The cardiovascular system

-the triscupid valve is located between the right atrium and ventricle.

-the biscupid valve is located between the left atrium and ventricle. 

-the aortic semi-lunar (aorta) and the pulmonary (pulmonary artery) semi-lunar valves are located between the arteries and the atriums/ventricles. 

The inter-nodal pathway;

-SAN (generates heartbeat) --> AVN (relays between upper and lower heart) --> bundles of his-->punkinjie fibres (send impulses to ventricles to contract them to send blood round body). This allows hear rate to increase or decrease via the sympathetic and parasympathetic nervous systems. 

Both these nervous systems are coordinated by the cardiac control centre which is stimualted by the chemoreceptors, baroreceptors and proprioceptors. 

-Chemoreceptors detect an increase in carbon dioxide levels. During excersise, detected increase in C02 levels stimulates the sympathetic nervous system.

-Barorecptors detect changes in blood pressure, where it will set a point of blood pressure and an increase or dcrease triggers a response. During excersise a decrease will be signalled to the cardiac control centre and will engage the sympathetic nervous system in order to make sure enough blood is reaching the working muscles. 

-Proprioceptors detect muscle movements, so during excerise an increase in muscle movement is detected and signalled to the cardiac control centre to engage the sympathetic nervous system to increase heart rate to maintain the movements. 

-Hormones can also have an affect, as a release of adrenaline stimulates the SAN and triggers an increase in the speed and force of heart contraction which increase cardiac output (stroke volume x heart rate). 

-Stroke volume is the volume of blood pumped out by the ventricles in each contraction.                  -Heart rate is the number of beats per minute.                                                                                    

--Starling's law; increased venous return leads to greater diastolic filling and streaching of the cardiac muscle creating greater contraction force and increased ejection fraction. 

-CHD (coronary heart disease) is a build up of fatty deposits in the artieries that can decrease blood flow. Sometimes the fat can break off and clog an artery to the heart causing a heart attack. 

-High blood pressure puts an extra strain of the heart and arteries and if left untreated can cause; heart attack, kidney failure and dementia etc. 

-Cholestorol levels- there are two types; LDL that transports cholestrol into the blood and is linked to an increased risk of heart disease. --HDL transports excess cholestrol into the liver to be broken down and can lower the risk of developing heart disease. 

-Stokes; Ischemic strokes are where a blood cot in the brain stops supply and Heamorrhagic strokes are where a weak blood vessel supllying the brain bursts. 

Regular excerise can grow the heart and help maintain; the flexibilty of blood vessels, ensure good blood flow, normal blood pressure, low cholosterol levels and a healthy weight. Can also reduce the risk of strokes by 27%. 

-During steady state excersise, heart rate slowly climbs. 

-Known as cardiovascular drift, it is characterised by a progressive decrease in stroke volume and arteriol blood pressure, with a progressive rise in heart rate. 

-Occuring in a warm environment, heart rate increases --> stroke volume decreases --> fluid is lost as sweat --> resulting in a reduced plasma vloume --> reduced venous return --> cardiac output increases due to more energy needed to cool body/sweat. 

--Venous return is the return of blood to the right heart via tye vena cava (up to 70% of blood is contained in the veins at rest). This means a large amount of blood can be returned to the heart if needed. ---> During excersise venous return increases.

-During excersise, oxygen diffuses into the capillaries and combines with haemoglobin yo from oxyhaemoglobin (fully saturated can carry 4 oxygen molecules). 

-When it reaches the tissues, oxygen dissacoiates from the oxyhaemoglobin due to the lower pressure. -- The oxygen is then stored in myoglobin within the muscles until used up by the mitochondria for aerobic respiration. 

---

Bohr shift - as muscles require more oxygen, the dissociation of oxygen from the haemoglobin because more readily availiable - (shown as a shift in the curve of partail pressure). 

Also responsible for; (which contribute to more readily dissociation). 

-increase in blood temperature - blood and muscle temperature rise 

-partail pressure of co2 increases - as blood carbon levels rise. 

-Blood Ph levels decrease as co2 lowers blood ph. 

-A-VO2 diff 

-The difference between the oxygen content of the arterial blood arriving at the muscles and the venous blood levaing the muscles. 

-At rest A-VO2 diff is low due to lower volumes of oxygen being required by the muscles. 

-During excersise, higher volumes of oxygen are required so A-VO2 diff is high.

-This increase will affect gaseous exchange at the alveoli as more oxygen is taken in and more carbon dioxide is removed. 

-As both oxygen and carbon dioxide diffuse they always look to move from a high to a low concentration gradient. 

- For oxygen, partial pressure lowers as it moves through in order to create a strong enough gradient so oxygen can move rapidly along such. 

Environment - Lungs - Alveoli - Blood - Muscles --- This helps move oxygen through the body and to the working muscles. 

-For carbon dioxide, partail pressure is in reverse so it lowers as it moves upwards to create a strong enough gradient to move it out the body. 

Muscles - Blood - Alveoli - Lungs - Environment. 

-Venous return - the return of blood to the right side of the heart via the vena cava. During exercise, venous return increases so that stroke volume will increase.  

Venous return mechanisms; 

-Skeletal pump - a change in muscle shape that presses on the vein and squeezes the vein to pump a greater volume of blood to the heart. 

-The respiritory pump - muscles that contract and relax in breathing cause pressure changes that compress nearny veins and assit blood return to the heart. 

-Pocket valves - once the blood has passed through flwoing in only one direction, they close to prevent backflow. 

-Important to maintain venous return to ensure muscles are receiveing enough oxygen to meet the demands of the activity. 

-During exercise, blood is redistributed to keep up with the greater oxygen demand via the vascular shunt mechanism. 

-Sports performers should not eat less than an hour before competition as a full gut requires more blood to be redistributed to it, reducing availiable oxygen for other muscles then decreasing performance through inability to meet demands. 

---------

-During exercise, chemical changes e.g. rise in blood c02 or latic acid count trigger the chemoreceptors that sends a message to the vasomotor centre which will then tell the blood vessels to vasoconstrict or vasodilate.