Electrical Activity, Cardiac Cycle, and ECGs
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Questions and Answers

Which component of the ECG corresponds to the depolarization of the atria?

  • QRS complex
  • P wave (correct)
  • ST segment
  • T wave

The QRS complex on an ECG represents which electrical event in the heart?

  • Ventricular repolarization
  • Atrial depolarization
  • Ventricular depolarization (correct)
  • Atrial repolarization

What physiological event does the ST segment of an ECG correlate with?

  • Atrial contraction
  • Ventricular contraction (correct)
  • Ventricular repolarization
  • Atrial repolarization

What causes the first heart sound (S1 or 'Lub')?

<p>Closing of the atrioventricular (AV) valves (C)</p> Signup and view all the answers

During which phase of the cardiac cycle is the Stroke Volume ejected?

<p>Ventricular Ejection (D)</p> Signup and view all the answers

If the End Diastolic Volume (EDV) is 130 mL and the Stroke Volume (SV) is 70 mL, what is the Ejection Fraction (EF)?

<p>Approximately 54% (A)</p> Signup and view all the answers

What is the state of the heart valves during Isovolumetric Ventricular Relaxation?

<p>Both AV and semilunar valves are closed (C)</p> Signup and view all the answers

During what phase of the cardiac cycle does the atrial pressure exceed ventricular pressure?

<p>Ventricular Filling (C)</p> Signup and view all the answers

During intense exercise, the sympathetic nervous system (SNS) releases norepinephrine. Which of the following is the MOST direct effect of norepinephrine on cardiac function?

<p>Increased stroke volume due to enhanced contractility. (D)</p> Signup and view all the answers

A patient has an end diastolic volume (EDV) of 150 mL and an end systolic volume (ESV) of 70 mL. What is their ejection fraction (EF)?

<p>53% (A)</p> Signup and view all the answers

Which scenario would MOST likely result in a decrease in stroke volume?

<p>Increased activity of the parasympathetic nervous system (PSNS) via the vagus nerve. (B)</p> Signup and view all the answers

According to the Frank-Starling Law, what is the immediate effect of increased venous return on cardiac output?

<p>Increased preload, leading to increased stroke volume and cardiac output. (A)</p> Signup and view all the answers

If a person's heart rate increases from 70 bpm to 140 bpm, and their stroke volume remains constant, what is the MOST likely effect on their cardiac output?

<p>Cardiac output will double. (C)</p> Signup and view all the answers

In the pulmonary circulation, what is the primary function of the alveolar capillaries?

<p>Exchanging oxygen and carbon dioxide with the alveoli. (A)</p> Signup and view all the answers

What is the key feature of the hepatic portal system that distinguishes it from typical systemic circulation?

<p>It involves blood passing through two capillary beds before returning to the heart. (A)</p> Signup and view all the answers

According to hemodynamic principles, how does an increased pressure difference (change in P) influence blood flow (F), assuming resistance remains constant?

<p>Blood flow increases proportionally to the increase in pressure difference. (C)</p> Signup and view all the answers

During blood pressure measurement using a sphygmomanometer, which Korotkoff sound indicates the diastolic pressure?

<p>The point when sounds disappear entirely. (B)</p> Signup and view all the answers

If a patient's blood pressure is measured as 140/90 mmHg, what is their pulse pressure?

<p>50 mmHg (B)</p> Signup and view all the answers

A patient has a blood pressure of 130/80 mmHg. Calculate their Mean Arterial Pressure (MAP).

<p>97 mmHg (B)</p> Signup and view all the answers

Which of the following best describes the primary difference between arteriosclerosis and atherosclerosis?

<p>Arteriosclerosis refers to the general hardening and thickening of arteries, while atherosclerosis is a specific type of arteriosclerosis involving plaque buildup. (C)</p> Signup and view all the answers

A patient consistently presents with blood pressure readings below 90/60 mmHg. Which condition is the MOST likely diagnosis and what physiological effect could result from it?

<p>Hypotension; inadequate perfusion of tissues and organs. (C)</p> Signup and view all the answers

How does vasodilation affect total peripheral resistance (TPR) and blood flow?

<p>Decreases TPR, increases blood flow (D)</p> Signup and view all the answers

What is the primary advantage of the body redirecting blood flow in a parallel arrangement?

<p>Allowing precise regulation of blood distribution to individual tissues based on their needs. (D)</p> Signup and view all the answers

According to the principles governing resistance in blood vessels, if the radius of a vessel decreases by half due to vasoconstriction, how would you expect the resistance to change, assuming all other factors remain constant?

<p>Increase by a factor of 16 (D)</p> Signup and view all the answers

Why is it important for blood to flow slowly through capillaries?

<p>To maximize the time available for exchange of gases, nutrients, and waste products. (D)</p> Signup and view all the answers

What is the primary mechanism by which the body ensures that all tissues receive blood of the same quality, despite variations in metabolic demand?

<p>Parallel arrangement of blood flow (B)</p> Signup and view all the answers

Which of the following best describes the tunica media's composition and primary role in blood vessels?

<p>Smooth muscle and varying amounts of elastic tissue controlling vessel diameter and blood pressure. (C)</p> Signup and view all the answers

How do veins adapt to accommodate varying blood volumes, and why is this important for circulatory function?

<p>Veins have thin walls and high elasticity, allowing them to expand and store a large blood volume, crucial for maintaining cardiac output. (C)</p> Signup and view all the answers

In an arteriovenous anastomosis, what is the functional significance of blood bypassing the capillary beds?

<p>It enables blood to bypass tissues, regulating temperature and blood flow to adjust to physiological needs. (B)</p> Signup and view all the answers

If a thrombus (blood clot) completely occludes the right subclavian artery, which of the following regions would be most immediately affected by reduced blood flow?

<p>The right upper extremity. (A)</p> Signup and view all the answers

Why is the hepatic portal system essential for maintaining homeostasis in the body?

<p>It allows the liver to process nutrients and filter toxins absorbed from the digestive system before they enter systemic circulation. (C)</p> Signup and view all the answers

Why do arteries, unlike veins, tend to remain open and retain their shape after death?

<p>Arteries are thicker and contain more smooth muscle and elastic tissue in their walls than veins. (A)</p> Signup and view all the answers

In a patient with severe liver disease, the hepatic portal system's function is compromised. What immediate physiological consequence would you expect to observe?

<p>Accumulation of toxins and unprocessed nutrients in systemic circulation. (C)</p> Signup and view all the answers

A patient has a condition that reduces the elasticity of their arterial walls. How would this specifically affect their blood pressure and overall cardiovascular function?

<p>It would increase systolic pressure and potentially lead to hypertension due to reduced arterial compliance. (D)</p> Signup and view all the answers

Which of the following conditions is characterized by a chronic systolic blood pressure consistently greater than 130 mmHg and a diastolic pressure greater than 80 mmHg at rest?

<p>Hypertension (B)</p> Signup and view all the answers

A patient is diagnosed with arteriosclerosis. How does this condition contribute to high blood pressure?

<p>By reducing arterial elasticity, making the vessels more rigid. (B)</p> Signup and view all the answers

Which of the following best describes how arterial elasticity affects blood pressure during systole and diastole?

<p>Arterial dilation during systole leads to a systolic value of ~120 mmHg, while arterial constriction during diastole leads to a diastolic value of ~75/80 mmHg. (D)</p> Signup and view all the answers

If arteries were completely rigid and lacked elasticity, what would be the likely effect on blood pressure during systole and diastole, respectively?

<p>Systole: 380 mmHg; Diastole: 0 mmHg (D)</p> Signup and view all the answers

Which of the following is NOT a benefit of elastic recoil in arteries?

<p>Increasing stress on the heart and vessels. (A)</p> Signup and view all the answers

How does blood pressure change as blood flows from the aorta towards the capillaries?

<p>Blood pressure decreases due to increasing distance from the left ventricle and friction. (B)</p> Signup and view all the answers

Why is blood pressure non-pulsatile in capillaries and veins compared to arteries?

<p>Because capillaries and veins are not elastic and are farther from the heart. (A)</p> Signup and view all the answers

Which of the following explains why veins have the lowest blood pressure in the circulatory system?

<p>To ensure blood flows from areas of high pressure to low pressure. (C)</p> Signup and view all the answers

Flashcards

P wave

Indicates depolarization of the SA node and atrial contraction.

QRS complex

Represents ventricular depolarization and atrial repolarization (not visible).

T wave

Shows ventricular repolarization after contraction.

Cardiac Cycle

One full contraction and relaxation of all four heart chambers.

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Stroke Volume

Amount of blood ejected from the ventricles each beat, approximately 70 mL.

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End Systolic Volume (ESV)

Amount of blood remaining in the ventricles after contraction, around 60 mL.

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Ejection Fraction (EF)

Percentage of blood ejected from the heart with each beat; important for cardiac health.

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Isovolumetric Ventricular Relaxation

Phase when all heart valves are closed, and ventricular volume remains unchanged.

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Heart Rate (HR)

The number of times blood pumps through an artery in one minute.

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Stroke Volume (SV)

The amount of blood ejected by the heart with each contraction; approximately 70 mL.

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Cardiac Output (CO)

The total amount of blood ejected by the heart in one minute; calculated as HR x SV.

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Preload

The amount of blood in the ventricles before they contract; influences stroke volume.

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Vessel Walls

Consist of Tunica interna, Tunica media, and Tunica Externa.

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Arteries

Blood vessels that carry blood away from the heart, withstand high blood pressure.

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Capillaries

Exchange vessels with pores; allow material exchange; no muscle or connective tissue.

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Veins

Blood vessels that carry blood towards the heart; have valves to ensure one-way flow.

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Portal System

A system with two capillary beds, such as hepatic and hypothalamic-pituitary connections.

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Anastomosis

Connection between blood vessels, can be arteriovenous (no capillaries) or venous.

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Pulmonary Circulation

Pathway carrying deoxygenated blood to the lungs for oxygenation and back to the heart.

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Major Branches of Aorta

Includes the Brachiocephalic arch, left carotid, and left subclavian arteries; supplies head and arms.

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Resistance in blood vessels

Opposition to blood flow, influenced by vessel radius.

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Total Peripheral Resistance (TPR)

The overall resistance to blood flow in the systemic circulation.

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Vasodilation

Widening of blood vessels, leading to decreased resistance and increased flow.

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Vasoconstriction

Narrowing of blood vessels, resulting in increased resistance and decreased flow.

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Capillary Exchange

The process of nutrient and waste transfer between blood and tissues.

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Hypertension

Chronic high blood pressure, defined as >130/80 mmHg at rest.

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Hypotension

Chronic low blood pressure that can lead to insufficient blood flow.

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Arteriosclerosis

Loss of arterial elasticity, often termed 'hardening of the arteries'.

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Atherosclerosis

A form of arteriosclerosis with lipid accumulation blocking arteries.

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Systolic pressure

Pressure in arteries during heart contraction, typically ~120 mmHg.

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Diastolic pressure

Pressure in arteries during heart relaxation, typically ~75/80 mmHg.

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Peripheral resistance

Resistance blood encounters in vessels; affects blood pressure.

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Elastic recoil

Ability of arteries to spring back, maintaining blood flow and reducing pressure fluctuations.

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Hepatic Portal System

Blood flow through two capillary beds before reaching the heart, primarily from the GI tract to the liver.

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Hemodynamics

The study of blood flow and pressure in the circulatory system.

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Blood Pressure Measurement

Determined by using a sphygmomanometer, measuring systolic over diastolic pressure.

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Pulse Pressure

The difference between systolic and diastolic pressure; indicates pressure in arterioles.

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Mean Arterial Pressure (MAP)

The average blood pressure in a person's arteries during one cardiac cycle.

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Study Notes

Electrical Activity and Cardiac Cycle

  • Electrocardiograms (ECGs) are composite recordings of heart's electrical activity. They aren't single action potentials.
  • An ECG includes P waves (atrial depolarization), QRS complexes (ventricular depolarization), T waves (ventricular repolarization), PQ segments (atrial contraction), and ST segments (ventricular contraction). Atrial repolarization is usually hidden by the QRS complex.
  • The cardiac cycle is one complete contraction and relaxation of all four heart chambers (less than 1 second).

Cardiac Cycle Phases

  • Ventricular Filling (Diastole): Atria and ventricles relax. AV valves are open; aortic and pulmonary valves are closed. Atrial contraction adds about 30% of blood to the ventricles.
  • Isovolumetric Ventricular Contraction (Systole): Ventricles contract. AV valves close ("lub" sound or S1). Aortic and pulmonary valves are still closed.
  • Ventricular Ejection (Systole): Ventricular pressure exceeds arterial pressure. Aortic and pulmonary valves open. Blood is ejected.
  • Isovolumetric Ventricular Relaxation (Diastole): Ventricles relax. Aortic and pulmonary valves close ("dub" sound or S2).

Cardiac Cycle Volumes and Pressures

  • End Diastolic Volume (EDV): ~130 mL (per ventricle)
  • End Systolic Volume (ESV): ~60 mL (per ventricle)
  • Atrial pressure is higher than ventricular pressure during filling.
  • Ventricular pressure rises and exceeds atrial pressure, causing AV valves to close.
  • Ventricular pressure rises and exceeds arterial pressure. Semilunar valves open.
  • Ventricles continue to contract, pushing blood out.
  • Ventricular pressure drops below arterial pressure. Semilunar valves close.

Heart Sounds

  • Lub: AV valves closing during isovolumetric ventricular contraction
  • Dub: Semilunar valves closing during isovolumetric ventricular relaxation

Cardiac Output (CO), Stroke Volume (SV) and Heart Rate (HR)

  • Cardiac Output (CO) is the amount of blood pumped by each ventricle per minute (ml/min).
  • Stroke Volume (SV) is the amount of blood pumped by each ventricle per beat.
  • Heart Rate (HR) is the number of heart beats per minute.
  • CO = HR x SV (approximately 5 L/min at rest in healthy adults).

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Description

Explore the heart's electrical activity and the cardiac cycle phases: ventricular filling, isovolumetric ventricular contraction, and ventricular ejection. Understand ECG waves (P, QRS, T) and their correlation to heart function. Learn about the timing and events of a complete heartbeat.

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