1. Chapter 42: Circulation & Gas Exchange

2. Circulatory & Phylogeny Diffusion is inefficient over distances more than a few mm. Circulatory system ensures that no substance must diffuse very far and connects the aqueous environment of cells to organs that exchange gases, absorb nutrients, and dispose of wastes Those that lack a circulatory system utilize a gastrovascular cavity to digest and distribute substances throughout body Ex: hydra, jellyfish, planarians

3. Open vs. Closed Two types of circulatory systems: *both utilize fluid (blood), set of tubes (vessels or sinuses), and pump (heart) 1. Open system – no distinction between blood and interstitial fluid - hemolymph is pumped through sinuses to reach organs and parts of body 2. Closed system – blood is confined to vessels and separate from interstitial fluid - materials are exchanged by diffusion between vessels and fluid - higher blood pressure is more effective at transport of fluids to meet metabolic demands

4. Open vs. Closed

5. Cardiovascular System Most vertebrates have muscular heart with 1 or 2 atria, and 1 or 2 ventricles - always pumps atrium to ventricle 3 blood vessels of transport of blood, nutrients, and wastes 1. Arteries – carry blood away from heart 2. Veins – carry blood toward heart 3. Capillaries – exchange blood and gases between veins and arteries

6. Vertebrate Circulation

7. Fish - 2 chambers atrium and ventricle - gill capillaries pick up oxygen send it to systemic capillaries - return to heart Amphibians - 3 chambered heart 2 atria, 1 ventricle -pulmocutaneous circuit moves to lungs for oxygen -returns to heart; oxygen rich blood pumped from heart to systemic circuit

8. Vertebrate Circulation Reptiles ( true double circulation) -3 chambered heart; 2 atria, 1 ventricle with partially divided septum (less mixing of blood) -Separate pulmonary loop to lungs for oxygen; cycle back to heart and pump to systemic loop and back to heart Mammals and Birds -4 chambered heart; 2 atria, 2 ventricles -Right side separation of pulmonary loop to lungs for oxygen; back to left side of heart where ventricle pumps to systemic loop -Atrial valves to prevent backflow

10. Pathway of Circulation 1. De-oxygenated blood enters right side of the heart from both superior (anterior) and inferior (posterior) vena cava. 2. Blood moves from right atrium through the atrioventricular valve to the right ventricle 3. From the right ventricle blood exit the heart in the pulmonary artery to the lungs 4. Gas exchange in the lungs allows oxygenated blood to circulate back to the heart through the pulmonary vein. 5. Oxygenated blood enters left side of the heart into the left atrium. Blood flows through atrioventricular valve to the left ventricle 6. Aorta (largest artery) carries blood from the ventricle first to the coronary arteries that give blood to heart muscle, then to other organ systems throughout the body. 7. Deoxygenated blood is cycled back to the heart by way of Superior and inferior vena cava

11. Mammalian Heart

12. Cardiac cycle refers to the rhythmic cycle of contracting and relaxing or pumping and refilling blood systole – contraction of heart moving blood out of ventricle diastole – relax and refill of blood into the ventricle

13. Mammalian Heart Cardiac output – volume of blood per minute that the left ventricle pumps to system loop CO depends on heart rate ( beats per min.) and stroke volume Stroke volume – amount of blood pumped by ventricle with each contraction Pulse – stretching of arteries by pressure of blood pumped by contraction of ventricles

14. Mammalian Heart Valves – flaps of connective tissue that prevent backflow and circulate blood in correct direction - 2 atrioventricular - 2 semilunar between left ventricle and aorta, and pulmonary artery and right ventricle Heart murmur – condition caused by defect in one or more valves – hissing sound as blood squirts backward

15. Heart’s Rhythmic Beat Sinoatrial node (SA node) or pacemaker – sets the rate and timing of cardiac muscle contraction - located in wall of right atrium where superior vena cava enters heart - generates electrical impulses like nerve cells causing atria to contract in unison Atrioventricular node – main relay point between right atrium and ventricle Electrocardiogram (ECG) – record of electrical impulses that travel through the cardiac muscle during the heart cycle

16. Heart’s Rhythm SA node sets tempo, but is influenced by the following factors: 1. nerves that speed up and slow down pacemaker 2. Hormones – example epinephrine 3. Body temperature 4. Activity level

17. Principles of Circulation Same physical principles that govern a plumbing system influence functioning of animal circulatory system Infrastructure is network of blood vessels of varying size, speed, and pressures Law of continuity- fluid movement through pipes will increase speed if the diameter of the pipe decreases in order to maintain a constant flow rate.

18. Blood Pressure Blood pressure – hydrostatic pressure of blood against the wall of a vessel and that propels blood - arteries have higher pressure that other blood vessels because of smaller thick walls Peripheral resistance is created by the impedance of arterioles from relieving pressure of blood entering the arteries with each contraction

19. Lymphatic System Large accumulations of fluids and blood proteins can be lost each day flowing through capillaries Lymphatic system returns lost fluid and proteins (lymph) to the blood that intermingles with cardio system - maintains volume and protein concentration of blood Lymph vessels have valves to prevent backflow and rhythmic contractions move fluid toward the heart Lymphatic system also helps defend against infection (lymph nodes contain large clusters of WBCs)

20. Blood Composition Blood consists of several kinds of cells suspended in plasma - plasma is 90% water- solvent for transport - ions like Na, K, Mg, & Cl help regulate membrane permeability - proteins like Albumin along with ions help maintain osmotic balance and act as pH buffers - Fibrinogen is a protein clotting factor - Immunoglobulins serve as defense proteins against viruses or foreign agents

21. Blood Composition Cellular elements of blood 1. Red blood cells – transport oxygen with iron containing protein hemoglobin - most numerous blood cell 2. White blood cells (leukocytes) – defense against infections - monocytes, neutrophils engulf bacteria and debris - lymphocytes develop into B cells and T cells 3. Platelets – clotting factors that originate from pinched off cytoplasmic fragments - sealant is inactive form fibrinogen which is converted to fibrin to create clot - clotting factors begin cascade of reactions to convert to fibrin

22. Blood Clotting

23. Stem Cells Cellular elements of blood wear out and are replaced constantly All cellular elements develop from a common source – stem cells - located in marrow of ribs, pelvis, vertebrae and breastbone - termed as pluripotent meaning all have potential to develop into any kind of blood cell or platelet

24. Cardiovascular Disease Disease is result of disorders of the heart and blood vessels Cholesterol – LDL and HDL Artherosclerosis – disease caused from plaques narrowing the bore of the artery Hypertension – high blood pressure can be caused from atherosclerosis which narrows and reduces elasticity of vessels Heart attack – death of cardiac muscle from prolonged blockage of coronary arteries Stroke – death of nervous tissue in the brain

25. Gas Exchange Gas exchange – uptake of molecular O 2 from environment and discharge of CO 2 to outside Respiratory medium is the source of oxygen Respiratory surface is part of body where gases are exchanged - diffusion

26. Respiratory Systems Pathway of air flow: 1. Air enters the nostrils where hairs filter, warmed, humidified, and sampled for odors 2. Nasal cavity leads to pharynx- division between esophagus and trachea 3. Air moves past glottis into the trachea 4. Trachea forks into branches called bronchi 5. Bronchi divide into finer tubes called bronchioles (within the lungs) 6. At the tips of the bronchioles are the tiny grape- like clusters called alveoli - location of gas exchange across capillary walls

27. Respiratory System

28. Breathing Mammals ventilate lungs by negative pressure breathing - pulling air into the lungs instead of pushing - diaphragm – skeletal muscle at the bottom wall of chest cavity - contracts moving down to drawn air in (inhalation)and expand rib cage (pulling it up) - relaxes moving up to push CO 2 out (exhalation) Tidal volume – the volume of air a mammal inhales and exhales with each breath

29. Breathing

30. Control Centers of Breathing Main breathing control centers are 2 regions of the brain stem called the pons and medulla oblongata - set the basic rhythm - negative feedback mechanisms are used to regulate breathing activity between lungs and medulla