L5 physiology

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Questions and Answers

What is the normal duration of the P wave in an ECG?

0.16 sec

0.06 sec

0.10 sec (correct)

0.25 sec

Which component of the ECG is primarily associated with ventricular depolarization?

T wave

QRS complex (correct)

U wave

P wave

What is the amplitude of a normal T wave in an ECG?

0.4 mV

0.2 mV (correct)

1 mV

0.1 mV

How is the heart rate calculated using the number of large boxes between two consecutive beats?

Heart rate = 300 / number of large boxes Signup and view all the answers

In which condition is the PR interval most likely prolonged?

Atrial hypertrophy Signup and view all the answers

What does a prolonged PR interval indicate?

Delayed conduction through the AV node Signup and view all the answers

What does the U wave in an ECG typically indicate?

Repolarization of papillary muscle or Purkinje fibers Signup and view all the answers

What does Lead II in an ECG record?

Potential difference between the left leg and the right arm Signup and view all the answers

What is the standard speed of ECG paper?

25 mm/sec Signup and view all the answers

Which unipolar lead is assigned to the left leg?

aVF Signup and view all the answers

Where is the exploring electrode placed for lead V1?

In the fourth intercostal space at the right sternal border Signup and view all the answers

Which leads are used to assess the inferior surface of the heart?

Leads II, III, and aVF Signup and view all the answers

What does lead aVR primarily examine?

The right atrium Signup and view all the answers

What is the purpose of checking voltage calibration in ECG interpretation?

To ensure accurate measurements of the electrical signals Signup and view all the answers

Which leads look at the right ventricle?

V1 and V2 Signup and view all the answers

Which of the following is NOT a step in the commonly followed sequence of ECG interpretation?

Analyze the patient's background Signup and view all the answers

What is the role of capillaries in the circulatory system?

Connect arterioles to venules Signup and view all the answers

Which property of cardiac muscle allows it to initiate beats independently of nervous signals?

Rhythmicity Signup and view all the answers

What is the formula for calculating Stroke Volume (SV)?

SV = EDV - ESV Signup and view all the answers

How much blood is typically pumped by each ventricle per beat at rest?

70-80 ml/beat Signup and view all the answers

What is the primary function of the cardiovascular system?

Removing metabolic byproducts Signup and view all the answers

What characteristic of cardiac muscle allows it to spread electrical impulses throughout the heart?

Conductivity Signup and view all the answers

During which phase do all four chambers of the heart relax?

Diastole Signup and view all the answers

What is considered the steady-state volume of blood pumped by the heart per minute at rest?

5-5.5 L/min Signup and view all the answers

What does the equation CO = HR X SV represent?

The calculation of cardiac output Signup and view all the answers

What does preload represent in cardiac function?

Load acting on the ventricle before contraction Signup and view all the answers

Which statement regarding electrocardiography (ECG) is correct?

ECG captures the algebraic sum of electrical activity during the cardiac cycle Signup and view all the answers

What is the normal range for ejection fraction?

55-80% Signup and view all the answers

Einthoven's Triangle is used to illustrate what concept in ECG?

The placement of electrodes for recording electrical activity Signup and view all the answers

Which process occurs first in the cardiac cycle?

Atrial systole Signup and view all the answers

What is the primary function of the left ventricle in the cardiovascular system?

Pumps oxygenated blood to the body Signup and view all the answers

What does afterload signify in the context of heart function?

Load acting on the ventricle during contraction Signup and view all the answers

The electrical activity that precedes cardiac contraction is primarily due to what ion influx?

Na+ Signup and view all the answers

Which component of the heart controls blood flow from the atrium to the ventricle?

Atrioventricular valve Signup and view all the answers

Which sequence accurately describes the systemic circulation pathway?

Left ventricle → Aorta → Arteries → Capillaries → Veins → Right atrium Signup and view all the answers

What is the role of the right ventricle in the cardiovascular system?

Pumps deoxygenated blood to the lungs Signup and view all the answers

In the context of blood vessels, which statement is correct?

Capillaries are responsible for gas exchange Signup and view all the answers

What term describes the two circuits of blood flow in the cardiovascular system?

Pulmonary and systemic circulation Signup and view all the answers

Which statement accurately describes the function of semilunar valves?

Regulates the flow between the heart and major arteries Signup and view all the answers

What does the term 'Einthoven triangle' refer to?

The configuration of standard ECG leads Signup and view all the answers

Study Notes

Introduction to CVS and ECG

The cardiovascular system is composed of the heart and blood vessels (arteries, arterioles, capillaries, venules, and veins)
The heart has two halves (right and left), each with an atrium and a ventricle
Atrioventricular (AV) valves ensure one-way blood flow from atrium to ventricle
Left ventricle pumps blood to the systemic circulation at high pressure
Right ventricle pumps blood to the pulmonary circulation at lower pressure
Semilunar valves control blood flow between ventricles and major arteries

Learning Objectives

Describe heart chambers, valves, and blood flow direction
Describe systemic and pulmonary circulation
Define ECG
Describe the Einthoven triangle
List ECG leads used in recordings
Describe ECG waves and their relation to the cardiac cycle
Interpret ECG findings
Discuss ECG applications

Circulation

Systemic circulation carries oxygenated blood to body tissues
Pulmonary circulation carries deoxygenated blood to the lungs for gas exchange

Pressures in the Circulation

Right ventricle: 25/0 mm Hg
Pulmonary artery: 25/8 mm Hg
Mean pulmonary artery: 15 mm Hg
Capillary: 7-9 mm Hg
Pulmonary venous: 5 mm Hg
Left atrium: 5-10 mm Hg
Left ventricle: 120/0 mm Hg
Aorta: 120/80 mm Hg
Mean arterial blood pressure: 93 mm Hg
Capillary (skeletal, renal, glomerular): 30 mm Hg, 45-50 mm Hg
Peripheral veins: 15 mm Hg
Right atrium (central venous): 0 mm Hg

Blood Vessels

Form a closed system, beginning and ending at the heart
Arteries carry blood away from the heart
Veins carry blood towards the heart
Capillaries connect arterioles and venules, allowing gas and nutrient exchange

Vessel Types and Function

Arteries: Transport high-pressure blood from heart to smaller arteries/arterioles
Arterioles: Connect arteries and capillaries, act as resistance vessels
Veins: Connect capillaries and venules, transport low-pressure blood to heart
Venules: Connect capillaries to veins
Capillaries: Allow gas exchange, nutrient transfer, and waste removal between blood and tissues

Function of CVS

Transport and distribute essential substances to tissues
Remove metabolic byproducts
Adjust oxygen and nutrient supply in different physiological states
Regulate body temperature
Facilitate humoral communication

How Does the Heart Function?

Heart parts beat in an orderly sequence (atrial systole, ventricular systole, diastole)
Contraction preceded by electrical stimulation (action potential)
Heartbeat originates in specialized cardiac conduction system and spreads to myocardium

Properties of Cardiac Muscle

Excitability
Rhythmicity
Conductivity
Contractility

What is Pumped Out of the Heart?

Stroke Volume (SV): Volume of blood pumped per ventricle beat (70-80 ml/beat)
End Diastolic Volume (EDV): Blood volume remaining in the ventricle at end of diastole (135 ml)
End Systolic Volume (ESV): Blood volume remaining in the ventricle at end of systole (65-70 ml)

Cardiac Output (CO)

Volume of blood pumped by each ventricle per minute (5-5.5 L/min)
CO = Heart Rate (HR) x Stroke Volume (SV)
Cardiac Index = CO/surface area

Important Terms

Preload: Load on the ventricle before contraction (venous return, end-diastolic volume)
Afterload: Load on the ventricle during contraction (arterial resistance, TPR)

What is ECG?

Electrocardiography (ECG): Algebraic summation of electrical activity in cardiac muscle during cardiac cycle
Recording of cardiac muscle's electrical activity (depolarization & repolarization)
Depolarization (due to Na+ influx), Repolarization (due to K+ efflux)

ECG Recording

Body fluids conduct electrical signals
Metal electrodes on extremities & chest wall detect signals
Signals amplified & recorded
ECG can be unipolar (using one active electrode) or bipolar (using two active electrodes)

Einthoven's Triangle

A triangle with electrodes on arms and left leg, center represents zero potential
Used for reference point for unipolar leads
Lead II = Lead I + Lead III

Leads used in ECG Recording

Standard Bipolar Limb Leads (using 2 electrodes): Lead I, Lead II, Lead III
Unipolar Leads (aVR, aVL, aVF)
- aVR: Exploring electrode on right arm
- aVL: Exploring electrode on left arm
- aVF: Exploring electrode on left leg
Unipolar Chest Leads (V1-V6)

The value of different ECG leads

Leads I and aVL: Left lateral wall
Leads II, III, and aVF: Inferior surface
Lead aVR: Atrial activity
V1 and V2: Right ventricle
V3 and V4: Anterior and lateral walls of left ventricle

Normal ECG

P wave: Atrial depolarization
QRS complex: Ventricular depolarization
T wave: Ventricular repolarization
PR interval: Atrial depolarization to ventricular depolarization
QRS duration: Ventricular depolarization time
QT interval: Ventricular depolarization and repolarization

Interpretation of ECG

Voltage calibration
Heart rhythm
Heart rate
Intervals (PR, QRS, QT)
Mean QRS axis
Abnormalities of P wave
Abnormalities of QRS
ST segment and T wave abnormalities

Heart rate by RR interval

Heart rate (bpm) = 1500 / number of small boxes between two consecutive R waves
Heart rate (bpm) = 300 / number of large boxes between two consecutive R waves

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Description

This quiz covers the cardiovascular system, focusing on heart structure, blood flow, and the basics of ECG. You will learn about the heart's chambers, valves, circulation types, and how to interpret ECG findings. Test your knowledge on the functions and applications related to cardiovascular health.