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The circulatory system - Part 2 Let's fill in the details! 1) A few more details about the heart... Septum The wall dividing the heart in two, separating the right atrium and ventricle from the left atrium and ventricle Heart valves There are valves in the heart that prevent blood from flowing backwards There are 2 atrioventricular (AV) valves - these separate the atria and ventricles -One in between the left atrium and left ventricle, and the other in between the right atrium and right ventricle -There are 2 semilunar valves - these separate the ventricles and the arteries -One in between the left ventricle and the aorta, the other in between the right ventricle and the pulmonary artery Bicuspid valve = left AV valve Tricuspid valve = right AV valve Heart valves The lubb dubb sound of your heart beat is caused by valves closing Lubb - AV valve closes Dubb - semilunar valve closes Other sounds? Heart murmur -when blood in the heart flows back from a ventricle to an atrium -caused by AV valves not closing properly Some dark humor… Note: Mr. Graff does not support domestic violence Coronary arteries The heart has special coronary arteries. The heart, just like every other organ, requires oxygen. Coronary arteries provide the heart with oxygenated blood. Yes, the heart pumps blood to itself. Tempo of the heart There are special tissues in the heart that set the tempo that the heart beats at -The sinoatrial (SA) node - is the primary pacemaker of the heart. It sends nerve signals to the atrioventricular (AV) node -The AV node sends signals to Purkinje fibres -Purkinje fibres - send nerve impulses throughout heart, so the heart beats synchronously Signals are sent from the brain to the SA node to speed up or slow down the heart Animation: https://en.wikipedia.org/wiki/File:ECG_Principle_fast.gif 2) Blood pressure The beating of the heart can be described in two ways Systole - when the heart contracts, pushing blood out Diastole - when the heart relaxes, allowing the atria to fill with blood Systolic blood pressure - how much pressure the blood is under when the heart contracts Diastolic blood pressure - how much pressure the blood is under when the heart relaxes Normal systolic blood pressure is 120 mmHg, normal diastolic blood pressure is 80 mmHg (written 120/80) Hypertension - high blood pressure, caused by more resistance to the flow of blood Arteries are always under much higher blood pressure than veins 3) A few more details on blood vessels... Arteries Have thick walls to accommodate the high blood pressure they face Arteries expand following a heart contraction (systole) then recoil back Veins Since veins are under very low blood pressure, they rely on skeletal muscles to push the blood back to the heart There are also valves in veins that prevent blood from flowing backwards Diagrams of veins Selectivity Blood cannot be pumped to all areas of the body at once Vasoconstriction - When the body selectively constricts certain blood vessels to encourage blood to flow elsewhere For example, when stressed the blood vessels leading to the kidney, stomach and intestines constrict, so blood is sent to muscles, brain, heart instead Similarly, the body can expand certain blood vessels to encourage the flow of blood Health Problems Atherosclerosis - accumulation of fat deposits on the walls of the artery These fat deposits can get so big it bursts through the artery These fat deposits also narrow the arteries. If coronary arteries have extensive fat deposits, a heart attack can occur Aneurysm - bulge that forms in the wall of a weakened blood vessel (often due to atherosclerosis). Eventually the bulge ruptures. Cells around the bulge don't get blood and therefore die of oxygen starvation 4) Thermoregulation When the body is too hot, the skin starts sweating. This makes the skin colder than the rest of the body. Blood vessels near the skin expand, so more blood goes to the skin. This cools off the blood. When the blood returns to the body, it helps cool off your core Similarly, when the body is cold, blood vessels near skin constrict, limiting blood flow, so blood doesn't lose heat to the environment (so your core stays warm) 5) Lymphatic system -Small amounts of protein leak from capillaries into tissue space -The lymphatic system allows these proteins to be recycled -Lymph - the fluid that the lymphatic system transports -The lymphatic system is a series of open-ended vessels that are similar to veins; muscles push the lymph through the vessels, and various valves prevent backflow -Eventually the lymph rejoins the blood at the subclavian veins