Cardiology

To begin this chapter I found a great illustration of the explanation of the circulatory system. [|The Heart]

=Review of chapter:=

The Heart Sounds of the heart:
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//__Electrical Activity of the heart:__//
//__**SA Node or pacemaker-** The pacemaker region of the heart (SA node) exhibits a spontaneous depolarization that causes action potential, resulting in the automatic beating of the heart. [|SA Node]

The next portion of this chapter explains the difference in blood vessels of the body. TYPES- 1. Continuous- adjacent endothelial cells are closely joined together. These are found in muscles, lungs, adipose tissue and CNS. 2. Discontinuous- are found in the bone marrow, liver and spleen.
 * Arteries**- composed of elastin fibers between the smooth muscle of the tunica media. Arteries carry blood away from the heart. **Arterioles** are small muscular arteries that are 100 micrometer or less in diameter.
 * Capillaries**- The walls of capillaries are composed of just one cell layer.
 * Veins-** most of the total blood volume is contained in the venous system. Veins are able to expand as they accumulate additional amounts of blood. Veins are the only blood vessel that has valves.

Next we covered hardening of the arteries or atherosclerosis and LDL and HDL. The lymphatic vessels absorb excess interstitial fluid and transport this fluid- lymph-to ducts that drain into veins. It has 3 functions: 1: It transports interstitial fluid back to the blood; 2: It transpors absorbed fat from the small intestines to the blood; 3: its cells- called lymphocytes- help provide immunological defenses against disease.

Chapter 14
 * Cardiac Output, blood flow, and Blood Pressure

Cardiac output = stroke volume x cardiac rate**

Stroke volume is regulated by 3 variables 1. End-diastolic volume (EDV)- volume of blood in the ventricles at the end of diastole 2. Total Peripheral Resistance- frictional resistance, or impedance to blood flow 3. Contractility- or strength


 * Frank-Startling law**- states that the greater the volume of blood entering the heart during diastole, the greater the volume of blood ejected during systolic contraction, Stroke Volume and vice-versa.

Next we learned about the venous return: The return of blood to the heart via veins. and the regulation of blood volume by the kidneys.

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Next we learned about blood flow to the heart and skeletal muscles and the reaction of blood flow on exercise.

Blood flow to the Brain:

The purpose of the circle of willis is that of any one vessel is blocked that the blood flow will continue to the brain.

Blood Pressure The three most important variables affecting blood pressure are the cardiac rate, stroke volume, and total peripheral resistance. The rest of the chapter covers hypertension, shock and congestive heart failure. Circulatory shock occurs when there is inadequate blood flow and/or oxygen utilization by the tissues. Hypovolemic shock refers to circulatory shock that is due to low blood volume. Septic shock refers to a dangerously low blood pressure that may result from sepsis or infection. Anaphylactic shock and neurogenic shock results in rapid fall in blood pressure. Cardiogenic shock results from cardiac failure.

=**Questions:**=

What are the three most important variables that affect blood pressure? Describe each variable and how it affect blood pressure. Cardiac Rate- number of beats for minute Stroke Volume- volume of blood pumped per beat by each ventricle Total peripheral resistance- frictional resistance, or impedance to blood flow, in the arteries

If any of the three increase without one of them decreasing to compensate it will increase blood pressure

Describe two reflexes that help maintain blood pressure within limits.

Baroreceptor Reflex- stretch receptors located in the aortic arch and in the carotid sinuses. The baroreceptors are constantly active, producing a baseline frequency of action potentials in their sensory neurons. When BP is increased the walls of the aortic and carotid sinuses stretch and this produces an increased frequency of action potentials along their sensory nerve fibers. A fall in blood pressure causes a decrease in action potentials.

Atrial stretch receptors- located in the atria of the heart. These receptors are activated by increased venous return to the heart and in response stimulate reflex tachycardia as a result of increased sympathetic nerve activity and inhibit ADH release, resulting in the excretion of larger volumes of urine and a lowering of blood volume and promote increased secretion of atrial natriuretic peptide. The ANP lowers blood volume by increasing urinary salt and water excretion.

Personal Application: In this chapter the things that we learned about blood pressure and blood flow will all be very important in deciding what exercise program we should put our clients on and what intensity it should be at. This will be very important when training someone with heart disease or hypertension to not overwhelm them with intensity when their heart cannot handle it.

References: All references that I used in the text are labeled with the web address and also Human Physiology, Stuart Ira Fox