Lecture 12 3/6/14 Flashcards
What determines whether the valves open or close?
Depends on the pressure across the doors or valves
Atrial Diastole
Pressure steadily increases as the atria starts to fill up.
Atria fills up first, then the blood flows into the ventricles.
Atrial Systole
Atria contract, theres a momentary increase in pressure.
They send their blood into the ventricles, topping it off.
Ventricular Diastole
Ventricular Pressure continues to increase as blood fills the ventricles from the atria.
There is a mild increase in pressure as the atria contracts to top off ventricular volume.
Ventricular Systole
A huge ventricular pressure increase during ventricular contraction.
Also an increase in pulmonary trunk and aortic pressures during ventricular systole.
What does 25/8 mean?
the blood pressure in the walls of the vessels.
Never need to reinforce the walls of the vessels with collagen fiber, because the pressure never gets that high.
The vessels are very compliant. They can increase in diameter and decrease in diameter.
Stroke Volume
amount of blood ejected during ventricular systole.
Size of a person’s heart is different for every single person because it depends on the person’s surface area of their body.
Larger surface, your heart has to be bigger to be able to pump more blood with each contraction to all the tissues in your body.
Cardiac Output
amount of blood that’s ejected from the left ventricle into the aorta per given unit of time, that given unit of time is one minute.
What determines cardiac output?
Stroke volume (x) Heart Rate. Average stroke volume is 70 ml and 70 beats per minute, so 4900 ml per minute, and averages around 5000.
So an average cardiac output volume is between 5-6 Liters.
Cardiac Reserve
maximum % that the cardiac output that can be achieve above normal or increase above resting amounts.
It is the difference between normal and maximal cardiac output.
A certain amount above your cardiac output that you can achieve.
Cardiac Output Variations
differences can be seen in certain pathological conditions.
Hypovolumic Shock. Lose blood volume, stroke volume decrease, heart rate has to go up.
What is Hypovolumic Shock
low volume shock. Need to maintain cardiac output and maintain profusion of Oxygen to the tissues.
End Diastolic Volume
the amount of blood in the ventricle prior to systole and contracting them.
Largest volume is about 120 ml on average
End Systolic Volume
less volume and the amount of blood left in the ventricle after ventricular systole.
Less volume, 40-50 ml. Refer to stroke volume. Stroke volume is dependent on the individual.
Starlings Law
Says input has to equal output.
The greater amount of blood dumped into the ventricles the greater the force of contraction.
Reason for Starlings Law
The more the sarcomere stretches within it’s ability to stretch, the more forcefully it will contract.
Blood Vessels
a network of tubes that carry blood to and from the tissues.
Arteries
Always carry blood away from the heart
3 Types of Arteries
Elastic Arteries
Medium Sized Artery
Arterioles
Elastic Arteries
largest vessels, wall not very thick, but very resilient, meaning they have some elasticity in the vessels and will have collagen in them.
They have to have some give, a little bit, because they have to, to withstand the forces of the ventricular contraction, especially the left ventricle, it contracts very forcefully.
Examples are the Aorta and Pulmonary Trunk
Medium Sized Artery
Known as muscular arteries.
Distribute blood to peripheral organs, large amount of smooth muscle fibers in middle layer.
Examples are radial and brachial arteries
Arterioles
much smaller than medium sized arteries. They don’t have a lot of outside tissue.
Have an incomplete layer of smooth muscle fibers, these fibers allow for constriction and dilation of arterioles to send blood to different parts of the body.
Capillaries
the smallest and thinnest vessels. Flow is slow here. Most areas are one cell thick, and only allow one RBC through at a time.
Venules
small vessels continuing from the capillaries that collect Unoxygenated blood, but it is not completely unoxygenated.
Veins
larger vessels carrying unoxygenated blood from the venules to the heart.
Veins walls contain smooth muscle, but also a lot of elastic and collagen fibers.
Are extremely compliant, they serve as a blood reservoir.
Vein Valves
ensure the blood with low pressure continue to move upward towards the heart. The blood has to work against gravity.
Varicose Veins
standing in long periods of time, because gravity is pulling everything down that you develop varicose veins because the blood is being pushed down, so then the blood doesn’t get pushed back up, the vessel walls dilate dramatically.
And if they do, the vessel the cusp edges no longer come together, the valve becomes incompetent, and the blood flows beyond it.
If it pulls enough, we stretch and tear the wall vessel enough and lay down collagen fiber again and now that vessel is not able to constrict to come back into it’s original position.
Superficial Veins
Are subcutaneous. Not surrounded by muscle. No reinforcing wall to prevent them from dilating.
Three Layers to the Vessel Walls
Tunica Externa
Tunica Media
Tunica Interna
Tunica Externa
AKA Adventicia - outer layer, mostly connected tissue fiber.
Tunica Media
thickest layer - muscular layer.
Tunica Interna
or called the intima. Sub intimal thickening, this refers to an increase in cardiovascular disease.
