Cardiovascular System Notes (PDF)

# CARDIOVASCULAR SYSTEM 1 - **BLOOD PRESSURE CHANGES** - Blood comes out of left ventricle from heart through aorta at the highest pressure - As the blood travels through arteries the pressure drops - There is a rise and fall in pressure corresponding to contraction and relaxation of...

# CARDIOVASCULAR SYSTEM 1 - **BLOOD PRESSURE CHANGES** - Blood comes out of left ventricle from heart through aorta at the highest pressure - As the blood travels through arteries the pressure drops - There is a rise and fall in pressure corresponding to contraction and relaxation of the ventricles - The artery walls stretch and recoil, so smooth the pulsing to facilitate the substance exchange - As blood moves into arterioles the pressure drops as they are narrower vessel walls, so more friction with vessel walls - Capillaries have even lower pressure due to narrow cross-sectional area - In the veins, venules and vena cava the pressure is low. The blood pressure here is increased by the massaging effect of muscles - Valves ensure one-way blood flow. - **ARTERIOLES** - Connect arteries to capillaries - Share same features as arteries - Help regulate blood pressure - **OUTER COAT** - Smooth muscle - Endothelium - **CAPILLARIES** - Carry blood from arterioles to organs and body areas - Walls 1 cell thick to facilitate substance exchange - Endothelium - **VENULES** - Connect capillaries to veins - Share same features as veins - Under low blood pressure - Smooth muscle - Endothelium - Valve - **VEINS** - Carry blood to the heart under low pressure - Less elastic fibre and smooth muscle as pressure is lower - Contain valves to prevent backflow of blood - Smooth muscle - Valve - Outer coat # CARDIOVASCULAR SYSTEM 2 - **THE HEART IS THE MAIN ORGAN OF THE SYSTEM** - **MYOGENIC STIMULATION** - Fills the right ventricle then pressure from behind the valve closes it - The blood leaves via the pulmonary artery to the lungs - The blood re-enters the heart from the lungs via the pulmonary vein - The oxygenated blood enters the left atrium - The left atrium contracts forcing the blood through the bicuspid value into the left ventricle - The left ventricle fills, then pressure from behind the valve closes it - The left ventricle contracts forcing blood through the semi-lunar valves - The blood leaves via the aorta to the body - **VALVES** - The valves in the heart ensure blood flow is uni-directional - They stop backflow of blood - **CARDIAC MUSCLE (MYOCARDIUM)** - Septum - **BUNDLES OF HIS** - Purkinje fibres - **SAN** - The SAN initiates a wave of depolarization, causing the Atria to contract. - This is the Atrial Systole and shows as the P wave on an ECG - There is a region of non-conducting tissue between the Atria and ventricles, this stops the wave of depolarization spreading to the ventricles. - **AVN** - There is then a slight delay to ensure the ventricles contract after the Atria - The AVN then stimulated and passes the stimulation along the bundle of His - The bundle of His is a collection of conducting tissues in the septum. - The bundle of His divides into two conducting fibres (Purkinje fibres). They carry the stimulation around the ventricles. - This initiates the depolarization of the ventricles. - This is the Ventricular Systole and shows as the QRS complex on an ECG. # CARDIOVASCULAR SYSTEM 3 - **THE WAVE OF DEPOLARIZATION IS CARRIED TO THE AVN** - **THERE IS THEN A SLIGHT DELAY TO ENSURE THE VENTRICLES CONTRACT AFTER THE ATRIA.** - **THE AVN IS THEN STIMULATED AND PASSES THE STIMULATION ALONG THE BUNDLE OF HIS** - **THE BUNDLE OF HIS IS A COLLECTION OF CONDUCTING TISSUES IN THE SEPTUM** - **THE BUNDLE OF HIS DIVIDES INTO TWO CONDUCTING FIBRES - THE PURKINJE FIBRES - THEY CARRY THE STIMULATION AROUND THE VENTRICLES.** - **THIS INITIATES THE DEPOLARIZATION OF THE VENTRICLES.** - **THIS IS THE VENTRICULAR SYSTOLE AND SHOWS AS THE QRS COMPLEX ON AN ECG.** - **PRESSURE CHANGES IN THE HEART DURING SYSTOLE AND DIASTOLE - THE HEART VALVES OPEN AND CLOSE BASED ON PRESSURE CHANGES.** - **DURING DIASTOLE** - **Bicuspid and tricuspid open** - **Semi-lunar closed** - **DURING SYSTOLE** - **Bicuspid and tricuspid closed** - **Semi-lunar open** - **REGULATION OF HEART RATE** - **Chemoreceptors and Baroreceptors in the Aortic Arch measure blood pH and pressure** - **Excess CO₂ leads to blood being more acidic** - **They send messages to the Cardiac Control Centre in the Medulla oblongata.** - **This sends messages down one of two pathways to the heart** - **Sympathetic pathway - message to SAN to speed up impulses** - **Parasympathetic pathway - message to SAN to slow down impulses** - **Chemoreceptors =** - **Baroreceptors =** # CARDIOVASCULAR SYSTEM 4 - **BLOOD** - **There are 4 main components to blood** - Erythrocytes - Leucocytes - Thrombocytes - Plasma - **ABO BLOOD GROUPING** - **Your blood group depends on the protein antigen molecules on your erythrocytes and the antibodies found in your plasma.** - **Erythrocyte** - Responsible for carrying O₂ by binding it to haemoglobin - **Leucocyte** - Responsible for our immune system and destroying pathogens - **Thrombocyte** - Responsible for blood clotting - **Plasma** - The final part is plasma, this is mostly water and dissolved chemicals - The plasma carries the CO₂ around the body. - **RHESUS BLOOD GROUPING** - **Sometimes people have another antigen present** - **This antigen is the Rhesus (Rh) antigen** - **If the blood contains this antigen, your blood group is Rh positive** - **If the blood does not contain this antigen you are Rh negative** - **BLOOD GROUPING** - **Your blood group is an inherited characteristic** - **There are two blood grouping systems:** - **ABO Blood Grouping** - **Rhesus Blood Grouping**