L2 Human Organization PDF

Understanding the Organization of Human Body HPHS4072 Anatomy and Physiology in Rehabilitation Chloe Mo AHRC Intended Learning Outcomes Briefly describe the organelles of a typical cell, and indicate the specific functions of each. Explain the functions of the cell nucleus and discuss the nat...

Understanding the Organization of Human Body HPHS4072 Anatomy and Physiology in Rehabilitation Chloe Mo AHRC Intended Learning Outcomes Briefly describe the organelles of a typical cell, and indicate the specific functions of each. Explain the functions of the cell nucleus and discuss the nature and importance of the genetic code. List the functions of the plasma membrane and the structural features that enable it to perform those functions. Describe the stages of the cell life cycle, including mitosis, interphase, and cytokinesis, and explain their significance. Identify the four major types of tissues in the body and describe their roles. Understand how different types of tissues are organized in organs and systems. Explain the concept of homeostasis, negative feedback and positive feedback. 5 2 Outline An introduction to human cells Structure of a typical mammalian cell Subcellular organelles Plasma membrane Cell life cycle Mitosis, Meiosis Different types of body tissues Epithelial, Connective, Muscular, Neural Homeostasis An Introduction to Human Cells Sex Cells (Germ Cells) i Reproductive cells > meiosis - Male sperm Female oocyte (a cell that develops into an egg) E Somatic Cells # Soma = body > - mitosis All body cells except sex cells 4 Anatomy of a Model Cell (Part 1) A Typical Cell = Plasma membrane = Nonmembranous organelles = Membranous organelles Secretory vesicles Centrosome and Centrioles Cytoplasm contains two Functions Essential for moveent of chromosomes during cell division; D receive centrioles at from isRER right angles; each centriole , a) glycosylation SER composed of 9 microtubule triplets in a 9 + 0 array 2) modification Centrosomeonly b) phosphorylation > - molecules - resicles n-type (nitrogen) o-type coxger) > - form by Golgi CYTOSOL organization of 3) packaged > vesicle with protein microtubules in - cytoskeleton a) lysosome lipich Centrioles protein b) membrane NUCLEUS I excreted  Anatomy of a Model Cell (Part 2) = 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 Cell membrane : Lipid bilayer containing phospholipids, a) phospholipidbilayer steroids, proteins, and carbohydrates Free ribosomes ⑨holida alr Functions Isolation; channela + ↑ cholesteral b) Cholesterol 14 fluidity protection; ↓ cholesterol sensitivity; support; ↓ fluidity controls entry > and out of material and exit of 2) protein - in materials Cytosol (distributes materials by diffusion) diffusion a) Barrier el) 2) transport Plasma Membrane cytoplasm Er Extracellular Fluid (Interstitial Fluid) A watery medium that surrounds a cell Plasma membrane (cell membrane) separates cytoplasm from the extracellular fluid Cytoplasm Cytoplasm As Cytosol Cytosol = liquid Intracellular structures collectively known as organelles 7  (wbc) EXTRACELLULAR FLUID Anatomy of a Model Cell (Part 3) Microvilli Microvilli are extensions of the plasma membrane containing microfilaments. Function Increase surface area to facilitate absorption of extracellular materials = Plasma membrane = Nonmembranous organelles = Membranous organelles  Cilia (see Figure 3-4b) Anatomy of a Model Cell (Part 4) Cilia are long extensions of the plasma membrane containing microtubules. There are two types: primary and motile. = Plasma membrane Functions A primary cilium acts as a = Nonmembranous organelles (nose) sensor. Motile cilia move materials over cell surfaces = Membranous organelles couts Protesomes Hollow cylinders of proteolytic enzymes with regulatory proteins at their ends Functions Breakdown and recycling of damaged or abnormal intracellular proteins Ribosomes RNA + proteins; fixed ribosomes bound to rough endoplasmic reticulum; free ribosomes scattered in cytoplasm Function Protein synthesis  Golgi apparatus Stacks of flattened membranes Anatomy of a Model Cell (Part 5) (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 I reticulum Smooth endoplasmic reticulum Rough endoplasmic V ribosome X ribosome acissaid transcription 1) Lipid Synthesise)Fatty DNA > - nuclear I pores > - mRNA) cholestal (hormone) biotransformation mRNA 2) enzyme Cyp450 > liver > - - binda detoxification makeprotein translation a ribosome metabolism (glucose synthesis) 3) glucose-6 phosphate = Plasma membrane ->D) site of protein Synthesis = Nonmembranous organelles a) Lysosome 4) store calcium = Membranous organelles b) membrane c) excreted 2) protein folding 3) glycosylation D r i e ze protein Sugar Organelles and the Cytoplasm Cytoplasm All materials inside the cell and outside the nucleus A 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 12 Cell Nucleus Nucleus Largest organelle The cell’s control center Nuclear envelope # Double membrane around the nucleus Perinuclear space #F Between the two layers of the nuclear envelope Nuclear pores *** 6 Communication passages - 13  - Anatomy of a Model Cell (Part 7) Doublembu (nuclear - envel a nucleus 1 : blinner > - Lamins (protein) & nucleus between cytoplasm ) nuclear & pores > transportion - nucleolus RNAsynthesis ribusine 3) > - > - with combine protein O 4) Chromatin (DNA + histone protein) of DNA a) enchromatin (loose)(central) > replication - (boarder) b) heter chromatic (tights : transcription Function DNA -> RNA 1) DNA replication : a) tRNA A translation b) m(NH c) rRNA Cell Nucleus (cont’d) - Contents of the Nucleus DNA All information to build and run organisms Nucleouplasm ↑ Fluid containing ions, enzymes, nucleotides, and some RNA Nuclear matrix Support filaments 15  Nucleus Sister chromatids Kinetochore Centromere Supercoiled region Cell prepared for division Visible chromosome Nondividing cell Chromatin in nucleus DNA double helix Nucleosome Histones The Organization of DNA within the Nucleus 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 = 1 amino acid 17 Protein Synthesis (cont’d) synthesis Protein 2) Translation I 1) Transcription DNA > mRNA mRNA > protein - - The Role of Gene Activation in Protein Synthesis 1) Gene activation — uncoiling DNA to use it & Transcription F Copies instructions from DNA to mRNA (in nucleus) RNA polymerase produces messenger RNA (mRNA) region ona bind with promotet Transcription : In nucleus Stepiation DRNA : polymerase helix template strand DNA-const strand DNA + RNA polymerase > - mRNA Uncoil DNA double , template strand from 3, it along Cenzyme) DNA 2) Elongatison : DANA polymerasemoving mRNA (A to U TtoA , GtoC , C to G) Coding templea , > mRNDemplate ribonucleotides - 2) + 5) codon strand formed 3) mRNA a i od to terminator region 3) Termination : "RNAmerce more release 2) mRNA 18  Ribosome in cytoplasm Protein Synthesis (cont’d) Translation mRNA + ribosome : tRNA - protein anima · CMANs) anti-codon CERNA) to a ribosome attach 1) mRNA codon on MRMA. AUG(starts tRNA binds to 2) on anticodon acids joined by peptide bond 3) amino The Role of Gene Activation in Protein Synthesis 4) Step codon 3) Translation Ribosome reads code from mRNA (in cytoplasm) Assembles amino acids into polypeptide chain # Processing (v) RER and Golgi apparatus produce protein 19 Protein Synthesis (cont’d) 23 pairs DNA-46 chromosome Step 1: Gene activation Chromatin DNA histone protein = Uncoils DNA, removes histones protein Start (promoter) and stop codes(stop codon?) on DNA mark location of gene Coding strand is code for protein enzyme Template strand is used by RNA polymerase molecule 20 mRNA Transcription DNA 1 2 3 Template Coding strand strand Codon mRNA 1 strand RNA enzyme polymerase Promoter Codon 2 i Codon Triplet 1 1 3 & i Codon Gene Complementary 1 Codon 4 (stop codon) triplets Triplet 2 2 2 copy Triplet 3 3 RNA nucleotide Triplet 4 4 KEY Adenine Uracil (RNA) After transcription, the two DNA strands re-associate Guanine Thymine (DNA) Cytosine Protein Synthesis (cont’d) Step 2: DNA to mRNA Enzyme RNA polymerase transcribes DNA Binds to promoter (start) sequence Reads DNA code for gene Binds nucleotides to form messenger RNA (mRNA) mRNA duplicates DNA coding strand, uracil replaces thymine A-u u - T 22 Protein Synthesis (cont’d) Step 3: RNA processing At stop signal, mRNA detaches from DNA molecule Code is edited (RNA processing) (splicing) Unnecessary codes (introns) removed Good codes (exons) spliced together Triplet of three nucleotides (codon) represents one amino acid - 23 Protein Synthesis (cont’d) Translation mRNA moves: From the nucleus through a nuclear pore mRNA moves: (In cytoplasm) To a ribosome in cytoplasm surrounded by amino acids mRNA binds to ribosomal subunits tRNA delivers amino acids to mRNA 24 Protein Synthesis (cont’d) https://www.youtube.com/watch?v=gG7uCskUOrA * Protein Synthesis > make cells - > growth - Translation tRNA anticodon binds to mRNA codon One mRNA codon translates to one amino acid Enzymes join amino acids with peptide bonds ↳ Polypeptide chain has specific sequence of amino acids At stop codon, components separate 25 Cell Life Cycle Cell Life Cycle Most of a cell’s life is spent in a nondividing state (interphase) AG Body (somatic) cells can divide in three stages I DNA replication duplicates genetic material exactly 2) Mitosis divides genetic material equally (1 cell 2 cell) > - 3) Cytokinesis divides cytoplasm and organelles into two daughter cells 26  3 cells : (keep synthesising) Dabie cells 3) Permanent cells Cell Life Cycle (cont’d) 9) epithelium of sksn a) neurons b) Skeletal music 2) Caralan musile frast (s) GI trast urinary 2c) Hematopoetic , stem cells in red bone marrow ~ cell division of red blood calls Interphase 2) a)Stableliver cells (Hepectocytes) cells The nondividing period b) epithelium kidney tubules of G growth - G-zero (G0) phase — specialized cell functions only S synthesis G1 phase — cell growth, organelle duplication, protein synthesis (eg?) > - S phase — DNA replication and histone synthesis ↑ in no G2 phase — finishes protein synthesis and centriole replication (mitochondria) G phase , : Sphase : 1) Make organelles 2) synthesis protein & enzyme 3) Repair Thymidine Dimers 27 Cell Life Cycle (cont’d) Mitosis Divides duplicated DNA into two sets of chromosomes DNA coils tightly into chromatids Chromatids connect at a centromere Protein complex around centromere is kinetochore- 28  Nucleus Sister chromatids Kinetochore Centromere Supercoiled region Cell prepared for division Visible chromosome Nondividing cell Chromatin in nucleus DNA double helix Nucleosome Histones The Organization of DNA within the Nucleus Cell Life Cycle (cont’d) *** I PM AT CD Mitosis Prophase : Nucleoli disappear Centriole pairs move to cell poles Microtubules (spindle fibers) extend between centriole pairs Nuclear envelope disappears Spindle fibers attach to kinetochore - Metaphase equator Falk Chromosomes align in a central plane (metaphase plate) : 30  Cell Life Cycle (cont’d) Mitosis sitter chromated separate i) spindle tible contract, F Anaphase Microtubules pull chromosomes apart Daughter chromosomes group near centrioles Telophase 4 Nuclear membranes re-form Chromosomes uncoil Nucleoli reappear?· Cell has two complete nuclei 31 Cell Life Cycle (cont’d) Cytokinesis CD Division of the cytoplasm Cleavage furrow around metaphase plate Membrane closes, producing daughter cells 32 Meiosis Process by which two cell-division steps produce gametes (ova and sperm) Only occurs in the gonads (ovaries and testes) Video clip: Meiosis (https://www.youtube.com/watch?v=kQu6Yfrr6j0) 33  ' Phaploid daughter cells Meiosis I. > - 1) Prophase I: Homologous chromosomes pair up. 2) Parts are often swapped in a process called crossover. Crandom) Metaphase I: Homologous chromosomes line up in the center of the cell. Cells line up at random; maternal and paternal chromosomes are shuffled.(random distribution) Crossover and shuffling result in genetic diversity. 34  Crossing : over Meiosis I & Anaphase I: Homologous chromosomes are pulled apart. - Telophase I: Homologous chromosomes are separated. This results in two daughter cells with 23 chromosomes each. This is reduction division since each cell now has half as many chromosomes. Necessary for sexual reproduction chromatids A different lister 35 Meiosis II Proceeds like mitosis with phases prophase II through telophase II. Sister chromatids line up in the center of the cell. Centromeres are broken and pulled to opposite poles. Results in 4 cells with 23 chromosomes each. 36 An Introduction to Tissues Tissues G 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(表皮), Nervous, Endocrine, Skeletal, Muscular, Circulatory, Immune, Respiratory, Urinary, Digestive and Reproductive Systems 37 Four Types of Tissue Tissues Are collections of cells and cell products that perform specific, limited functions Four types of tissue skin) (e g things.. cover 1. Epithelial tissue > - 2. Connective tissue 3. Muscle tissue 4. Neural tissue 38  Epithelial Tissue 1) Epithelia Layers of cells covering internal or external surfaces Glands > liver , pancreas 2) - Structures that produce secretions (eg.?) outside of 3) Coving > - skins , organs Unins of stomach 4) lining > - 39 Epithelial Tissue features : Characteristics of Epithelia Cellularity (cell junctions) Polarity (apical 頂 and basal底 surfaces) Attachment (basement membrane or basal lamina) (@the base) Avascularity (a-vascular-ity 無血管)(capillaries?) ↓ provide nutrient and on regeneration Regeneration 40 The Polarity of Epithelial Cells. Cilia Microvilli Apical surface Golgi apparatus Nucleus lamina basal lamina treticular Mitochondria ↓ Basement membrane Basolateral surfaces Epithelial Tissue 1) protection 5)Secretion Functions of Epithelial Tissue 2) absorption 6) sensory reception 1. Provide Physical Protection 3) filtration 2. Control Permeability 4) excretion 3. Provide Sensation (A primary cilium acts as a sensor.) 4. Produce Specialized Secretions (glandular epithelium) (epithelium in glands) 42 Epithelial Tissue Specializations of Epithelial Cells 1. Move fluids over the epithelium (protection) 2. Move fluids through the epithelium (permeability) 3. Produce secretions (protection and messengers) Polarity (Apex top) - 1. Apical surfaces Microvilli increase absorption or secretion Cilia (ciliated epithelium) move fluid 2. Basolateral surfaces 43 Epithelial Tissue Regenerative : Epithelial Maintenance and Repair Epithelia are replaced by division of germinative cells (stem cells) Near basement membrane 44 Classification of Epithelia Singular = Epithelium; Plural = Epithelia Classes of epithelia 1. Based on shape Squamous epithelia — thin and flat & Cuboidal epithelia — square shaped ⑱ cube - Columnar epithelia — tall, slender rectangles long jo column FX , 2. Based on layers Simple epithelium — single layer of cells Stratified epithelium — several layers of cells 45 Classifying Epithelia (Part 1 of 2) A E i He oral nucli · layer tally this cell with round & narrow nuclei one flat layer cells with flat nuclei one cubed layer cell with round contral nuclei one 1) alveoli cell 1) Diffusion INephrengland 1) absorption 1) GI tract stomara) absorption 2) Glomerulus 2) 3) Filtration 2) Secretion 2) Glands I Secretion 3) Blood vessels lubrication 3) Kallney gland 3) intestine  Classifying Epithelia (Part 2 of 2) A pseudostratified ciliated columnar > - fake stratified Cona layer) e g Trachea.. Multiple layers cells Ex Keratinized : underlyingcells protection of palms feet) V Dry impermeable (skin , , , X Keratinized : nucleus ~ moisture) esophagus * Apical > no - Diffusion with capillances 2) Vagina Basal > - 0 nucleus ~ alive Unucleus 3) Epiders is Classification of Epithelia (cont’d) Glandular Epithelia endocrine glands -hormones Endocrine glands bloodsteam > directly to - # Release hormones (blood) > no - duct Into interstitial fluid (e.g. ? Into blood stream) ande 2. 9. itute No ducts 3) adrenal gland #Exocrine glands Produce secretions exocrine gland sweets) Onto epithelial surfaces secretion (enzyme , > - Through ducts (e.g. sweating/ tears) > - have dust to epithelial surfac · 4) mammary gland, 1) Salivary gland 2) Sweat gland 48 3) pancreas 2) Connective Tissue 1) Proper 2) cartilage X 3) bone Cells + Gal + Fibre 4) blood Characteristics of Connective Tissue 1. Specialized cells (e.g.rbc?) 2. Solid extracellular protein fibers (collagens) It 3. Fluid extracellular ground substance The Extracellular Components of Connective Tissue (Fibers and Ground Substance) (2,3) materials Make up the matrix extracellular matrix > - nonliving Majority of tissue volume Determines specialized function 49  Connective Tissue (cont’d) ) ligament , wbc- Functions of Connective Tissue Ce % blood, ·.. Establishing a structural framework for the body Transporting fluids and dissolved materials (connected) Protecting delicate organs Supporting, surrounding, and interconnecting other types of tissue Storing energy reserves, especially in the form of triglycerides (loose – adipose?) Defending the body from invading microorganisms Immunity 1) protect 55 2) support 3) bind 4) Transport 50 Connective Tissue (cont’d) Classification of Connective Tissues 1. Connective tissue proper (固有締結組織/ 一般性) Connect and protect 2. Fluid connective tissues Transport 3. Supporting connective tissues Structural strength 51 Connective Tissue (cont’d) Categories of Connective Tissue Proper I Loose connective tissue For example: areolar tissue, fat (adipose tissue) More ground substance, fewer fibers LESE) F 2) Dense connective tissue For example: tendons More fibers, less ground substance 52  Connective Tissue (cont’d) 2) Dense Connective Tissues tightly packed with high numbers of collagen or elastic fibers Also a kind Connective tissues proper 3 types of dense connective tissues - to muscle bone 2 1). Dense regular connective tissue (eg tendon) 2 2). Dense irregular connective tissue (eg deep dermis). 2 3) Elastic tissue (ligament) ↓ bone to bone (more tough) 53 Dense Connective Tissue – Dense Regular Connective Tissue Dense Regular Connective Tissue LOCATIONS: Between skeletal muscles and skeleton (tendons and aponeuroses); between bones or stabilizing positions Collagen of internal organs (ligaments); fibers covering skeletal muscles; deep fasciae FUNCTIONS: Provides firm attachment; conducts Fibroblast pull of muscles; reduces nuclei friction between muscles; T stabilizes positions tendon of bones a Tendon LM × 440 Dense Connective Tissue – Dense Irregular Connective Tissue Dense Irregular Connective Tissue LOCATIONS: Capsules of visceral organs; periostea and perichondria; nerve and muscle sheaths; dermis FUNCTIONS: Provides strength to resist forces Collagen from many directions; fiber helps prevent bundles overexpansion of organs, such as the urinary bladder b Deep dermis LM × 111 Dense Connective Tissue – Elastic Tissue Elastic Tissue LOCATIONS: Between vertebrae of the spinal column (ligamentum flavum and ligamentum nuchae); ligaments supporting penis; Elastic ligaments supporting transitional fibers epithelia; in blood vessel walls FUNCTIONS: Stabilizes positions of vertebrae and Fibroblast penis; cushions shocks; nuclei permits expansion and contraction of organs c Elastic ligament LM × 887  Connective Tissue (cont’d) 3) 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)I cells White blood cells (leukocytes, white blood cells) Platelets #--A 56 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. Connective Tissue (cont’d) Lymph Extracellular fluid Collected from interstitial space Monitored by immune system Transported by lymphatic (lymphoid) system Returned to venous system FATK (deoxynated blood) 59 Supporting Connective Tissues Support Soft Tissues and Body Weight 1) Cartilage E Gel-type ground substance For shock absorption and protection 2) Bone Calcified (made rigid by calcium salts, minerals) For weight support 60  Supporting Connective Tissues (cont’d). 1) Bone or Osseous Tissue 2 Strong (calcified calcium salt deposits) Resists shattering (flexible collagen fibers) Bone Cells or Osteocytes 2. ) Arranged around central canals within matrix. Small channels (canaliculi) through matrix (canaliculi) access blood supply Periosteum Covers bone surfaces Fibrous layer Cellular layer 61  Bone Fibrous layer Canaliculi Periosteum Cellular Osteocytes layer in lacunae Matrix Osteon Central canal Blood vessels Osteon LM × 375 "Menser 3) Muscle Tissue Muscle Tissue Specialized for contraction Produces all body movement Three types of muscle tissue 3 1.. ) Skeletal muscle tissue Large body muscles responsible for movement 3/ 2. Cardiac muscle tissue. 3 3.J Found only in the heart Smooth muscle tissue. => FEEEEEE) non-autonomous Found in walls of hollow, contracting organs (blood vessels; urinary bladder; respiratory, digestive, and reproductive tracts) 63 Types of Muscle Tissue - Skeletal Muscle Skeletal Muscle Tissue Cells are long, cylindrical, striated, and multinucleate. LOCATIONS: Combined Striations with connective tissues and neural tissue in Nuclei skeletal muscles FUNCTIONS: Moves or stabilizes the position of the skeleton; guards Muscle entrances and exits to the fiber digestive, respiratory, and urinary tracts; generates heat; protects internal organs LM × 180 a Skeletal muscle Types of Muscle Tissue - Cardiac Muscle Cardiac Muscle Tissue Cells are short, branched, Nuclei and striated, usually with a single nucleus; cells are Cardiac interconnected by muscle intercalated discs. cells LOCATION: Heart FUNCTIONS: Circulates Intercalated blood; maintains discs blood pressure Striations LM × 450 b Cardiac muscle Types of Muscle Tissue - Smooth Muscle Smooth Muscle Tissue Cells are short, spindle- shaped, and nonstriated, with a single, central nucleus. LOCATIONS: Found in Nuclei the walls of blood vessels and in digestive, respiratory, urinary, and reproductive organs FUNCTIONS: Moves food, urine, and reproductive Smooth tract secretions; controls muscle diameter of respiratory cells passageways; regulates diameter of blood vessels LM × 235 c Smooth muscle 4) Neural Tissue 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 66 Neural Tissue (cont’d) Two Types of Neural Cells 1. Neurons Nerve cells Perform electrical communication 2. Neuroglia(神經膠質細胞) Supporting cells Repair and supply nutrients to neurons 67 Neural Tissue (cont’d) 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 68 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) Axon (conducts Contact with other cells (synapse) 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 Organ System An organ is composed of two or Organs that perform related more tissues that serve different functions are grouped into functions in the organ. systems. The skin is the largest organ in the body. The skin has all four primary 1) 2) tissues: epithelial, connective, 3) 4) muscular and nervous tissues (blood vessel) Homeostasis Homeostasis -E All body systems working together to maintain a relatively stable internal conditions in the body’s internal environment Systems respond to external and internal changes to function within a normal range (body temperature, fluid balance) s blood glucose level water , 71  body temperature Homeostasis (cont’d) e it E. g. Feedback system 72 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 73 Negative Feedback - 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 At hypothalamus dilate, constrict, RESPONSE: sweating sweating Increased heat loss, increases decreases body temperature Temp. drops Body temperature (°C) > - regulation Normal EFFECTORS 37.2 Sends >↓ - temp 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. Negative and Positive Feedback (cont’d) 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 75 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. What would happen if there was homeostatic imbalance? > BAR - Clinical Checkpoint 77