SC.912.L.14.36 The Cardiovascular System

You need to know the factors that affect blood flow through the cardiovascular system:

blood pressure, blood volume, resistance, disease and exercise.

You need to know how these factors affect blood flow (increases or decreases blood flow)

TUTORIALS
What Makes Your Blood Flow?
Circulatory System
Heart
Blood
Blood Pressure
EOC Practice Questions

The cardiovascular system is a transport system that carries nutrients and oxygen to the cells of the body and carries waste products such as carbon dioxide away from the cells. Also, transports chemical messages between cells and plays a role in fighting disease

The cardiovascular system is made up of the heart, blood vessels and blood

1. The Heart pumps blood

2. Blood vessels are hollow tubes. The three main types are:

Arteries: carry oxygen-rich blood away from the heart

Veins: carry oxygen-poor blood to the heart

Capillaries: Tiny blood vessels that connect arteries to veins. The walls of capillaries are very thin. Gases and nutrients can pass through them and be exchanged between the blood and the cells of the body.

3. Blood is a tissue made up of plasma, blood cells and platelets

Plasma the liquid part of blood made up mostly of water. Plasma contains dissolved nutrients, minerals, salts, and gases.

Red blood cells carry oxygen to the cells of the body and carry carbon dioxide from the cells to the lungs.

White blood cells: There are several types; they fight disease either by engulfing microorganisms or by producing chemical called antibodies to fight infection.

Platelets: Platelets are irregularly shaped cell fragments that clump together into clots that help prevent blood loss from injury. Form a blood clot.

Arteries have strong walls

Veins are less muscular than arteries. There are valves in most veins to prevent backflow. If veins did not have valves blood would have difficulty returning to the heart.

YOU NEED TO KNOW Factors affecting blood flow through the cardiovascular system (blood pressure, blood volume, resistance, disease and exercise)

1.BLOOD PRESSURE

When your heart beats, it pumps blood through your body to give it the energy and oxygen it needs. As the blood moves, it pushes against the sides of the blood vessels. The strength of this pushing is your blood pressure.

Blood Pressure: pressure that is exerted by the blood upon the walls of the blood vessels and especially arteries as the heart pumps blood through the body

Any factor that causes cardiac output to increase, by elevating heart rate or stroke volume or both, will elevate blood pressure and promote blood flow.

Conversely, any factor that decreases cardiac output, by decreasing heart rate or stroke volume or both, will decrease arterial pressure and blood flow.

Hypertension (High Blood Pressure)

A condition present when blood flows through the blood vessels with a force greater than normal. Abnormal high blood pressure increases the resistance to the flow of blood and reduces blood flow. Hypertension can strain the heart, damage blood vessels, and increase the risk of heart attack, stroke, kidney problems, and death.

2. BlOOD VOLUME

Blood volume is the volume of blood (both red blood cells and plasma) in the circulatory system of any individual.

Low blood volume, called hypovolemia, may be caused by bleeding, dehydration, vomiting, severe burns and some medications for hypertension.

Example: If an individual experience a severe injury leading to a drop in blood volume, a decrease in blood pressure will occur, as a result the flow of blood will decrease.

“As blood volume decreases, pressure and flow decrease. As blood volume increases, pressure and flow increase”

3. RESISTANCE

Resistance to blood flow within a vascular network is determined by the size of individual vessels (length and diameter) and the physical characteristics of the blood (viscosity)

A substance called PLAQUE sometimes builds up inside blood vessels. CHOLESTEROL is a waxy substance that is a major component of plaque. PLAQUE MAKES BLOOD VESSELS NARROWER and SLOWS the flow of blood.

Atherosclerosis is a condition in which fatty deposits called plaque build up in artery walls and eventually causes arteries to stiffen. Decreasing the radius of an artery would increase the resistance to blood flow and reduces the flow of blood. A narrowed artery sometimes become blocked by a blood clot.

Hypertension causes small tears in blood vessels, which sets the stage for ARTERIOSCLEROSIS buildup of plaque in arteries. Decreasing the radius of an artery would increase the resistance to blood flow.

Arteriosclerosis begins with injury to the endothelium of an artery, which may be caused by irritation from high blood glucose, infection, tobacco use, excessive blood lipids, and other factors. Artery walls that are constantly stressed by blood flowing at high pressure are also more likely to be injured—which means that hypertension can promote arteriosclerosis, as well as result from it.

4. BLOOD VISCOSITY

Viscosity is the thickness of fluids that affects their ability to flow. Clean water, for example, is less viscous than mud.

Disease like Diabetes affects the flow of blood. Patients with diabetes have a high level of sugar in blood which increases the viscosity of blood. A high viscosity of blood decreases blood flow

In a patient experiencing hypothermia, blood viscosity may increase. The resistance to blood flow would increase, and the flow of blood will decrease.

As the viscosity of the blood increases, resistance increases and the flow of blood decreases

As the viscosity of the blood decreases, resistance decreases and the flow of blood increases

5. Diseases that affect blood flow

Patients with diabetes have a high level of sugar in blood which increases the viscosity of blood. A high viscosity of blood decreases blood flow

Heart attack or Stroke due to blood clots that block arteries which reduces blood flow

6. EXERCISE

Exercise increases blood flow.

When a person exercises heart rate increases and blood vessels in the muscles dilate to increase blood flow.

Athletes’ heart rate is lower than normal. Exercise strengthens the athletes heart muscle so more blood is pumped with each beat.