Lecture 13: Circulation

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Questions and Answers

How many kilometers of vessels are present in the human body?

150,000 km

75,000 km

50,000 km

100,000 km (correct)

What is the estimated number of blood cells in the human body?

50 million

60 million

100 million

75 million (correct)

How many times does the heart beat in a person's lifetime of 80 years?

2 billion times

2.5 billion times

3.5 billion times (correct)

4 billion times

What is the direction of blood flow in the human body?

Unidirectional Signup and view all the answers

What type of circulatory system do humans have?

Closed circulatory system Signup and view all the answers

What is unique about the human heart?

It is divided into right and left sides Signup and view all the answers

What is the purpose of the lymphatic system?

To complete the circuit back to the heart Signup and view all the answers

What is the term for the study of the circulatory system?

Angiology Signup and view all the answers

What type of cells in the heart generate an electrical signal to coordinate contraction?

Autorhythmic cells Signup and view all the answers

What is the volume of blood ejected from the heart during each contraction?

70 mL Signup and view all the answers

What is the formula to calculate cardiac output (CO)?

CO = SV x HR Signup and view all the answers

What system alters heart rate (HR) by changing the depolarization of the autorhythmic cells?

Autonomic nervous system Signup and view all the answers

What is the heart rate (HR) in the example given in the text, where CO = 5.4 L/min?

72 bpm Signup and view all the answers

What is the amount of blood remaining in the heart after each beat, at rest?

65 mL Signup and view all the answers

What percentage of the blood is made up of water?

92% Signup and view all the answers

What is the main function of erythropoietin (EPO)?

To stimulate the production of erythrocytes Signup and view all the answers

What is the purpose of blood doping in athletic performance?

To improve the body's ability to transport O2 Signup and view all the answers

What is the main component of the cardiac muscle?

Cardiac muscle Signup and view all the answers

What is the trigger for erythropoietin (EPO) release?

Hypoxia Signup and view all the answers

What is the function of the circulating portion of the blood?

To act as a buffer between the cells and the external environment Signup and view all the answers

What is the percentage of protein in the blood composition?

7% Signup and view all the answers

Where is erythropoietin (EPO) produced?

The kidneys Signup and view all the answers

What is the direction of blood flow in the arterial system?

From arteries to arterioles to capillaries Signup and view all the answers

Why does blood pressure decrease as blood flows away from the heart?

Due to the resistance in the vascular system Signup and view all the answers

What is the significance of the two numbers in a blood pressure reading?

The top number is the systolic pressure and the bottom number is the diastolic pressure Signup and view all the answers

What is the relationship between blood pressure and the distance from the heart?

Blood pressure decreases as you move away from the heart Signup and view all the answers

What is the main reason for the difference in pressure between the arterial and venous systems?

The heart pumps blood more forcefully into the arteries Signup and view all the answers

What is the direction of blood flow in the venous system?

From veins to capillaries to heart Signup and view all the answers

What is the systolic pressure in the arteries when the heart has contracted?

120 mmHg Signup and view all the answers

What is the term for the condition where the blood pressure drops when standing up?

Postural hypotension Signup and view all the answers

Why does blood 'pool' in the feet when standing?

Because the blood is not returning to the heart efficiently Signup and view all the answers

What is the function of the venous valve in the circulatory system?

To prevent backflow of blood Signup and view all the answers

What is the term for the movement of fluid through the capillary walls?

Bulk flow Signup and view all the answers

What is one of the key functions of the lymphatic system?

To return filtered fluid to the circulatory system Signup and view all the answers

What is the term for the pressure in the arteries when the heart is fully relaxed?

Diastolic pressure Signup and view all the answers

What happens when not enough blood is returning to the heart?

The person faints Signup and view all the answers

What is the purpose of the action of venous valves?

To permit flow of blood toward the heart Signup and view all the answers

What is the term for the movement of fluid in both directions on squeezing a fluid-filled tube?

Fluid moving in both directions Signup and view all the answers

Study Notes

Human Circulatory System

The human circulatory system is a closed system, physically separated from the rest of the body, consisting of vessels and a pump.
The human heart is divided into right and left sides, making it a "double" circulatory system.

Blood Composition

Blood is a connective tissue made up of cellular elements suspended in a fluid matrix called plasma.
It makes up a quarter of the extracellular fluid (ECF) and acts as a buffer between cells and the external environment.
Blood composition is 92% water, 7% protein, and 1% dissolved organic molecules.

Erythropoiesis

Erythropoiesis is controlled by the glycoprotein erythropoietin (EPO) and cytokines produced by the kidneys.
The trigger for EPO release is hypoxia, which relieves reduced oxygen-carrying capacity.

Blood Doping

Blood doping is used to improve athletic performance by artificially improving the body's ability to transport oxygen to tissues/muscles.
Three common types of blood doping are blood transfusion, injection of EPO, and injection of synthetic oxygen carriers.

The Heart

The heart is the "workhorse" of the body, generating pressure to force blood continuously around the body.
It is composed predominantly of cardiac muscle.

Heart Contraction

Specialized cells within the heart generate an electrical signal to coordinate contraction.
This electrical signal depolarizes the membrane, spreading rapidly through the conducting pathway.

Mechanical Events of the Heart

The heart's mechanical events are controlled by the electrical signal, leading to contraction and relaxation.

Heart Rate

The heart rate is altered by the autonomic nervous system, changing the depolarization of the autorhythmic cells.
Cardiac output (CO) is measured by the stroke volume (SV) x heart rate (HR).

Blood Flow

Blood flows from an area of high to low pressure, driven by blood pressure.
The arterial system is under high pressure, and the venous system is under low pressure.

Blood Pressure

Blood pressure is recorded as two numbers: systolic pressure (120 mmHg) and diastolic pressure (80 mmHg).
Systolic pressure is the pressure in the arteries when the heart has contracted, and diastolic pressure is the pressure in the arteries when the heart is fully relaxed.

Postural Hypotension

Postural hypotension occurs when standing causes blood to "pool" in the feet, leading to a decrease in blood pressure.
This can cause fainting, especially in cases where the person does not move their legs.

Capillary Transport

There are three mechanisms of exchange in capillary transport: movement between endothelium, transcytosis, and bulk flow.

Lymphatic System

The lymphatic system has three key functions: returning filtered fluid to the circulatory system, fat reabsorption from the gut into circulation, and destroying foreign pathogens.

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Description

Explore the pulmonary and systemic circuits of the human circulatory system, and how the heart drives blood flow.