Structure of the heart, cardiac cycle and control

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  • Created by: Steff06
  • Created on: 11-02-16 18:43
Describe difference between right and left side of the heart
The right side of the heart carries deoxygenated blood to the lungs. The left side carries oxygenated blood to the rest of the body.
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Where are the coronary arteries and what do they do?
They lie over the surface of the heart and carry oxygenated blood to the heart muscle. If they become constricted, less oxygen can be delivered and it may cause angina or a heart attack (myocardial infarction).
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Describe how the heart is divided and the atria
The heart is divided into 4 chambers. The 2 upper chambers are the atria which receive blood from the vena cava (right) and the pulmonary vein (left). Blood flows from atria through atrioventricular valves into ventricles.
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Describe the ventricles and this process
When ventricles contract, they fill with blood+atrioventricular valves remain closed.Ensures blood doesn't back flow.A wall of muscle(septum)separates ventricles from eachother to ensure blood is kept separate.Semilunar valves lead to aorta/pulmonary
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Explain blood pressure in the atria
Blood pressure in atria is low as blood is only pumped from atria to ventricle, so muscle is thin.
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Explain blood pressure difference between the right and left ventricle
Right ventricle thicker walls than atria to pump blood to lungs. But much thinner than left ventricle as lungs contain alveoli and capillaries which could burst with high pressure. Left ventricle takes blood around body through aorta.
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State the 3 stages in the cardiac cycle
Atrial systole, ventricular systole and diastole
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Describe the diastole/filling stage
While the atria and ventricles are relaxed, blood flows into the heart from vena cava and pulmonary vein. Blood flows into the atrium, through atrioventricular valves into ventricles.
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Describe atrial systole/contraction
Heart beat starts when atria contract. Right+left atria contract together. Pressure increase by contraction helps push blood into ventricles. Stretches walls of ventricles and ensures they are full of blood.
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Describe ventricular systole/contraction stage.
Heart valves are closed. Ventricle walls contract which raises pressure in ventricles.Contraction starts at apex to push blood up towards the arteries. Semilunar valves open and blood is pushed out the heart.
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How do the atrioventricular valves work?
Ventricular walls relax after contracting,pressure in ventricles drops below atria.Atrioventricular valves open.Blood entering heart flows through atrium to ventricles.Pressure in atria/ventricles increases and valves are open when atria contract.
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How do the semilunar valves work?
Ventricles contract,pressure arteries=higher than ventricles.Semilunar valves=closed.When pressure in ventricles when they contract is higher than arteries,semilunar valves pushed open+blood forced out of ventricles.Relaxing=ventri
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Sound of the heart
1st sound 'lub' made when atrioventricular valves shut. 2nd sound 'dub' made when semilunar valves close. Atrioventricular valves snap shut so this noise is louder.
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What is the heart described as and what does this mean?
Myogenic. The heart muscle can initiate its own contraction.
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Explain how the heartbeat starts
The Sinoatrial node (SAN) is a small patch of tissue near the vena cava that generates electrical activity. It initiates a wave of excitation at regular intervals.
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Explain contraction of the atria/next node
Wave of excitation spreads over atria walls+causes muscle to contract (atrial systole). At atria base there is disc of tissue that cannot conduct electrical activity.Gives time for atria to contract. Top of the septum is atrioventricular node(AVN).
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Explain contraction of the ventricles
After delay, wave carried down conducting tissue (Purkyne tissue) and septum.Excitation spreads from apex and causes contraction to push blood out of the heart.
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How can the electrical activity of the heart be monitored?
Using an electrocardiogram (ECG).
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Explain electrocardiogram use
Sensors attached to skin. Sensors pick up electrical excitation created by the heart and convert this into a trace.
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Describe the trace of a healthy person
Consists of waves P,Q,R,S,T. P shows excitation of atria (small rise), QRS shows excitation of ventricles (R=up,S=dip). T shows diastole (small rise).
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An ECG can show if heart is what
Beating irregularly (arrhythmia), if it is in fibrillation (beat is not coordinated), or if it has suffered a heart attack (myocardial infarction). Can show if Purkyne system is not conducting electrical activity.
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Other cards in this set

Card 2

Front

Where are the coronary arteries and what do they do?

Back

They lie over the surface of the heart and carry oxygenated blood to the heart muscle. If they become constricted, less oxygen can be delivered and it may cause angina or a heart attack (myocardial infarction).

Card 3

Front

Describe how the heart is divided and the atria

Back

Preview of the front of card 3

Card 4

Front

Describe the ventricles and this process

Back

Preview of the front of card 4

Card 5

Front

Explain blood pressure in the atria

Back

Preview of the front of card 5
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