Cardiovascular System Flashcards
What major factors affect the rate of blood flow
Pressure differential between two points (directly) and the resistance to flow (inversely)
How does radius of the vessel affect the rate of flow
The flow is proportional to the radius to the power of 4
What are the systolic pressures of the heart
15-30 mmHg in right vent. 100-140 mmHg in left vent.
How do elastic arteries maintain pressure
Elastic recoil during diastole will cause the blood to be forced forward again keeping pressure high
In which artery is blood pressure taken
Brachial artery in the upper arm
What is pulse pressure
The systolic pressure minus diastolic pressure
What is the P wave
The first wave on the ECG graph which represents atrial depolarisation and then contraction
What is the QRS complex
Ventricular depolaristion and therefore contraction (and atrial repolarisation although not seen)
What is the T wave
Repolarisation of the ventricular myocardium the last section of an ECG
What is preload
The amount at which myocardium is stretched in diastole to allow for blood into ventricle
What is Contractability
The amount of force the muscle contracts with in the heart during systole
What is afterload
The force required to open the semi lunar valve and allow blood to be ejected from the ventricle
What is auto regulation of local blood flow
The ability to change the flow of blood in specific local regions as demand changes for blood. This is in response to certain stimuli and is supported by vasodilatory metabolites
Why are the capillary sphincters important
They control the amount of blood allowed into the capillary bed
How does baroreceptor inhibition increase heart rate and blood pressure
Cardioacceleratory centre activated, Cardioinhibitory centre inhibition, Vasomotor centre activation supported by endocrine response from endocrine glands (adrenaline)
How does more CO2 in blood lead to a regulatory response in heart rate
Chemoreceptors detect a drop in pH as dissolved CO2 creates carbonic acid
What are the important compounds in the renin angiotensin aldosterone system
Angiotensinogen is cleaved by renin which forms angiotensin 1 which is converted by angiotensin converting enzyme to angiotensin 2 which stimulates the adrenals to produce aldosterone (Angiotensinogen formed by liver, renin in kidney, ACE lungs) Angiotensin 2 causes vasoconstriction and aldosterone increases fluid absorption in kidneys.
What is Anti diuretic hormone
This is a hormone secreted by posterior pituitary gland to increase fluid reabsorption in collecting duct increasing blood volume
How do natriuretic peptides reduce blood pressure
ANP and BNP reduce thirst and increase water loss to reduce overall blood volume. They also inhibit ADH aldosterone, noradrenaline and adrenaline from being released which helps to prevent vasoconstriction.
What is the difference between fenestrated, continuous and sinusoid cappilaries
Continuous are a normal capillary with intercellular clefts and no extra pores with a basement membrane, fenestrated has water filled pores that allow for rapid substance exchange, sinusoid have large pores and incomplete basement membranes which allow for rapid exchange and the exchange of large solutes e.g. proteins.
How do lipid soluble molecules move across a capillary
They move through the membranes of the endothelial cells
How do ions move through the capillary endothelium
They have ion channels in the endothelium that allows it to be transported across the endothelium
How does small water soluble molecules move through the capillary endothelium
They can move between the extra cellular clefts with the flow of water
How do large molecules such as glycoproteins move through the capillary
Transcytosis, the process of it being packaged and then expelled from cells in a vesicle.
In what areas of the endothelium does bulk flow occur and via what force
Hydrostatic pressure is the force pushing blood out of (arteriole end) and into (venue end) the capillaries. It is facilitated by extracellular clefts and even more so by fenestrations if present.
How can you calculate the net filtration pressure and what is filtration pressure?
Net filtration pressure is the net hydrostatic pressure - net osmotic pressure and filtration pressure represents the force at which fluid is pushed through and in which direction through extra cellular clefts and fenestrations.
How does filtration compare to absorption and why
filtration is more prevalent and occurs across more of the capillary due to a greater filtration pressure compared to the absorption pressure. This means net fluid movement by filtration is greater than total fluid movement via absorption
What happens to filtration when blood pressure changes
Hypertension can lead to increased amounts of filtration and less absorption which puts too much strain on the lymphatic system potentially leading to systemic oedema (swelling due to fluid retention in interstitial fluid). Hypotension from severe haemorrhage can lead to increased reabsorption and reduced filtration which will lead to increased blood volume acting as a negative feedback loop to correct the low blood pressure.
What is classified as hypertension
Above 140mmHg systolic or 90mmHg diastolic bloop pressure
What is one way to treat hypertension via reducing vasoconstriction
Inhibiting the RAAS system (renin-angiotensin-aldosterone-system) via drugs blocking various steps in the RAAS
How do Ca2+ blockers reduce hypertension
Contractility of vascular muscles and heart myocardium is reduced
How might diuretics help with hypertension
They reduce blood volume by lowering water retention in the kidneys.
What is an atherosclerosis and why can it increase risk for thromboembolism
Atherosclerosis is the formation of large plaque buildups in blood vessels and if a embolus reaches the atherosclerosis it can easily block the vessel
