[SET 2] 40 The Circulatory System

40.3 Mammalian Heart and Blood Vessels 40.4 Blood Flow and Blood Pressure Regulation

What are the three divisions of the circulatory system?

Coronary, pulmonary, and systemic.

What is the primary function of the heart?

To pump blood through the body.

How many chambers does the human heart have?

Four chambers: two atria and two ventricles.

What separates the right atrium from the right ventricle?

The tricuspid valve (atrioventricular valve).

What is the role of the bicuspid (mitral) valve?

It separates the left atrium from the left ventricle.

What happens during the systole phase of the cardiac cycle?

The heart contracts, pushing blood out of the chambers.

What happens during the diastole phase of the cardiac cycle?

The heart relaxes and fills with blood.

What is the function of the coronary arteries?

To supply blood to the heart muscle.

What is atherosclerosis?

The blockage of an artery by the buildup of fatty plaques.

What is myocardial infarction commonly known as?

A heart attack.

What is the significance of Marie M. Daly's research?

She was the first to associate cholesterol and high blood pressure with atherosclerosis.

What is the sound produced by the closing of the atrioventricular valves?

A monosyllabic 'lup' sound.

What is the sound produced by the closing of the semilunar valves?

A monosyllabic 'dup' sound.

What type of circulation is found in all mammals?

Double circulation.

What is the role of the pulmonary circuit?

To carry deoxygenated blood to the lungs for re-oxygenation.

What is the main artery that carries oxygenated blood from the heart?

The aorta.

How does blood flow from the right atrium to the lungs?

Through the right ventricle, then through the pulmonary artery.

What is the myocardium?

The thick muscle layer of the heart.

What is the epicardium?

The outer layer of cells surrounding the heart.

What is the endocardium?

The inner lining of the heart.

What is the function of the pericardium?

To protect the heart and reduce friction during pumping.

What is the role of the coronary veins?

To take deoxygenated blood back to the right atrium.

What is the significance of the cardiac cycle?

It coordinates the filling and emptying of the heart.

What does the term 'systole' refer to?

The contraction phase of the heart.

What does the term 'diastole' refer to?

The relaxation phase of the heart.

What is the primary purpose of the heart's valves?

To prevent backflow of blood.

What occurs during atrial systole?

The atria contract, pushing blood into the ventricles.

What happens during atrial diastole?

The ventricles contract, forcing blood out of the heart.

What are cardiomyocytes?

Distinctive muscle cells that are striated like skeletal muscle but pump rhythmically and involuntarily like smooth muscle.

What connects cardiomyocytes?

Intercalated disks, which are exclusive to cardiac muscle.

How do cardiomyocytes behave when isolated?

They can beat if given the correct balance of nutrients and electrolytes.

What regulates the autonomous beating of cardiac muscle cells?

The heart's internal pacemaker, which uses electrical signals.

Where is the sinoatrial (SA) node located?

Near the wall of the right atrium.

What is the function of the atrioventricular (AV) node?

It pauses the electrical impulse for approximately 0.1 seconds before spreading it to the ventricles.

What is the bundle of His?

A pathway for electrical impulses from the AV node to the left and right bundle branches.

What do Purkinje fibers do?

Conduct the impulse from the apex of the heart up the ventricular myocardium, leading to ventricular contraction.

What is an electrocardiogram (ECG)?

A recording of the electrical impulses of the cardiac muscle.

What is the main function of arteries?

To carry blood away from the heart.

What is the largest artery in the body?

The aorta.

What do capillaries do?

They are the sites for the exchange of nutrients, waste, and oxygen with tissues at the cellular level.

What are venules?

Small vessels that connect capillaries to minor veins.

How do veins differ from arteries?

Veins have thinner walls and valves to prevent backflow of blood.

What is blood pressure (BP)?

The pressure exerted by blood on the walls of a blood vessel that helps push blood through the body.

What is systolic blood pressure?

The pressure in blood vessels while the heart is beating, with an optimal value of 120 mm Hg.

What is diastolic blood pressure?

The pressure in blood vessels between heartbeats, with an optimal value of 80 mm Hg.

What factors can affect blood pressure?

Hormones, stress, exercise, eating, sitting, and standing.

How does blood flow through the body?

Blood is pushed through the body by the pumping heart, initially at high pressure through the aorta.

What happens to blood flow speed as it moves from arteries to capillaries?

The rate of movement slows dramatically to about 0.026 cm/sec in capillary beds.

What is the relationship between the diameter of capillaries and blood flow rate?

Although individual capillaries are narrower than the aorta, the total diameter of all capillaries is greater, resulting in a slower blood flow rate through capillary beds.

Why is slow blood flow through capillary beds beneficial?

It assists with gas and nutrient exchange and promotes the diffusion of fluid into the interstitial space.

How does blood flow increase after passing through capillary beds?

Blood flow increases as it moves through venules and veins, but remains slower than in the aorta.

What mechanisms help blood move through veins?

Blood moves in veins primarily through the rhythmic movement of smooth muscle in the vessel wall and the action of skeletal muscles.

What role do one-way valves play in veins?

They prevent blood from flowing backward, especially against gravity.

What is the importance of movement after prolonged sitting?

It prevents blood from pooling in the extremities due to the assistance of skeletal muscle contraction in venous blood flow.

How is blood flow through capillary beds regulated?

It is regulated by nerve and hormone signals based on the body's needs.

What happens to blood flow after a large meal?

Blood is diverted to the stomach through vasodilation of digestive vessels, while vasoconstriction occurs in other vessels.

What are precapillary sphincters?

Small muscles that control blood flow into capillary beds; they can open or close to direct blood flow.

What occurs if all precapillary sphincters are closed?

Blood flows directly from the arteriole to the venule through the thoroughfare channel.

What are varicose veins?

Enlarged veins that occur when valves fail to close properly, allowing blood to flow backward.

What percentage of capillary beds typically have blood flowing through them at any given moment?

About 5-10%.

What happens to proteins and large solutes in capillaries?

They cannot leave the capillaries, creating a hyperosmotic solution that causes most plasma to return to the capillaries.

What is lymph and how does it relate to blood flow?

Lymph is fluid that drains from interstitial fluid into lymphatic vessels and is similar in composition to interstitial fluid.

What role do lymph nodes play in the circulatory system?

They filter lymph to remove infectious agents before it returns to the bloodstream.

How do vertebrates adapt blood circulation to their environments?

Different adaptations exist based on pressure requirements, organ locations, and sizes, such as in long-necked animals or those in cold environments.

What is the hydrostatic pressure in blood circulation?

It is the pressure of blood against the walls of blood vessels, driving fluid movement from high to low pressure areas.

What happens to artery walls during systole and diastole?

During systole, they stretch to accommodate increased pressure; during diastole, they return to normal due to elasticity.

What is peripheral resistance?

The resistance to blood flow in the arterioles, affecting blood pressure and flow rate.

How is cardiac output calculated?

By multiplying heart rate by stroke volume, representing the volume of blood pumped by the heart in one minute.

What factors can increase cardiac output?

Increasing heart rate or stroke volume can enhance cardiac output, especially during exercise.

What physiological changes occur during heavy exertion?

Blood vessels relax and increase in diameter to ensure adequate oxygenated blood reaches the muscles.

How does stress affect blood pressure?

It triggers a decrease in the diameter of blood vessels, consequently increasing blood pressure.