2018 Biology2 Chapter 23. Circulation

Most animals have a circulatory system The major functions of the circulatory system Transportation of O2 and nutrients to the tissue Transportation of metabolic wastes to waste disposal organs (e.g., lung and kidney) Hormone distribution Homeostasis Body defense Temperature regulation

The circulatory system associates intimately with all body tissues Capillaries are microscopic blood vessels They form an intricate network among the tissue cells Red blood cell Capillary

Capillary Interstitial fluid Cell Tissue cell Diffusion of molecules

23.1 Circulatory systems facilitate exchange with all body tissues MECHANISMS OF INTERNAL TRANSPORT 23.1 Circulatory systems facilitate exchange with all body tissues In cnidarians and flatworms, the gastrovascular cavity functions in both digestion internal transport Mouth Circular canal Figure 23.2A

Most animals have a separate circulatory system, either open or closed Open circulatory systems A heart pumps blood through open-ended vessels into spaces between cells (the blood is not confined to the vessels) No distinction between blood and interstitial fluid

Closed circulatory systems The blood is confined to the vessels Three kinds of vessels Artery: heart  tissue Vein: tissue  heart Capillary: tissue에서 artery와 vein사이의 미세혈관

23.2 Vertebrate cardiovascular systems reflect evolution A fish has a single circuit of blood flow Heart: 1 atrium + 1 ventricle

The cardiovascular system of land vertebrates has two circuits The pulmonary circuit conveys blood between the heart and gas-exchange tissues The systemic circuit carries blood between the heart and the rest of the body Mammal’s heart: 2 atria + 2 ventricles

Endotherms have higher metabolic rates than equal-sized ectotherms Necessary to deliver more fuel and oxygen to body tissues The circulatory system consists of two circuits Artery : Aorta (대동맥), artery (동맥), arteriole (소동맥) Vein : Vena cava (대정맥), vein (정맥), venule (소정맥)

THE MAMMALIAN CARDIOVACULAR SYSTEM 23.3 The human cardiovascular system illustrates the double circulation of mammals The human heart is about the size of a clenched fist The heart is formed mostly of cardiac muscle tissue The right atrium and ventricle Vena cava (superior and inferior)  right atrium right ventricle  pulmonary artery The left atrium and ventricle Pulmonary vein  left atrium  left ventricle  aorta

The valves in the heart 1. Semilunar valve Located between the ventricle and the artery Prevent backflow of blood from the artery to the ventricle 2. Atrioventricular valve -Located between the atrium and the ventricle -Prevent backflow of blood from the ventricle to the atrium

23.7 The structure of blood vessels fits their functions A single layer of epithelial cells forms capillary walls  simple squamous epithelium The epithelium is wrapped in a thin basal lamina Arteries and veins have smooth muscle and connective tissue in addition to the epithelium Valves in veins prevent the backflow of blood

23.4 The heart contracts and relaxes rhythmically Cardiac cycle Diastole Blood flows from the veins into the heart chambers Systole The atria briefly contract and fill the ventricles with blood Then the ventricles contract and propel blood out

Heart valves prevent backflow The heart sounds we can hear with a stethoscope are caused by closings of the heart valves Cardiac output The amount of blood pumped into the aorta by the left ventricle per minute Stimulants such as caffeine and exercize can increase cardiac output

23.5 The pacemaker sets the tempo of the heartbeat Pacemaker (sinoatrial node, SA node) -It regulates the tempo of the heartbeat -It is situated in the wall of the right atrium It generates electrical signals

Atrium muscle cell들 사이에 전기신호가 전달 Atrium muscle cell과 ventricle muscle cell들 사이에 전기신호 전달 X (due to the presence of connective tissue) The contraction of the ventricles Pacemaker  atrioventricular node (AV node)  specialized muscle fibers (atrioventricular bundle [bundle of His], Purkinje fiber)  contraction of the ventricles

An electrocardiogram (ECG) is a recording of electrical changes in the skin resulting from the electrical signals in the heart Control centers in the brain (medulla, 연수) adjust heart rate to body needs Decrease in blood pH  medulla  nervous system  pacemaker  increase in heartbeat and the strength of ventricular contraction Hormone (epinephrine, norepinephrine) Nervous system (autonomic nervous system): sympathetic (up) and parasympathetic (down) division Body temperature

23.6 Connection: What is a heart attack? A heart attack occurs when a coronary artery feeding the heart is blocked

23.8 Blood pressure and velocity reflect the structure and arrangement of blood vessels the force that blood exerts against the walls of our blood vessels Pulse: the rhythmic streching of the arteries

Pressure is highest in the arteries It drops to zero by the time the blood reaches the veins

Three factors keep blood moving back to the heart muscle contractions one-way valves relaxation of heart and breathing

23.9 Connection: Measuring blood pressure can reveal cardiovascular problems Blood pressure is measured as systolic and diastolic pressures (normal blood pressure: 120/70 mmHg)

Hypertension is persistent systolic pressure higher than 140 mm Hg and/or diastolic pressure higher than 90 mm Hg It is a serious cardiovascular problem

23.10 Smooth muscle controls the distribution of blood Muscular constriction of arterioles and precapillary sphincters controls the flow through capillaries Precapillary sphincters Thoroughfare channel Thoroughfare channel Arteriole Venule Arteriole Venule Capillaries 1 2 Sphincters relaxed Sphincters contracted Figure 23.11

Homeostatic control of blood pressure *Baroreceptor Specialized pressure-sensing nerve cells detect decreases in blood pressure It is found in the walls of heart and the major arteries Low blood pressure Increase in cardiac output Arterioles such as the skin and intestines constrict. Arteriolar constriction diverts blood to more critical organs Veins constrict

23.11 Capillaries allow the transfer of substances through their walls

The transfer of materials between the blood and interstitial fluid can occur by leakage through clefts in the capillary walls (e.g.,water and small solutes such as sugars and salts)  blood pressure/osmotic pressure diffusion through the wall endocytosis/exocytosis

23.12 Blood consists of cells suspended in plasma STRUCTURE AND FUNCTION OF BLOOD 23.12 Blood consists of cells suspended in plasma Blood = blood cells (45%) + plasma (55%) Blood cells Red blood cell (erythrocyte) White blood cell (leukocyte) Platelet

White blood cells help defend the body 5 major kinds of white blood cells (leukocyte) Formed in the bone marrow Basophil: release of histamine  dilation of blood vessels  allowance of other white blood cells to move out of capillaries and into surrounding tissues Basophil Eosinophil Myeloid leukocytes Monocyte Neutrophil Lymphocyte

Neutrophil, monocyte: phagocytes They eat bacteria, foreign proteins and debris from other body cells that have died Eosinophil: It kills multicellular parasites, related with allergic reactions Lymphocyte: Production of antibodies (B cell) Attack pathogen-infected body cells and cancer cells (T cell) Help activate B cells, T cells, and macrophage (T cell) Natutal killer cell

23.13 Two few or too many red blood cells can be unhealthy Red blood cells contain hemoglobin – oxygen carrier Lack nuclei and mitochondria Formed in the bone marrow Life span: 3-4 months Old red blood cells are broken and their molecules are recycled in the liver and spleen Anemia: an abnormally low amount of Hb or low number of red blood cells Biconcave shape

Hypoxia conditions in tissues (Low oxygen conditions) Production of erythropoietin In the kidney Stimulation of the bone marrow Production of more red blood cells In the bone marrow

23.14 Blood clots plug leaks when blood vessels are injured When a blood vessel is damaged, platelets respond They help trigger the formation of an insoluble fibrin clot that plugs the leak Platelets derive from megakaryocytes in the bone marrow Figure 23.16B

Figure 23.16A Platelet releases chemicals that make nearby platelets sticky Injury to lining of blood vessel exposes connective tissue; platelets adhere 1 2 3 Platelet plug forms Fibrin clot traps blood cells Connective tissue Platelet plug Clotting factors from: Platelets Damaged cells Calcium and other factors in blood plasma Prothrombin Thrombin Fibrinogen Fibrin Hemophilia

23.17 Connection: Stem cells offer a potential cure for leukemia and other blood cell diseases Multipotent stem cell  lymphoid stem cell, myeloid stem cell Stem cells in the bone marrow (ribs, vertebrae, breast bones, and pelvis) Red blood cell White blood cell Megakaryocyte platele