Chapter 7 The Cardiovascular System The respiratory System.pdf

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Department
Biology - Biological Sciences
Course
BSC 3096
Professor
chu
Semester
Fall

Description
Chapter 7 The Cardiovascular System; The respiratory System Monday, July 15, 2013 8:42 AM 1. Cardiovascular Anatomy a. b. The cardiovascular system consists of the heart, blood, and blood vessels i. Beginning with the left ventricle, blood is pumped through the aorta ii. From the aorta branch many smaller arteries which themselvesbranch into smaller arterioles, which branch into smaller capillaries iii. Blood from the capillaries is collectedinto venules, which themselvescollect into larger veins, which collect again into the superior and inferior vena cava iv. The vena cava empties into the right atrium v. From the right atrium, blood is squeezed into the right ventricle vi. The right ventricle pumps blood through the pulmonary arteries, to arterioles,to the capillaries of the lungs vii. From the capillaries of the lungs, blood collectsin venules, then in veins, and finally in the pulmonary veins leading to the heart viii. The pulmonary veins empty into the left atrium, which fills the left ventricle c. The blood vessels that carry blood from the left side of the heart to the right side is called systemiccirculation d. The second half of the circulation is called pulmonary circulation e. Since there are no openings for the blood to leave the vessels, the entire system is said to be a closed circulatory system f. The heart is a large muscle, and unlike skeletal muscle, is not attached to bone g. Systole occurs when the ventricles contract, diastole occurs during relaxation h. The blood os propelled by the hydrostatic pressure created by the contractionof the heart i. The rate of contractionsis controlled by the autonomicnervous system,but the autonomicnervous system DOES NOT initiate the contractions i. The heart contracts automatically,paced by a group of specialized cardiac muscle cells called the sinoatrial node (SA node) located in the right atrium i. ii. The SA node is auto rhythmic (contractsby itself at regular intervals), spreading its contractionsto the surrounding cardiac muscles via electrical synapses made from gap junctions 1) The pace of the SA node is faster than normal heartbeats, but the parasympatheticvagus nerve innervates the SA node, slowing the contractions iii. The action potential generated by the SA node spreads around both atria causing them to contract, and, at the same time, spreads to the atrioventricular node (AV node) located in the interatrial septa (the wall of the cardiac muscle between the atria) 1) iv. The AV node is slower to contract, creating a delay which allows the atria to finish their contraction and to squeeze their contents into the ventricles before the ventricles begin to contract v. From the AV node, the action potential moves down the conductive fibers called the bundle of HIS 1) The bundle of his is located in the wall separating the ventricles 2) vi. The action potential branches out through the ventricular walls via conductivefibers called Purkinje fibers 1) The Purkinje fibers in the ventricles allow for moreunified, and stronger 1) The Purkinje fibers in the ventricles allow for moreunified, and stronger contractions 2) j. Arteries are elastic, and stretch as they fill with blood k. When the ventricles finish their contraction, the stretched arteries recoil, keeping the blood moving more smoothly i. Arteries are wrapped in smoothmuscle that is typically innervated by the sympathetic nervous system l. Epinephrine is a powerful vasoconstrictorcausing arteries to narrow m. Larger arteries have less smoothmuscle per volume and are less affected by sympathetic innervation 2. Capillaries are microscopicblood vessels a. b. Capillary walls are only one cell thick, and the diameter of a capillary is roughly equal to that of a single red blood cell c. Nutrient and gas exchange with any tissue other than vascular tissue takes places only across capillary walls d. There are four methods for materials to cross capillary walls i. Pinocytosis ii. Diffusion or transport through capillary cell membrane iii. Movementthrough pores in the cells called fenestrations iv. Movementthrough the space between the cells e. Capillaries are found close to all cells of the body f. As blood flows into a capillary, hydrostatic pressure is greater than osmoticpressure, and the net fluid flow is out of the capillary, and into the interstitium i. Hydrostatic pressure is the lateral pressure componentof blood flow that pushes fluid out through the capillary pores 1) Decreasesalong the length of the capillary as energy is lost to friction a) Higher at the arterial end vs. the venous end ii. Osmoticpressure is determined by solute concentrationof a compartment 1) The main solute difference between plasma and interstitial fluid is due to proteins, which are present in the plasma but mostly absent from interstitial fluid 2) The osmoticpressure created by the presence of these proteins is known as 2) The osmoticpressure created by the presence of these proteins is known as colloid osmoticpressure, also called oncotic pressure a) Anything that can flow through the capillary wall, which as ions and other solutes do not contribute to the osmotic gradient 3) Colloid osmoticpressure is higher in the plasma than in the interstitial fluid a) Therefore,the osmoticgradient favors water movementby osmosisfrom the interstitial fluid into the plasma iii. Net fluid flow across the capillary is determined by the difference between the hydrostatic pressure gradient favoring filtration and the colloid osmoticpressure gradient favoring absorption iv. v. About 10% of incoming fluid is lost to the lymph system 3. Veins, venules and venus sinuses in the systemiccirculation hold about 64% of the blood in a body at rest, and act as a reservoir for blood a. Cross sectional area of the veins is about four times that of the arteries b. Blood moves speed is inverselyproportional to cross sectional area c. 4. Although Bernoulli's equation tells us that pressure is inversely related to cross sectional area, this is not the case in blood vessels a. Blood is not an ideal flow b. b. 5. The respiratory system a. Providesa path for gas exchange between the external environmentand the blood b. As air enters through the nose, movesthe pharynx, larynx, trachea, bronchi, bronchioles, and into the alveoli where oxygen is exchanged for CO2 with the blood c. We breathe when the medulla oblongata signals the diaphragm to contract i. When relaxed, the diaphragm is dome shaped ii. It flattens upon contraction,expanding the chest cavity and creating negative gauge pressure iii. Intercostal muscles (rib muscles) also help to expand the chest cavity iv. Atmospheric pressure forces air into the lungs v. Upon relaxation of the diaphragm, the chest cavity shrinks and the elasticity of the lungs along with the increased pressure in the chest cavity forces air of the body vi. d. The nasal cavity is the space inside the nose i. It filters,moistens, and warms incoming air ii. Coarse hair at the front of the cavity traps large dust particles iii. Mucus secreted by goblet cells traps smaller dust particles and moistens the air iv. Capillaries within the nasal cavity warm the air v. Cilia movesthe mucus and dust back toward the pharynx, so that it may be removed by spitting or swallowing vi. e. The pharynx (throat) functions as a passageway for food and air f. The larynx is the voice box i. It sits behind the epiglottis, which is a piece of cartilage that prevents food from entering the trachea during swallowing ii. The larynx contains the vocal cords iii. iv. g. The trachea, or windpipe, lies in front of the esophagus i. Like the nasal cavity, the mucus and cilia in the trachea collect dust and usher it toward the pharynx ii. Before entering the lungs, the trachea splits into the right and left bronchi iii. Each bronchus branches many more times to become tiny alveoli iv. From the alveolus,oxygen diffuses into a capillary where it is picked up by red blood cells in exchange for CO2 h. Chemistry of Gas Exchange i. Normal alveolar PO2 is about 100mmHG ii. The PO2 of venous blood arriving at the lungs is about 40mmhg iii. Oxygen therefor movesdown its partial pressure gradient from the alveoli into the iii. Oxygen therefor movesdown its partial pressure gradient from the alveoli into the capillaries iv. v. 98% of the oxygen in the blood binds rapidly and reversibly to hemoglobin forming oxyhemoglobin 1) Each of the four subunits houses an iron heme group 2) 3) The central iron atom of each heme group can bind reversibly with one oxygen molecule 4) Because there are four iron atoms per hemoglobin, each hemoglobin can bind four oxygen molecules vi. As O2 pressure increases, the O2 saturation of hemoglobin increases sigmoidally 1) Once hemoglobin is saturated, small fluctuations in oxygen pressure have little effect 2) However,the oxygen saturation of hemoglobin also depends on CO2 pressure, pH and temperature. 3) The oxygen dissociationcurve is shifted to the right with increases of all three 4) a) A shift to the right indicates a lowering of hemoglobins affinity for oxygen 5) The shift due to pH is called the Bohr Shift i. As the blood movesthrough the systemic capillaries, oxygen diffuses to the tissues and CO2 diffuses to the blood j. CO2 can be carried in three forms i. In physical solution ii. As bicarbonate ion iii. In carbamino compounds (CO2 plus bicarbonate k. Ten times as much is carried as bicarbonate than as either of the other forms l. The bicarbonate ion formationis governed by the enzyme carbonic anhydrase i. m. Because carbonic anhydrase is inside the red blood cells and not in the plasma, when CO2 is absorbed in the lungs (as CO2), bicarbonate ion diffuses into the red blood cell (le chatlier) i. To balance the electrostatic forces, chlorine moves out of the cell in a phenomenon called the chloride shift ii. n. Co2 has a dissociation curve as well i. The greater the pressure of CO2, the greater the blood content of CO2 ii. However,when hemoglobin becomes saturated with oxygen, its capacity to hol
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