Understanding the Physiology of the Cardiovascular System Flashcards
The term cardiopulmonary unit can be used to described what?
- heart and lungs working together
What is one of the important reasons why the lungs are able to receive all of the blood from the body?
- ⬇️ pressure
- ⬇️ resistance
What is a portal system?
- where blood moves from one capillary bed to another capillary bed
- blood contains only CO2
- can be different or same organ
What is the hepatic portal system?
- digestive tract absorbes nutrients
- liver processes nutrients
- delivered to heart
What is stroke volume?
- volume of blood pumped by the left ventricle per beat - - measured as ml/min
- denoted as SV
What is cardiac output?
- volume of blood pumped by the heart per unit time
- measured as L/minute
- denoted by Q (SV x HR)
What is perfusion?
- passage of blood through the circulatory system to the body’s tissues
- measured as ml of blood per minute per gram of tissue
What is preload?
- degrees of stretch in sarcomeres at end of diastole
- stretch is related to ventricles filling
- measured as end-diastolic volume in mL
- denoted by EDV.
What is contractility?
- innate ability of the myocardium to contract
What is afterload?
- resistance heart has to pump against during systole
- proportional to average arterial pressure. If aortic or pulmonary pressure increases so to does afterload on left and right ventricles
- measured as aortic pressure during systole divided by cardiac output
What is compliance?
- ability of blood vessels to stretch and contract with changes in blood pressure
- measured as unit of volume change per unit of pressure change
- denoted by C
What is the atrial reflex, also referred to as the Bainbridge reflex?
- bodies ability to change HR in response to pressure changes
- ⬆️ BP (stretch) or ⬆️ right atrium volume = ⬆️ HR
- prevents the pooling of blood in the venous system
What receptors provide information about blood pressure and stretch response in the cardiovascular system?
- baroreceptors on aortic arch and carotid sinus
- stretch receptors in heart (venoatrial stretch receptors)
If baroreceptors or venoatrial stretch receptors detect and increase in BP or stretch response due to increased venous return to right atrium, what does the autonomic system do?
- afferent receptors transmit signal along vagus nerve
- signal received in medulla
- response is to ⬇️ parasympathetic activity and ⬆️ sympathetic activity
Which hormones are likely to increase heart rate?
- adrenergic receptors of sympathetic system
- fight of flight response
- noradrenaline and adrenaline
What are the 3 main variables that contribute top stroke volume?
- preload (ventricle filling after systole)
- afterload (systemic resistance)
- contractility (cardiac ability to contract)
What is venous return?
- volume of blood returning to heart
What is venous filling?
- how quickly heart fills
What 2 factors contribute to preload, a measure of how much the sarcomeres stretch at end of diastole, which is proportional to ventricle filling?
1 - venous return
2 - filling time
If preload is reduced what effect can this have on cardiac output?
- could ⬇️ SV
- ⬇️ SV = ⬇️ Q
How does the autonomic system contribute to contractility of the heart?
- ⬆️ sympathetic activity = ⬆️ contractility
- ⬆️ parasympathetic = ⬇️ contractility
What would an increase in sympathetic and parasympathetic activity do to cardiac output?
- ⬆️ sympathetic activity = ⬆️ contractility = ⬆️ SV
- ⬆️ parasympathetic = ⬇️ contractility = ⬇️ SV