1. Circulatory System 2. Respiration. Text: Chapters 23 & 24 (skip the invert material if you like) Then chapters 21 & 22 (skim Chapter 20)

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1 Lecture 19, 25 Oct 2005 Chapter Circulation, Oxygen and Carbon Dioxide Transport 1. Circulatory System 2. Respiration Vertebrate Physiology ECOL 437 (aka MCB 437, VetSci 437) University of Arizona Fall 2005 instr: Kevin Bonine t.a.: Kristen Potter 1 Text: Chapters 23 & 24 (skip the invert material if you like) Then chapters 21 & 22 (skim Chapter 20) 14-25, Vander Gravity and BP From body From Lungs Chordae tendinae 3 To Lungs (Eckert, 12-4) Mammalian Heart To Body via AORTA 4 (Eckert, 12-8) P (Q,R,S masks atrial repolarization) 5 (Eckert, 12-8) Q, R, S T 6 1

2 Wiggers Diagram Valves open/close where pressure curves cross 760 mmhg = 1 atm = 9.8 m blood Sherwood 1997 Atrial Kick 14-25, Vander :2 7 Heart filled ~same with increased HR 8 Sherwood 1997 Frank-Starling Curve Cardiac Output: CO = cardiac output (ml/min from 1 ventricle) SV = stroke volume (ml/beat from 1 ventricle) = EDV ESV (end-diastolic end-systolic volume) HR = heart rate (beats/min) CO = HR x SV MABP = CO x TPR MABP = DP + 1/3(SP-DP) Systole = Ventricular Emptying Diastole = Ventricular Filling (rest) Vander Heart can utilize different types of energy sources (unlike brain) 10 Cardiac Output Control Cardiac Output 6x Sympathetic speeds heart rate and increases contractility Exercise 1. Norepinephrine binds to beta 1 adrenergic receptors 2. Increases camp levels and phosphorylation Oxygen Consumption X Activates cation channels (Na + ) and increases HR Knut Schmidt-Nielsen Epi and Norepi activate alpha and beta 1 adrenoreceptors which increase contractility and rate of signal conduction across heart 12 2

3 HR control Parasympathetic vs. Sympathetic How increase contractility? More Ca 2+ (Eckert, 12-5) Vander HR control Parasympathetic slows heart rate -Innervate Atria (Vagus nerve = Xth cranial nerve) -Cholinergic (ACh) -Alter SA node pacemaker potential by K + permeability Ca 2+ permeability Peripheral Circulation - Endothelium lining vessels - Middle layer with smooth muscle (esp. arteries) -Outer fibrous layer Capillaries with ~ only Endothelium Parasympathetic innervation of AV node slows passage of signal between atria and ventricles (Eckert, 12-26) Peripheral Circulation Compliance vs. Elasticity ~ Veins vs. Arteries Volume Reservoir vs. Pressure Reservoir

4 Volume Reservoir vs. Pressure Reservoir Venous System - low pressure (11 mm Hg or less) - thin walled veins with less muscle 14-34, Vander more compliant and less elastic - valves -blood moved by skeletal muscle (and smooth) - breathing creates vacuum (low pressure) in chest to aid blood flow to heart (Eckert, 12-27) ~Constant P and Q at Capillaries! Microcirculation - endothelium in capillaries is permeable Bulk Flow (Eckert,12-38) 1. continuous 2. Fenestrated (kidney, gut) 3. Sinusoidal (liver, bone) Less permeable More permeable Fluid Pressure vs. Osmotic Pressure - Movement across walls, between walls, in vesicles Faster than diffusion -Bulk Flow Filtration > Uptake 21 Lymph System to return excess fluid 22 Bulk Flow Lymph System -Edema -Starvation - Lungs -Kidneys - No RBCs; therefore not red - Drains interstitial spaces -has valves and smooth musculature - empties into thoracic duct at vena cavae - transport system for large hormones and fats into blood stream - filariasis, elephantiasis - Reptiles and Amphibians with lymph hearts 23 Circulatory System Regulation 1. Feed Brain and Heart First 2. Next Feed Tissues in Need 3. Maintain volume, prevent edema, etc. Baroreceptors Chemoreceptors Mechanoreceptors Thermoreceptors Info. integrated at Medullary Cardiovascular Center medulla oblongata and pons Depressor Center Parasympathetic Effectors Pressor Center Sympathetic Effectors 24 4

5 Circulatory System Regulation Baroreceptors increase AP firing rate when BP increases Sensed at carotid sinus, aortic arch, subclavian, common carotid, pulmonary (Eckert, 12-43) Circulatory System Regulation Arterial Chemoreceptors in carotid and aortic bodies (More details when discuss ventilation) e.g., low O 2, high CO 2, low ph leads to bradycardia and peripheral vasoconstriction (diving and not inflating lungs) Usually leads to Sympathetic suppression to decrease BP What about when not diving? Circulatory System Regulation Cardiac Mechanoreceptors and Chemoreceptors Alter heart rate AND blood volume e.g., ANP (Atrial Natruiretic Peptide) released in response to stretch - leads to increased Na + excretion and therefore greater urine output 27 Circulatory System Regulation Extrinsic vs. Local Control Neuronal or Hormonal Most arterioles with sympathetic innervation Also respond to circulating catecholamines: -At high levels, alpha adrenoreceptors are stimulated vasoconstriction (to increase BP) -At low levels, beta 2 adrenoreceptors are stimulated vasodilation (to increase flow to tissue) -Response depends on tissue type, receptor type(s), level of catecholamines (epi, norepi), etc. 28 Circulatory System Regulation Extrinsic vs. Local Control stretch Circulatory System Regulation Extrinsic vs. Local Control NO (nitric oxide) temp. O 2 CO 2 ph adenosine K + Decreased O 2 levels with opposite effect in lungs Released from vascular endothelium: -Vasodilation -Relaxation -Viagra acts by blocking breakdown of cgmp 29 (Eckert, 12-45) 30 5

6 Circulatory System Regulation Extrinsic vs. Local Control Histamine Released in response to injury of connective tissue and leukocytes: -Vasodilation (Hill et al., 2004 Fig 23.11) Hemodynamics in Vessels Flow depends primarily on pressure gradient and resistance Hemodynamics - Poiseuille s Law: Use to approximate flow 14-11, Vander 2001 Flow rate Pressure Gradient radius 4 Q = (P 1 P 2 )πr 4 8Lη Vander 2001 length viscosity 33 Small change in radius large change in flow rate 34 Hemodynamics - From Poiseuille s Law: Summed resistance reduces pressure Resistance Pressure Gradient length viscosity R = (P 1 P 2 ) Q = 8Lη πr 4 Flow rate radius 4 Small change in radius large change resistance Modifiable if vessel distensible under pressure 35 (Eckert, 12-25) 36 6

7 Total Flow Rate same all along Circulatory System (Eckert, 12-23) Shapes of curves slightly different because of RBCs (viscosity) River River Lake 37 (Eckert, 12-24) 38 Why does blood in the lower extremities of aquatic organisms not pool as it may do in legs of humans, giraffes, etc.? FISH: Blood tends to pool in tail b/c inertia and compression waves when swimming -Veins in middle of body -Accessory caudal (tail) heart in some species 39 Hill et al., 2004, Fig Lung Anatomy Nonrespiratory -Trachea -> -Bronchi -> -Bronchioles -> Respiratory -Terminal bronchioles -> -Respiratory bronchioles -> -Alveoli (Eckert, 13-21) -Gas Diffusion Barriers: (Eckert, 13-22) -Cilia and Mucus

8 Hill et al., 2004, Fig Hill et al., 2004, Fig Lung Ventilation Lung Ventilation -Small mammals with greater per gram O 2 needs and therefore greater per gram respiratory surface area -Dead Space (anatomic and physiological) Swan (Eckert, 13-24) 45 (Eckert, 13-23) 46 Mammalian Ventilation -lungs are elastic bags -suspended in pleural cavity within thoracic cage (ribs and diaphragm define, fluid lines) -low volume pleural space between lung and thoracic wall -negative pressure to inflate lungs (increase volume) -pneumothorax Mammalian Ventilation (Eckert, 13-28)

9 Mammalian Ventilation -expiration usually passive Mammalian Lung Alveoli and Capillaries (Eckert, 13-30) 49 RBC (not to scale) 50 Bird Lung Ventilation Unidirectional!! Bird Ventilation -lung volume changes very little, air sacs instead (Eckert,13-32) (Eckert,13-32) Unidirectional Frog Ventilation -Positive pressure ventilation 1. Into mouth (buccal cavity) Mammal Lung Alveoli Bird Lung Parabronchi Knut Schmidt_Nielsen Close nares, open glottis and force air into lungs by raising buccal floor (Eckert, 13-33) 54 9

10 Pulmonary Surfactants Panting Dogs? -Reduce liquid surface tension in alveoli -Allows for compliance and low-cost expansion of lung -Lipoproteins -keep alveoli from getting stuck closed Atelectasis = collapsed lung -premature babies may need artificial surfactant Knut Schmidt_Nielsen 1972 Fish Gill 57 Hill et al., 2004, Fig Relative Gill Surface Area in Fishes Hill et al., 2004, Fig

11 Fish Gill -breathing in water -need much higher ventilation rate -unidirectional -pump water across gills (or ram ventilation) GILLS breathing in water -need much higher ventilation rate -unidirectional -pump water across gills (or ram ventilation) Floor of Mouth (buccal cavity) (Eckert, 13-40) Lake Titicaca Frog Gas Exchange Across Skin Hill et al., 2004, Fig (Bolivian Navy; Peru-Bolivia border) Hill et al., 2004, Fig Hill et al., 2004, Fig

12 Rate and Depth Regulation -Primarily via CO 2 changes (central) Rate and Depth Regulation -Peripheral Chemoreceptors PO 2, PCO 2, ph (Eckert, 13-48) -Innervate Medullary Respiratory Center (phrenic nerve to diaphragm and intercostals) (Eckert, 13-46) -Emotions, sleep, light, temperature, speech, volition, etc. Long term -Central Chemoreceptors -O2 controls respiration in aquatic vertebrates Hering-Breuer reflex To Diaphragm -Stimulation of stretch receptors inhibits medullary inspiratory center -Prevent overinflation alveolar -Ectotherms often breathe intermittently (Eckert, 13-45) Oxygen Partial Pressure (Eckert, 13-45) To Diaphragm 71 Hill et al., 2004, Fig