Curriculum

17 Sections
1548 Lessons
100 Days

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U01.01 Biochemistry
This biochemistry review for USMLE Step 1 covers essential topics including metabolism, enzymology, and molecular biology.
126
U01.02 Immunology
Prepare for USMLE Step 1 Immunology with a comprehensive review covering foundational concepts, immune system mechanisms, and key disorders to solidify your understanding and boost exam readiness.
42
U01.03 Microbiology
Review essential microbiology topics for the USMLE Step 1, covering key pathogens, mechanisms of disease, and antimicrobial principles critical for mastering infectious disease concepts.
172
U01.04 General Pathology
Explore key concepts in general pathology essential for the USMLE Step 1. This review covers fundamental principles, disease mechanisms, and clinical correlations to help you excel in your medical exam.
35
U01.05 Pharmacology
Master key pharmacology concepts for the USMLE Step 1 with a focus on drug mechanisms, therapeutic uses, adverse effects, and interactions essential for high-yield exam performance.
43
U01.06 Public Health Sciences
Review essential Public Health Sciences topics for the USMLE Step 1, covering epidemiology, biostatistics, health policy, and ethics to strengthen your understanding of foundational public health principles.
53
U01.07 Cardiovascular system
Comprehensive review of essential cardiovascular system topics to help you excel in the USMLE Step 1 exam, covering key concepts from anatomy to pathology.
73
U01.08 Endocrine system
Master essential concepts of the endocrine system for USMLE Step 1, covering hormone regulation, feedback mechanisms, and key disorders to boost your exam readiness.
51
U01.09 Gastrointestinal system
Review key topics in the gastrointestinal system for the USMLE Step 1, covering essential concepts in anatomy, physiology, pathology, and pharmacology to reinforce your understanding and test readiness.
131
U01.10 Hematology and Oncology
This review covers essential Hematology and Oncology topics for the USMLE Step 1, including hematopoiesis, coagulation, anemias, leukemias, lymphomas, and neoplastic syndromes.
148
U01.11 Musculoskeletal, Skin, and Connective Tissue
Review essential topics for the USMLE Step 1 Musculoskeletal, Skin, and Connective Tissue systems, covering anatomy, physiology, pathology, and pharmacology fundamentals critical for exam success.
178
U01.12 Neurology and Special Senses
Master the foundational concepts of Neurology and Special Senses with our USMLE Step 1 review, covering essential topics like neuroanatomy, neurophysiology, and sensory pathways.
143
U01.13 Psychiatry
Psychiatry for the USMLE Step 1 focuses on understanding the pathophysiology, diagnosis, and treatment of psychiatric disorders, with an emphasis on key concepts like neurotransmitter imbalances, mental health disorders, and pharmacology.
83
U01.14 Renal System
The Renal System review for USMLE Step 1 covers key concepts including renal physiology, nephron function, acid-base balance, electrolyte regulation, and renal pathology, crucial for understanding both normal and abnormal kidney functions.
81
U01.15 Reproductive System
The USMLE Step 1 Reproductive System review covers key concepts in human reproduction, including anatomy, physiology, endocrinology, and common pathologies affecting both male and female reproductive health.
124
U01.16 Respiratory System
The Respiratory System review for the USMLE Step 1 covers key concepts in anatomy, physiology, pathophysiology, and pharmacology essential for understanding respiratory diseases and treatments.
61
U01.17 Rapid Review
he USMLE Step 1 Rapid Review covers essential topics across multiple disciplines, providing a concise, high-yield overview to reinforce key concepts and optimize your exam preparation.
5

U01.07.008 Cardiac output equations

Stroke Volume (SV)

Equation: SV = EDV − ESV

Explanation:

SV: Stroke Volume – the volume of blood pumped out of the left ventricle during each systolic contraction.
EDV: End-Diastolic Volume – the volume of blood in the left ventricle at the end of diastole (ventricular filling).
ESV: End-Systolic Volume – the volume of blood remaining in the left ventricle at the end of systole (ventricular contraction).

Ejection Fraction (EF)

Equation: EF = SV / EDV = (EDV − ESV) / EDV

Explanation:

EF: Ejection Fraction – the percentage of blood ejected from the left ventricle with each beat.
It is an index of ventricular contractility.
EF is typically reduced in systolic heart failure (HF).
EF is usually normal in diastolic heart failure (HF).

Cardiac Output (CO)

Equation: CO = SV × HR

Explanation:

CO: Cardiac Output – the total volume of blood pumped by the heart per minute.
HR: Heart Rate – the number of heartbeats per minute.

Cardiac Output During Exercise:

In the early stages of exercise, CO is maintained by an increase in both HR and SV.
In later stages of exercise, CO is maintained primarily by an increase in HR because SV plateaus.

Impact of Heart Rate on Diastole and Stroke Volume:

A significant increase in HR (e.g., ventricular tachycardia) leads to shortened diastole.
Shortened diastole results in decreased diastolic filling time, leading to a decrease in SV, which ultimately reduces CO.

Fick Principle

Equation: CO = Rate of O2 consumption / (arterial O2 content – venous O2 content)

Explanation:

The Fick principle states that cardiac output can be calculated based on the rate of oxygen consumption by the body and the arteriovenous oxygen difference.

Pulse Pressure (PP)

Equation: PP = SBP – DBP

Explanation:

PP: Pulse Pressure – the difference between the systolic blood pressure and the diastolic blood pressure.
SBP: Systolic Blood Pressure – the maximum pressure in the arteries when the heart contracts.
DBP: Diastolic Blood Pressure – the minimum pressure in the arteries when the heart relaxes.

Factors Affecting Pulse Pressure:

PP is directly proportional to stroke volume (SV).
PP is inversely proportional to arterial compliance (the ability of arteries to stretch and recoil).

Conditions with Increased Pulse Pressure (↑ PP):

Hyperthyroidism
Aortic regurgitation
Aortic stiffening (isolated systolic hypertension in the elderly)
Obstructive sleep apnea (due to increased sympathetic tone)
Anemia
Exercise (transient)

Conditions with Decreased Pulse Pressure (↓ PP):

Aortic stenosis
Cardiogenic shock
Cardiac tamponade
Advanced heart failure (HF)

Mean Arterial Pressure (MAP)

Equation: MAP = CO × TPR

Explanation:

MAP: Mean Arterial Pressure – the average arterial pressure throughout one cardiac cycle.
TPR: Total Peripheral Resistance – the resistance to blood flow in the systemic circulation.

Approximation of MAP at Resting Heart Rate:

MAP ≈ 2/3 DBP + 1/3 SBP
MAP ≈ DBP + 1/3 PP

Points to Remember

Stroke volume is determined by the difference between the blood volume in the ventricle at the end of filling (EDV) and the volume remaining after contraction (ESV).
Ejection fraction provides a measure of how effectively the ventricle is pumping blood and is a key indicator of systolic function.
Cardiac output is the product of heart rate and stroke volume, representing the total blood flow from the heart.
During exercise, the body initially increases both heart rate and stroke volume to meet increased oxygen demands, but at higher intensities, further increases in cardiac output rely primarily on heart rate increases.
A very high heart rate can impair ventricular filling, leading to a reduction in stroke volume and consequently cardiac output.
Pulse pressure reflects the pulsatile nature of arterial blood flow and is influenced by stroke volume and the elasticity of the arteries. Changes in pulse pressure can indicate various physiological and pathological conditions.
Mean arterial pressure is a crucial indicator of tissue perfusion and is determined by cardiac output and total peripheral resistance.

Sample Calculations

1. Stroke Volume:

Assume EDV = 120 mL and ESV = 50 mL.
SV = EDV – ESV = 120 mL – 50 mL = 70 mL

2. Ejection Fraction:

Using the SV and EDV from above:
EF = SV / EDV = 70 mL / 120 mL = 0.583 or 58.3%

3. Cardiac Output:

Using the calculated SV (70 mL) and assuming a heart rate (HR) of 75 beats/minute:
CO = SV × HR = 70 mL/beat × 75 beats/minute = 5250 mL/minute = 5.25 L/minute

4. Pulse Pressure:

Assume SBP = 120 mmHg and DBP = 80 mmHg.
PP = SBP – DBP = 120 mmHg – 80 mmHg = 40 mmHg

5. Mean Arterial Pressure (Approximation):

Using the SBP and DBP from above:
MAP ≈ 2/3 DBP + 1/3 SBP = (2/3 × 80 mmHg) + (1/3 × 120 mmHg) = 53.33 mmHg + 40 mmHg = 93.33 mmHg
Alternatively, using DBP and PP:
MAP ≈ DBP + 1/3 PP = 80 mmHg + (1/3 × 40 mmHg) = 80 mmHg + 13.33 mmHg = 93.33 mmHg

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USMLE Step 1 Review Series

Curriculum

U01.07.008 Cardiac output equations

Stroke Volume (SV)

Ejection Fraction (EF)

Cardiac Output (CO)

Fick Principle

Pulse Pressure (PP)

Mean Arterial Pressure (MAP)

Points to Remember

Sample Calculations

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