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
What hormones are able to affect contractility?
- noradrenaline
- adrenaline
- thyroid T3-T4
What are the 2 main variables that influence contractility and ultimately affect the stroke volume?
- autonomic control
- hormones
Afterload is a measure of the resistance in which the heart has to pump against at the end of systole. What is the main driving factor that contributes to this, and ultimately affects Q?
- systemic vascular resistance
- vasoconstriction and vasodilation
When looking at afterload, preload and contractility, which contribute to end diastolic volume (EDV)?
- preload only
When looking at afterload, preload and contractility, which contribute to end systolic volume (ESV)?
- preload
- afterload
- contractility
How do we calculate stroke volume?
- EDV - ESV
- EDV = end diastolic volume
- ESV = end systolic volume
What did Otto Frank discover as his contribution to the Frank Sterling Law?
- ⬆️ SV = ⬆️ EDV prior to contraction
When we have an increased preload, this provides more blood to be pumped out and increase SV during the hearts contract. But there is another variable that contributes to the Frank-Sterling Law, what is this?
- elastic recoil of cardiac muscle
- ⬆️ preload = stretch of ventricles
- ⬆️ stretch = ⬆️ elastic recoil force
- ⬆️ preload + ⬆️ elastic recoil force = ⬆️ SV
What did the Starling aspect of the Frank-Starling Law indicate?
- that ⬆️ SV = ⬆️ EDV prior to contraction are not always constant
When talking about the Frank-Starling law we can plot a curve, where an increase in preload (can be measured as LVEDV as a measure of preload) causes an increase in SV, what factors may influence the shape of that curve?
- ⬆️ sympathetic =⬆️ HR and ⬇️ SV
- ⬆️ afterload = ⬇️ preload
- ischemic heart disease ⬇️ elastic recoil and preload
What is a pressure volume diagram a measure of in the heart?
- a measure of work the heart is completing
What does one full cycle in a pressure volume diagram from the heart represent?
- 1 heartbeat
What does extrinsic control of the heart mean?
- influence on heart from outside of the heart
What are some of the factors that contribute to extrinsic control of the heart?
- autonomic control
- sympathetic and parasympathetic control
Which nerve of the autonomic system has a parasympathetic effect and slows the heart down?
- vagal nerve via cholinergic receptors
- via M2 receptors with acetylcholine
Does the parasympathetic system contribute to vasodilation of blood vessels?
- no
- generally sympathetic system reducing activity
What does inotrophic mean?
- force of contract
What does chronotrophic mean?
- speed of contraction
What does dromotrophic mean?
- speed electrical impulse moves through heart
What is the renin–angiotensin system, or renin–angiotensin–aldosterone systems role?
- hormone system
- regulates blood pressure, fluid and electrolyte balance, - ⬇️ systemic vascular resistance
Where is renin generally released from?
- juxtaglomerular cells in kidney
What organ secretes angiotensin?
- liver
How is angiotensin converted into angiotensin 1?
- renin acts on angiotensin
- angiotensin 1 is formed
How is angiotensin 1 converted into angiotensin 2?
- angiotensin converting enzymes from the lungs turns angiotensin 1 into angiotensin 2
What is aldosterone?
- main mineralocorticoid steroid hormone
- produced by the zona glomerulosa of the adrenal cortex in the adrenal gland
What is the role of aldosterone?
- stimulates H2O, Na+ and Cl- reabsorption
What does natriuresis mean?
- sodium excretion in the urine
What are natriuretic peptides?
- short chains of proteins
- peptides that induce natriuresis
What 2 natriuretic peptides does the heart produce?
- atrial natriuretic peptide (ANP)
- brain natriuretic peptide (BNP)
Why is atrial natriuretic peptide (ANP) released from the atrium of the heart?
- ⬆️ in blood volume
- ⬆️ stretch in atrium
Once atrial natriuretic peptide (ANP) is released from the atrium of the heart, what organ does it target and what are the effects of this?
- kidneys
- ⬆️ Na+ excretion
- ⬆️ urine excretion as H2O follows Na+ by osmosis
- causes an overall ⬇️ in blood volume
Where is brain natriuretic peptide (ANP) released from in the heart?
- cardiomyocytes of the ventricles
When is brain natriuretic peptide (ANP) released from the ventricles of the heart?
- ⬆️ stretching of ventricles
- caused by ⬆️ ventricular blood volume
What are the effects of brain natriuretic peptide (ANP) released from in the heart?
- identical fo atrial natriuretic peptide
- ⬇️ systemic vascular resistance
- ⬇️ central venous pressure
- ⬇️ afterload
