Tissues and Systems PDF from California State University Dominguez Hills

Tissues and Systems Ryan R. Williams, M.D., Ph.D. Biology 122 California State University Dominguez Hills Problems of Why isn’t a butterfly wing one giant cell? scale: what Why aren’t there bacteria the size of frogs? limits cell size? Why do elephants...

Tissues and Systems Ryan R. Williams, M.D., Ph.D. Biology 122 California State University Dominguez Hills Problems of Why isn’t a butterfly wing one giant cell? scale: what Why aren’t there bacteria the size of frogs? limits cell size? Why do elephants and mice have cells that are the same size? As a cell increases in size, what happens to its surface area? 1. Solve surface area-to-volume 2. Plot! ratio Cells must acquire nutrients and remove wastes waste O2 cell food CO2 How does surface area (A) relate to the rate at which something can cross the cell membrane? How do the SA/V ratios compare in each scenario shown below? Red blood cell Single SA ≈ 130 µm2 large cell 5.5 µm Multicellular Spherical cell Tissue with similar total volume SA ≈ 90 µm2 Overview of Tissues Multicellularity evolved: To increase surface area for diffusion across cell membranes For specialization Tissue—a collection of cells that perform a common function There are 4 major tissue types in the body Epithelial—covers body surfaces; lines body cavities Connective—binds and supports body parts Muscular—moves the body and its parts Nervous—conducts electrical impulses to communicate with and regulate body functions Epithelial Tissue Epithelial tissue Made of tightly packed cells Lines body cavities, covers body surfaces, and is found in glands Anchored by specialize extracellular matrix called basal lamina (basement membrane) Named for the number of cell layers and the shape of the cells Simple or stratified Simple epithelium has a single layer of cells Stratified epithelium has multiple layers of cells  Epithelial Tissue Simple Pseudostratified columnar Stratified Classes of epithelium Squamous Cuboidal Columnar Cell shapes  Epithelial Tissue Cells are packed closely together with limited extracellular space Classified by the number of layers and shape of the cell Single layer = simple Multiple layers = Stratified Epithelial Tissue Simple epithelia has a single layer of cells Simple squamous epithelium Flattened cells Ex: blood vessels and capillaries where it allows for gas exchange Simple cuboidal epithelium Cube-shaped cells Ex: found in glands and kidney tubules Simple columnar epithelium Single layer of column-shaped cells Used for absorption and secretion (i.e. digestive tract) Pseudostratified columnar epithelium Because of the location of the nuclei, appears stratified but every cell touches the basement membrane Often has cilia, which move mucus across its surface Ex: respiratory system (trachea) Epithelial Tissue Stratified squamous epithelia Have several layers of cells Protective, tough, resists abrasion Forms the outer layer of the skin and lines the mouth, esophagus Transitional epithelia Cells change shape in response to tension (from cuboidal to squamous) Ex: the urinary bladder Epithelial Tissue Simple Squamous Simple cuboidal lining of alveoli, lining of kidney blood vessels, & tubules, various body cavities glands 250× 250× basement membrance basement membrance  Epithelial Tissue Simple columnar Pseudostratified, Stratified squamous small intestine, Columnar lining of nose, absorbs nutrients, lining of trachea mouth, esophagus, and secretes sweeps impurities anal canal, vagina toward throat protects 250× 100× 250× cilia goblet cell secretes goblet cell mucus secretes mucus basement basement membrane membrane basement membrane  Transitional Epithelium LOCATIONS: Urinary bladder; renal pelvis; ureters FUNCTIONS: Permits expansion and recoil after stretching Epithelium (relaxed) Basal lamina Relaxed bladder Connective tissue and smooth muscle layers LM × 450 Epithelium (stretched) Basal lamina Connective tissue and Stretched bladder smooth muscle layers LM × 450 b Transitional epithelium. A sectional view of the transitional epithelium lining the urinary bladder. The cells from an empty bladder are in the relaxed state, while those lining a full urinary bladder show the effects of stretching on the arrangement of cells in the epithelium. © 2015 Pearson Education, Inc. Epithelial Tissue Form different kinds of barriers Have many functions: Protection Absorption and secretion Fluid transport Gas exchange Cells have “polarity” Apical surface is exposed to the environment Basal surface faces internally Both sides function differently Avascular (lack blood vessels) Connective Tissue Connective tissue Three types: fibrous, supportive, and fluid Each type has specialized cells and extracellular matrix (ECM) ECM includes the ground substance and protein fibers Ground substance—noncellular material between the cells Varies in consistency from solid (bone) to fluid (blood) There are three types of protein fibers Collagen fibers—flexible and strong Reticular fibers—thin, highly branched Elastic fibers—contain elastin, a protein that stretches and recoils Extracellular Matrix Connective tissues consist of different forms of ECM made of the same primary components Collagen, fibronectin, laminin, proteoglycan, hyaluronan The ECM provides a scaffolding for cell attachment The basal lamina (basement membrane) is a specialized ECM “fence” that separates epithelial tissue from connective tissue Connective Tissue  Types of Connective Tissue Fibrous Supportive Fluid Loose Dense Cartilage Bone Blood Lymph Fibers create Fibers are Solid yet Solid and Contained in Contained in open framework densely packed flexible matrix rigid matrix blood vessels lymphatic vessels Connective Tissue Fibrous connective tissue Contains fibroblasts separated by matrix (ground substance and fibers) Fibroblasts produce collagen and other ECM proteins Loose fibrous connective tissue Supports epithelium and many internal organs Includes areolar, reticular, and adipose tissue Adipose tissue Functions in energy storage, insulation and cushioning Found primarily under the skin and around some organs Has very little extracellular matrix Adipocytes—cells filled with liquid fat Loose Connective Tissue Loose connective tissue is composed of loosely woven collagen and elastic fibers. The fibers and other components of the connective tissue matrix are secreted by fibroblasts. Adipose Connective Tissue Adipose is a connective tissue is made up of cells called adipocytes. Adipocytes have small nuclei localized at the cell edge. Connective Tissue Dense fibrous connective tissue Contains densely packed collagen fibers Fibers may be oriented irregular (random) or regular (parallel) Dense regular fibrous connective tissue includes: Tendons (connect muscles to bones) Ligaments (connect bones to bones) Dense Fibrous Connective Tissue Fibrous connective tissue from the tendon has strands of collagen fibers lined up in parallel. Connective Tissue Supportive connective tissue Two major types: cartilage and bone Functions in structure, shape, protection, and leverage for movement. Cartilage composed of chondrocytes—cells that lie in small spaces called lacunae. matrix is solid but flexible lacks blood vessels (avascular), so heals slowly Hyaline cartilage—fine collagen fibers Found in the tip of the nose, ends of long bones and the fetal skeleton Elastic cartilage—lots of elastic fibers Found in the outer ear. Fibrocartilage—strong collagen fibers Found in the disks between vertebrae Cartilage Connective Tissue Hyaline cartilage consists of a matrix with cells called chondrocytes embedded in it. The chondrocytes exist in cavities in the matrix called lacunae. Connective Tissue Bone The most rigid connective tissue Matrix is made of collagen and calcium Two types of bone tissue: compact and spongy Compact bone makes up the shafts of long bones Consists of cylindrical structural units called osteons The central canal contains blood vessels and nerves Osteocytes (bone cells) are located in lacunae Spongy bone is inside the ends of long bones Lighter than compact bone, but strong Bone Connective Tisssue (a) Compact bone is a dense matrix on the outer surface of bone. Spongy bone, inside the compact bone, is porous with web-like trabeculae. (b) Compact bone is organized into rings called osteons. Blood vessels, nerves, and lymphatic vessels are found in the central Haversian canal. Rings of lamellae surround the Haversian canal. Between the lamellae are cavities called lacunae. Canaliculi are microchannels connecting the lacunae together. (c) Osteoblasts surround the exterior of the bone. Osteoclasts bore tunnels into the bone and osteocytes are found in the lacunae. Connective Tissue Fluid connective tissue Two types of fluid connective tissue: blood and lymph Blood Made of a fluid matrix called plasma and cellular components called formed elements (cells) Red blood cells (erythrocytes)—cells that carry oxygen White blood cells (leukocytes)—cells that fight infection Platelets (thrombocytes)—pieces of cells that clot blood Lymph Contains specific types of white blood cells Lymphatic vessels absorb excess interstitial fluid and return lymph to the cardiovascular system Interstitial fluid is the extracellular fluid that is outside of blood vessels and surround tissues Fluid Connective Tissue Blood is a connective tissue that has a fluid matrix, called plasma, and no fibers. Erythrocytes (red blood cells), the predominant cell type, are involved in the transport of oxygen and carbon dioxide. Also present are various leukocytes (white blood cells) involved in immune response.  Connective Tissue elastic fiber fibroblast collagen fiber collagen fibroblast fibers Loose fibrous tissue 250× Dense fibrous tissue 250× fat nucleus Adipose tissue 250 × matrix canalic osteon uli centr cell al within osteocyte canal a lacuna within a Hyaline cartilage 250× lacuna Compact bone 320 × Connective Tissue Muscle Tissue Specialized to contract and produce movements Cells (myocytes) are called muscle fibers Three types Skeletal Smooth Cardiac Excitable Can change their membrane potential Charge inside the cell relative to the outside (measure in mV) All animal cells have net negative charge inside Muscle Tissue Skeletal muscle Attached to the skeleton by tendons Contraction moves the skeleton Voluntarily controlled Muscle fibers are very long; can run the entire length of the muscle Have multiple nuclei Striated, or striped, in appearance Muscle Tissue Smooth muscle No striations Spindle-shaped (elongated) cells with one nucleus Involuntarily controlled Found in the walls of viscera (organs) Cardiac muscle Only found in the walls of the heart Striated Involuntary Single nucleus Cells are connected by intercalated disks Gap junctions Muscle Tissue Muscle Tissues  Muscle Tissue Skeletal muscle Smooth muscle Cardiac muscle has striated cells spindle-shaped cells, has branching, with multiple nuclei. each with a single nucleus. striated cells, each functions in voluntary cells have no striations. with a single nucleus. movement of body. functions in movement of occurs in the wall of the heart. substances in lumens of body. functions in the pumping is involuntary. of blood. is found in blood vessel walls and is involuntary. walls of the digestive tract. 250 striation nucleus × 400 250× × smooth muscle cell nucleus intercalated disc nucleus Nervous Tissue Consists of neurons and glia Neurons Have three parts: dendrites, a cell body, and an axon Dendrites—carry information toward the cell body The cell body contains the nucleus and other organelles Axon conducts nerve impulses away from the cell body Some axons are covered in myelin, a fatty substance Nerves—bundles of axons traveling to and from the brain and spinal cord Glia Main function is to support and nourish neurons Outnumber neurons 9 to 1 Nervous Tissue Neurons are excitable Generate and transmits electrical impulses Action potentials and graded potentials Three primary functions: Sensory input Integration Motor output Regulates all of our body functions  dendrite dendrite nucleus nucleus cell body cell body (soma) axon myelin sheath Micrograph of a neuron 400 axon × Structure of a neuron Glands Gland One or more cells that make and secrete a product Two types: exocrine and endocrine Exocrine glands Secrete into ducts (tubes) that empty into the “environment” outside the body Usually composed of epithelial tissue Endocrine glands Secrete hormones into the bloodstream or lymph Do not have ducts “Adeno-” means glandular  Body Fluids Intracellular fluid (ICF) (inside body cells) Tissue cell Blood vessel Blood cell Interstitial fluid Blood (between body cells) plasma Extracellular fluid (ECF) (outside body cells) Copyright © 2017 John Wiley & Sons, Inc. All Body Cavities Coelom means cavity Posterior cavity (dorsal cavity) Cranial cavity: contains the brain Spinal (Vertebral) cavity: contains the spinal cord Anterior cavity (ventral cavity) is separated by the diaphragm into the: Thoracic Abdominopelvic (peritoneal) Body Cavities Two main body cavities: ventral and dorsal Ventral cavity Contains the thoracic, abdominal, and pelvic cavities Thoracic and abdominal cavities are separated by the diaphragm Dorsal cavity Contains the cranial cavity and vertebral canal Body Cavities Body Cavities Body Membranes Composed of both an epithelial tissue and an underlying connective tissue Mucous membranes Line the tubes of the digestive, respiratory, urinary, and reproductive systems Contains goblet cells that secrete mucus Serous membranes Line ventral cavities and cover the surface of the organs Composed of mesothelial cells (simple squamous) Pleurae line the thoracic cavity and cover the lungs Pericardium forms the pericardial sac and covers the heart Peritoneum lines the abdominal cavity and covers its organs Synovial membranes Line freely moveable joints Secrete synovial fluid for lubrication Cutaneous membrane (skin) Meninges (in the dorsal cavity around the brain and spinal cord) Body Planes A sagittal plane divides the body into right and left portions. A midsagittal plane divides the body exactly in the middle, making two equal right and left halves A frontal plane (also called a coronal plane) separates the front from the back. A transverse plane (or, horizontal plane) divides the animal into upper and lower portions Sometimes called a cross-section If the transverse cut is at an angle, it is called an oblique plane Body Planes Frontal or coronal plane A frontal, or coronal, section separates anterior and posterior portions of the body; coronal usually refers to sections passing through the skull. Plane is oriented parallel to long axis Directional term: frontally or coronally Frontal plane  Sagittal plane A sagittal section separates right and left portions. You examine a sagittal section, but you section sagittally. In a midsagittal section, the plane passes through the midline, dividing the body in half and separating right and left sides. A parasagittal section misses the midline, separating right and left portions of unequal size. Plane is oriented parallel to Midsagittal plane long axis Directional term: Sagittally  Transverse, horizontal, or cross-sectional plane A transverse, or horizontal, section separates superior and inferior portions of the body; sections typically Transverse plane pass through head and trunk regions. Plane is oriented perpendicular to long axis Directional term: transversely or horizontally Organ Systems Organ—a group of tissues performing a common function Organ System Combination of various organs make up a specific system For example: the stomach, small intestine, large intestine, liver, gallbladder, and pancreas make up the digestive system The heart and blood vessels make up the cardiovascular system Humans are composed of 11 organ systems Organ Systems ORGAN SYSTEM MAJOR FUNCTIONS Integumentary Protection from environmental system hazards; temperature control Skeletal Support, protection of soft tissues; system mineral storage; blood formation Muscular Locomotion, support, heat system production Nervous Directing immediate responses to system stimuli, usually by coordinating the activities of other organ systems Endocrine Directing long-term changes system in the activities of other organ systems Cardiovascular Internal transport of cells and system dissolved materials, including nutrients, wastes, and gases Organ Systems ORGAN SYSTEM MAJOR FUNCTIONS Lymphatic Defense against infection and system disease Delivery of air to sites where Respiratory gas exchange can occur between system the air and circulating blood Digestive Processing of food and system absorption of organic nutrients, minerals, vitamins, and water Urinary Elimination of excess water, system salts, and waste products; control of pH Reproductive Production of sex cells and system hormones The Integumentary System Protects against environmental hazards; Hair helps control body temperature Epidermis and associated glands Organ/Component Primary Functions Skin Epidermis Covers surface; protects deeper tissues Dermis Nourishes epidermis; provides strength; contains glands Hair Follicles Produce hair; innervation provides Fingernail sensation Hairs Provide protection for head Sebaceous glands Secrete lipid coating that lubricates hair shaft and epidermis Sweat Glands Produce perspiration for evaporative cooling Nails Protect and stiffen distal tips of digits Sensory Receptors Provide sensations of touch, pressure, temperature, pain Subcutaneous Layer Stores lipids; attaches skin to deeper structures and insulates against heat loss The Skeletal System Provides support; protects tissues; stores minerals; forms blood cells AXIAL APPENDICULAR SKELETON Skull SKELETON Supporting bones (scapula and clavicle) Sternum Upper Ribs limb bones Vertebrae Organ/Component Primary Functions Sacrum Bones, Cartilages, Support; protect soft tissues; bones and Joints store minerals Axial skeleton (skull, Protects brain, spinal cord, sense vertebrae, sacrum, organs, and soft tissues of thoracic coccyx, sternum, ribs, cavity; supports the body weight over supporting cartilages lower limbs and ligaments) Appendicular skeleton Provides internal support and Pelvis (supporting bones plus sacrum) (limbs and supporting positioning of the limbs; supports and bones and ligaments) moves axial skeleton Bone Marrow Primary site of blood cell production (red marrow); storage of energy reserves in fat cells (yellow marrow) Lower limb bones The Muscular System Allows for locomotion; provides support; produces heat Axial Appendicular muscles muscles Organ/Component Primary Functions Skeletal Muscles Provide skeletal movement; control entrances to digestive and respiratory tracts and exits to digestive and urinary tracts; produce heat; support skeleton; protect soft tissues Axial muscles Support and position axial skeleton Appendicular muscles Support, move, and brace limbs Tendons, Aponeuroses Harness forces of contraction to perform specific tasks The Nervous System Directs immediate responses to stimuli, CENTRAL NERVOUS usually by coordinating SYSTEM the activities of other organ systems Brain Spinal cord Organ/Component Primary Functions Central Nervous Acts as control center for nervous system; System (CNS) processes information; provides short-term control over activities of other systems Brain Performs complex integrative functions; controls both voluntary and autonomic activities Spinal cord Relays information to and from brain; PERIPHERAL NERVOUS performs less-complex integrative activities SYSTEM Special senses Provide sensory input to the brain relating to sight, hearing, smell, taste, Peripheral and equilibrium nerves Peripheral Nervous Links CNS with other systems and with System (PNS) sense organs The Endocrine System Directs long-term changes in activities of Pineal gland other organ systems Pituitary gland Thyroid and parathyroid glands Thymus Pancreas Suprarenal gland Organ/Component Primary Functions Pineal Gland May control timing of reproduction and set day-night rhythms Pituitary Gland Controls other endocrine glands; regulates growth and fluid balance Thyroid Gland Controls tissue metabolic rate; regulates calcium levels Ovary in Testis in male Parathyroid Glands Regulate calcium levels (with thyroid) female Thymus Controls maturation of lymphocytes Suprarenal Glands Adjust water balance, tissue metabolism, cardiovascular and respiratory activity Kidneys Control red blood cell production and elevate blood pressure Pancreas Regulates blood glucose levels Gonads Testes Support male sexual characteristics and reproductive functions Ovaries Support female sexual characteristics and reproductive functions The Cardiovascular System Transports cells and dissolved materials, including nutrients, wastes, and gases Heart Capillaries Artery Organ/Component Primary Functions Vein Heart Propels blood; maintains blood pressure Blood Vessels Distribute blood around the body Arteries Carry blood from the heart to capillaries Capillaries Permit diffusion between blood and interstitial fluids Veins Return blood from capillaries to the heart Blood Transports oxygen, carbon dioxide, and blood cells; delivers nutrients and hormones; removes waste products; assists in temperature regulation and defense against disease The Lymphatic System Defends against infection and disease; returns tissue fluid to the bloodstream Thymus Lymph nodes Spleen Organ/Component Primary Functions Lymphatic Vessels Carry lymph (water and proteins) and lymphocytes from peripheral tissues to veins of the cardiovascular system Lymph Nodes Monitor the composition of lymph; engulf pathogens; stimulate immune response Spleen Monitors circulating blood; engulfs pathogens and recycles red blood cells; Lymphatic vessel stimulates immune response Thymus Controls development and maintenance of one class of lymphocytes (T cells) The Respiratory System Delivers air to sites where gas exchange can occur between the air and Nasal cavity circulating blood; produces sound Sinus Pharynx Larynx Trachea Bronchi Lung Diaphragm Organ/Component Primary Functions Nasal Cavities and Filter, warm, humidify air; detect smells Paranasal Sinuses Pharynx Conducts air to larynx, a chamber shared with the digestive tract Larynx Protects opening to trachea and contains vocal cords Trachea Filters air, traps particles in mucus, conducts air to lungs; cartilages keep airway open Bronchi Same functions as trachea; diameter decreases as branching occurs Lungs Responsible for air movement during movement of ribs and diaphragm; include airways and alveoli Alveoli Blind pockets at the end of the smallest branches of the bronchioles; sites of gas exchange between air and blood The Digestive System Processes food and absorbs nutrients Salivary gland Pharynx Esophagus Liver Gallbladder Stomach Organ/Component Primary Functions Pancreas Oral Cavity Receptacle for food; works with associated Small intestine Large structures (teeth, tongue) to break up food intestine and pass food and liquids to pharynx Salivary Glands Provide buffers and lubrication; produce enzymes that begin digestion Pharynx Conducts solid food and liquids to esophagus; chamber shared with respiratory tract Esophagus Delivers food to stomach Anus Stomach Secretes acids and enzymes Small Intestine Secretes digestive enzymes, buffers, and hormones; absorbs nutrients Liver Secretes bile; regulates nutrient composition of blood Gallbladder Stores and concentrates bile for release into small intestine Pancreas Secretes digestive enzymes and buffers; contains endocrine cells Large Intestine Removes water from fecal material; stores wastes The Urinary System Eliminates excess water, salts, and waste products Kidney Ureter Urinary Organ/Component Primary Functions bladder Kidneys Form and concentrate urine; regulate blood pH and ion concentrations; perform endocrine functions Ureters Conduct urine from kidneys to urinary bladder Urethra Urinary Bladder Stores urine for eventual elimination Urethra Conducts urine to exterior The Male Reproductive System Produces sex cells and hormones Prostate gland Seminal gland Organ/Component Primary Functions Ductus deferens Testes Produce sperm and hormones Urethra Accessory Organs Epididymis Acts as site of sperm maturation Ductus deferens Conducts sperm from the epididymis and (sperm duct) merges with the duct of the seminal gland Seminal glands Secrete fluid that makes up much of the Epididymis volume of semen Testis Prostate gland Secretes fluid and enzymes Urethra Conducts semen to exterior Penis Scrotum External Genitalia Penis Contains erectile tissue; deposits sperm in vagina of female; produces pleasurable sensations during sexual activities Scrotum Surrounds the testes and controls their temperature The Female Reproductive System Produces sex cells and hormones; supports embryonic development from fertilization to birth Mammary gland Uterine Organ/Component Primary Functions tube Ovaries Produce oocytes and hormones Ovary Uterine Tubes Deliver oocyte or embryo to uterus; normal site of fertilization Uterus Uterus Site of embryonic development and exchange between maternal and fetal bloodstreams Vagina Vagina Site of sperm deposition; acts as a birth External canal during delivery; provides genitalia passageway for fluids during menstruation External Genitalia Clitoris Contains erectile tissue; provides pleasurable sensations during sexual activities Labia Contain glands that lubricate entrance to vagina Mammary Glands Produce milk that nourishes newborn infant Homeostasis To function properly, cells, tissues, and organs require ideal physical conditions Ex: Temperature and pH These conditions must be maintained within a narrow range, despite environmental changes Homeostasis is the process of keeping the internal environment of the body (and cells) in a “steady-state” balance with the environment Requires the ability to sense and respond to the environment Fluctuates around a “set point” Set point can change and homeostasis mechanisms will still work towards the new set point Most of our energy is dedicated to processes that maintain homeostasis Body Systems and Homeostasis The nervous and endocrine systems coordinate the other organ systems to maintain homeostasis The nervous system Fast Effects do not last long Neurotransmitters have a short “half-life” The endocrine system Secretes hormones—chemical messengers that travel in blood or lymph Longer lasting effects Body Systems and Homeostasis Endocrine System All systems of the body contribute to Endocrine glands secrete homeostasis. These systems in particular are especially noteworthy hormones, which also regulate and coordinate the activities of other systems. Works more slowly than the nervous system. Nervous System Respiratory System Regulates and coordinates the activities of all the other systems. Supplies blood with oxygen for It responds quickly to internal and tissue cells and rids blood of external stimuli. carbon dioxide. Helps regulate the acid–base balance of the blood. Cardiovascular System Urinary System Transports oxygen and nutrients Excretes nitrogenous and other to tissue cells and transports wastes. Regulates water–salt wastes away from cells. Also balance of the blood. Helps transports hormones secreted by regulate the acid–base balance of the endocrine glands. the blood. Digestive System Lymphatic System Supplies blood with nutrients Helps maintain blood volume by and water for tissue cells. Rids collecting excess interstitial fluid the body of non-digestible and returning it via lymphatic remains. vessels to the cardiovascular system. Defends against disease. Muscular System Integumentary System Produces heat that maintains Helps maintain body temperature body temperature. Protects and and protects internal organs supports internal organs. Homeostasis Negative feedback loop – counteracts any internal changes (reverses the direction of the change) Most biological systems are on negative feedback Examples: Blood glucose Temperature pH Blood calcium Homeostasis With negative feedback, there is an acceptable range around which the internal state may oscillate (fluctuate) Effectors respond Increase in blood reducing blood glucose glucose Measured factor level time Pancreas releases insulin Effectors respond Pancreas releases increasing blood glucagon glucose Homeostasis Positive feedback loop – maintains and potentially strengthens the response to a stimulus Not many biological systems are on positive feedback Example: Oxytocin The birth of a human infant is the result of positive feedback. Homeostasis Examples of Negative Feedback Homeostasis 70-100mg/dl Examples of In this example, what is Homeostasis acting as the homeostatic sensor? A. Insulin/Glucagon B. Glucose C. Hypothalamus D. Liver E. Pancreas Homeostasis 70-100mg/dl Examples of In this example, what is Homeostasis acting as the homeostatic sensor? A. Insulin/Glucagon B. Glucose C. Hypothalamus D. Liver E. Pancreas Homeostasis 70-100mg/dl  Patients with Type 2 Examples of Diabetes produce insulin, but Homeostasis target cells do not respond to insulin and blood glucose levels become elevated. Which component of the feedback system is broken in these patients? A. Stimulus Homeostasis 70-100mg/dl B. Sensor C. Effector D. Response  Patients with Type 2 Examples of Diabetes produce insulin, but Homeostasis target cells do not respond to insulin and blood glucose levels become elevated. Which component of the feedback system is broken in these patients? A. Stimulus Homeostasis 70-100mg/dl B. Sensor C. Effector D. Response Blood Sugar Regulation When blood glucose levels increase, the hormone insulin signals liver cells to take up and store Homeostasis glucose 70-100mg/dl When blood glucose levels decrease, the hormone glucagon signals liver cells to release glucose