Blood pressure Flashcards

Question

How would you calculate peripheral resistance?

Answer 1

Total peripheral resistance = BP / CO. You can get a good estimate of deltaBP from brachial arterial pressure.

Answer 2

Pulse pressure = systolic pressure – diastolic pressure

Answer 3

MAP = P(diastolic) + (0.333 x pulse pressure)

Answer 4

The aorta has a much bigger radius (as well as a much higher pressure), so its wall has to withstand much more tension. Thus the walls of the aorta are much thicker than the walls of the capillary

Answer 5

Aortic arch (innervated by the Vagus nerve (CN X)) Carotid sinus of both left and right internal carotid arteries (innervated ultimately by Cranial Nerve IX)

Answer 6

Mismatch between blood volume and circulatory capacity. Autonomic nervous system & brain. Humoural component & endocrine. Local control. OR: Kidney controls blood volume, blood vessels control circulatory capacity and heart controls pressure

Answer 7

It is a physiological mechanism Whereby the skeletal muscles of respiration increase the pumping of blood through the circulatory system During inspiration, the intrathoracic pressure is negative (suction of air into the lungs), and abdominal pressure is positive (compression of abdominal organs by diaphragm). This makes a pressure gradient between the infra- and supradiaphragmatic parts of v. cava inferior, "pulling" the blood towards the right atrium.

Answer 8

The effects of O2, CO2 and PH are opposite of those in the systemic system. It has a very low vascular resistance. It makes angiotensin converting enzyme. High capillary density Acts as a filter (and protects against emboli

Answer 9

* The effects of O2, CO2, pH are opposite to those in systemic circulation * In pulmonary system, if O2 is low in a region of the lung, the arterioles constrict * (likewise if CO2 or H+ are high, vasoconstriction) * Thus, Poor ventilation leads to reduced perfusion • •This minimises the amount of blood that is poorly oxygenated

Answer 10

Aneurysm or stroke. Myocardial infarct, kidney failure, heart failure, cardiac hypertrophy.

Answer 11

•Low BP on standing –decreased venous return – •Dizziness or syncope

Answer 12

* Critically low perfusion (associated with low blood pressure) * Caused because the heart is not pumping blood fast enough or with enough force * Medical emergency * Affects critically ill patients * Example: haemorrhagic shock

Answer 13

If the radius of a length of a blood vessel increased, the resistance along that stretch of the blood vessel would decrease, so the flow rate in the vessel would tend to immediately increase, and the pressure would immediately decrease. If the end of that vessel connected to a capillary with a stable amount of back pressure, a new equilibrium would occur in which slightly faster flow and lower pressure would exist Note that the rate of pressure falling may be lower because the resistance has decreased (although the flow rate has increased)

Answer 14

The capillary has much higher resistance, so flow would be much slower. At the entrance to the capillary, there would be a large loss in pressure (and kinetic energy) associated with the friction of getting so much fluid into an capillary

Answer 15

The relationship between how much fluid will flow through a tube vs the dimensions of the tube and the forces in the tube. ΔP = 8 Q ηL / π r4 where nu = viscosity, r = radius, L = length of tube, and Q = flow This is called Poiseuille’s Law

Answer 16

Wall tension is proportional to be pressure and radius. Normally a capillary has a much lower pressure and a smaller radius than an arteriole, so that although it has less wall strength, the tension is usually so much lower that the capillary wall will not rip. Plainly this depends on the pressure and wall tension. For identical pressures, a capillary has a much smaller radius, so the tension might be lower. However, the higher pressure in the arteriole might be too much for the capillary. The capillary definitely has less wall strength, and for identical amounts of tension, the capillary’s wall would rip first

Answer 17

The resistance would shrink dramatically (to the power of 4) as the radius becomes larger. This is from Poiseuille’s law.

Answer 18

More resistance would be created by doubling the length. Doubling the number in parallel would actually halve the resistance

Answer 19

Decreased peripheral resistance leads to decreased pressure

Answer 20

The pulse pressure would be smaller (because the wall would absorb energy during systole and release it during diastole). This would mean the flow would be slower during systole, but might be higher during diastole Flow slows down in more compliant vessels because the pressure (ie force) can not only push the rest of the blood forward, but it can also stretch the wall, expending energy while essentially storing both the energy and the blood volume in the now stretched vessel.

Answer 21

* Ionic flow (current) à blood flow * Transmembrane voltage à pressure difference across the valve * Electrical resistance à hydrostatic resistance (both decrease when something opens)

Answer 22

•Blood vessel: decreased by increasing radius, increased by length, obstructions, turbulence (bends), viscosity • •Cell membrane: decreased by channel openings, holes; increased by lipid composition

Answer 23

During exercise sympathetic activity has the following effects: increased myocardial contractility and increased heart rate (leading to greatly increased cardiac output), and some vasoconstriction (especially to kidney and splanchnic circulation), but also some vasodilatation (esp. to skeletal muscles). The net effect on peripheral resistance is a slight reduction. As a result, during systole the blood pressure is much higher (because of the increased contractility of the heart), but the additional blood flow is easily conducted to the muscles, reducing back pressure, so that during diastole the decreased peripheral resistance leads to a net reduction in pressure