Chapter 9 - The Cardiovascular System Flashcards
Arteries
Vessels that carry blood away from the heart. These vessels are muscular and do not have valves.
Mnemonic: arteries = away
Arterioles
Small diameter blood vessels in the microcirculation that extend and branch out from an artery and lead to capillaries.
Capillaries
Blood vessels composed of a single layer of endothelial cells, facilitating exchange between the blood and interstitial fluid.
Veins
Vessels that carry blood toward the heart. These vessels are thin-walled and have valves to prevent back flow.
Know the diagram and order for the somatic circulatory system
How does the blood get to and from capillaries, and then back to the heart?
Aorta → Arteries → Arterioles → Capillaries → Venules → Veins → SVC/IVC → Right Atrium (and so on)
Portal system
Circulatory routes in which blood travels through two capillary beds before returning to the heart. Examples include the hepatic portal system, which connects the vasculatures of the digestive tract and the liver, and the hypophyseal portal system, which connects the vasculatures of the hypothalamus and the pituitary gland. Some non-mammals have a renal portal system.
Provide a brief mechanical analogy for the heart
The heart consists of two pumps connected in series.
- The right heart (right pump) accepts deoxygenated blood returning from the body and moves it to the lungs for oxygenation (pulmonary circulation).
- The left heart (left pump) receives oxygenated blood from the lungs and forces it out to the body (systemic circulation).
What are the two chambers of the each side of the heart called? What are the functions of each?
Each side of the heart consists of an atrium and a ventricle.
- Atria - thin walled, can be thought of as waiting rooms or lobbies for blood that has just entered the heart
- **Ventricles **- more muscular, do the actual work of pumping the blood out of the heart (to the body or the lungs)
Define: Atria
The two thin-walled upper chambers of the heart. The right atrium receives deoxygenated blood from the vena cava, while the right atrium receives oxygenated blood from teh pulmonary vein.
Define: Ventricles
The muscular lower chambers of the heart. The right ventricle pumps deoxygenated blood to the lungs through the pulmonary artery (pulmonary circulation), while the left ventricle pumps oxygenated blood throughout the body (systemic circulation)
Inferior Vena Cava (IVC)
A large vein that returns deoxygenated blood from the lower body and the extremities to the right atrium of the heart.
Superior Vena Cava (SVC)
A large vein that returns deoxygenated blood from the head and neck regions to the right atrium of the heart.
Pulmonary artery
Blood vessel that connect the heart right to the lungs. The pulmonary artery carries deoxygenated blood from the right ventricle into the lung capillaries, where it absorbs oxygen.
Pulmonary Veins
Large blood vessels that receive oxygenated blood from the lungs and drain into the left atrium of the heart. There are four pulmonary veins, two from each lung. The pulmonary veins are among the few veins that carry oxygenated blood.
Pulmonary Circulation
Second half of circulation process: Right Ventricle → Pulmonary Arteries → Lungs → Pulmonary Veins → Left Atrium → Left Ventricle
Aorta
The largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it bifurcates into two smaller arteries (the common iliac arteries). The aorta distributes oxygenated blood to all parts of the body through the systemic circulation.
Systemic Circulation
First half of circulation process: Left Ventricle → Aorta → Body → SVC/IVC → Right Atrium
Tricuspid Valve
A valve located between the right atrium and the right ventricle. The valve consists of three cusps that prevents backflow of blood from the right ventricle to the right atrium.
Mitral (Bicuspid) Valve
A valve located between the left atrium and the left ventricle. The valve consists of two cusps and prevents backflow of blood from the left ventricle to the left atrium.
Atrioventriclar Valves
Valves located between the atria and ventricles. These are the tricuspid valve in the right heart and the mitral (bicuspid) valve in the left heart.
Mnemonic: LAB RAT
(Left Atrium Bicuspid)
(Right Atrium Tricuspid)
Semilunar Valves
Valves that prevent backflow of blood from the arteries back into the ventricles. The pulmonic valve in the right heart prevents backflow from the pulmonary artery, while the aortic valve in the left heart prevents backflow from the aorta.
Blood flow in the body
Body → IVC/SVC → Right Atrium → Right Ventricle → Pulmonary Artery → Lungs (oxygenation) → Pulmonary Veins → Left Atrium → Left Ventricle → Aorta → Body → repeat
Diagram of heart anatomy and blood flow
Compare the size of the right heart and left heart
Because the right heart pumps blood only to the lungs, which are nearby and whose vasculature offers lower resistance, it can operate at lower pressures. Consequently the walls of the right heart are not as thick as those of the left. In the left heart, which is responsible for systemic circulation, the walls are thicker and more muscular because they must generate stronger contractions to maintain higher pressures to move blood over a longer distance and against higher resistance.
Systole
The stage of the heart cycle in which the heart muscle contracts and pumps blood. During this stage the ventricles contract and the atrioventricular valves close; blood is pumped out of the heart.
Diastole
The stage of the heart cycle in which the heart muscle relaxes and collects blood into its four chambers. The semilunar valves close to prevent backflow of blood from the pulmonary arteries and aorta into the heart.
Compare the pressures in the heart during the different stages of contraction
Contraction of the ventricular muscles generates the higher pressures of systole, while their relaxation during diastole cases the pressure to decrease.
Cardiac Output (plus equation)
The total volume of blood the left ventricle pumps into circulation per minute. The cardiac output can be increased by increasing either the heart rate or the stroke volume. Cardiac output is the product of heart rate and stroke volume:
(Cardiac output) = (heart rate) x (stroke volume)
(volume/minute) = (beats/minute) x (blood volume/beat)
What controls the rate of the heart’s contractions?
Autonomic nervous system
What initiates the heart’s contractions?
Cardiac muscle cells located in sinoatrial node (SA node), in right atrium
Sinoatrial (SA) node
Group of special cardiac cells located in the right atrium. Causes atria to contract.
Atrioventricular (AV) node
Located in the wall of muscle between the atria. Causes ventricles to contract (after atria have finished pumping contents into ventricles).
bundle of His
Conductive fibers in heart. Located in wall separating ventricles. Action potential spreads here after AV node.
Purkinje fibers
Conductive fibers in heart. Located in ventricular walls. Allow for more unified, stronger contraction of the heart.
Electrical signaling pathways of the heart (diagram)
Path of action potential in the heart
SA node ⇒ (atrial contraction) → AV node ⇒ (signal delay, ventricles fill) → bundle of His → Purkinje fibers ⇒ (ventricular contraction, systole)
How does Sinoatrial (SA) node cause heart contractions?
SA node is autorhythmic (contracts by itself at regular intervals). Impulse initiation begins at the SA node. Depolarization spreads from SA node causing both atria to contract simultaneously and blood is pumped into ventricles. Action potential spreads to atrioventricular node (AV node) and signal is delayed until ventricles are filled. From AV node, potential moves down bundle of HIS (conductive fibers) and splits in two (left and right). The signal subsequently branches out through Purkinje fibers to the ventricular walls. Depolarization at the neuromuscular junction causes the ventricles to contract, and blood is forced out of the heart.
What part of the nervous system influences cardiac contractions?
The autonomic division, which consists of the parasympathetic (“rest and digest”) and sympathetic (“fight or flight”) branches, controls the heart.
Parasympathetic - slows heart rate via the vagus nerve (utilyzes vagusstoff).
Sympathetic - utilyzes neurotransmitters (norepinephrin) to speed up heart rate
What nerve innervates the SA node, and what does it do?
The parasympathetic vagus nerve innervates the SA node. Slows heart contractions and increases digestive activity.
What phenomenon results from cardiac muscle’s abiiity to exhibit myogenic activity?
While neural signals from the autonomic nervous system can modulate the rate at which the heart beats, since cardiac muscle demonstrates myogenic activity, the heart will continue to function even without input from the nervous system.
Arteries: physiology
Elastic; stretch as they fill with blood. Wrapped in smooth muscle (innervated by sympathetic nervous system). Larger arteries have less smooth muscle than medium ones, so are less affected by innervation. Medium arteries can constrict with sympathetic stimulation to reroute blood.
Arterioles: physiology
Smaller than arteries. Also wrapped by smooth muscle (innervated by sympathetic nervous system). Constriction/dilation can regulate blood pressure AND reroute blood.
Capillaries: physiology
Blood vessels with a single endothelial cell layer; nutrient/gas exchange (except vascular tissue) takes place only across capillary walls. Capillaries are usually so small that blood cells must traverse them single-file.
Veins: physiology
Thin-walled and inelastic; capacitive and stretch out easily as they fill with blood, but do not recoil. Wrapped in smooth muscle, but with a thinner (or absent) layer compared to arteries. Larger vains have one-way valves to prevent backflow. Most large veins are surrounded by skeletal muscle, which squeezes the vains as muscles contract, forcing the blood forward.
How do molecules cross capillary walls?
- Pinocytosis (endocytosis of small molecules)
- Diffusion/transport through capillary cell membrane
- Movement through pores (fenestrations)
- Movement through space between cells
Capillaries: how does fluid move in/out (forces involved)?
Arteriole end: hydrostatic pressure greater than osmotic pressure, so net flow is OUT of the capillary
Venule end: Hydrostatic pressure drops, osmotic pressure (which is pretty constant) overcomes hydrostatic pressure and net flow is INTO capillary.
Net result: 10% loss of fluid to interstitium.
Which blood vessel type contains greates volume of blood?
Veins (venules, etc.); they act as a blood reservoir.
Where does blood move slowest (blood vessel type)?
Capillaries (blood flow inverseley proportional to cross-sectional area).
Blood pressure
A measure of the force per unit area that is exerted on the wall of blood vessels. Measured by a sphygmomanometer as the gauge pressure (that above atmospheric pressure, 760 mmHg). Expressed as a ratio of systolic (ventricular contraction) to diastolic (ventricular relaxation) pressures.
In the bloodstream, what two pressure gradients are essential for maintaining a proper balance of fluid volume and solute concentration in the interstitium?
- **Hydrostatic pressure **- force per unit area that the blood exerts against the vessel walls. Hydrostatic pressure forces fluid (and nutrients) out of the bloodstream and into the tissues.
- **Oncotic (osmotic) pressure **- the osmotic pressure generated by the concentration of particles (mostly proteins) in the plasma compartment. Unlike hydrostatic pressure, oncotic/osmotic pressure exerts an inward force and draws fluid, nutrients, and wastes out of the tissue.
Where is blood pressure highest and lowest (blood vessel type)?
Blood pressure is highest in the arteries and lowest in the veins. Although osmotic pressure is constant, hydrostatic pressure drops significantly as blood moves through the capillaries.
Blood pressure: high → low (trend) by vessel type
Given the low blood pressure of the veins, how is blood transported back to the heart?
A valve system in the veins prevents backflow of blood, and skeletal muscle contraction (from general movement) squeezes blood forward into the heart.
Coronary circulation
The circulation of blood in the blood vessels of the heart muscle (myocardium).
Coronary arteries
Blood vessels that supply heart muscle (myocardium) with oxygenated blood. Originate from the aorta. Blockage of the coronary arteries can lead to a heart attack.
Coronary veins
Blood vessels that transport deoxygenated blood from the heart muscles (myocardium). It delivers deoxygenated blood to the right atrium, as do the superior and inferior vena cava.
Bohr effect
Increasing cncentration of H+ and CO2 reduces hemoglobin’s affinity for oxygen, allowing for the transfer of oxygen to cells that require it most.
The Hb-O2 dissociation curve is not static – it can shift to the left or right depending on circumstances. How is the binding curve of hemoglobin affected by environemental conditions
Several conditions produce a rightward shift, meaning that for a given partial pressure of O2, less O2 will be bound to Hb due to decreased affinity. These conditions include an increase in the partial pressure of CO2, a decrease in pH, and an increase in temperature. These conditions often correspond to periods of increased metabolic rate (lactic acid buildup, increased CO2 generation, increased temperature) and signal a need for more oxygen.
Carbonic anhydrase
Enzyme that catalyzes the conversion of carbonic acid to carbon dioxide and water, as well as the formation of carbonic acid from carbon dioxide and water. The reaction proceeds according to the following equation:
H2CO3 ⇔ H2O + CO2
Blood: function
Transports nutrients, waste products, hormones, heat. Protects from injury and invasion. Contains matrix and cells (is connective tissue).
Blood: composition
Plasma - 55% of blood volume, liquid portion of blood that is an aquous mixture of nutrients, salts, respiratory gases, hormones, and blood proteins (albumin, apolipoproteins, antibodies, etc.).
Cells - 45% of blood volume, consists primarily of erythrocytes, leukocytes, and platelets. All blood cells originate from hematopoetic stem cells in the (red) bone marrow.
Albumin
Transport fatty acids and steroids; regulate blood osmotic pressure.
Where are most plasma proteins formed?
Liver
Where are gamma globulins (which make up antibodies) formed?
Lymph tissue
Erythrocytes
The oxygen carrying component of blood (red blood cells). These anaerobic cells, which lack organelles, are packed with hemoglobin and have a characteristic biconcave, disclike shape that facilitates gas exchange and mobility within blood vessels.
Hemoglobin
A protein found in erythrocytes made up of four polypeptide chains, each containing a heme group. Hemoglobin is responsible for transporting oxygen from the alveoli to the cells. Hemoglobin exhibits cooperativity: one O₂ binds (or releases), others do so more easily. This results in an S-shaped binding curve and is an allosteric effect.
Leukocytes
White blood cells; the component of blood involved in cell defense and immunity. Comprise both the active and innate immune systems. Basophils, neutrophils, and eosinophils are granular leukocytes; monocytes, megakaryocytes, and lymphocytes are agranular leukocytes.
Lymphatic system
A system of vessels and lymph nodes that collect interstitial fluids and return them to the circulatory system, thereby maintaining a plasma protein and fluid balance. The lymphatic system is also involved in lipid absorption and lymphocyte maturation.
Lymph nodes
Swellings along the lymph vesses where lymph is filtered by leukocytes to remove antigens.
Granular leukocytes
Named because cytoplasmic granules that are visible by light microscopy, these consist of neutrophils, eosinophils, basophils. Granular leukocytes mount nonspecific, innate immune responses such as inflammatory reactions, allergies, pus formation, and destruction of bacteria and parasites.
Agranular leukocytes
Named because they do not contain cytoplasmic granules, these consist of monocytes and lymphocytes.
- Monocytes mature into macrophages, which phagocytose foreign matter such as bacteria.
- Lymphocytes are important in specific immune responses against viruses and bacteria. Lymphocytes mature into B- and T-cells.
B-Cells
Lymphocytes that mature in the spleen or lymph nodes. B-cells are responsible for antibody generation.
T-Cells
Lymphocytes that mature in the thymus, T-cells kill infected cells and activate others. There are four types of T-cell: helper, memory, suppressor, and killer T cells.
Know the diagram for blood cell lineage
Active immunity
Immunity resulting from the production of antibodies during a previous infection or a vaccination.
Primary response
The initial response to a specific antigen. During primary response, T and B lymphocytes are activated adn specific antibodies and memory cells to the antigen are produced.
Secondary response
Subsequent infections by antigens trigger more immediate response by the memory cells produced during primary response
Passive immunity
A short-lived immunity resulting from the transfer of antibodies into an individual who does not produce those antibodies
Humoral immunity
The synthesis of specific antibodies by activated B-cells in response to an antigen. These antibodies bind to the antigen and either clump together to become insoluble or attract other cells that engulf them.
Inflammation
First reaction to tissue injury / infection. Blood vessel dilation, capillary permeability, swelling, migration of granulocytes and macrophages. Purpose: sequester affected tissue and keep infection from spreading.
Immunoglobulins
A protein antibody produced in response to a specific foreign substance that recognizes and binds to that specific antigen and triggers an immune response.
Blood antigens
Proteins found on the erythrocyte cell surface. Three antigens are used to differentiate blood: A, B, and Rh. If a host organism is transfused with erythrocytes containing antigens that the host does not have, an immune response will be triggered, such as in the case of erythroblastosis fetalis.
What are the two major blood type antigen families?
- ABO group - based on the existence of three alleles for a cell surface protein that defines blood type. A and B alleles are codominant. O is recessive and does not code for a recognized antigen. Universal blood donor is Type O, while universal blood acceptor is Type AB.
- Rh factor - one predominant variant whose presence or absence defines blood type and is indicated by a superscript on the ABO blood type (e.g. O+, AB-). The presence of the Rh factor is a dominant condition.
Platelets
Pieces of membrane-bound cytoplasm from megakaryocytes. Like tiny cells w/o nucleus. Make prostaaglandins, some enzymes. Membrane d/n adhere to healthy endothelium, but DOES adhere to injured endothelium. Coagulation of injured tissue involves platelets, and many other factors including prothrombin and fibrin (plasma proteins).
Thromboplastin
Enzyme released by platelets in response to exposed collagen. Thromboplastin converts prothrombin into thrombin. Its cofactors are calcium and vitamin K.
Fibrin
Protein responsible for blood clotting. Fibrin is the processed, active form of the inactive zymogen fibrinogen. Fibrinogen is converted to fibrin by thrombin.
