Cardiovascular System Notes PDF

Cardiovascular System Types of Circulation 1. Systemic circulation: Responsible for delivering oxygenated blood from the heart to the rest of the body, and returning deoxygenated blood back to the heart. (Providing body with O2 and nutrients) ○ Oxygenated blood enter L atr...

Cardiovascular System Types of Circulation 1. Systemic circulation: Responsible for delivering oxygenated blood from the heart to the rest of the body, and returning deoxygenated blood back to the heart. (Providing body with O2 and nutrients) ○ Oxygenated blood enter L atrium through pulmonary veins, passes through bicuspid valve, is pumped from the L ventricle to aorta, travels through arteries to body. 2. Pulmonary Circulation: Carries deoxygenated blood from the body to the heart heart to the lungs for oxygenation and returns oxygen-rich blood back to the heart. (Gas exchange needed) ○ Enters heart from superior and inferior vena cava, intro R atrium, enters R ventricle through tricuspid valve, pumped into the pulmonary artery ○ Goes to capillaries the lungs, leads to gas exchange (Co2 for O2, in alveoli), returns back to heart 3. Coronary Circulation: The coronary circulation is the system of blood vessels that supplies blood to the heart muscle (myocardium) itself. ○ Oxygenated blood flows to heart through coronary arteries, branches of aorta that sit behind flaps of aortic valve ○ Delivers O2 through capillary beds in myocardium, deoxygenated blood is returned through the cardiac veins, which drain into the right atrium via the coronary sinus. How body responds to ↑ oxygen demands in muscle during exercise. Changes in Q ↑ in HR and SV, depending on intensity of activity, therefore ↑ Q Incremental Exercise: Untrained ppl level of SV at 40% of Vo2 max, HR and Q can continue to ↑, plateau at Vo2 max Q can ↑ due to higher systolic pressure (blood must pump with more force → higher SV), and lower peripheral resistance (vasodilation in small vessels) Prolonged exercise Cardiovascular drift: SV decreases slightly (sweating) as HR ↑s to maintain Q, higher bode temp leads to dehydration, less plasma volume, blood flow to skin. Less venous return to heart = less SV If below the lactate threshold, steady state is reached in 1- 4 minutes (like VO2) Redistribution of Blood flow: Flow to muscles ↑ from 15-20% of Q at rest→80-85% of Q @ max. exercise Reduced in liver, kidneys, skin, etc: ↑ in brain in heart Why do we call the heart a double pump? The left half pumps blood to the body (systemic circulation), while the right side pumps blood to the lungs (pulmonary circulation) What is Myocardium? Heart muscle tissue, responsible for contractions to pump blood Involuntary, striated, activated by calcium & sliding filament theory Cells (similar to type 1 fibres, aerobic) connected by intercalated discs allowing signals to pass between them for functional syncytium (all contract at once) Myocardial Infarction Heart attack: When blood flow can’t reach some myocardium, they start to be damaged and die from lack of oxygen Fatty plaque builds up in coronary arteries, causing clot that blocks blood flow Severity based on location and # of coronary arteries blocked Path of blood flow in heart Function of valves in the heart Ensure blood only flows in one direction in the heart ○ ( AV) Tricuspid and Bicuspid: Closes to prevent back↑ stroke volume flow between atria and ventricles in ventricular systole ○ (Semilunar) Pulmonary and Aortic: Closes when pumped into pulmonary artery/aorta in ventricular diastole Backwards turbulent flow = leaks that create vibrations = murmurs Phases of Cardiac cycle: Systole: Atria contract (0.1sec) and blood is pumped into ventricles (relaxed) ○ Time – 0.5 seconds ○ Regulated by AV node ○ AV valves close Diastole: Ventricles contract and blood is pumped to the lungs and to systemic circulation (rest of body) ○ Time – 0.3 seconds ○ Regulated by SA node ○ Semilunar valves close Blood Pressure: Systolic: Force/pressure when ventricles contract / heart pumps blood Diastolic: Pressure in vessels when heart is at rest Electrical activity in heart to set up contraction: Conductive Pathway ○ SA node sends signal through R and L atria ○ Both atria contract @ same time, forcing blood to ventricles (diastole) ○ Signal then moves to R atria to the AV node ○ After delay of 0.1sec, AV node transmits signal via Bundle of His (IVS) ○ Travels to Purkinje fibres in myocardium of ventricles. ○ Ventricles contract (systole) to push blood into pulmonary arteries/aorta. Conductive Pathway & Electrocardiogram ○ P wave - when SA node sends signal which spreads through both atria ○ QRS complex - when ventricles contract after signals reaches them through Purkinje fibres (systole) ○ T wave: After contraction, ventricles reset/expand (diastole) Blood Functions ○ Transports oxygen and nutrients ○ Regulates temperature and pH, distributes heat throughout body Components ○ Plasma: transport medium, 55% of blood, mostly water ○ RBC (erythrocyte): made in bone marrow, carry hemoglobin, carry oxygen and nutrients to body, co2 away for gas exchange and remove waste ○ WBC (leukocyte): made in bone marrow, fight off diseasr  ○ Platelets: blood clotting, fragments Methods of Venous Return Skeletal muscle pump: when muscles contract, veins are massaged so pressure in them increases, and blood is pushed back up to heart (one way valve) Thoracic pump: As you breathe, pressure in chest cavity (and veins) is lower than in abdominal cavity, so blood is pushed up to chest cavity (veins). Venoconstriction: When more Q is needed during exercise, nervous system sends signals to veins to constrict, pushes blood to heart Factors that regulate stroke volume LVEDV (preload): According to Frank Starling law, myocardium in L ventricle can stretch to accommodate more blood during diastole. This leads to a more forceful contraction, so SV increases Afterload (aortic pressure against heart): Pressure in L ventricle must > aortic pressure for blood to be pumped. Arterioles dilate during exercise (more blood needed to flow), reduces pressure in aorta and more blood can be pushed. Strength of ventricular contraction: Epinephrine in blood during exercises makes more Ca available to heart → greater contractile ability. Terms in Cardiac output 1. Q (Cardiac Output): The total volume of blood pumped by the heart per minute - HR x SV, decreases with age. 2. HR (Heart Rate): The number of heartbeats per minute, 60–100 bpm (at rest). a. MHR: 220 - age, THR: 50-85% of MHR. 3. SV (Stroke Volume): The amount of blood ejected by the left ventricle per heartbeat. Range: 60–100 mL/beat (at rest). 4. LVESV (Left Ventricular End-Systolic Volume): The volume of blood remaining in the left ventricle after systole. 5. LVEDV (Left Ventricular End-Diastolic Volume): The volume of blood in the left ventricle at the end of diastole. 6. EF (Ejection Fraction): The percentage of the left ventricular end-diastolic volume ejected with each heartbeat. SV / LVEDV Range: 55–70% (normal). Blood flow redistribution during exercise The circulatory system decreases the amount of blood flow to organs like the stomach, intestine, and kidneys so that more blood flow is available to working muscle during exercise. These other organs are not as active during exercise, so the extra blood is given to skeletal muscle, as it would have a much higher demand for oxygen and nutrients. Blood flow increases to skin through vasodilation, as this lets the body lose heat and regulate its temperature. Cardiovascular effects of training Improvements in efficiency at rest and sub-max and maximal exercise ○ ↑ mass and dimensions of the heart (change In myocardium) ○ ↑ ventricular volume: able to hold more blood = ↑SV ○ ↑ thickness of ventricular walls (hypertrophy) ○ ↑ force of contraction of ventricle (because of above two) ○ ↑ stroke volume , ↑ Q ○ ↑ capillaries to deliver blood to myocardium - due to O demand ○ ↑ diameter of coronary arteries ○ ↑ blood volume (plasma, erythrocytes) ○ ↓ HR - increased SV → heart can beat less and have same Q ○ More venous return ○ Bradycardia (HR ≤ 60 bpm) (above)