BIO 11 Reviewer for LE#4 PDF

Circulation and Gas Exchange Concept: Circulatory systems link exchange surfaces with cells throughout the body. Example: Unicellular organisms exchange materials through diffusion (random thermal motion) BUT it is only rapid over very small distances. Evolutionary adaptation 1. Simple b...

Circulation and Gas Exchange Concept: Circulatory systems link exchange surfaces with cells throughout the body. Example: Unicellular organisms exchange materials through diffusion (random thermal motion) BUT it is only rapid over very small distances. Evolutionary adaptation 1. Simple body plan i.e. flatworms that maximize surface area and minimize diffusion distances 2. Circulatory system Gastrovascular Cavities Present in hydras, cnidarians, and jellies Planarians and flatworms can survive w/o a circulatory system Basic components of a Circulatory system 1. Circulatory fluid 2. Interconnected vessels 3. Muscular pump - heart Types 1. Open circulatory system Hemolymph - both circulatory and interstitial fluid Contraction - pump hemolymph to interconnected sinuses Relaxation - draw hemolymph back from the pores Seen in arthropods (i.e. grasshoppers) and crustaceans (i.e. crab) Lower hydrostatic pressure = less energy expedited 2. Close circulatory system Blood - circulatory fluid is different from interstitial fluid Seen in annelids (earthworms), cephalopods (squids and octopuses), and all vertebrates. Effective transport of gas and nutrients Cardiovascular system Types of b blood vessels 1. Arteries (“away”)- carry blood from the heart to organs throughout the body. Arteries → arterioles → capillaries → venules → veins 2. Veins - vessels that carry blood back to the heart. 3. Capillaries Capillary beds - network of capillaries > blood vessels are distinguished by their direction (away or back to the heart) > Exception: Portal Veins carry blood between pairs of capillary beds (i.e. hepatic portal vein or HPV - digestive system to liver) Atria - chamber for receiving blood Ventricle - chamber for pumping blood out of the heart Single Circulation Blood travels through the body and returns to its starting point in a single loop Two chambers - atria and ventricle Seen in sharks, rays, and bony fishes Double Circulation Two circuits of blood flow seen in amphibians, reptiles, and mammals Pumps of the two circuits are combined into a single organ - heart. Pulmonary circuit vs Systemic circuit (pulmocutaneous circuit “lungs & skin” in amphibians) Pulmonary circuit - right side of the heart pumps oxygen-poor blood to lungs where gas exchange occurs. Systemic circuit - left side of heart pumps oxygen-rich blood to capillary beds of organs and tissues throughout the body. Blood pressure is higher in systemic circulation than gas exchange circulation. Evolutionary variation in double circulation Some amphibians are intermittent breathers in which they periodically fill in air using their skin as another gas exchange tissue 1. Frog & some amphibians Have 3 chambers: 2 atria and 1 ventricle Oxygen-rich blood from the left atrium to the systemic circuit Oxygen-poor blood from right atrium to the pulmocutaneous circuit Uses the incomplete division to temporarily shut off its lungs when underwater and uses its skin as the only site of gas exchange 2. Turtles, snakes, and lizards Have an incomplete septum that divides a single ventricle into right and left chambers Two aorta Coordinated cycles of heart contraction drive double circulation in mammals 1. Right atrium receives deoxygenated blood from the anterior and posterior vena cava. 2. Right ventricle pumps blood to the lungs through pulmonary artery 3. Gas exchange occurs (CO2 → O2) 4. Left atrium receives oxygenated blood from the pulmonary vein 5. Left ventricle pumps blood throughout the body from the aorta Heart Size of clenched fist and mostly cardiac muscle Atria - relatively thin walls and serve as collection chambers. Right and left ventricle pumps the same amount of blood but the latter has more force Cardiac Cycle Involves the dynamic sequence of pumping and filling. Systole - contraction phase Diastole - relaxation phase Cardiac Output - volume of blood each ventricle pumps per minute 1. Heart rate - rate of contraction (number of beats per minute) 2. Stroke volume - amount of blood pumped in a single contraction (ave. 70mL) Atrioventricular (AV) valve Lies b/w each atrium and ventricle Tricuspid valve (right atrium & ventricle) and mitral/ bicuspid valve (left atrium & ventricle) “Lub” - closing of AV valves Semilunar valves Located at the exits of the heart Pulmonary artery and aorta “Dub” - closing of semilunar valves Heart murmur - condition where blood abnormally flows back the valves Sinoatrial (SA) node Autorhythmic cells located in the wall of the right atrium that acts as pacemaker. Generate currents measured by electrocardiogram (ECG or EKG) Atrioventricular (AV) node Bundle of His ○ Found in the interventricular septum that transmits electrical impulses from AV node to the ventricles Purkinje Fiber ○ Found in the inner walls of ventricles that receive electrical impulses from the bundle branches Regulation of the SA node 1. Sympathetic (increase heart rate) and parasympathetic (decrease heart rate) 2. Can also be influenced by hormones such as epinephrine or the “fight-or-flight” hormone 3. Body temperature Systolic pressure Arterial blood pressure is highest when the heart contracts during ventricular systole Pulse Diastolic pressure When ventricles are relaxed Vasoconstriction - arterioles narrow which increases blood pressure upstream in the arteries Vasodilation - arterioles increase in diameter which decreases blood pressure p.932 Excretory System > maintenance of the volume and composition of extracellular fluid > removes metabolic wastes > Homeostasis requires osmoregulation - control of solute concentration and balance water gain and loss. >Nitrogenous waste → Ammonia (toxic) Osmolarity : maintenance of proper internal salt and water concentration → cell relative to its surroundings and movement of water is passive diffusion.  1. Hypoosmotic - dilute solution 2. Isoosmotic - two solutions with same osmolarity 3. Hyperosmotic - higher concentration of solute Stenohaline - can tolerate narrow osmolarity ex. Spider crab Euryhaline - can tolerate wider osmolarity ex. Shore crab Osmoregulatory Challenges and Mechanisms 1. Osmoconformer - isoosmotic with its surroundings i.e. hagfish, skate, and shark 2. Osmoregulator - control internal osmolarity 3. Independent of that of the external environment; allows animals to live in uninhabitable environments. Freshwater fish Marine fish Environment High H2O Low H2O Low NaCl High NaCl Direction of Inside Outside water Cell relative to Hyperosmotic; Hypoosmotic; environment Water intake Water loss Gills Active absorption Active secretion of NaCl of NaCl Glomerulus Large Small Kidney Excretes dilute Excretes less urine water Anhydrobiosis (“life without water”)  Dormant state of an microorganism when habitats is in a state of dessication Example: tardigrades or water bears Anhydrobiotic roundworm show that desiccated individuals contain large amount of sugars - trehalose that act as membrane protectant. Evolutionary Adaptations 1. Waxy cuticle in land animals i.e. insect, snails, vertebrates 2. Nocturnal desert-dwellers Camels can tolerate a 7 degrees increase in body temp. > Maintaining an osmolarity difference between the body and its external environment comes with an energy cost. The higher the need to regulate osmolarity, the higher the energy cost. > Transport epithelia : epithelial cells specialized for the transport of solutes in specific directions. Example: transport epithelia in marine birds move salt from the blood into secretory tubules (nasal glands) draining into their nostrils (beaks) Ammonia : toxic metabolic waste produced by dismantling of nitrogenous molecules. Urea Nephridial organ but lack nephrostomes Unlike marine animals, terrestrial animals (i.e. protein -free filtrate is absorbed and secreted mammals) do not have access to sufficient water throughout the tubule to excrete ammonia and instead secrete urea. Kidneys → Ureter → Urinary bladder → Urethra NH3 + CO2 (from liver) = urea Low toxicity and high solubility Kidney Disadvantage: high energy cost Function in osmoregulation and excretion Example: in amphibians Regions: renal cortex and renal medulla ○ While in water - secrete ammonia (energy Nephrons: functional units of the vertebrate saving) kidney ○ In land - secrete urea ○ Cortical nephrons Uric acid ○ Juxtamedullary nephrons (extend deep Relatively nontoxic and does not readily dissolve into the medulla) in water (insoluble) Types of Kidneys: Archinephros → Pronephros → Excreted at semi solid paste with little water loss Mesonephros → Metanephros Higher energy cost than urea Gout: inflammation of the joint due to deposition of uric acid crystals Excretory System 1. Filtration : excretory tubules collect filtrate from blood through hydrostatic pressure. 2. Reabsorption : transport epithelium absorbs important nutrients (i.e. sugar, vitamins, hormones, amino acids) from filtrate through active transport. 3. Secretion : secretes toxins and excess ions 4. Excretion : altered filtrate (urine) leaves the body. Contractile vacuole Tiny, spherical, intracellular vacuole found in protozoa Expel excess water gained by osmosis Protonephridia Network of dead-end tubules Flame bulb caps the end Found in flatworms, rotifers, larval mollusks, lancets Glomerulus Closed system Filters the blood to produce glomerular filtrate Metanephridia into the lumen of the Bowman’s capsule (covers Excretory organs that collect fluid directly from the glomerulus). coelom Afferent (towards) arteriole → efferent (away) Tubules open at both ends arteriole Found in earthworms in which each segment Glucose, salts, amino acids, vitamins, nitrogenous contains a pair of metanephridia waste and other small waste products Malpighian Tubules Extend from dead-end tips (with hemolymph) into Process of Filtration openings of the digestive tract 1. Proximal convoluted tubule (PCT) No filtration reabsorption and secretion of various Found in insects solutes i.e. uric acid Antennal gland Helps maintain a relatively constant pH in Excretory found in crustaceans i.e. prawns & body fluids through the reabsorption of shrimps HCO3- (called Bicarbonate Buffer system)  2. Descending limb of loop of Henle (in renal To prevent these substances to leave medulla) filtrate Consist of aquaporin protein channels 3. Concentrated Urine that facilitate passive water diffusion Filtrate becomes concentrated urine (high permeability to water vs. low which is hyperosmotic relative to its permeability to salt) surrounding environment (body fluids) Filtrate loses water thereby increasing > Reason why we have concentrated urine when we don’t solute concentration as it descends drink enough water. In mammalian kidney, the production 3. Ascending limb of loop of Henle of hyperosmotic urine is possible because considerable Transport epithelium lacks water energy is expended for the active transport of soluets channels (impermeable) against concentration gradients. Specialized regions: thin segment and Dilute Urine (when the body needs to get rid of excess thick segment water) Filtrate loses solutes and becomes dilute > Closing of Aquaporin channels → collecting ducts Primary function: water reabsorption become permeable to NaCl without water → produce 4. Distal convoluted tubule dilute urine secretes ammonia, hydrogen, and potassium ions Countercurrent multiplier system 5. Collecting duct Process in the kidneys that creates a receives processed filtrate into urine corticopapillary osmotic gradient (osmolarity gradient in the interstitial space of the kidney) to concentrate urine. System that uses active transport to move NaCl from the tubular fluid to the interstitial space of the kidneys. Importance: to prevent dilute urine meaning people don’t need to drink lots of water Example: countercurrent heat exchanger in endotherms (i.e. dolphins, sharks, bees) and countercurrent exchange system in bony fishes (oxygen gradient) Vasa recta - network capillaries that supply blood and nutrients to the renal medulla highly permeable to water and salt. The kidney’s osmolarity gradient is opposite to the blood flow of the vasa recta Adaptation of the Vertebrate Kidney to Diverse Environments 1. Hyperosmotic urine (in mammals that need to reduce water loss in desert environment) → many Water Conservation juxtamedullary nephrons with longer loop of Situation: during dehydration when the body lacks Henle sufficient water to function properly, the kidneys will reuse 2. Hypoosmotic urine (freshwater mammals) → and conserve water. higher cortical nephrons with lower ability to 1. Water conservation in the collecting ducts occurs concentrate urine through the opening of aquaporins - protein 3. Unique excretory challenges - vampire bat channels that allow water to leave the filtrate (Desmodue rotundus) →alternate between (pre-urine) into the surrounding kidney tissues producing large amounts of dilute urine (during (interstitial fluid) by osmosis. feeding) and small amounts of concentrated urine 2. Selective permeabilty (during the day) Collecting ducts → impermeable to NaCl Renal Cortex → impermeable to urea Regulation of Excretion  Homeostatic regulation of the kidney is controlled by the nervous and endocrine system. 1. Antidiuretic Hormone (also called vasopressin) ADH bind and activates membrane receptors in the collecting ducts resulting in the opening of aquaporins (leading to an increase in water reabsorption). Diuresis - high level of urine production Fun fact :) → caffeinated drinks do not substantially increase urine production as compared to your normal water intake. However, alcohol inhibits ADH release leading to excessive water loss and dehydration (symptoms of hangover). The reason why we cannot drink seawater and why dehydration causes low blood pressure. Diabetis insipidus : rare condition that causes 3. Atrial Natriuretic Peptide (ANP) extreme thirst and production of large amounts of Opposes RAAS where the walls of the urine due to the lack of ADH. atria release ANP in response to an increase in blood volume and pressure. Inhibits release of renin, NaCl reabsorption, and aldosterone release. Lowers blood pressure. > marine bony fishes have the lowest volume of urine production because of their need to conserve water in a salty environment. > filtration is the least selective process in the nephron. 2. Renin-Angiotensin-Aldosterone System (RAAS) Occurs due to the excessive loss of both salt and body fluids (i.e. blood loss due to an injury OR severe diarrhea) without increasing osmolarity. Responds to the drop in blood volume and pressure by increasing water and Na+ reabsorption Involves juxtaglomerular apparatus (JGA) - specialized tissue in the afferent arteriole supplying blood to the glomerulus that releases renin (an enzyme). Angiotensinogen (Liver) → angiotensin I → angiotensin II triggers vasoconstriction which increases blood pressure → Aldosterone causes distal tubules and collecting ducts to absorb more Na+ and H2O Immune System animal is infected with helminths or > Innate Recognition: receptors recognize a molecule parasitic worms common to a type of pathogen 5. Natural Killer (NK) cells : attack virus-infected Virus → dsRNA cells and cancerous cells; release chemicals Bacterium → Flagellin leading to cell death (lyse) instead of engulfing Fungus → Mannan cells. > Adaptive Recognition : receptors recognize a particular 6. Basophils and Mast cells : found in connective set or pattern of protein in one pathogen i.e. influenza tissues for inflammatory response. virus Evolution of microbes to evade phagocytic destruction Two types of immune defenses Mycobacterium tuberculosis and Streptococcus 1. Innate immunity: defense common to all animals pneumoniae are resistant to lysosomal destruction Barrier defenses i.e. insect exoskeleton - and reproduce inside macrophages chitin found in their skin and intestines; Primary (Gohn) complex *** try to search for digestive system - lysozyme related literature Hemocytes - immune cells in insects that Local inflammatory response ingest and breakdown microorganisms Set of events triggered by signaling molecules through phagocytosis. upon injury or infection. ○ Can trap Plasmodium - unicellular 1. Activated macrophages release cytokines parasite causing malaria in Cytokines (cyto - “cell”; kine - “kinetics”) - humans. signaling molecules that attract ○ Release antimicrobial peptides neutrophils (cell-to-cell communication) In mammals, Toll-like receptor (TLR) ○ Chemokines: type of cytokines binds to a set of pathogens that attract phagocytes and ○ TLR3 → double stranded RNA triggers lysosomal production produced by specific viruses Basophils and Mast cells release ○ TLR4 → lipopolysaccharide in histamine which triggers blood vessels bacteria to dilate increasing permeability ○ TLR5 → flagellin protein in Increases skin temperature → produces bacterial flagella redness and swelling 2. Adaptive immunity: set of molecular and cellular Leukocytes also discharge defense found only among vertebrates prostaglandins to promote blood flow in First line of Defense site of injury ***(related also to uterine Sebaceous and sweat glands → 3 to 5 pH in skin contractions) Salive, tears, and mucous secretions 2. Activated proteins promote histamine release Lysozyme further attracting phagocytic cells Second line of Defense - phagocytosis Help deliver antimicrobial peptides that Include complement system “relay”: system of result in accumulation of pus - fluid rich in plasma protein that help the immune system white blood cells, dead pathogens and Interferons - innate defense for viral infections tissue debris. 1. Neutrophils (60 to 70%) : type of white blood 3. Pus and excess fluid are taken as lymph cells that fight infections (phagocytic defense) Lymph nodes contain macrophages that 2. Monocytes: Macrophages (“big eaters”) engulf pathogens 3. Dendritic cells : found in tissues in contact with the environment (i.e. skin) that stimulates adaptive immunity. 4. Eosinophils (1.5%) : found in epithelium of the GI tract that defend against parasitic invaders Ex. blood fluke Schistosoma mansoni Positions in the external wall and discharge destructive enzymes Helminthiasis (worm infection) : disease where a body part of a human or Lymphatic System (role in adaptive immunity) 1. Interstitial fluid and lymph enters lymphatic vessels 3. Appendix 2. Within lymph nodes, pathogens and foreign Blind-ended tube connected from the particles get engulfed by macrophages. caecum 3. Lymphatic vessels (ex. Lacteals in small intestine Vestigial (remnant) of a part of caecum receive lipoproteins) return lymph to the blood via House mutualistic bacteria that help two ducts that drain into veins digest cellulose > Organs of the Lymphatic System Appendicitis - inflammation of the 1. Spleen appendix Mechanical filtration of RBC Systemic and Chronic Inflammation Active immune response through humoral Caused by extensive tissue damage or infection and cell-mediated immune response involved in fever as response to certain pathogens 2. Thymus or pyrogens released by certain leukocytes Active immune response through humoral **** Benefits of fever are still a subject of debate and cell-mediated immune response Higher body temperature → phagocytosis and Site for development of T-cells from tissue repair hematopoietic progenitor cells (HPC) Overwhelming systemic inflammatory response or hematopoietic stem cells (HSC) - leads to septic shock which is a result of a rapid immature cells that can develop into all drop in blood pressure causing organ failure. types of blood cells → research in stem Chronic inflammation : Crohn’s disease cell therapy to treat leukemia and hodgkin (inflammatory bowel disease or IBD that causes disease chronic inflammation of the GI tract) and Atrophy (shrinks) during early teens as ulcerative colitis (form of IBD that causes ulcers stroma gets replaced with adipose tissue in large intestine) Third line of defense - Adaptive immunity > receptors provide pathogen-specific recognition (cell recognition) Lymphocytes (formed in the bone marrow) ○ B lymphocytes (B cells) “B” - bursa of fabricius Humoral immune response: antibodies defend against infection in body fluids Also mature in the bone marrow ○ T lymphocytes (T cells) “T” - thymus  cell-mediated immune response: cytotoxic cells defend against infection in body cells Antigen - foreign molecule (i.e. bacteria, pollen, virus, parasite, etc.) that triggers a specific response by lymphocytes; recognition occurs through a protein called antigen receptors (membrane antibodies) in a B or T-cell which are identical → specificity ○ B cell antigen receptor → two (2) antigen binding sites; Y-shaped protein Heavy chains and light chains Binds to intact antigen ○ T cell antigen receptor → only one (1) antigen binding site Epitope or “antigenic determinant” - small, accessible portion of an antigen that binds into an antigen receptor. Antibody - protein produced by lymphocytes that fight antigens. ○ Immunoglobulins (Igs) - type of antibody that have two identical antigen-binding sites (like B-cells) but lack a membrane anchor which interacts with epitope. Antigen Recognition by T cells ○ Consist of 2 diff. Polypeptide chains: alpha and beta chains linked by a disulfide bridge ○ Binds only to fragmented antigens ○ Major histocompatibility complex (MHC) molecule ○ Antigen presentation - like a hotdog bun Characteristics of Adaptive Immunity 1. Immense repertoire of lymphocytes and receptors for detection of antigens never encountered before → diversity lies in the ability to create combinations that lies in the structure of Ig genes  2. Self tolerance: lack of reaction towards the animal’s own cells; antigen receptors of lymphocytes are tested in the bone marrow and are destroyed by apoptosis (programmed cell death) if it reacts with the body’s own cells 3. Cell proliferation (divide and differentiate) Clonal selection ○ Effector cells : short-lived cells ○ Memory cells : long-lived cells that can give rise to effector cells if the same antigen is encountered again Active Immunity 4. Stronger and rapid response to an antigen → Defense that occurs when a pathogen infection immunological memory : long-term protection prompts an immune response Primary immune response → plasma cells Passive immunity (type of immune cell that makes a large Antibodies in the recipient are produced by amount of the same antibodies) another individual Secondary immune response Example: IgG antibodies cross the placenta of a ○ Basis for immunization - uses of pregnant women to its fetus and IgA antibodies antigens artificially introduced to present in breastmilk provide additional immunity generate adaptive immunity. I.e. to the infant’s GI tract Vaccination Artificial passive immunization: snake bites are treated with antivenin Five (5) classes of immunoglobulins (from B cells) 1. IgM First to be produced Promotes neutralization and cross-linking 2. IgG Most abundant Ig in blood Promotes opsonization, neutralization and cross-linking of antigens Only Ig that can cross the placenta 3. IgA Present in tears, saliva, mucus, and breastmilk 4. IgD Neutralization - process that blocks the ability of a virus Present on surface of B cells to spread Acts as antigen receptor Opsonization - process that helps ma 5. IgE Cytotoxic T cells (Tc) - bind to class I MHC molecules Present in blood at low concentrations Use toxic proteins to destroy infected cells before Cause allergic reactions they fully mature Monoclonal Antibodies: are laboratory produced Require signals from helper T cells and interaction molecules engineered to serve as alternative antibodies to with an antigen-presenting cell restore, enhance, or mimic the immune system’s attack on Accessory protein - CD8 a specific antigen or cell i.e. cancer cells. Found in somatic cells Basis for pregnancy test kits → monoclonal Helper T cells (Th) - bind to class II MHC molecules antibodies that detect human gonadotropin (hCG) Send out chemical signals that incite other cell which is produced by a fetus implanting itself in types to fight the pathogen; found in macrophages. the uterus Binds to an antigen fragment via its antigen Immune Rejection → because MHC proteins are different receptor and an accessory protein called CD4. between two people, except identical twins. ***see skin grafting Agglutination or hemagglutination: clumping of blood immune system attacks the fetus’ red particles together as the body’s response to a specific blood cells (hemolytic - “breaking down of antibody. RBC”) ○ Mother - Rh negative blood ; Exaggerated, Self-Directed and Diminished Immune fetus - Rh positive blood. → first Responses pregnancy will not be affected 1. Allergies : exaggerated (hypersensitive) response but second pregnancy will cause to certain antigens called allergens. the mother’s immune cells to involve antibodies of IgE which pollen attack and destroy the fetus’s grains attach thereby inducing mast cells cells (hemolysis) to release histamine. ○ Effect → severe anemia (low Hay fever symptoms: sneezing, runny levels of red blood cells) nose, smooth muscle contractions in ○ Also called hemolytic disease of lungs that inhibit breathing the newborn (HDN) Treatment: antihistamines 4. Exertion and Stress can lower the immune system Anaphylactic shock: acute allergic 5. Immunodeficiency Diseases response leading to life threatening Defective or absent response to antigens reaction. Symptoms: inability to breath Inborn immunodeficiency - Severe results in lower blood pressure (death) → combined immunodeficiency (SCID) lacks treatment: epinephrine or has no functional lymphocytes. Treatment: bone marrow transplant Acquired immunodeficiency - acquired immunodeficiency syndrome (i.e. HIV) Concept check 43.3 1. If a child were born without a thymus gland, what cells and function would be deficient? No T cells. Without helper T cells to activate B cells, the child would be unable to produce antibodies. 2. Why will the same treatment of antivenin to a 2. Autoimmune diseases: loss of self-tolerance second snake bite cause harmful side effects? IgE where the immune system mistakes its own cell creates an allergic response because the handler and attacks it. developed immunity against antivenin proteins. Example: Systemic lupus erythematosus 3. In the condition myasthenia gravis, antibodies (lupus) and rheumatoid arthritis bind to and block certain receptors on muscle cells (damaging and painful inflammation of to prevent muscle contraction. What type of the cartilage and bone in joints) disorder? Considered a autoimmune disease 3. Hemolytic disease 4. People with herpes simplex type 1 viruses often Erythroblastosis fetalis - rare pregnancy get mouth sores when they have a cold or similar complication in which the mother’s infection. How might this location benefit the virus?  5. WHAT IF? How would a macrophage deficiency likely affect a person’s innate and adaptive Endocrine System p1001 defenses? Frequent infections Variables that shape a hormone’s effect > Kaposi’s sarcoma 1. Concentration Caused by infection with a virus called the Kaposi 2. Presence of hormone receptor sarcoma herpesvirus (KSHV), also called human 3. Response of the cell after binding herpesvirus 8 (HHV8) which is related to Intercellular communication Epstein-Barr virus (EBV) - causes Through molecules that serve as signals → target mononucleosis. cells that bind to receptors Cells that line blood and lymphatic vessels are Hormone - secreted molecule that circulates and infected with KSHV. endothelial cells form new stimulates specific cells blood cells → turn into cancer cells Related to the nervous system > Hepatitis B can cause liver cancer (2) two criteria: type of secreting cell and route in Vaccine was introduced in 1986 reaching its target > Human papillomavirus (HPV) Types of intercellular communication A vaccine was released in 2006 1. Endocrine signaling causes cervical cancer in women as well as oral Secreted hormones by diffuse into cancer in men. bloodstream (or hemolymph) > Cytomegalovirus Function: maintain homeostasis Related to viruses that causes chicken pox, Regulate properties: mononucleosis, and herpes simplex (cause painful ○ Blood pressure and volume blisters or ulcers) ○ Energy metabolism ○ Solute concentration ○ Response to environmental stimuli ○ Growth and development 2. Paracrine signaling (para- “beside”) Secrete molecules locally and trigger neighboring cells (local regulators) Function: blood pressure regulation, nervous system, reproduction 3. Autocrine signaling Secrete molecules locally and trigger a response on the cell that secreted them 4. Synaptic signaling Neurotransmitter (molecules from neurons) diffuse across synapses and trigger responses in cells of tissues (muscles, neurons, or glands) Function: sensation, memory, cognition, and movement 5. Neuroendocrine signaling Neurohormones diffuse into bloodstream and trigger response anywhere in the body Example: ADH (antidiuretic hormone) Signaling Molecules 1. Local regulators Growth factors - proteins and polypeptides that stimulate cell proliferation Cytokines - immune response  Prostaglandins ○ promote inflammation and sensation of pain in response to injury. Ibuprofen and aspirin drugs inhibit these activities. ○ Modified fatty acids ○ Uterine contractions if secreted in placenta Nitric Oxide (NO) ○ gas released by endothelial cells in blood vessel in response to low oxygen which then results in vasodilation (increase blood flow) ○ Reason for erection ***Viagra (sildenafil citrate) - treatment for erectile dysfunction sustains NO response ○ Neurons → neurotransmitter ○ WBC → kills bacteria and cancer cells 2. Neurotransmitters > Water-soluble and lipid-soluble hormones differ in their Diffuse short distance and bind on target response pathways or mode of transportation cells Water-soluble hormones 3. Neurohormones Secreted by exocytosis (because hydrophobic head 4. Pheromones of the plasma membrane) Release to external environment Travel freely in bloodstream Functions: Cannot diffuse through target cells but instead ○ Mark trails for food i.e. foraging bind to cell-surface receptors which triggers ants cellular response ○ Territories and Warning Cause proteins to move into the nucleus and alter ○ Attracting mates i.e. sex transcription of genes → process called signal pheromones released by transduction polyphemus moth can range up Example: stressful situation → adrenal glands to 4.5km away secrete epinephrine or adrenaline → liver → 5. Hormones - body’s chemical messengers synthesis of cyclic AMP (cAMP) as second messenger → activate protein kinase A → activate enzyme for breakdown into glucose → energy (basis of fight-or-flight response) Summary: LIVER - epinephrine → glycogen deposits → glycogen breaks down and glucose is released Different receptors in skeletal muscle blood vessel (beta receptor) and intestinal blood vessel (alpha receptor) Lipid-soluble hormones Exit endocrine by diffusion Bind to transport proteins Activates steroid hormone receptor to trigger gene regulation i.e. binding to estrogens necessary for female reproductive function Example: in birds and frogs, estradiol (form of estrogen) binds to receptors in liver which  activates transcription of vitellogenin gene → a. Anterior pituitary (adenohypophysis) produce egg yolk Synthesizes and secrete hormones in response to hormones from hypothalamus i. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) → stimulate gonads ii. Thyroid stimulating hormone (TSH) → thyroid glands iii. Adrenocorticotropic hormone (ACTH) → adrenal glands iv. Prolactin → stimulates mammary gland growth and milk synthesis v. Growth Hormone (GH) → stimulates growth and metabolic functions → GH targets liver by releasing insulin-like growth factors (IGFs) that stimulate bone and cartilage growth. vi. Melanocyte-stimulating hormone (MSH) → affects color of melanocytes Endocrine Tissues and Organs p1005 Endocrine system Integrative system that controls body’s activities b. Posterior pituitary using chemical messengers - hormones Extension of the neural tissue of Hormones are transported by the circulatory hypothalamus and stores system to distant target cells which stimulates a neurohormones response. i. Antidiuretic hormone (ADH) or Endocrine glands - secrete directly onto the vasopressin → targets kidney surrounding body fluid tubules and promotes water Exocrine glands - have ducts that carry secreted retention substances i.e. sweat and saliva ii. Oxytocin → uterine contraction Major Endocrine glands and stimulates mammary glands 1. Hypothalamus *** Vasopressin regulates social behavior [notes] Connection between endocrine system 3. Thyroid gland and nervous system a. Thyroid hormone (T3 and T4) Function: keep the body’s homeostasis Function: regulates bioenergetics, Infundibulum is connected to the anterior maintain normal blood pressure, and posterior pituitary gland heart rate, and muscle tone Neurosecretory cells secrete Regulation: sensory neurons neurohormones (hypothalamus) → Can be affected by breeding season in neurosecretory cells release which the hypothalamus releases Thyrotropin-releasing reproductive hormones hormone (TRH) → anterior Types: pituitary release Thyroid ○ Releasing hormones : stimulate stimulating hormone (TSH) → the anterior pituitary to secrete bloodstream → thyroid gland hormones secretes thyroid hormone (T3 ○ Inhibiting hormones : inhibit Triiodothyronine and T4 the anterior pituitary from thyroxine) → body - secreting hormones ○ Negative feedback: as 2. Pituitary gland thyroid hormone returns  to normal, it also blocks and adrenal medulla (develop from TRH release neural tissue) b. Calcitonin : lowers blood calcium level > Adrenal Medulla (short term stress) (only needed during extensive bone Catecholamines (class of amine hormones growth in childhood in humans. Unlike synthesized from tyrosine) → 1.) other animals that uses it to maintain Epinephrine (adrenaline) 2.) homeostasis) norepinephrine (noradrenaline) c. Disorders of Thyroid function and Functions: regulation ○ Raise glycogen breakdown in i. Goiter liver and skeletal muscles > enlargement of thyroid gland due to ○ Release of glucose in liver and iodine deficiency in which TSH overstimulates the fatty acids in fat cells thyroid gland to produce thyroid hormones; pituitary ○ Increase heart rate and dilate gland receives no negative feedback. bronchioles in lungs ii. Pituitary gigantism → excess ○ Increased blood flow → heart, GH brain, and skeletal muscles iii. Acromegaly → excess GH but ○ Decreased blood flow → skin, affects the face and extremities digestive organs, and kidney (less iv. Hypopituitary dwarfism → low urine production and urge to eat) levels of GH v. Cretinism > malfunction of thyroid gland at early age that results into stunted physical and mental growth due to congenital hypothyroidism 4. Parathyroid glands Parathyroid hormone (PTH) raises blood calcium level Low Ca level → muscle contractions; high Ca level → forms precipitate and cause organ damage In bones → breakdown of Ca then released to blood In kidneys → stimulates Ca absorption Hypoparathyroidism - lack of PTH can result into tetany (involuntary muscle > Adrenal Cortex (long term stress) contractions and overstimulated Secretes corticosteroids regulated by peripheral nerves) hypothalamus Becomes active in times of low blood sugar, blood pressure, and shock Glucocorticoids i.e. cortisol ○ Raises blood glucose ○ Can also cause breakdown of muscle proteins to amino acids ○ Hypothalamus → anterior pituitary gland releases ACTH → bloodstream → adrenal cortex releases corticosteroids ○ Can suppress some components of immune system → used to treat inflammatory diseases i.e. 5. Adrenal glands (response to stress) arthritis but cause lasting effects Located on top the kidneys and composed so NSAIDs are used i.e. aspirin of adrenal cortex (true endocrine cells)  ○ High levels of glucocorticoids Synthesize estrogen → estradiol may cause cushing syndrome Estrogen → maintenance of the Symptoms: rapid weight female reproductive system gain, buffalo hump, Progesterone → maintenance of moon face uterus to support the growth and Mineralocorticoids development of an embryo ○ Maintain salt and water balance Gonadotropin secretion is ○ Promotes reabsorption of Na+ controlled by GnRH in the and excretion of K+ in kidneys hypothalamus. ○ RAAS system Sex hormones regulate formation of reproductive 6. Pineal gland structures Found in diencephalon of brain Starts out first as bipotential gonads (can Secretes melatonin → modified amino develop in two forms) acid that regulates functions related to In males, bipotential gonads become the testes light and season that secrete testosterone and anti-Müllerian Also affects skin pigmentation hormone that causes female ducts to degenerate Release of melatonin is controlled by and form male reproductive organs group of neurons called suprachiasmatic In females, there is an absence of these hormones nucleus (SCN) which can be affected by which causes the male ducts to degenerate and blue light → biological body clock form female reproductive organs See cachexia (Wasting Syndrome) *** diethylstilbestrol (DES) is recognized as an endocrine 7. Pancreas disruptor that interrupts normal hormone pathway Exocrine function: secretes bicarbonate Feedback regulation ions and digestive enzymes 1. Simple endocrine pathways Endocrine function: insulin and Internal or environmental stimulus → glucagon secreted by islets of endocrine cells release hormones → langerhans into the bloodstream travel via bloodstream → interaction with ○ Insulin: lowers blood glucose receptor → signal transduction → ○ Glucagon: raises blood glucose response Hyperinsulinism → diabetes mellitus Example: low pH in duodenum gets → S ○ Cause: hereditary and obesity cells secrete secretin → bloodstream → ○ Symptoms: excessive urination pancreas → release bicarbonate to ducts and thirst, sugar in urine → duodenum (neutralization of pH) ○ Type I (insulin-dependent) ○ Negative feedback = reduces Autoimmune disorder the stimulus which helps restore Treatment - insulin pre existing state involved in injections keeping homeostasis ○ Type II (non-insulin 2. Simple neuroendocrine pathways dependent) Stimulus is received by a sensory neuron Cause: decreased Sensory neuron → neurosecretory cell responsiveness to insulin (hypothalamus) → neurohormone Treatment: biguanide (pituitary gland) → bloodstream → target metformin cells 8. Gonads Example: suckling (stimulus) → sensory Sex hormones (corticosteroids): neurons in nipples → nerve impulses to androgen, estrogen, and progesterone hypothalamus → secrete neurohormone a. Testes oxytocin → contraction of mammary Synthesize androgen → glands testosterone ○ Positive feedback = increases Androgen is responsible for the stimulus secondary male sex Often organized into hormone cascade → characteristics regulation in which multiple endocrine b. Ovaries organs and signals act in series  ○ Reason why anterior pituitary hormones are also called tropic hormones because it redirects signals to other endocrine organs to release their own set of hormones ○ Example: Hypothalamus (releasing hormone) → anterior pituitary (FSH and LH) → gonads (estrogen, progesterone, testosterone) Invertebrates Neurosecretory cells in the brain of invertebrates secrete PTTH which induces the prothoracic gland to release ecdysteroid responsible for the Neurons, Synapses and Signaling p1068 molting Juvenile hormone (JH) modulates endysteroid activity. High JH → suppress metamorphosis while low JH → induces metamorphosis A neuron receives information and transmits it through an axon and transmits it to other cells via specialized junctions called synapses. Dendrites (dendron - “tree”) - cell body contains highly branched extensions. Axons are longer than dendrites (i.e. > 1m in giraffes) Neurotransmitters - chemical messengers in synapses i.e. cone snail venom is lethal because it  interferes with signaling along axons and across Ciliated cells lining the ventricular walls synapses in the brain and central canal in the spinal Nerves - bundles of axons of neurons cord Information processing Function: production and flow of Sensory input → integration (CNS) → motor output cerebrospinal fluid (CSF), brain (PNS) metabolism, waste products Example: snail senses scents for prey (i.e. fish) → network Nature of Nerve Signals of neurons process information → initiates attack through Voltage or Membrane Potential → localized the release of harpoon-like tooth electrical gradient 1. Sensory neurons or afferent neuron ○ Anions (negative) = within the cell Transmit information about external Proteins, amino acids, sulfate, stimuli and phosphate → intracellular 2. Interneurons Cl- → extracellular Form local circuits connecting the ○ Cations (positive) = extracellular fluid neurons K+ → intracellular Analysis and interpretation of sensory Na+ → extracellular input Resting potential → -70mV (not sending out 3. Motor neurons or efferent neuron signals) Transmit signals to muscle cells for ○ formed through the ions moving rapidly contraction through ion channels and the buildup of Central Nervous System (CNS) negative charge Include brain or simple clusters called ganglia ○ the change that occurs when a neuron and the spinal cord receives a stimulus is called action The brain also contains ventricles continuous to potentials the central canal Sodium-potassium pump → maintains Na+ and Carry out sorting, processing, and integration K+ concentration gradients and uses ATP Peripheral nervous system (PNS) hydrolysis to actively transport Na+ and K+ Contains cranial nerves, ganglia (outside CNS), ○ Three (3) Na+ (out) : Two (2) K+ (in) and spinal nerves. Ungated ion channels (leak channels), on the Carry information out of CNS other hand, allows ions to diffuse across plasma Both systems require glia (glia - “glue”) for membrane → always open support Action potentials Neuroglia or glial cells (present in CNS) Non-neuronal cells that maintain homeostasis, form myelin, and provide support for the brain’s neurons 1. Astrocyte Support for endothelial cells that form the blood-brain barrier (BBB) → defend the brain from harmful substances and restricts passage of pathogens Provide nutrients Maintain extracellular ion balance Role in repair and scarring process after in brain and spinal cord traumatic injury 2. Oligodendrocyte Insulation of axons through the production of myelin (insulating sheath) Provide nutrients Signals conducted by axons in which membrane 3. Microglia potential changes Resident macrophages that act as first Gated ion channels respond to stimuli which active immune defense alters the plasma membrane’s permeability 4. Ependymal cells  1. Chemically-gated ion channels : in depolarization → saltatory conduction response to chemical stimulus (saltare meaning “to leap”) 2. voltage-gated ion channels : change in ○ Space efficiency membrane potential Graded potentials : changes in membrane Neurons communicate with other cells at synapses potential that varies on the strength of stimulus 1. Electrical synapses (larger stimulus → larger graded potential) Contain gap junctions that allow ○ Hyperpolarization (increase) electrical current to flow directly from Gated K+ channels open and one neuron to another potassium diffuses out into cell Found in vertebrate heart and brain → make the cell more negative Presynaptic cells → gap junctions → ○ Depolarization postsynaptic cells Gated Na+ channels open and 2. Chemical synapses sodium diffuses into the cell → More common make cell more positive Release of chemical neurotransmitter by Action potential “since it’s open, let's open some presynaptic neuron to transfer more then and there’s no coming back~” information to target cell ○ Happens when graded potentials reach a Postsynaptic chemically-gated channels threshold potential ~55mV for Na+, K+, and Cl- ○ Lead to further depolarization (more Process: sodium channels open) → Positive 1. [resting state] presynaptic feedback → inactivation of gated channels neuron synthesizes Process: neurotransmitters packaged in Resting state → depolarization → rising phase of the synaptic vesicles action potential (more sodium channels open)→ falling 2. Action potential goes to phase of action potential (sodium channels become presynaptic membrane inactivated; potassium channels open) → undershoot 3. Depolarization opens voltage-gated ion channels Conduction of Action Potentials 4. Synaptic vesicles release Depolarization is large enough to influence neurotransmitters to synaptic neighboring cells which is repeated along the axon cleft (“like a domino cascade”) 5. Neurotransmitter binds to Action potential starts at axon hillock (origin) postsynaptic membrane toward synaptic terminals Ligand-gated ion channels (ionotropic Louder sounds → more action potentials (rate of receptor): receptor protein that binds and action potential is proportional to signal strength) responds to neurotransmitter Myotonia → periodic spasming of muscles in Excitatory postsynaptic potential (EPSP) → which mutations affecting voltage-gated sodium toward threshold channels occurred Inhibitory postsynaptic potential (IPSP) → further ○ Neuromuscular condition where from the threshold relaxation of a muscle is impaired EPSP and IPSP → essence of integration Wider Axon → increase conduction speed (for Summation = combination of individual rapid behavioral responses) postsynaptic potential ○ How do vertebrate (narrow) axons Resting state → clear neurotransmitter in the conduct high speed action potentials? synaptic cleft Answer: insulation Myelin sheath - electrical insulation covering the axons produced by oligodendrocytes in CNS and Schwann cells in PNS ○ Nodes of Ranvier - gaps in myelin sheath where action potentials occur ○ Unmyelinated regions are in contact with extracellular fluid (ions) resulting in  synaptic transmission to facial muscles 2. Biogenic amines Epi- / Norepinephrine (made from tyrosine) ○ Excitatory neurotransmitter from autonomic nervous system Dopamine (made from tyrosine) ○ Excitatory but may be inhibitory at some sites Parkinson’s disease Lack of dopamine Degenerative disorder of CNS that impairs motor skills and Chemical Synapses at Metabotropic Receptors speech Neurotransmitter binds at G protein receptor → Symptoms: muscle rigidity, signal transduction → postsynaptic cell tremor, postural abnormalities, Example: metabotropic receptor for the slowing of movement neurotransmitter norepinephrine (bradykinesia - brady “slow” ; Slower than ionotropic receptors but last longer kinesia - “movement”) and loss of movement (akinesia) Neurotransmitters Schizophrenia 1. Acetylcholine Excessive dopamine Function: muscle stimulation, memory Mental disorder characterized by formation, and learning disintegration of thinking process Excitatory → skeletal muscle and emotional responsiveness ○ Neuromuscular junction: site Symptoms: auditory where motor neuron forms hallucinations, paranoid, social synapse with skeletal muscle dysfunction ○ Process: Acetylcholine is released Serotonin (made from tryptophan) in neuromuscular junction → ○ Inhibitory EPSP → acetylcholinesterase ○ Secreted only by CNS (terminates neurotransmitter) ○ Affect sleep, mood, attention, and Inhibitory → cardiac muscle learning (same with dopamine) ○ Neurons activate signal ○ Supposedly have something to do transduction in which G proteins with feelings of pleasure inhibit adenylyl cyclases (ATP → 3. Amino acids cAMP) and open K+ channels that a. Gamma aminobutyric acid (GABA) reduce heart rate Postsynaptic cells increase CL- Application: permeability → IPSP (inhibitory) ○ Nicotine (in tobacco) - toxic Diazepam (Valium) reduce stimulant that binds to anxiety by increasing response to acetylcholine receptor in CNS GAPA ○ Sarin (nerve gas) - potent b. Glycine inhibitor of acetylcholinesterase Inhibitory and secreted by CNS (degrades acetylcholine in the c. Glutamate synaptic cleft) → high Excitatory acetylcholine may lead to muscle Neurotransmitter at twitching, seizure, and neuromuscular junctions in respiratory failure invertebrates (same with GABA) ○ Botulism (food poisoning) → Long term memory Botox (trade name) inhibits d. Aspartate Excitatory and secreted by CNS  4. Neuropeptides a. Substance P Parasympathetic Sympathetic Division Excitatory Division Dilates pupils Secreted by CNS and PNS Constrict pupils Inhibits salivary Mediates our perception of pain Stimulates secretion b. Met-enkephalin (endorphin) salivary glands Increases heart Inhibitory Reduces heart rate Secreted by CNS rate Dilates bronchi Constricts bronchi Inhibits activity in Natural analgesic which in lungs pancreas, decreases pain perception Stimulates activity stomach, Reduce urine output, decrease in pancreas, intestines, and respiration and produce euphoria stomach, kidneys Ex. opiates (morphine and intestines, and Involved in heroin) mimic endorphins kidneys fight-or-flight Stimulate responses i.e. 5. Local regulators in gas relaxation epinephrine a. Nitric oxide Not stored in cytoplasmic vesicles but synthesized on demand Brain and Spinal cord b. Carbon monoxide Central canal - contain cerebrospinal fluid (CSF) which is formed in the brain by filtering arterial Nervous system p1086 blood Ganglion = cluster of nerve cell bodies within the PNS ○ Cerebrospinal fluid contains nutrients Nucleus = cluster of nerve cell bodies within the CNS and hormones and removes waste products Nervous system organization White matter - composed of myelinated axons and 1. Diffuse type or nerve net i.e. Hydras, jellies, located in the outer layer cnidarians, and echinoderm → radial symmetry Gray matter - composed of unmyelinated axons, 2. Ladder Type in flatworms where a pair of ganglia nuclei and dendrites and located in the inner layer (cluster of neurons) are located in the head region Meninges consists of the inner pia mater and outer 3. Ganglionic type in annelids i.e. earthworms dura mater that protects the brain from trauma 4. Tubular type in vertebrates and acts as shock absorber Reflex - autonomic response to certain stimuli. It protects the body by providing rapid, involuntary responses. ○ Example: The hand jerks back upon contact with a hot burning object before the brain can process pain ○ Example 2: knee-jerk reflex in lifting heavy objects (sensory neuron → motor neurons) The vertebrate brian is regionally specialized 1. Forebrain consists of cerebrum, thalamus, and hypothalamus 2. Midbrain consists of the colliculi, the tegmentum, and the cerebral peduncles. 3. Hindbrain consists of the pons, medulla oblongata, cerebellum Autonomic nervous system → involuntary i.e. process of digestion Somatic nervous system → voluntary i.e. respiration is both autonomic and somatic  Vomiting Digestion Pons (means “bridge” in latin) ○ Connects the cerebellum and cerebrum ○ Functions in in visceral activities and pain perception Cerebellum ○ Motor coordination ○ Relay sensory information to cerebrum “Different brain regions are associated with different functions.” 1. Frontal lobe → memory, emotion, planning, and judgement 2. Parietal lobe → sensory reception, taste Brain Regions Main Functions 3. Occipital lobe → visual processing components 4. Temporal lobe → learning, memory, sensory Telencephalon Cerebrum Controls voluntary recognition, and emotional behavior movements; sensory 5. Cerebellum → balance and coordination perception; processing center (i.e. thinking & Lateralization of brain function learning) Left hemisphere ○ Specialize in language, math, logic, serial Diencephalon Hypothalamus Control autonomic function and endocrine sequences of information system Right hemisphere ○ Specialize in pattern recognition, spatial Thalamus Part of Limbic system relationships, nonverbal ideation, that regulates emotions emotional processing and parallel and behavior processing of information (when the Mesencephalon Optic lobes Visual and auditory brain takes in information from different functions senses at the same time) Broca’s Area → speech production Metencephalon Cerebellum Involuntary Wernicke’s Area → speech comprehension and pons coordination The Limbic system consists of the hippocampus, olfactory cortex, inner portions of cortex’s lobes, Myelencephalo Medulla Regulates heart rate and n oblongata respiration and parts of thalamus and hypothalamus that regulate emotions (basic: fear and anger) and establish emotional memory. Example: the Brain stem - consist of midbrain, pons, medulla amygdala is responsible for recognizing emotions oblongata which connects the brain and spinal in facial expressions. cord Short term memory → Frontal lobe ○ Function: homeostasis, movement Long term memory → hippocampus coordination, relays information to and ○ Transfer is enhanced by repetition and from higher brain centers influenced by emotional states Midbrain “Sensory receptors have their own resting potentials.” ○ Superior colliculi → regulation of visual Sensations → action potentials that reach the reflexes brian from sensory neurons ○ Inferior colliculi → regulation of Perception → awareness and interpretation of auditory reflexes sensation Medulla Oblongata Sensory reception begins with the detection of ○ Control autonomic homeostatic functions stimulus by sensory receptors Breathing Receptor potential → graded potential of sensory Heart Rate receptors Swallowing  Amplification → strengthening of stimulus i.e. Hearing and equilibrium sensory perception is amplified in the eyes of cats ○ Vibrations in the cochlear fluid → basilar that is why they are able to see well at night membrane vibrates → hair cells brush Transmission → conduction of sensory impulses against the tectorial membrane → to CNS i.e. there are chemical receptors with generation of action potential in sensory higher concentrations for specific taste receptors neuron (like sugar or salt) in the tongue. ○ Endolymph - clear fluid found in the ○ Strength of stimulus and receptor inner ear’s membranous labyrinth that potential affects the action potential. helps maintain balance example: Integration → processing of sensory information endolymph is still moving when you spin ○ Sensory adaptation: decrease in and suddenly stop responsiveness to continued stimulation. ○ Pitch → based on location of hair cells Example: We can feel the texture of that depolarize clothes at first but eventually the body ○ Volume → amplitude of sound wave will ignore the action potential generated by the clothes. Muscle spindle → interoceptor that respond to stretching of skeletal muscle Hair cells → detect motion Pacinian corpuscle → mechanoreceptor in skin that detects pressure and vibration Pain receptors (nociceptors) → different types of pain receptor respond to different types of pain ○ Prostaglandin (in uterine contraction School of fishes move in unison because of the during childbirth) decreases the lateral line canal as it allows fishes to determine threshold of the action potential thereby the direction and rate of water movement increasing pain perception. Photoreceptors ○ Eye cups in planaria with no image formation and only detection of light and direction ○ Compound eyes in arthropods and crustaceans consists of ommatidia each with its own light-focusing lens ○ Single-lens eyes of invertebrates Eye of octopus is similar to vertebrates and is due to convergent evolution ○ Accommodation → focusing of light in the retina In mammals, changing the shape of lens Visual processing occurs to Make an image sharper through the process of lateral inhibition Has many pathways Hyperpotential More negative at the presences of light ○ Optic chiasm - where the optic nerves of the two eyes meet (crossing of the eyes) Taste buds → depolarization action potentials