Applied Cardiovascular System Flashcards
What is pulse?
The rhythmic expansion of an artery, which corresponds to each contraction of the heart
What is heart rate?
The speed of the hearts contractions (bpm)
What is stroke volume?
The volume of blood pumped out of the ventricles with each heart beat (approx 70ml)
What is total peripheral resistance?
The force exerted on circulating blood by the vascular urge of the body
What are the 3 factors affecting total peripheral resistance (TPR)?
(1) autonomic activity - sympathetic system»_space;>vasoconstriction
(2) blood viscosity - increased thickness of blood leads to an increased TPR
(3) medications - vasoconstrictor and vasodilator drugs
What is cardiac output?
The volume of blood your heart pumps each minute»_space;> CO = SV x HR
Understanding cardiac output
Remember the heart is a pump
- it pumps blood around the body and the blood delivers oxygen and removes carbon dioxide
If the body has a need for more oxygen what will happen to cardiac output?
- cardiac output will increase so more oxygen is available throughout the body - it does this by increasing heart rate and TPR - through vasoconstriction
- this increases blood pressure
The cardiac cycle
The heart goes through a rhythmic cycle of contraction and relaxation
- ventricular contraction = systole
- ventricular relaxation = diastole
- systole refers to ventricular systole
- atrial systole is not included as a part of systole as it occurs when the ventricles are relaxed
What is an ECG?
- the heart has its own electrical conduction system
- an ECG records the electrical signals in your heart
- it looks at HR, rhythm and electrical activity»_space;> it can also indicate enlargement of the heart (cardiomyopathy) and evidence of a previous heart attack
- sensors are attached to the skin and detect electrical activity
What can an ECG tell us?
- you can see the HR and rhythm
- you can check for abnormalities such as lack of P wave or arrhythmias
- you can see if there is any evidence of damage
- raised, depressed, flipped or even flat ST waves can show evidence of ischaemic heart damage
What is blood pressure?
- blood pressure is a measure of the force that moves blood around your body»_space;> generated by the heartbeat
- the force of your blood punching against the walls of your arteries is what is measured as blood pressure
- arterial blood pressure
- BP = CO x TPR
How do we control blood pressure?
Short term»_space;> via baroreflex receptors found in the carotid sinus’ and the aorta - these detect changes in blood pressure and vasoconstrictor or dilate vessels as required - innervation the parasympathetic (vasodilation and slow HR) to decrease BP or the sympathetic system (vasoconstriction and fast HR) to increase BP
Long term»_space;> via renin-angiotensin- aldosterone system (RAAS) - a hormonal system that controls BP
The renin-angiotensin-aldosterone system (RAAS)
(1) renin is released from the kidneys into the blood
(2) it converts angiotensen, which released from the liver, into angiotensin (AT1)
(3) AT1 is converted into AT2 via angiotensin converting enzymes (ACE) in the lungs and kidneys
(4) it binds to AT2 receptors on tissues to elicit a response
(5) AT2 stimulates the release of ADH and aldosterone
How does hypertension affect the heart?
- the constant increased pressure against the walls of the heart can cause them to stretch and either become stiff or baggy
- this then leads to the heart pumping led efficiency and in severe cases can cause heart failure
- this is where the heart is unable to meet the needs of the body for an increase in cardiac output and causes significant symptoms
