1. Introduction To CVS Flashcards
What does blood transport?
O2, metabolic substrates, CO2 and waste products.
How do different molecules diffuse at the capillaries?
O2 and CO2 and other lipid soluble molecules diffuse directly through the capillaries’ lipid bilayer. Other molecules, like glucose, that are hydrophilic and not lipid soluble, move through small pores. Every molecules moves down its concentration gradient.
How is the rate of diffusion affected?
Area, diffusion resistance and concentration gradient.
How does area affect rate of diffusion in capillaries?
A higher area available for exchange increases the rate of diffusion. The area between capillaries and tissues is very large usually (dependent on capillary density, usually high) to promote diffusion.
What contributes to the diffusion resistance?
Nature of the molecule - hydrophobic or hydrophilic.
Nature of the barrier - larger pores mean larger molecules can move through.
Path length - rate of diffusion is inversely proportional to the square of the distance needed to travel.
How does concentration gradient affect rate of diffusion in capillaries?
Greater concentration gradient means a greater rate of diffusion. So the concentration gradient between capillary blood and tissues is high to promote diffusion.
What does the concentration gradient between capillary blood and tissues depend on?
Rate of use of the substance by the tissues. Rate of blood flow through the capillary bed. A substance which is used by the tissue will have a lower concentration in capillary blood than arterial blood.
How is the concentration gradient between capillaries and the tissues maintained?
The rate of blood flow through the capillaries must be high enough to maintain a sufficient contraction gradient for diffusion, the lower the blood flow, the lower the capillary concentration.
What is perfusion rate and how does it adapt to its needs?
The rate of blood flow. A greater metabolic rate of tissues will increase the perfusion rate so enough O2 and nutrients are supplied to match the demand.
What is the average cardiac output at rest and in exercise of a 70kg man?
5.0 l/min at rest, 25 l/min in exercise.
What are the key components of the cardiovascular system?
Pump - the heart, distribution system - vessels & blood, exchange mechanism - capillaries, flow control - arterioles & pre-capillary sphincters.
Why does blood flow have to be regulated?
If it’s not regulated, the blood will just flow to the places most easily perfused - this would mean harder to perfuse places, like the brain, won’t be perfused. Adding resistance to the system means blood flow is directed to the more difficult to perfuse areas too.
What are the two circulations in series that the heart pumps?
The systemic circulation (left), and the pulmonary circulation (right).
What is the pathway of systemic circulation from the heart?
Heart pumps blood to the arteries via the aorta, the arteries supply the arterioles. Arterioles supply the capillaries, which drain into venules, that drain into veins that take the blood back to the heart.
How can the heart adapt to an increased need of blood?
It has to pump more blood out. This can only happen if the more blood goes into the heart, so the veins act as a reservoir for when more blood is needed - capacitance.
