The Cardiovascular System

Everything you need to know about the Cardiovascular system shortened down into handy revision cards

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Cardiac Cycle

Cardiac Cycle

1. Atrial Diastole - Atria fill with blood

2. AV Valves open

3. Ventricular Diastole - Ventricles fill with blood

4. SA Node Fires

5. Atrial Systole - Last bit of blood squeezed out of Atria

6. AV Node fires - Slows electrical impulse down

7. Bundle of His

8. Purkinje Fibres

9. Ventricular Systole

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Redistribution Of Blood Flow Chart


1. Exercise

2. Chemoreceptors - Loacted in Aorta

3. Chemoreceptor sends signal to Medulla Oblongata/ Vaso Motor Centre

4. Sympathetic nervous system takes over

5. Pre capillary sphincters - located in arterioles

6. Vasoconstriction (Organs)

7. Vasodilation (Muscles)

8. Blood flow decreases in organs

9. Blood flow increases in muscles, increased oxygen supply

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Neural control of Heart Rate

1. Parasympathetic nerve is dominant

2. Exercise starts

3. Chemoreceptors detect change in PH in blood + mechanoreceptors detect movement

4. Chemo and mechanoreceptors send message to medulla oblongata to spped up heart rate

5. Medulla oblongata tells sympathetic nervous system to speed up heart rate

6. Sympathetic nervous system is now dominant

7. Exercise stops

8. Parasympathetic nervous system now takes over to slow everything back down

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Hormonal Control Of Heart Rate

Adrenaline - Adrenal glands located at the top of the kidneys

Rest- Parasympathetic nerve is keeping heart rate down with help form baroreceptors, pre anticipatory rise from adrenal glands increases heart rate slightly

During Exercise - Sympathetic Nerves overide Parasympathetic nerves via infromation from the chemoreceptors and the mechanoreceptors and also Noradrenaline

Recovery Phase (After exercise) - Parasympathetic nerves overide the sympathetic nerves because of information from the baroreceptors, heartv rate is slowed back down to normal like in rest phase

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Defintions + Formulas

Cardiac Output (Q) - The volume of blood ejected from the heart per minute

Stroke Volume (SV) - The volume of blood ejected form the herat per beat

Heart Rate (HR) - The number of completed cardiac cylces per minute

Formula- Cardia Output = Stroke volume x Heart Rate

Untrained Athlete - Q= 5 Litres SV= 70ml HR= 72bpm

Trained Athlete - Q= 5 Litres SV= 85ml HR= 60bpm

Bradycardia - The reduction of resting heart rate to below 60 beats per minute. This usually accompanies endurance training

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Venous return mechanism

Venous Return - the volume of blood that returns to the right side of the hearts via the venules

Skeletal Muscle Pump - create a massaging effect on the veins which squeezes the blood back towards the heart

Pocket Valves - The pocket valves snap shut ensuring no backflow of blood meaning there is only one way, back towards the heart

Smooth Muscle in veins - Thin layer of smooth muscle, works in conjunsction with skeletal muscle pump to squeeze blood back to the heart

Respiratory pump - increased rate of breathing changes pressure in the thoracic cavity, increased pressure causes the veins to be squeezed pushing blood back to the heart

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