BIL 360: Class Notes Exam 3
BIL 360: Class Notes Exam 3 BIL 360
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Date Created: 09/29/15
End Ch 16 endocrineneuroendocrine part 2 10212014 V Endocrine Control of Nutrient Metabolism Animals don t eat continuously 0 May eat meals with nutrients in proportions diff from that needed by body 0 Cells require continuous supply of nutrients 0 Management of nutrients under endocrine control Storage mobilization interconversion Insulin and glucagon produced by beta and alpha cells of islets of Langerhans in pancreas 0 Main hormones responsible for management of nutrients 0 They regulate blood glucose conc Need mechanisms for storage after a meal and other mechanisms to release nutrients o Insulin most important hormone in managing uctuations of nutrient availability 0 Insulin dominant hormone when animal fed Favors storage of nutrient molecules carbohydrates AAs fatty acids from blood into tissues esp muscle and fat 0 Binds to receptors on musclefat cells leads to incorporation of glucose transporters in membrane allows target cells to take up glucose thru facilitated diffusion Causes decrease in blood glucose concentration hypoglycemic effect 0 Stimulates production of enzymes that synthesize glycogen from glucose storage molecule triglycerides proteins from glucose fatty acids AAs Removes glucose from blood and bind together into large storage molecules Carbohydrate meal at time 0 0 Prior to meal lower blood glucose level 0 Immediately after meal rich in carbohydrates have higher blood glucose level 0 As blood glucose level goes up so does insulin level 0 As blood glucose levels decrease because of insulin insulin levels also go down 0 Spike in blood glucose shows that nutrient concentration level in blood not constant 0 But insulin acts to keep conc level more constant 0 Levels of insulin also incr to favor storage of digested compounds from the meal Glucagon works with insulin to keep blood glucose levels stable 0 Release stimulated by low blood glucose level sympathetic nervous system incr in AA in blood 0 Hyperglycemic causes incr in glucose Glucagon o Stimulates breakdown of glycogen glycogenolysis o Stimulates gluconeogeneisis in liver taking other molecules and making glucose from them Taking AA and creating new glucose molecules interconversion o Stimulates fat cells to secrete glucose 0 Mobilizes glucose inhibits formation of storage molecules and stimulates breakdown of storage molecules lnsulin favors nutrient storage Glucagon favors nutrient mobilization Glucagon secreted in unfed state low glucose level 0 Higher levels of glucagon before carbohydrate meal 0 Favoring stored nutrients being released to fuel animal while in fasting state 0 After meal have rise in glucose causes decline in glucagon Also secreted when levels of AA in blood high Higher levels of glucagon in fed state after high protein meal 0 Very adaptive glucose availability 0 After protein meal incr in insulin and glucagon o Insulin incorporates storage of AA into proteins 0 Glucagon works via interconversion guconeogenesis Brain runs on glucose energetically expensive even if meal not high in carbs glucagon gives brain the amount it needs VI Endocrine Control of Water Balance Hormone involved vasopressinantidiuretic ADH o Arginine vasopressin AVP same thing but in animals ADH conserves water and prevents water loss in body by limiting urine production ADH stimulates cells in nephrons of kidneys to take up water by increasing membrane aquaporins o Tubules of nephron Epithelial tissue lining collecting duct 0 Aquaporin2 only present in apical when ADH present No ADH l any water in collecting duct can t pass thru cells follow duct out and leave with urine 0 In absence of AVP water cannot exit collecting duct excreted in urine ADH present bind to receptor on basal side activates 2rml messenger system stimulates release of aquaporin2 to apical membrane increase membrane permeability to water allow water to leave cell keeps water in body water conservation 0 Aquaporin3 always on basal side Not much water sensory detectors for that signals to brain to stimulates AVP secretion VII Chemical Signals Along a Distance Continuum Chemical messengers help coordinate physiological processes in body 0 How cells communicate using chemical messengers 0 Lowest level chem mess in gap junctions conexon proteins physically connect cells messengers can diffuse directly 0 Cell adhesion molecules on external part of cell important in development cell growth and differentiation 0 Neurotransmitters released at presynaptic terminal in response to electrical stimulate diffuses across cleft binds to receptor on postsynaptic cell Paracrine and autocrines diffuse over short distances 0 Autocrine come back and affect itself 0 Paracrine affect local neighborhood of cell Hormones long distance Pheromones even longer distance act outside of animal usually of same species 0 Kairomones act bw species Paracrines diffuse short dist to in uence cells locally Ex Neuromodulators similar but not same as neurotransmitter 0 Cause changes to post cell depending on how sensitive post cell is 0 Also affect other close by cells not just post cell different from neurotransmitter 0 Can diffuse across synapse and diffuse locally to other cells Newts rapidly disengage from amplexus sex position can last hours in face of a stressor with the help of a neuromodulator an endocannabinoid 0 Position lasts a long time but sudden stressful event can rapid release and get away lnjected males with corticosterone a stress steroid hormone usually works by diffusing into cell and acting as transcription factor 0 stops amplexus happens too quickly for normal steroid hormone 0 here corticosterone does not go into cell instead binds to receptors in target cells producing an endocannabinoid self produced substances that have marijuana effect acts as a neuromodulator o inhibits release of excitatory neurotransmitters reduces probability of AP in neurons that control clasping behavior Pheromones chem signals that act bw individuals of same species Used to convey info for social communications dominances sex sexual readiness food abundance alarms Tend to elicit stereotyped behavior in animal receiving the pheromone Ex ants have exocrine glands that produce pheromones for diverse purposes 0 Anal gland produce mate attraction pheromone o Sternal gland trail marking o Dufours gland warning 0 Postpharyngeal gland ants have waxy covering to keep from drying out do allogrooming social grooming these secretions help give ants of same colony a signature VII Insect Metamorphosis Metamorphosis controlled by hormones o Hormones also control many of same processes in inverts as those in vertebrates 2 main types of metamorphosis o hemimetabolous happens in true bugs grasshoppers cockroaches egg hatch into nymph stage looks like adult but smaller goes thru multiple moltsecdysis of cuticle until reaches adult 0 homometabolous butter ies moths egg hatch into larva larvae goes thru larval stages into a pupa pupa metamorphoses into adult have molt of cutical made of chitin o molt called ecdysis 0 can have many differ enstars Hormones involved P39ITH ecdysone JH Synaptic input day length temp etc stimulate molting ln brain have neuroendocrine cells that produce P39ITH o Axon of neuroendocrine cells extend to corpus allatum o P39ITH hemolymph quotbloodquot of insects stimulates prothoracic gland to produce ecdysone Travels thru hemplymph thru thorax to prothoracic glands P39ITH hormone that has stimulating effect on another endocrine gland Activates ecdysone at target cells and stimulates epidermis digests old cuticle and creates a new one Juvenile hormone maintains immature characteristics in animals secreted by nonendocrine cells of corpous allatum surround axon terminals 0 Activated ecdysone acts on epidermis and creates a larger version of the same thing larger instar o lfJH absent ecdysis results in pupa or adult structure Activated ecdysone and JH lipid soluble diffuse into cell and work thru transcription control expression of genes during development Experimentally removed corpus allatum removes JH end up with early instars molt into tiny sterile adult 0 Can do opposite treat late instar with JH don t metamorphose into adults get giant larvae or nymphs Applications Silk production 0 Silk casing of worms 0 Use JH to get larger larvae thus more silk Forensic entomology 0 Some insects feed and lay eggs on dead tissue 0 Community of insects and their phase of metamorphosis can give insight to how long body there o Blow y rst to show up lay eggs maggots hatch 0 Adults ies attracted later on Many types of reproduction in animal kingdom Asexual budding in coral Parthenogenesis development of an egg wo fertilization sh bugs We focus on sexual reproduction Reproductive Physiology Reproduction is an extended process 0 Development nding mate l signaling l fertilization l production of offspring l parental care Physiology studied many aspects of reproductive system Mate association nding mates pheromones Annual reproductive cycle seasonal changes 0 Reproductive mechanisms 0 Reproductive coordination and control Provisioning of offspring process of feeding young Distinctive physiology of young developmental stages maturation Reproductive once or more Semelparity programmed to reproduce at a single time in life 0 Parents sacri ce vigor for offspring 0 Ex salmon Iteroparity capable of 2 or more separate periods of reproductive activity in lifetime 0 Parental provisioning is complex Must refrain from risking own life to reproduce again Life span important determinant of parental investment I High probability of parental death greater sacd ceforyoung o Undergo reproductive cycles endocrine controlled Eggs provisioning and parental care 0 Eggs and prenatal provisioning transfer nutrients from bloodstream of mom to that of embryo yolk or placenta 0 Low provisioning ancestral Huge eggs broadcast spermeggs More eggs smaller eggs with less yolk l lower survival rate 0 High provisioning placental animals Fewer eggs larger more nutrients l higher survival rate 0 Postnatal provisioning parents gather food for young 0 Provisioning aids offspring but imposes costs on parents 0 Evolutionary tradeoffs bw many lightlyprovisioned offspring or fewer wellprovisioned offspring 0 Ex lactation providing food Environment as a player in reproduction Nutritional aspects reproductive success threatened if amt food inadequate 0 Eggs hatch in areatime with sufficient food 0 Emergence of caterpillars and chicks global warming decouples 0 Social aspects mates must nd each other and achieve states of mutual sexual readiness 0 red deer must be capable of dominating other males before gaining access to females for mating o Clownfish sex change mediated by social hierarchy o Males have territories to have access to females 0 Physical aspects 0 Photoperiod daylight hours 24 varies with time of year gives info on season many animals synchronize reproduction with season seasonal breeders pineal gland secretes melatonin at night uses as indication of photoperiod a decreasing melatonin incr daylight Mammals melatonin an endocrine signal in photoperiod control of reproduction n Secreted at night inversely related to photoperiod a Pattern of melatonin encodes the photoperiod ne tunes timing by photoperiod tempdependent sex determination nest temp determines whether egg develops into malefemale turtles in uences how fast offspring grow ll Reproductive Endocrinology of Placental Mammals Female reproductive anatomy o Vagina l cervix I uterus Internal organs 000 O Ova ry O O Endometrium glandular epithelia lining of uterus Myometrium smooth muscle on uterine wall Ovaries where oocyte produced Oviducts fallopian tubes where fertilization occurs Primordial follicle primary oocyte and its layer of somatic cells have when born Primary oocyte egg cell in ovary completes rst meiotic division when ovulated Primary follicles primary oocyte surrounded by layer of granulosa cells made when start ovulation Granulosa cells formed when somatic cells around primordial follicle become cuboidal Secondary follicle larger secondary oocyte with zona pellucida Formed at ovulation when primary oocyte concludes rst meiotic division Meiosis only completed if fertilized by sperm Theca cells outer layer of secondary follicle formed when connective tissue on outer part of granulosa cells differentiate Mature follicle fully developed follicle under outer epithelium of ovary Oocyte egg cell Mature corpus luteum endocrine structure in ovary formed by reorganization of follicle that has undergone ovulation lf fertilized remains active during pregnancy otherwise degenerates Oogenesis production of eggs haploid thru meiosis in ovary O 0 Creation of eggs takes years to complete In humans meiosis only completed in secondary oocytes fertilized by sperm Female Endocrine control 0 Events in ovary o Follicular phase when follicles mature Several follicles l single mature follicle start developing o Ovulation process of releasing an egg from ovary end of follicular phase and start of luteal phase Menstrual phase menstruation shedding of uterine lining if unfertilized occurs after ovulation Estrus heat time during ovulation with female uses behavior to indicate that she s ready to conceive a Endometrium reabsorbed o Luteal phase after ovulation corpus luteum forms degenerates if unfertilized Female reproductive cycles names according to observable external events 0 Human females have menstrual cycle menstruate each cycle that doesn t result in pregnancy 0 Many other mammals have an estrus cycle based on behaviors that synchronize mating and ovulation Endocrine control of follicular phase Neuroendocrine cells of hypothalamus release gonadotropinreleasing hormone GnRH o GnRH stimulates secretion of luteinizing hormone LH and folliclestimulating hormone FSH o LH acts on theca cells stimulate androgen production LH surge activates ovulation o FSH acts on granulosa cells stimulate aromatase production Androgens aromatized to estrogens released to general circulation o LH and FSH levels peak at ovulation Steps 0 1 Blood levels of estrogen rise during follicular phase prior to ovulation positive feedback E produced by granulosa stimulates mitotic division of granulosa l incr granulosa l incr amt E l supports continued proliferation o 2 Estrogen stimulates growth of endometrium stimulates production of progesterone receptors 0 3 At end of follicular phase granulosa cells secrete inhibin l inhibits FSH secretion 0 4 LH surges in response to high estrogen stimulates ovulation creates corpus luteum production of progesterone Male reproductive anatomy o Penis male genitalia Urethra allows passage of urinesemen Testis spermhormone production Scrotum sac suspended outside body cavity contains testes Vas deferens empties urethra connects testis to urethra Testes and spermatogenesis o Sperm produced in coiled seminiferous tubules of testis l coiled tube next to testis in scrotum l vas deferens o Seminiferous tubules contain Spermproducing cells in various stages Sertoli cells layer of somatic cells supportregulate production of sperm 0 Leydig cells located in connective tissue bw seminiferous tubules secretes T o Spermatogenesis production of sperm thru meiosis in testis Spermatogonia develop into primary spermatocytes then secondary spermatocytes then spermatids then sperm 0 Sperm cell acrosome on head contains enzymes that help sperm penetrated egg during process leading to fertilization Endocrine control males Testosterone the main male hormone androgen Testosterone over life span 0 Important in fetal development for differentiating male characteristics 0 Few weeks after T secretion decreases Then have a spike after birth 0 Then low until puberty where it becomes high and remains high throughout rest of life peaks 0 Production of T controlled similarly to female endocrine control 0 Hypothalamus l GnRH l anterior pituitary l FSH l sertoli cells n In uenced by T from Leydigs a Help nourish developing sperm LH l Leydig cells l Testosterone T stimulates spermatogenesis o In general circulation masculinizes tissues Fertilization event that results in formation of a zygote Sperm travels to upper part of oviduct to meet secondary oocyte Eggs from ovary covered in layer of granulosa cells 0 Sperm must go thru possible because of enzymes in head of sperm acrosome O Acrosomal reaction sperm head releases acrosase when binds to zona pellucida of secondary oocyte 0 Some will reach cell membrane 0 Fertilization officially when sperm membrane connects o Creates a zygote Zygote travels thru oviduct to uterus o Undergoes mitotic divisions folding in on itself to form the blastocyst cells that ultimately develop into newborn plus trophoblast don t contribute to newborn form placenta 0 To implant blastocyst enzymes from tropoblast enable blastocyst to bury in nutrientrick endometrium implantation Chorion membrane that forms placenta secretes CG helps corpus luteum produces progesterone from degrading supports the embryo n Progesterone maintains endometrium First 5070 days placenta forms and takes role of producing progesterone o Embryo rst supported with nutrients by endometrium then by placenta Placenta blood vessels are connected get transfers of gases and other materials also secretes estrogen and progesterone n prepares mother s body for birth and lactation Birth 0 Period before birth many changes to prepare body 0 High levels of estrogen and progesterone o Rising estrogen stimulates myometrium to form gap junctions creates coordinated contractions during birth smooth muscle to synthesize oxytocin receptors 0 Oxytocin principle hormone controlling forces that produce delivery o Oxytocin secreted by neuroendocrine cells released into circulation at posterior pituitary Stimulates smooth muscle contraction secretion of prostaglandins Smooth muscle contractions push fetus toward cervix o Oxytocin and prostaglandins cause contractions Stimulated mechanoreceptors that send APs to hypothalamus sets up positive feedback loop 0 Delivery of placenta dramatically lowers progesteroneestrogen levels dropping Ch 21 I Neural control of skeletal muscle in the mechanistic basis of animal behavior 0 Major function of nervous system is to control behavior 0 From re exes to complex behaviors tool use foraging courtship dance lnvert and vert neural circuits generally similar 0 2 key differences 0 inverts have individual neurons can be identi ed and play functional roles that remain through individual animals verts individual neurons cant be identi ed 0 inverts neurons can work on own verts many neurons work together 0 simple invert re ex have sensors that sense changes in air 0 mechanoreceptors airwind the stimulus 0 creates APs from hair receptors to CNS travels down ventral nerve cord 0 interneurons are excited stimulate motor neurons that cause contraction of extensor neurons exion decreasing angle ofjoint extension incr angle ofjoint 0 other stimulated interneurons also inhibitory of opposite exor muscles 0 neural circuit only 10 neurons because its an invert vertebrate spinal re exes involve many more neurons vert stretch re ex sensory input from receptors of skin muscle that goes to spinal cord 0 muscle spindles sensitive to stretch synapses with other neurons in spinal cord 0 excites some neurons extensor muscle and inhibits others exor muscles 0 motor neurons synapse with like muscles Proprioseptors receptors provide input on position of body 0 muscle spindle within muscle bers extrafusal 0 within muscle spindles have intrafusal muscle bers 0 if these are stretched stimulates AP in afferent axons that travels back to spinal cord to alert that that muscle is being stretched reciprocity muscles arranged in antagonist pairs signals activate movement contract agonists while relaxing antagonists stretching muscle spindle causes 1a afferent neurons to generate APs 1a afferent axons synapse with inhibitory interneurons that inhibit motor neurons to antagonist opposing muscles exor 1a input generates EPSPs in motor neurons stretched muscle extensor contracts vertebrate exion re ex spinal re exes protect body step on a tack re ect by pulling back maintain posture adapts to change in weight load sensory neurons in skin joints sensitive to painful stimulus o excite interneurons in CNS causes excitation of motor neurons innervating exor muscles and inhibition of motor neurons to extensors o maintains reciprocity cross extension re ex have other nonhurt foot behind to lean on after pulling away from tack sensory neurons synapse on interneurons that cross midline of spinal cord 0 excites extensor muscles of opposite leg opposite leg extended to support weight primary synaptic input of spinal motor neurons if from the CNS sensory re ex input is secondary re exes adjust movements programmed by CNS ex load compensation muscle bers also innervated by gamma motor neurons 0 can cause contraction in intrafusal muscle bers 0 this can send a signal back picking up a pamphlet is a voluntary movement under CNS control CNS estimates amount of force necessary to pick up object sends to muscle stretch re ex mediates load compensation augmenting contraction if necessary if object heavier than expected can compensate coactivation alpha motor neurons activate muscle and gamma motor neurons activate muscle spindle o ensures muscle spindle maintains sensitivity to stretch if remain too loose cant sense as well O as muscle contracts muscle spindle contracts as well 0 pamphlet light and CNS correctly estimated weight 0 match bw extra and intrafusal motor neurons no activation is stretch receptors no message sent back to CNS 0 if load heavier than estimated by CNS excitation of intrafusal ber activated stretch receptor producing error signal of APs O O O 0 still have coactivation but don t have muscle contraction but still have contraction of muscle spindle while muscle remains long this sends stretch message back to CNS that muscle did not contract 1a afferent neurons synapse with alpha motor neurons generating additional tension to overcome load ll neural generation of rhythmic behavior 0 Most behavior from action patterns Rhythmic behavior happen same every time predictable 0 Walking swimming ying Ex ying in locusts 00000 0 Movement of single wing oscillation of the wing Can record electrical activity associated with wing position Depressor pulls wing down Levator pulls wing up activated when wing down Wing hinge proprioceptor How are these neurons activated in rhythmic motion 2 hypotheses lst peripheralcontrol hypothesis activation of 1 neuron send signal to next neuron to activate 2nd centralcontrol hypoth neural circuit in CNS that gives central pattern stimulation doesn t require sensory feedback to test remove sensory input from wing deafferentation o locust maintain ight without sensory feedback suggest central control 0 but sensory input affects quality of performance of rhythmic behaviors ight frequency lower than normal Ill control and coordination of vertebrate movement Many of same principles of inverts apply How does a cat walk Nervous system has 3 parts brain spinal cord sensory afferent motor neurons 0 Motor neurons get input from brain proprioreceptors local input from internal spinal circuits Locomotion in cats involves spinal central pattern generator 0 Test experimental lesions of CNS and peripheral nerves allow isolation of effects of these compartments 0 Lesion 1 lesions of cerebrum remove brain in uences Can still maintain fairly normal walking with electrical stimulation at mesencephalic locomotor command region More electrical stimulation faster walking So brain may modulate and initiate walking movements but not necessary to maintain o Lesion 2 cut dorsal roots remove sensory input Can still walk 0 Indicate that cat spinal cord contain some pattern for walking movements Brain is important in initiating coordinating and regulating normal movements 0 Regions of brain involved in generating movement 0 Cerebral cortex Primary motor cortex body regions represented by a somatotopic map a Governs voluntary movements Neurons project to brainstem spinal cord Premotor areas have complex functions a Mirror neurons of premotor area 5 re when animal performs action and when animal observes other performing action a Understanding of actions learning by imitation a Mirror neurons re when macaque grasps food or watched human grasp food 0 Cerebellum large region at dorsal side of hindbrain Adjusts coordinates movements Motor learning 0 Basal ganglia forebrain nuclei Select some movements suppress others 0 These 3 regions act together thru connected circuits to coordinate and control movement 0 Muscle tissue composed of specialized contractile cells 2 major categories of muscle cells striated muscle skeletal and cardiac muscle smooth muscle Vertebrate Skeletal Muscle Tissue Muscle bers contain myofibrils Sarcomere smallest contractile unit of a muscle ber 0 composed of 2 kinds of myofilaments thick and thin thick myosin thin actin when muscle ber contracts thick and thin lament do not shorten but slide by one another 1 Rigor conformation myosin bound to actin no ATP 2 Binding of ATP myosin unbinds from actin 3 ATP hydrolyzed energy released stored 4 Myosin moves to cocked position binds actin 5 Myosinactin attachment triggers Pi release and power stroke 0 6 ADP released myosin still bound to actin rigor Calcium regulates muscle contraction o In resting state regulatory proteins troponin and tropomyosin block myosin binding site on actin proteins No Ca2 ions present in cytoplasm relaxed 0 When calcium ions bind to troponin causes a conformational change in troponin tropomyosin l allows formation of cross bddges Ca2 ions released from the sarcoplasmic reticulum 0 00000 ll ExcitationContraction Coupling Skeletal muscle contraction triggered by neural excitation O 0 AP causes rise in intracellular Ca2 When ttubules depolarized DHPRs change conformation altering conformation of associated RyRs Calcium released into cytoplasm When AP ends ttubules repolarize RyRs close Calcium returns to sarcoplasmic reticulum via active transport Ca2ATPase pumps Ill Smooth and Cardiac Muscle Cardiac muscle 0 O O O 0 Only in heart Involuntary control Branched organization of contractile units lntercalated discs with gap junctions Pacemaker cell impose rhythm Smooth muscle 0 O 0 Wall of hollow tubular organs Eye arrector pilli Involuntary control Not organized into sarcomeres Changes organ size volume Propels materials Maintains tension Animations Sarcomere Shortening In relaxed muscle actinmyosin myo laments lie side by side and H zones and l bands are at max width 0 During contraction actinmyosin myo laments interact o Actin slides toward center of each myosin 0 Results sarcomeres shorten ln contracted muscle end of actin myo lament overlap o H zones disappear and l band becomes very narrow Cross Bridge Cycle 0 I Properties of gases in gas mixtures and aqueous solutions 0 Total pressure exerted by a mixture of gases is the sum of the partial pressures exerted by the individual constituents on the mix 0 partial pressure hypothetical pressure exerted by one component of a gas 0 gas is dissolved in liquid diffuses to different parts and reacts based on its pressure not concentration 0 the partial pressure and the concentration of a gas are proportional to each other 0 P nVRT Partial pressure of each gas can be calculated from the universal gas law 0 PV nRT Partial pressure of a gas dissolved in an aqueous solution is de ned to be equal to the partial pressure of the gas in a gas phase with when the solution is at equilibrium Henry s law relates partial pressure and concentration in aqueous solutions 0 Cx APx o Cx dissolved conc of the gas 0 A absorption coefficient proportionality factor Measure of gas solubility Varies for different gases C02gt02 Solubilities of gases decr with incr temp Solubilities of gases decr with incr salinity o Px partial pressure of gas in solu Partial pressure determines thermodynamics of a gas 0 proportional to conc of the gas 0 but in aqueous solution conc more complicated ll Diffusion of gases Gases diffuse from areas of high partial pressure to areas of low partial pressure Gases diffuse more readily thru gas phases air than thru aqueous solu 0 Consequences for animals that burrow or bury eggs receive 02 by diffusion of air thru interstitial spaces If soil wet spaces ll with water and rate of 02 diffusion decr can result in death 0 Small amt of uids in air spaces of lungs can cause dire emergency Lose ability to absorb 02 at levels required by body Ill Fundamental concepts of external respiration External respiration breathing 02 transported to gasexchange membrane from envir medium C02 transported away from membrane to medium Ventilation bulk ow of air from envir to body by convection 0 Partial pressure inside must be lower than outside 0 High surface area to help diffusion Gasexchange membranes very thin 0 Dark purple dots nuclei Breathing structures Usually have 1 main breathing organ can have multiple Have foldings of gasexchange membrane to incr surface area 0 Airbreathing invageonated membrane lungs o Waterbreathing evagonated membrane in external medium gills External gills on external body surface and extend into external medium Internal gills same basic structure enclose in protective structure Ventilation of lungs and gills may be passive or active 0 Active utilizes metabolic energy to create currents of air or water ow using muscles beating cilia Can be a unidirectional airwater pumped over membrane in 1 way path a tidal bidirectional airwater ows tofrom membrane via same passage ways a nondirectional airwater ows in many directions 0 see with external gills More reliable controllable and vigorous than passive 0 Passive no energy used IV Principles of gas exchange by active ventilation Active ventilation an animal creates a current of airwater to gas exchange membrane Rate of 02 uptake depends on 0 Volume of airwater ow per unit time o Amt of 02 removed per unit volume 0 Rate of 02 uptake Vmedium CiCe 02 utilization coefficient how thoroughly an animal uses 02 in medium pumped thru breathing organ 0 How well does the organ take 02 out of the envir o 100CiCeCi Efficiency of breathing organ measured by 02 partial pressure in blood leaving organ Breathing organs differ in blood 02 partial pressure they maintain based on spatial relationship bw ow of blood ow of medium Methods of gas exchange tidal bidirectional exchange bc air coming inout thru same pathways creates a mix of stale and new air going into organ 02 partial pressure of medium always lower than that of external envnr 02 diffuses into blood across membrane 02 partial pressure of blood rises but remains lower than the exhaled medium Methods of unidirectional gas exchange Concurrent blood and medium ow in same direction 0 First come into contact afferent blood no 02 coming into breathing structure low partial pressure 0 See movement from high partial pressure to low 0 Continues along gas exchange medium until reaches equilibrium 0 Final blood 02 partial pressure lt exhaled medium Countercurrent blood and medium ow in opposite directions 0 When afferent 02 depleted blood comes into contact with medium rst interaction is with air that has little 02 and about to be exhaled but still have diffusion bc 02 in blood still lower 0 As blood moves thru medium interacts with medium of increasing 02 partial pressure 02 continues to move from medium to blood along length of membrane 0 Much more ef cient more 02 being taken out of external medium 0 Blood 02 gt exhaled medium Crosscurrent blood ows all take different path thru medium 0 Mixed blood has higher 02 partial pressure than exhaled medium 0 Some blood pathways interact with moreless 02 rich medium absorb different amounts 0 Blood ow breaks up into multiple streams some blood exchanged with 02 rich medium some with 02 poor medium 0 Efficiency how well they utilize 02 from medium 0 Countercurrent gt crosscurrent gt concurrent and tidal V Vertebrate Breathing Total surface area of gasexchange membrane an allometric function of body size 0 Mammal and birds have greater SA relative to body size 0 Suggests that when verts went onto land was not large change 0 Mammals and birds have relatively thin membranes separating medium and blood 0 Among verts role of skin in gas exchange varies widely 0 Many sh and most reptiles have skins allowing little gas exchange 0 In some sh reptiles and many amphibians gt25 of gas exchange occurs across skin 0 Most mammals and birds rely almost exclusively on lungs When spinal cord severed posterior to brainstem efferent impulses traveling to skeletal muscles responsible for breathing are cut off 0 Vert breathing under control of a central pattern generator in the brainstem o
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