Body organization Different types of body tissues Epithelial, Connective, Muscular, Neural Homeostasis 3 An Introduction to Human Cells Sex Cells (Germ Cells) – Reproductive cells – Male sperm – Female oocyte (a cell that develops into an egg) Somatic Cells – Soma = body – All body cells except sex cells 4 Plasma Membrane Membrane Lipids – Phospholipid bilayer Hydrophilic heads — toward watery environment, both sides Hydrophobic fatty-acid tails — inside membrane Barrier to ions and water — soluble compounds “Water loving” outside cell Water like content Water like content “Oil loving” Inside cell The Plasma Membrane embedded with protein. EXTRACELLULAR FLUID Phospholipid Integral protein Integral Glycolipids bilayer with channel glycoproteins Hydrophobic tails Cholesterol Peripheral Hydrophilic proteins heads Gated channel Cytoskeleton = 2 nm (Microfilaments) CYTOPLASM Membrane Proteins in plasma membrane 1. Anchoring proteins (stabilizers) – Attach to inside or outside structures 2. Recognition proteins (identifiers) – Label cells as normal or abnormal 3. Enzymes – Catalyze reactions 4. Receptor proteins – Bind and respond to ligands (ions, hormones) 5. Carrier proteins – Transport specific solutes through membrane 6. Channels – Regulate water flow and solutes through membrane 7 Plasma Membrane (Cont’d) The plasma membrane separates the living cell from its surroundings. The plasma membrane is a fluid mosaic structure. – Fluidic because molecules that make up the membrane can move with respect to one another. – A mosaic because of the diversity of proteins in the membrane. https://www.youtube.com/watch?v=LKN5sq5dtW4 8 © 2013 Pearson Education, Inc. Anatomy of a Model Cell = Plasma membrane = Nonmembranous organelles Cytoskeleton = Membranous organelles Proteins organized in Microfilament fine filaments or slender tubes Functions Strength and support; movement of cellular structures and materials Microtubule Plasma Membrane Lipid bilayer containing phospholipids, steroids, proteins, and carbohydrates Free ribosomes Functions Isolation; protection; sensitivity; support; controls entry and exit of materials Cytosol (distributes materials by diffusion) 10 Surface of the cell can be different shape Microvilli Cilia (see Figure 3-4b) Microvilli are extensions of the plasma Cilia are long extensions of the membrane containing microfilaments. plasma membrane containing microtubules. There are two Function types: primary and motile. Increase surface area to Functions facilitate absorption of A primary cilium acts as a extracellular materials sensor. Motile cilia move materials over cell surfaces (e.g. intestine) (e.g. respiratory tract) 12 Cytoplasm All materials inside the cell and outside the nucleus Cytosol (intracellular fluid) Dissolved materials Nutrients, ions, proteins, and waste products High potassium/low sodium High protein High carbohydrate/low amino acid and fat Organelles Structures with specific functions Extracellular Fluid (Interstitial Fluid) A watery medium that surrounds a cell 13 Cell Nucleus Largest organelle; The cell’s control center – Nuclear envelope Double membrane around the nucleus – Nuclear pores Communication passages 14 Contents of the Nucleus – DNA All information to build and run organisms – Nucleoplasm Fluid containing ions, enzymes, nucleotides, and some RNA – Nucleoli (singular called Nucleolus) Are made of DNA, RNA, enzymes, and histones Synthesize ribosomal RNA (rRNA) and ribosomal subunits 15 Anatomy of a Model Cell Chromatin Nuclear NUCLEUS envelope Nucleoplasm containing nucleotides, enzymes, NUCLEOPLASM nucleoproteins, and Nucleolus chromatin; surrounded (site of rRNA by a double membrane, synthesis and the nuclear envelope assembly of ribosome) Functions Control of metabolism; storage and processing of genetic information; control of protein Nuclear synthesis pore The Organization of DNA within the Nucleus Nucleus Sister chromatids Kinetochore Centromere Centromere Supercoiled region Cell prepared for division Visible chromosome Nondividing cell Chromatin in nucleus DNA double helix Nucleosome Histones Cell Nucleus (cont’d) Information Storage in the Nucleus – DNA Instructions for every protein in the body – Gene DNA instructions for one protein – Genetic code The chemical language of DNA instructions – Sequence of bases (A, T, C, G) Triplet code – 3 bases (a codon) = 1 amino acid 18 Nitrogenous bases Adenine (A) Guanine (G) Thymine (T) Cytosine (C) Nucleotide 19 2 1 3 20 Anatomy of a Model Cell Golgi apparatus Stacks of flattened membranes (cisternae) containing chambers Functions Storage, alteration, and packaging of secretory products and lysosomal enzymes Mitochondria Double membrane, with inner membrane folds (cristae) enclosing important metabolic enzymes Function Produce 95% of the ATP required by the cell Endoplasmic reticulum (ER) Network of membranous Rough ER channels extending modifies and NUCLEUS packages newly throughout the cytoplasm synthesized Functions proteins Synthesis of secretory products; intracellular storage Smooth ER and transport; detoxification of synthesizes lipids drugs or toxins and carbohydrates = Plasma membrane = Nonmembranous organelles = Membranous organelles Endoplasmic Reticulum (ER) Golgi Apparatus (post-office) Golgi Apparatus (cont’d) 24 Products of Golgi Apparatus = Plasma membrane = Nonmembranous organelles = Membranous organelles Peroxisomes Vesicles containing degradative enzymes Functions Catabolism of fats and other organic compounds; neutralization of toxic compounds generated in the process Free ribosomes Lysosomes Vesicles containing digestive enzymes Function Intracellular removal of damaged organelles or pathogens Protein Synthesis The Role of Gene Activation in Protein Synthesis – Gene activation — uncoiling DNA to use it – Transcription https://www.youtube.com/watch?v=WsofH466lqk (reference) Copies instructions from DNA to mRNA (in nucleus) RNA polymerase produces messenger RNA (mRNA) – RNA polymerase binds to “promoter” region on template strand – RNA processing: introns will be removed and exons will be spliced together mRNA leaves nucleus to cytoplasm through nuclear pores – Translation https://www.youtube.com/watch?v=5bLEDd-PSTQ Ribosome (on Rough ER) reads code from mRNA (in cytoplasm) Assembles amino acids into polypeptide chain with help of tRNA – Processing RER and Golgi apparatus produce protein 26 Comparison between DNA and RNA DNA RNA C C Nitrogenous G G base A A T U Sugar Deoxy- Ribose ribose Number of 2 1 strands 27 mRNA Transcription. DNA 1 2 3 Template Coding strand strand Codon mRNA 1 strand RNA polymerase Promoter Codon 2 Codon Triplet 1 1 3 Codon Gene 1 Complementary Codon 4 (stop codon) triplets Triplet 2 2 2 Triplet 3 3 RNA nucleotide Triplet 4 4 KEY Adenine Uracil (RNA) After transcription, the two DNA strands re-associate Guanine Thymine (DNA) Cytosine 29 Anatomy of a Model Cell = Plasma membrane = Nonmembranous organelles = Membranous organelles Secretory vesicles Centrosome and Centrioles Cytoplasm contains two centrioles at right angles; each centriole is composed of 9 microtubule triplets in a 9 + 0 array Functions Essential for Centrosome movement of chromosomes during cell division; organization of microtubules in cytoskeleton Centrioles NUCLEUS Cell Life Cycle Most of a cell’s life is spent Cytokinesis in a nondividing state (G0) Body (somatic) cells can divide in three stages DNA replication (S) duplicates genetic material exactly Mitosis divides genetic material equally Cytokinesis divides cytoplasm and organelles into two daughter cells Interphase: G1, S and G2 31 (G2) The nuclear envelope Forming the mitotic disappears spindles Spindle start attach to Chromatin condense the centromere to form visible Move chromosomes to chromosome the center of the cell Sister chromatids Nuclear envelope separate at the forms around The mitotic spindle is fully centromeres chromosomes at each formed and attached to Mitotic spindle shorten pole, forming the two centromere and daughter identical daughter Chromosomes align at chromosomes pull to nuclei the cell equator the opposite poles of Chromosome uncoils the cell The spindle disappears https://www.youtube.com/watch?v=g7iAVCLZWuM Meiosis Process by which two cell-division steps produce gametes (ova and sperm) – Only occurs in the gonads (ovaries and testes) Germ cells in ovaries / testes 34 Meiosis I Meiosis II https://www.youtube.com/watch?v=E6HF2otWE8k 37 Tissues & Body Organization Recommended Textbook (Chapters 1 & 4): Martini FH, Nath JL and Bartholomew EF (2015). Fundamentals of Anatomy and Physiology (10th ed.). Pearson, ISBN 10:0-321-73553-6. Body Organization Learning Outcomes 4-1 Identify the four major types of tissues in the body and describe their roles. 4-2 Understand how different types of tissues are organized in organs and systems. 4-3 Explain the concept of homeostasis. 4-4 Describe how negative feedback and positive feedback are involved in homeostatic regulation, and explain the significance of homeostasis. 39 An Introduction to Tissues Tissues – Structures with discrete structural and functional properties – Tissues in combination form organs, such as the heart or liver – Organs can be grouped into 11 organ systems: Integumentary, Nervous, Endocrine, Skeletal, Muscular, Circulatory, Immune, Respiratory, Urinary, Digestive and Reproductive Systems Four types of tissue 1. Epithelial tissue 2. Connective tissue 3. Muscle tissue 4. Neural tissue 40 1. Epithelial Tissue Characteristics of Epithelia – Cellularity (cell junctions) Cilia – Polarity (apical and basal Microvilli surfaces) Apical surface – Attachment (basement membrane or basal lamina) – Avascularity – Regeneration Golgi apparatus Functions of Epithelial Tissue Nucleus 1. Provide Physical Protection 2. Control Permeability Mitochondria 3. Provide Sensation Basement membrane 4. Produce Specialized Secretions Basolateral surfaces (glandular epithelium) 41 Classification of Epithelia Singular = Epithelium; Plural = Epithelia Classes of epithelia 1. Based on shape Squamous epithelia — thin and flat Cuboidal epithelia — square shaped Columnar epithelia — tall, slender rectangles 2. Based on layers Simple epithelium — single layer of cells Stratified epithelium — several layers of cells 42 Classifying Epithelia Classification of Epithelia (cont’d) Glandular Epithelia – Endocrine glands Release hormones – Into interstitial fluid – No ducts – Exocrine glands Produce secretions – Onto epithelial surfaces – Through ducts 44 2. Connective Tissue Characteristics of Connective Tissue 1. Specialized cells 2. Solid extracellular protein fibers 3. Fluid extracellular ground substance The Extracellular Components of Connective Tissue (Fibers and Ground Substance) – Make up the matrix Majority of tissue volume Determines specialized function 45 2. Connective Tissue (cont’d) Functions of Connective Tissue – Establishing a structural framework for the body (Bone) – Transporting fluids and dissolved materials (Blood) – Protecting delicate organs (Fat) – Supporting, surrounding, and interconnecting other types of tissue (Tendon) – Storing energy reserves, especially in the form of triglycerides (Fat) – Defending the body from invading microorganisms (Blood) 46 2. Connective Tissue (cont’d) Classification of Connective Tissues A. Connective tissue proper Connect and protect B. Fluid connective tissues Transport C. Supporting connective tissues Structural strength 47 2. Connective Tissue (cont’d) A. Categories of Connective Tissue Proper – Loose connective tissue More ground substance, fewer fibers For example: areolar tissue, fat (adipose tissue) – Dense connective tissue More fibers, less ground substance For example, tendons 48 Loose Connective Tissues 49 Dense Connective Tissues 50 2. Connective Tissue (cont’d) B. Fluid Connective Tissues – Blood and lymph – Watery matrix of dissolved proteins – Carry specific cell types (formed elements) Formed elements of blood – Red blood cells (erythrocytes) – White blood cells (leukocytes) – Platelets 51 Formed Elements in the Blood (Part 1) Formed Elements in the Blood (Part 2) Red blood cells Platelets Red blood cells, or Platelets are erythrocytes membrane-enclosed (e-RITH-ro-sits), ˉ ˉ are respon- packets of cytoplasm sible for the transport of that function in blood oxygen (and, to a lesser clotting. degree, of carbon dioxide) in the blood. Red blood cells These cell fragments account for about are involved in the half the volume of clotting response that whole blood and seals leaks in dam- aged or broken blood give blood its color. vessels. Formed Elements in the Blood (Part 3) White blood cells White blood cells, or leukocytes ˉ ˉ leuko-, white), help defend the (LOO-ko-sits; body from infection and disease. Neutrophil Eosinophil Basophil Monocytes Lymphocytes are Eosinophils and neutro- are phagocytes uncommon in the blood phils are phagocytes. similar to the but they are the dominant Basophils promote inflam- free macro- cell type in lymph, the mation much like mast cells phages in second type of fluid in other connective tissues. other tissues. connective tissue. 2. Connective Tissue (cont’d) Lymph – Extracellular fluid Collected from interstitial space Monitored by immune system Transported by lymphatic (lymphoid) system Returned to venous system 54 2. Connective Tissue (cont’d) C. Supporting Connective Tissues Support Soft Tissues and Body Weight – Cartilage Gel-type ground substance For shock absorption and protection – Bone Calcified (made rigid by calcium salts, minerals) For weight support 55 Cartilage 56 2. Connective Tissue (cont’d) Bone or Osseous Tissue – Strong (calcified calcium salt deposits) – Resists shattering (flexible collagen fibers) Bone Cells or Osteocytes – Arranged around central canals within matrix – Small channels through matrix (canaliculi) access blood supply Periosteum – Covers bone surfaces – Fibrous layer – Cellular layer 57 Bone Fibrous layer Canaliculi Periosteum Cellular Osteocytes layer in lacunae Matrix Osteon Central canal Blood vessels Osteon LM × 375 3. Muscle Tissue – Specialized for contraction – Produces all body movement – Three types of muscle tissue 1. Skeletal muscle tissue – Large body muscles responsible for movement 2. Cardiac muscle tissue – Found only in the heart 3. Smooth muscle tissue – Found in walls of hollow, contracting organs (blood vessels; urinary bladder; respiratory, digestive, and reproductive tracts) 59 60 4. Neural Tissue – Also called nervous or nerve tissue Specialized for conducting electrical impulses Rapidly senses internal or external environment Processes information and controls responses – Neural tissue is concentrated in the central nervous system Brain Spinal cord 61 4. Neural Tissue (cont’d) Two Types of Neural Cells 1. Neurons Nerve cells Perform electrical communication 2. Neuroglia Supporting cells Repair and supply nutrients to neurons Cell Parts of a Neuron – Cell body Contains the nucleus and nucleolus – Dendrites Short branches extending from the cell body Receive incoming signals – Axon (nerve fiber) Long, thin extension of the cell body Carries outgoing electrical signals to their destination 62 Neural Tissue. NEURONS NEUROGLIA (supporting cells) Nuclei of neuroglia Maintain physical structure of tissues Cell body Repair tissue framework after injury Perform phagocytosis Provide nutrients to neurons Regulate the composition of the Axon interstitial fluid surrounding neurons Dendrites Nucleolus Nucleus of neuron LM × 600 Dendrites (contacted by other neurons) Contact with Axon (conducts other cells Microfibrils and information to microtubules other cells) Cell body (contains nucleus and major organelles) Nucleus Nucleolus Mitochondrion A representative neuron (sizes and shapes vary widely) Organs and Systems Organs An organ is composed of two or more tissues that serve different functions in the organ. The skin is the largest organ in the body. – The skin has all four primary tissues: epithelial, connective, muscular and nervous tissues Systems Organs that perform related functions are grouped into systems. 64 Homeostasis Homeostasis – All body systems working together to maintain a stable internal environment Systems respond to external and internal changes to function within a normal range (body temperature, fluid balance) 65 Homeostasis (cont’d) Mechanisms of Regulation – Autoregulation (intrinsic) Automatic response in a cell, tissue, or organ to some environmental change – Extrinsic regulation Responses controlled by nervous and endocrine systems Receptor – Receives the stimulus Control Center – Processes the signal and sends instructions Effector – Carries out instructions 66 Negative and Positive Feedback The Role of Negative Feedback – The response of the effector negates the stimulus – Body is brought back into homeostasis Normal range is achieved The Role of Positive Feedback – The response of the effector increases change of the stimulus – Body is moved away from homeostasis Normal range is lost – Used to speed up processes 67 Negative Feedback Example - Control of Body Temperature RECEPTORS Temperature Information sensors in skin affects Normal and temperature hypothalamus CONTROL disturbed CENTER STIMULUS: Body temperature rises HOMEOSTASIS Thermoregulatory Normal body center in brain Vessels Vessels temperature dilate, constrict, RESPONSE: sweating sweating Increased heat loss, increases decreases body temperature drops Body temperature (°C) Normal EFFECTORS 37.2 Sends Set point Normal temperature 37 Sweat glands commands range restored in skin increase 36.7 to secretion Blood vessels in skin dilate Time a Events in the regulation of body temperature, which are comparable to b The thermoregulatory center those shown in Figure 1–2. A control center in the brain (the hypothalamus) keeps body temperature fluctuat- functions as a thermostat with a set point of 37°C. If body temperature ing within an acceptable range, exceeds 37.2°C, heat loss is increased through enhanced blood flow to the usually between 36.7°C and skin and increased sweating. 37.2°C. Positive Feedback - Blood Clotting Clotting accelerates Positive feedback loop Chemicals Blood clot Chemicals Damaged cells in the blood The chemicals start chain As clotting continues, each This escalating process vessel wall release chemi- reactions in which cells, step releases chemicals is a positive feedback cals that begin the clotting cell fragments, and soluble that further accelerate the loop that ends with the process. proteins in the blood begin process. formation of a blood clot, to form a clot. which patches the vessel wall and stops the bleeding. Negative and Positive Feedback (cont’d) Systems Integration – Systems work together to maintain homeostasis Homeostasis is a state of equilibrium – Opposing forces are in balance – Dynamic equilibrium — continual adaptation Physiological systems work to restore balance – Failure results in disease or death 70
