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Date Created: 09/28/15
Circulation and gas exchange Basic function to provide the body with oxygen nutrients remove wastes and C02 lungs gills generally don t do much with nutrients and wastes but as usual there are exceptions Reason for having a circulatory system all cells in the body need access to oxygen etc Methods of granting access to oxygennutrients Fig 423 p 900 open circulatory system some blood vessels may be present but no capillaries In other words heart beats uid moves into some large vessels and from there into the body All parts of the body are therefore bathed in this uid eg insects many arthropods closed circulatory system blood is always con ned to blood vessels Small blood vessels are present throughout the tissues and thus insure that blood can get to all parts of the body eg cephalopods earthworms vertebrates Vertebrate cardiovascular systems Fig 424 amp 425 p 901 amp 902 heart is composed of at least two parts an atrium and a ventricle But higher vertebrates may add to this e g two atria atrium receives blood from the body then moves blood to ventricle ventricle pumps blood out of heart arteries gt arterioles gt capillaries ampcapillary beds gt venules gt veins NOTE that this says nothing about what parts of the body the blood is going to just the names ofthe blood vessels The ow of blood in mammals Fig 232 p 469 compared to other animals all parts of the body get newly oxygenated blood under high pressure Mammals right ventricle gt lungs gt left atrium gt left ventricle gt body gt right atrium gt right ventricle But we need special arrangements in a fetus Fig not in book l l l right ventricle gt dutus arteriosus gt BODY gt right lt atrium l l il l l l l left atrium gt left ventricle gt BODY note the above diagram may not show up correctly using ASCII text ie it might not look right on the web body is actually body amp placenta Note that blood going to the lungs is considered to be in the pulmonary circuit whereas blood going to the body is in the systemic circuit Human heart details Figs 426 and 427 p 903 amp 904 go through overheads mention all parts mostly a review of the above Cardiac cycle basically what happens from one heart contraction to the next First a few terms heart rate of times heart beats in one minute pulse is always recorded as beats minute though often is measured over 30 seconds or so average is about 70 stroke volume amount of blood pumped by left ventricle with one beat average about 75ml per beat cardiac output amount of blood pumped by left ventricle Question what about the right in one minute cardiac output is about 525 L if heart rate is about 70 This is about the amount of blood present in humans steps in cardiac cycle Fig 428 p 904 systole contraction phase diastole relaxation phase l atria and ventricles are relaxed 2 atria contract ventricles remain relaxed 3 ventricles contract atria relax repeat during step 3 lub sound is produced as AV valves close during step 1 dub sound is heard as semilunar valves close Comments AV valves prevent back ow of blood from ventricles to atria semilunar valves prevent back ow of blood from aortas to ventricles heart murmur can be caused by a back ow of blood against the valves Electrical properties of heart Cardiac muscle cells will contract without any kind of external stimulus OVERHEAD g 429 p 905 Something needs to coordinate these cells gt the SA node which is located in the wall of the right atrium will release the signal to beat Note when cells do not beat in a coordinated fashion gt blood is not pumped and heart needs to be reset This is when a defibulator can be used Intercalated disks at the ends of cardiac cells allow rapid dissemination of electrical stimulus and so the atria contract Then signal reaches AV node Here signal is delayed to ensure atria get done contracting and then specialized muscle bers transmit signal to ventricles which then contract These signals can be picked up with an EKG or ECG Note that these signals are electrical in nature and while they correspond to various steps in the cardiac cycle they do not directly measure such things as ventricles contracting Stuff in uencing heart rate hormones epinephrine causes an increase in heart rate body temperature fever increases the heart rate stimuli from nerves reaching the heart ie nerves coming from brain and elsewhere condition if one is in excellent condition heart rate is often much lower eg average rate is 70quot but in good condition might be as low as 55 or even 50 Rate of blood ow is controlled by two things 1 Heart rate gt how fast is the heart beating already discussed 2 Blood pressure Systolic pressure maximum pressure when ventricles contract Diastolic pressure minimum pressure when ventricles are relaxed Blood pressure is measured in mm Hg Fig 4213 p 909 Why is there a minimum pressure Why not 0 elasticity of artery walls peripheral resistance this is basically the resistance due to entering capillary beds go through sphygmomanometer function using overhead as one moves away from the heart blood pressure drops It makes a difference where you measure blood pressure sometimes this is used diagnostically Blood pressure drops and smooths out as you move into capillaries and finally veins Fig 4211 p 907 Venous blood pressure is so low that blood needs assistance to move back to heart Fig 4214 p 909 valves in veins skeletal muscles contracting some contraction by muscles in veins more details in lab nice demo of the valves in the veins Capillary function many capillary beds can be turned off by muscles sphincters that control access to capillaries Fig 4215 p 910 useful for instance when exercising for instance diverts blood from digestive system when hot shunts blood to s 39 when suffering from blood loss shunts blood to vital systems opposite during anaphylactic shock many capillary beds may open at once causing a drastic fall in blood pressure details of how oxygen is diffused into the tissues are in your text if you re interested Essentially substances are transferred through diffusion or differences in pressure Lymphatic system Fig 437 p 934 Nature Fluid leaves capillaries as capillaries enter tissues But not all uid is returned to capillaries Therefore there needs to be a way for uid to be returned to the circulatory system Fluid enters lymphatic system by diffusing into small lymph capillaries that then come together and eventually drain into the circulatory system near the junction of the vena cava with the right atrium Lymph vessels function very much like veins in moving lymph back to heart Throughout this system there are lymph nodes that filter lymph and attack viruses and bacteria that are in the lymph Blockage of the lymph system can be painful and cause serious deformities eg filarial worms nematodes that causes elephantiasis of blood consists of Fig 4217 p 912 l 55 blood plasma uid that contains water solvents ions proteins nutrients etc 2 45 cells red blood cells transport of oxygen carbon dioxide white blood cells body defense and immunity platelets blood clotting Some comments each RBC contains about 250 million molecules of hemoglobin a protein that can carry oxygen cells are all generated from stem cells that exist in bone marrow Occasionally this may malfunction leading to overproduction of certain types e g leukemia can be caused by overproduction of leukocytes Fig 4219 p 913 Blood clotting involves a complicated pathway see Fig similar to 4218 p 913 Essentially if platelets encounter a rough surface it becomes sticky and releases a substance that causes nearby platelets to become sticky as well If damage is more severe this causes the release of substance that changes prothrombin into thrombin which will then change fibrinogen into fibrin which interweaves itself into the clot Note two steps are involved WHY MIGHT YOU WANT TWO STEPS HERE Addendum on Heart Disease 1 Causes risk factors see Fig not in text Preventable factors dietlack of exercise smoking Factors that can t be prevented agingfamily history amp diseasebeing male these can all contribute to heart disease Some details on some of these diet cholesterol is thought to increase the tendency to form blockages in vessels this is LDL cholesterol or bad cholesterol though other types of cholesterol HDL s may actually help here exercise mostly aerobic helps strengthen the heart muscle and increase circulatory system efficiency Also helps increase HDL levels good cholesterol levels approximately halves the risk of having a heart attack smoking decreases levels of HDL good cholesterol constricts blood vessels surrounding the heart we ll see what it does to lungs when we do the respiratory system approximately doubles the risk of having a heart attack aging condition deteriorates as one gets older Plaques and other blockages start to form family history things like high cholesterol can run in families Not much that can be done about genetic history except take medication other diseases can cause heart disease very high fevers can damage heart valves various infections can interfere with the correct functioning of the heart males are more subject to heart disease 11 Hypertension high blood pressure causes increased stress on the heart has to work harder increased pressure can cause damage to the blood vessels which can cause the build up of plaque amp atherosclerosis often leads directly to heart attack stroke or kidney disease has many of the same risk factors as above but the exact connections between some of these factors and hypertension are not understood very well 111 Results of heart disease Some can be minor eg require a pacemaker some major eg heart attack Lots of different types of heart disease congenital heart disease genetic defect in the heart arrythmias irregular heart beat heart valve disease e g mitral valve prolapse usually heart valves allow leakage to occur heart failure heart does not work as well as it should heart attack in general coronary heart disease Fig not in text Part I Nutrition 1 How to obtain food This is descriptive general zoologists might be interested in this suspension feeders whales gills clams substrate feeders live in or on food source uid feeders mosquitos bulk feeders eat large pieces offood what about parasites substrate feeders corals 11 What kind of food plant herbivore animal carnivore both omnivore also note that food can be live or dead or in between carrionfungusmention parasitoid wasps 111 Reason for feeding l to obtain energy Biological organisms need energy Most biological molecules have some kind of energy associated with them Krebs cycle plants get energy from sunlight usually gt autotrophic animals get energy from other organisms usually gt heterotrophic some strange bacteria get energy from heat or other sources they39re also autotrophic 2 to get raw materials for synthesizing needed compounds dilTers from 3 since these are raw materials 3 to get essential nutrients that can t be synthesized a little similar to 2 but these materials are not synthesized The details i Energy Energy is obtained by oxidation of organic molecules Remember the Krebs cycle demonstrates how ATP is produced in the presence of oxygen from organic molecules Primary molecules for providing energy are i fats ii carbohydrates iii proteins Fats give about twice the energy of the other two ii Energy balance short term Excess energy is stored as glycogen consists of glucose subunits in the liver and muscle If energy is needed glycogen is released and metabolized oxidized iii Energy balance long term Fig not in book Excess energy is stored as fat Great for living through rough times but in Us fortunately we have more than enough food to go around Result gt obesity is a serious problem has very negative in uences on health diet and exercise are huge industries in the US partly due to the obesity problem Fig not in book This illustrates the need for balance Insuf cient energy causes weight loss then protein breakdown muscle breakdown etc Result gt undernourishment and in extreme cases death iv raw materials Brie y animals need organic carbon to manufacture needed organic molecules Another example is nitrogenous compounds can t fix nitrogen so animals need to get this from diet Important for amino acids see below v essential nutrients These are compounds the animal can not manufacture but are needed for survival A good example is Vitamins Note the following not all animals work the same some can make Vitamin C for instance four classes of essential nutrients 1 amino acids animals make about half of these They are essential for protein synthesis 2 fatty acids most diets are more than sufficient in these one example cell membranes rely on linoelic acid see text book 3 vitamins required in small amounts but are essential These are needed for various functions throughout the body See table 411 on page 877 Memorize columns 1 and 4 for exam know what vitamins go with a given symptom both insuf cient amp excess Note that excess vitamins are bad for you Give example of carnivore livers 4 minerals again required in small amounts See table 412 p 878 Please look it over but don t worry about memorizing stuff Part II Anatomy and physiology of digestion Overview Ingestion gt Digestion gt Absorption gt Elimination Fig 417 p 882 For animals we re most familiar with digestion takes place outside the cells Usually in a gastrovascular cavity Snakes venom spiders etc start digesting their prey outside the body Gastrovascular cavities may be of two types 1 single opening eg hydras atworms Mouth and anus in the same place 2 two openings food proceeds from mouth to anus Most higher animals Fig 418 amp 419 p 882 and 883 Mammalian digestion not too dissimilar from other vertebrates Oral cavity gt Pharynx gt esophagus gt stomach gt small int gt lg int OVERHEAD g 4110 p 884 1 Oral cavity Fig not in text Physical and chemical digestion of food starts here teeth break food into smaller pieces taste monitors the food being eaten why saliva lubricates food and begins chemical digestion with amylase which breaks down starch and glycogen try this leave a piece of bread in your mouth for several minutes Also note that smell of food can start triggering release of amylase 2 Pharynx and esophagus food moves past trachea windpipe As it does the epiglottis closes off the opening to the trachea the glottis Prevents food from entering lungs ie prevents choking Fig 4111 p 885 esophagus conducts food from pharynx to stomach using peristalsis Peristalsis gt a muscular contraction that forces something e g food in a particular direction 3 Stomach food is broken down chemically and mechanically gastric juice gt has a pH of 2 Disrupts extracellular matrix ie dissolves stuff that holds cells together Note gastric inhibitors medicines such as prilosec etc seem to show that one can manage with a higher pH But indications are that the low pH is very important in ghting pathogens pepsin gt breaks proteins down into smaller polypeptides stomach actually releases pepsinogen which is converted to active form pepsin by stomach acids WHY contents are mixed and slowly released through the pyloric sphincter as acid chyme pyloric sphincter acts as a control to prevent particles that are too large from entering the small intestine cardiac sphincter controls entrance to stomach 4 Small intestine The first 25 cm or so is known as the duodenum Several substances are released in this area Fig similar to 4114 p 888 pancreas buffer neutralizes acid hydrolytic enzymes eg trypsin these break up proteins further nucleases deal with nucleic acids amylase starch also found in oral cavity lipase deals with fats but only after bile has been released various other compounds see table 4113 on p 887 if interested liver bile stored in gall bladder This acts as a detergent breaking fat down into small pieces so that lipase from pancreas can break down fat in essence carbohydrates fats nucleic acids amp proteins can all be digested this way within limits The rest of the small intestine is used to absorb resulting nutrients and water Most of the nutrients are absorbed in the capillaries lining the small intestine blood from the capillaries moves into the hepatic portal vein and thence into the liver Liver processes and stores nutrients as well as breaking down toxins Fig 4115 p 889 But fats are absorbed by the lymphatic system which returns blood to the heart structure of small intestine Folded structure Folds have villi Villi have microvilli which absorb nutrients Nutrients are then taken either to lymphatic system fats or blood vessels to liver Fig not in text 5 Large intestine colon The large intestine reabsorbs any leftover water if material moves too slowly gt constipation if material moves to rapidly gt diarrhea terminal portion of colon is rectum Feces are stored there until they are eliminated 6 Cecum helps digest cellulose this is difficult to digest bacteria help break it down In humans is small but does have a little lymphatic tissue appendix and so seems to function in the immune system Fossil history This is just a brief overview For more details take geology there are also a few more details in your text How to age fossils After all we want to know how old fossils are relative aging newer fossils are generally near the top in sedimentary rocks one finds similar fossils in the same age layers all around the world this can be used to construct a history of life on earth geological time scale by comparing the same layers in different parts of the world an overall relative age for various strata can be arrived at illustrate absolute dating pretty good though not necessarily 100 accurate It does give an actual age for fossils How radioactive dating certain elements for example C 14 U 238 are unstable and decay into other forms U 238 when rocks first form ie cool they have a certain percentage of these molecules these molecules or elements decay at a specific and well known rate So rock that has just formed through volcanism or whatever will have mostly U 238 Fig not in book Over time this changes into Pb 206 By looking at the ratio ofU 23 8Pb 206 we can then tell how long ago the rock formed rocks with more Pb 206 are older half life of U 238 is about 45 billion years half life the amount of time needed for half of the original material to disappear C 14 is used for more recent times When alive organisms have a of C 14C 12 that is the same as in the atmosphere When organism dies Carbon is no longer replaced and ratio changes since C 14 decays into N 14 Half life is about 56 thousand years problem C in the atmosphere is not a constant ratio so until recent adjustments were made for this this technique led to some errors on source of information for adjustments tree rings back that far and can be used to reconstruct Carbon levels Other isotopes can also be used but the two above are the most popular other techniques involving amino acids see book if interested p 488 Abrief history of life on earth Fig 254 p 511 amp 257 p 514 Comment Geologically life on earth is divided into a few long eras which are then divided into periods which are nally divided into epochs The division is usually based on changes in rocks andor fossils as one moves through geologic history Precambrian Mostly algae and bacteria Not much going on until late in the Precambrian 46 billion years 540 mya Late precambrian animals begin to diversify oldest animal fossils are about 700 my old Paleozoic huge explosion of life go through table 540 mya 245 mya Fig 251 p 515 gt7 4 numerous periods e g age of fishes reptiles diversify land is invaded by numerous different animals etc many groups we talked about were abundant trilobites ammonites crinoids etc A brief summary of the periods Cambrian Origin of most modern animal phyla Ordovician Plants marine algae Silurian Jawless sh abundant rst jawed sh Arthropods invade land Devonian Diversity in bony sh our age of sh from above rst amphibians and insects Carboniferous Reptiles appear amphibians dominant on land Permian Reptiles diversify mammals either originate here or in early Triassic most modern insect orders Massive extinctions take place at the end of Permian these may have been caused by several di erent factors some evidence that a meteor may have been involved here similar to the one that wiped out the Dinosaurs Mesozoic 245 65 mya Basically the age of the dinosaurs Greatest diversity near end of Mesozoic Three periods Triassic Dinosaurs take off Early mammals Birds Turtles show up Jurassic Dinosaurs dominant Animals such as Stegosaurus Brontosaurus Apatosaurus Brachiosaurus Allosaurus Cretaceous Greatest dinosaur diversity T reX Triceratops Iguanodon Duckbills etc an important nonzoological development is owering plants BUT dinosaurs did adapt to deal with them this was an old theory for dinosaur extinctions Birds rst show up in Mesozoic TriassicJurassic ArcheopteryX Fig not in book of course many people will say birds are dinosaurs Cenozoic 65 mya present Homeostasis De nition the steadystate environment of the body In particular we are interested in how this steadystate is maintained If the internal environment changes too much it can be fatal Example you39re thirsty Why Some receptor somewhere senses your need for water Why Because your body needs water to maintain a steady salt balance Example you39re hot Response Take off excess clothes sweat fan yourself etc Why Because an increase in body temperature can be dangerous Obviously there are many other examples Most of what we ll do here is to look at temperature regulation Other examples are interspersed throughout the rest of the organ systems we ll be looking at Temperature regulation Heat can be exchanged by Fig 4010 p 863 conduction Heat is conducted from one structure to another Example getting into a hot bathtub Heat goes from water to you Similarly picking up heat from surrounding structures such as a hot rock convection Movement of air or water past body surface Example Windchill is caused by wind sucking heat out body Fig not in book radiation Electromagnetic waves coming from a warm substance to body Example it s hotter in the sun than in the shade evaporation Evaporation of water from body surface causes cooling Example Feeling cold coming out of a pool or shower Humans are very efficient at this one of the few animals with sweat glands over most of the body surface horses are another example Some terminology describing how an animal adapts to or regulates temperatures ectotherm heat is absorbed from environment Little or no internal mechanism for controlling body temperature endotherm heat is generated by organism Organism can within limits control internal body 39 of 39 39 temperature poikilotherm body temperature varies a lot homeotherm body temperature is reasonably steady In general coldblooded and warmblooded are terms that everyone understands right away even though they may not be that accurate Osmoregulation and excretion Basic idea is to keep a balance of salts in your body Osmosis review definition diffusion of water across a semipermeable membrane diffusion movement of a substance from a high concentration to a low concentration Thus a simple example a beaker with 5 salt on one side 0 salt on the other divided by a semi permeable membrane in this case salt can t move across the membrane which way does water move CONVERT to water So we have 100 water on one side 95 water on the other Water will move from a high concentration to a low concentration we won39t worry about such terms as hyperosmotic hypotonic etc We39re running a bit behind so what follows is abbreviated from what we usually cover A problem for many animals sometimes the concentration of salt and therefore water in the surrounding environment is totally different from that inside the body Aquatic animals Types osmoconformer animal has the same salt concentration as surrounding water osmoregulator animal needs to regulate salt concentration since salt concentration in body is different that in the surrounding environment Fig 444 p 956 Fresh water problem is water will enter body Animal must get rid of excess water or it will explode How Fish will eliminate water through kidneys very dilute urine absorbs extra salt ions through the kidneys Many other animals similarly will excrete large amounts of dilute urine Marine water opposite problem Water will leave body because salt concentration outside the body is often higher than inside the body water goes to more concentrated salt area the animal would shrivel like a raisin Fish most will excrete highly concentrated urine thus keeping water inside the body will also remove excess salt ions by excretion across gills Invertebrates most are osmoconformers Terrestrial animals Excretion The problem is water conservation Water is lost due to respiration evaporation through surfaces remember amphibians for example urine etc Water is restored by drinking or conserved by behavioral adaptations active at night or physiological adaptations below Features that prevent water loss are dead keratinized skin exoskeleton and producing very concentrated urine Nitrogenous wastes excreted Fig 449 p 959 ammonia this is the basic byproduct of metabolism Ideally this is excreted directly into the environment Problem gt highly toxic But many aquatic organisms do this since they can easily replace water In sh some of this is often excreted across the gills urea for terrestrial animals ammonia is no good they can t get rid of it quickly enough Instead they convert ammonia into urea 100000 times less toxic than ammonia in the liver This is then transported to the kidney and eliminated This is also used by some marine organisms that need to conserve water since high concentrations of urea are readily tolerated e g sharks uric acid many terrestrial organisms excrete uric acid birds many reptiles insects etc Uric acid is not very water soluble so it can be excreted with very little loss of water This is also good if you re an egglayer since the waste material can be stored as a precipitate in the egg the other two compounds would remain dissolved and even urea would eventually rise to toxic levels Mammalian kidneys fairly complicated here s an overview Fig 4414 p 963 materials in blood are excreted through the glomerulus highly coiled capillaries into Bowman s capsule a collecting area important nutrients are then reabsorbed in the proximal tubule In addition water and salt are reabsorbed The resulting uid has about the same salt content as the surrounding tissues but there s less of it Details sodium is reabsorbed Chlorine and water then follow in some nephrons there exists the loop of Henle The main function of this loop is to establish a concentration gradient that can be maintained To do this salt is removed from the loop through passive and active transport The surrounding tissue is much saltier near the bottom of this loop As the ltrate moves to the top of the loop it again becomes more and more dilute This is because actual salt content of urine is controlled in the collecting duct ie you want to start with reasonably dilute material and then reabsorb as necessary at the distal tubule concentrations of Potassium and Sodium ions are controlled and pH is buffered using bicarbonate this is similar to what happens in the proximal tubule Finally at the collecting duct all that needs to be done is to change the permeability of the membrane and urine can be as concentrated or dilute as needed within limits This is much quicker than setting up the gradient every time Note that as one goes down collecting duct surrounding tissue becomes more and more salty If membrane stays permeable then a lot of water is reabsorbed If membrane is made impermeable then more water is expelled Details go through Fig 4415 p 965 note that water is removed as uid descends loop This is because loop is water permeable but not salt permeable as one moves up ascending loop salt is removed loop is now permeable to salt but not water so salt will move from a high concentration within loop to the outs1de salt is still removed as uid moves further up loop but this time due to active transport of molecules note that all this salt removal establishes a concentration gradient with lots of salt at the bottom and less salt at the top after going through the distal tubule uid now moves down collecting duct Here the permeability of the membrane can be changed rapidly depending on the need for water if interested in the real details see g 4416 p 967 So how is all this controlled Or in other words how is the permeability of the collecting duct changed remember the gradient is maintained all that changes is the permeability of the collecting duct Methods of controlling kidneys ADH pathway Fig 4419A p 970 ADH antidiuretichormone is produced in the hypothalamus and stored in pituitary The hypothalamus monitors salt concentration of blood
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