Blood Circulation PDF

Blood circulation You can resize the slide images, delete the ones that you don’t need and generally reorganize them to suit your needs. Remember that all GoogleSlides and GoogleDocs in this course have been set as “View Only” so you have to sign in with any Google acco...

Blood circulation You can resize the slide images, delete the ones that you don’t need and generally reorganize them to suit your needs. Remember that all GoogleSlides and GoogleDocs in this course have been set as “View Only” so you have to sign in with any Google account, go to “File” at the top left corner, and select “Download” or “Make a copy” to make your own notes. ○ Do NOT select “Request Edit Access” as you will not get a response. Treat the recording similar to an in-person lecture, ie watch the recording without pausing and rewinding to capture every single word: a 40 minute recording should take you 40 minutes to go through, not 4 hours. Dr. Elita Partosoedarso Recording can be found here. Blood circulation Systemic blood vessels Pathway Fetal circulation Unique features Cardiac Physiology Terms Definitions and interrelationship Control of CV function Neural vs hormonal 2  Systemic Arteries: the aorta and its branches The major systemic arteries deliver oxygenated blood throughout the body Blood from the LV enters the aorta which then branches off to smaller and smaller arteries → arterioles → capillaries 1.1 Ascending aorta: Initial portion, rising superiorly from LV 2. Aortic arch: connects ascending aorta to descending aorta 3.23 Descending aorta: continues inferiorly past aortic arch 4.4 Thoracic aorta: Portion of descending aorta superior to 2 aortic hiatus 1 3 5.5 Abdominal aorta: Portion of descending aorta inferior to aortic hiatus 6 6. Aortic hiatus: opening in the diaphragm that the 4 descending aorta passes through 5 6 3  4 Arterial circle or circle of Willis 2 1 5 3 6 The internal carotid artery continues through the carotid canal of the temporal bone and enters the base of the brain through the carotid foramen where it gives rise to several branches 11. Anterior cerebral artery: Supplies blood to frontal lobe of cerebrum 2. 2 Middle cerebral artery: Supplies blood to temporal and parietal lobes: most common sites of CVAs 3 3. Ophthalmic artery: Supplies blood to the eyes 4 4. Anterior communicating artery: anastomosis formed from right and left anterior cerebral arteries 5 5. Posterior communicating artery: posterior portion which branches from the posterior cerebral artery 6 6. Basilar artery: anastomosis formed from two vertebral arteries and sends branches to cerebellum and brain stem  Systemic Veins: vena cavae and its branches Blood leaves the capillaries to enter venules and are collected into increasing larger veins before being deposited into the RA Many of the main arteries have corresponding veins that bear the same name and are located alongside or near the arteries. Dural sinuses in the cranial cavity collect blood from the brain Superior vena cava collects venous blood from above the heart (head, neck, upper extremities, and thoracic cavity) to return to the RA Inferior vena cava collects venous blood from below the heart (lower extremities and abdomen) to return to the RA Coronary sinus collects venous blood from the heart to return to the RA Deep veins are in the deep parts of the body Superficial veins lie near the surface (below the skin) 5  Fetal circulation is different from circulation after birth because fetal blood secures oxygen and nutrients from the maternal blood at the placenta instead of from the fetal lungs and digestive organs. additional unique features allow most blood to bypass the lungs (& pulmonary circulation) and to deliver nutrients and wastes to and from maternal circulation. Fetal Circulation The placenta is an organ that permits the exchange of blood gases, nutrients, and wastes between the fetal blood and the maternal blood. Note that the maternal and fetal blood supply is completely separated within the placenta by a membranous barrier 1 1 3 2 2 3 6 Fetal Shunts- alternate paths for blood flow in fetal circulation In the fetus, pressure in the RA and pulmonary artery is higher than that in the LA and aorta, respectively due to the vasoconstriction within Unique features exist in the fetal circulation as the respiratory and the fetal pulmonary circulation digestive systems are not fully functional 1.1 Placenta: Site of gas, nutrient & waste exchange between maternal & fetal blood 2.2 Umbilical vein: Delivers nutrient rich oxygenated fetal blood from placenta directly to fetal heart with some blood going to the liver. 3.3 Umbilical arteries: return wastes and deoxygenated fetal blood to placenta 4.4 Ductus venosus: Extension of umbilical vein which drains into inferior vena cava, allowing most blood to bypass the liver 5.5 Foramen ovale: Opening in the septum between right and left atria to allow right-to-left shunt: diverts most of blood in pulmonary circuit to systemic circuit 6.6 Ductus arteriosus: Connects pulmonary trunk with aortic arch to allow right-to-left shunt: diverts most of blood in pulmonary circuit to systemic circuit 7  Changes in Circulation at Birth Immediately after birth when the lungs start working the unique features of the fetal circulation are no longer needed and so stop functioning The pulmonary blood vessels stop being constricted so that more blood can flow through it and pressure in the pulmonary circulation drops below that of the systemic circulation The inferior venae cavae stops carrying a mixture of oxygenated and deoxygenated blood and carried only deoxygenated blood to the heart. Changes that occur shortly after birth 1.2 Placenta is expelled as “afterbirth” along with part of the umbilical vessels 2.3 Umbilical vein becomes the round ligament of liver 3.4 Umbilical arteries become the umbilical ligaments 4.5 Foramen ovale becomes the fossa ovalis 5.6 Ductus venosus becomes the ligamentum venosum of the liver 6. Ductus arteriosus becomes the ligamentum arteriosum  1. Heart rate (HR): Number of contractions per Cardiac Physiology Terms minute (beats per minute, bpm). 2. Stroke volume (SV): Amount of blood pumped by each ventricle in a contraction 3. Cardiac output (CO): Amount of blood pumped by each ventricle in one minute 4. End diastolic volume (EDV): Amount of blood in a ventricle at the start of ventricular contraction 5. End systolic volume (ESV): Amount of blood in a ventricle at the end of ventricular contraction 6. Ejection fraction (EF): percentage of blood Normal values ejected from the heart with each contraction HR: 75 bpm at rest (range 60-100bpm), 7. Cardiac reserve: difference between maximum 150bpm at exercise and resting CO, residual capacity of the heart to SV: 70-80 ml at rest (range 55-100ml), pump blood 130ml at exercise CO: 75 bpm x 0.070L = 5.25 L/min at rest, CO = HR × SV 150 bpm x 0.130L = 19.5 L/min at exercise SV = EDV – ESV EDV: 130ml at rest EF = SV ÷ EDV ESV: 50-60ml at rest EF: 75/130ml= 58% (55-70%) at rest Variables in Determining Stroke Volume 1. Preload: stretch on the ventricles prior to contraction, proportional to EDV. dependent on filling time (duration of ventricular diastole when ventricular filling occurs) and is reduced with increased HR 2. Contractility: force or strength of the contraction, proportional to SV and inversely proportional to ESV 3. Afterload: force generated by the ventricles to pump blood against resistance in blood vessels, proportional to blood pressure in blood vessels Positive inotropic factors increase contractility (& SV), eg NE Frank-Starling mechanism: within Negative inotropic factors decrease contractility (& SV), eg ACh physiological limits, the force of cardiac contraction is directly proportional to the initial length of the muscle fiber, ie an increased preload will increase contractility. 10  Exercise and Maximum Cardiac Output Location Distribution at rest Veins: 64% 1. CO = HR × SV Systemic 84% Arteries: 13% circulation Capillaries: 7% 75 bpm x 0.070L = 5.25 L/min (total blood volume) at rest 150 bpm x 0.130L = 19.5 L/min during exercise (6-7 times increase!) Pulmonary Veins: 4% 9% Arteries: 2% HRs vary considerably, with age, exercise and fitness levels: gradually decreases until circulation Capillaries: 3% young adulthood and then gradually increases again with age. Heart 7% As one ages, the ability to generate maximum HR decreases= 220 – age (years) Mild Maximal Resting exercise exercise Organ (mL/min) (mL/min) (mL/min) Skeletal muscle 1200 4500 12,500 Heart 250 350 750 Brain 750 750 750 Integument 500 1500 1900 Kidney 1100 900 600 Digestive tract 1400 1100 600 Others: liver, 600 400 400 spleen, etc Total 5800 9500 17,500 11 Factors Affecting Cardiac Output 12  Inputs Outputs 1. Baroreceptors: Stretch receptors which 1. Control of heart rate (HR) monitor volume of blood in blood vessels ○ 2 paired cardiovascular centers in the The cardiovascular system 2. Chemoreceptors: Monitor concentration of brainstem (medullla oblongata) project blood CO2↔H+/pH, O2, lactic acid to SA and AV nodes, atria and ventricles 3. Proprioceptors: Monitor level of physical activity via position of skeletal muscles, 2. Control of blood pressure (BP) 4. Limbic system: Monitor emotional state, ○ Autoregulation especially for stress, anxiety, excitement ○ Neural control ○ Hormonal control  Control of the heart (and heart rate) 1 Resting HR is typically 80–100 beats per minute (bpm) 1.1 Parasympathetic NS decrease HR via cardioinhibitory centers ○ Stimulation slows HR via vagus nerve (CN X) ○ Dominant at rest: Most innervation travel to SA node in atria ○ Mechanism: ACh release → ligand gated K+ channels open → K+ efflux increase → prolong repolarization → increase time between contractions 2 2.2 Sympathetic NS increases HR via cardioaccelerator regions ○ Stimulation increases HR and strength of ventricular contractility ○ Mechanism: NE release → ligand gated Na+ and Ca2+ channels open → Na+ and Ca2+ influx increases → shortens repolarization → decrease time between contractions 2 1  Control of blood vessels (and blood pressure) 1.1 Autoregulation regulates local blood flow within tissue beds 2. Neural mechanisms are faster, short-lasting responses 3. Endocrine mechanisms are slower, longer-lasting responses 1  Control of blood vessels (and blood pressure) 1. Autoregulation regulates local blood flow within tissue beds 2.2 Neural mechanisms are faster, short-lasting responses 3.3 Endocrine mechanisms are slower, longer-lasting responses 2 3  Reflex Responses to control blood pressure Cardiac output (CO) ↓ Stimulus 1. The reverse mechanisms occurs when CO ↑ so that homeostasis is restored 2. When hemorrhage occurs, endocrine Chemoreceptors detect Baroreceptors mechanisms are activated as the severe blood + ↓O2, ↑CO2 (↑H &↓pH) detect ↓ stretch Sensor loss (CO ↓ ↓ ↓ ↓) cannot be reversed by this reflex alone ○ ↑ADH to ↑water retention in kidney ○ ↑EPO to replace RBC Cardiac inhibitory center output ↓ ○ RAAS activation to ↑water and Na+ retention Cardiac accelerator center output ↑ Integrator Vasomotor center output ↑ in kidney ↑ HR, SV and CO Response ↑ Vasoconstriction →↑BP starts Blood circulation increase Homeostasis Homeostasis is restored restored Interaction of the Circulatory System with Other Body Systems