Exercise Physiology Quiz: Cardiovascular Responses

Cardiovascular System Overview

• Cardiovascular system is the #1 cause of global mortality.
• Approximately 18,000,000 deaths occur annually due to cardiovascular issues.
• VO2max is the second leading predictor of all-cause mortality.
• VO2max represents the maximum amount of oxygen intake, transport, and utilization.
• A 1-MET increase in VO2max correlates with a 13% reduction in mortality risk.
• 1 MET is equivalent to 3.5 ml O2/kg/min (milliliters of oxygen per kilogram of body weight per minute).

Why Care About Cardiovascular Health?

• Cardiovascular disease is the leading cause of death globally.
• Understanding cardiovascular function and responses to exercise is crucial for overall health.

Components of the Cardiovascular System

• Heart and blood are the core components.
• Pulmonary circulation involves the flow of blood between the heart and lungs.
• Systemic circulation involves the flow of blood between the heart and the rest of the body.

Purposes of the Cardiovascular System

• Deliver oxygen and nutrients to tissues and transport carbon dioxide to the lungs.
• Maintain body temperature and blood pH.
• Transport hormones and nutrients to tissues.
• Maintain blood pressure.

Blood Basics

• The human body contains approximately 5 liters of blood.
• Blood is composed of:
  • 55% plasma (mostly water, plasma proteins, and other constituents)
  • 45% formed elements (red blood cells, white blood cells, and platelets).
• Male hematocrit ranges from 40-45%, and female hematocrit ranges from 35-40%.
• Polycythemia vera is a condition where there's an excess production of red blood cells, resulting in a hematocrit greater than 60%.

Quiz Questions

• Name the two types of circulation (pulmonary and systemic).
• What are the two primary components of blood (plasma and formed elements)?
• On average, how much blood is in the human body (approximately 5 liters)?

The Heart

• The heart's role is to pump blood throughout circulatory system.

Heart Anatomy/Structure

• Images provided show various heart structures including the vena cava (superior and inferior), pulmonary artery and veins, atria (right and left), ventricles (right and left), mitral valve, aortic valve, the tricuspid valve, and pulmonary valve.
• The pericardium surrounds the heart.

Automaticity

• The intrinsic ability of the heart to generate its own electrical impulses.

Intrinsic Conduction System

• The SA node initiates the heartbeat.
• Components of intrinsic conduction system include:
  • Sinoatrial (SA) node
  • Anterior, middle, and posterior internodal tracts
  • Atrioventricular (AV) node
  • Left and right bundle branches
  • Pathway conduction
• This system regulates the heartbeat's rhythm.

Extrinsic Conduction System

• The nervous system's control over the heart rate and its contractile strength.
• The vagus nerve (parasympathetic) decreases heart rate.
• Sympathetic cardiac nerves increase heart rate and contractile force.

Cardiac Muscle

• Cardiac muscle cells are interconnected via intercalated discs.
• Cells exhibit striations with branched fibers arranged in interwoven fashion.

Cardiac Muscle Cells

• Myocardium predominantly contains slow oxidative muscle fibers.
• Contains specialized structures like the nucleus and mitochondria, crucial for energy production and cell function.

Cardiac Muscle Arrangement

• Includes components like Z-disc, A-band, I-band, and H-zone.
• These components are key structural units in cardiac muscle fibers, crucial for contraction and relaxation.
• The diagram depicts layers like the myocardium and endocardium within the heart.

Background of the Heart Layers

• The epicardium is the outer layer of the heart, the innermost layer is the endocardium, and the myocardium is the thick muscular layer between them.
• The heart's layers, including the pericardium and its different layers, all contribute to protecting and enabling the heart to pump blood effectively.

Quiz Questions (Summary)

• What is the term for the heart's self-depolarization ability? (Automaticity)
• Which division of the nervous system controls the extrinsic conduction system? (Nervous system)
• What type of muscle fiber is mainly found in the myocardium? (Slow oxidative muscle fiber)

Vascular System

• The vascular system includes the arteries, veins, and capillaries.
• The tunics are the layers of the artery walls or veins (e.g., tunica intima, media, and adventitia).
• Blood flow is one-way in the circulatory system.
• Capillary beds deliver blood to tissues and then return it to a venule.
• Systemic circulation moves oxygenated blood from the heart to the body and deoxygenated blood to the heart.
• Pulmonary circulation moves oxygenated blood from the heart to the lungs and deoxygenated blood to the heart.

Systemic Circuit

• Blood moves from high to low pressure in this circuit.
• The highest cross-sectional area is in the capillaries.
• The lowest velocity is found in the capillaries.
• The greatest drop in blood pressure is from the aorta (highest pressure) to the vena cava (lowest pressure).

Pulmonary Circuit

• Pressure is lower compared to the systemic circuit.
• The cross-sectional area (CSA) of pulmonary capillaries is high.

Neural/Hormonal Control

• Sympathetic and parasympathetic systems regulate the heart.
• Catecholamines (e.g., epinephrine and norepinephrine) are important hormones.
• The systems compete for control while at rest.

Cardiac Function Terms

• Cardiac Output (Q): volume of blood pumped per minute
• Heart Rate (HR): number of heart beats per minute
• Stroke Volume (SV): volume of blood ejected per beat
• Ejection Fraction (%EF): The percentage of blood pumped out by the ventricle in each beat (normally 60% at rest)
• Mean Arterial Pressure (MAP): average pressure in the arteries
• Rate-Pressure Product (RPP): measure of myocardial work
• Total Peripheral Resistance (TPR): resistance to blood flow through the circulatory system

Cardiac Cycle

• Includes phases like ventricular filling, isovolumetric contraction, ejection, and isovolumetric relaxation.

Cardiac Cycle Summary

• A four-phase process that describes how blood flows out of and into the heart during each heartbeat.

Cardiovascular Responses to Exercise

• The cardiovascular system adjusts to meet the increasing demands of exercise through numerous ways.

Review of Systems

• Heart rate, Stroke volume, and Cardiac Output are assessed to evaluate the efficiency of the cardiovascular system.

Resting Heart Rate

• Normal range for adults is typically considered 60-100 bpm.
  • Below 60 bpm is bradycardia.
  • Above 100 bpm is tachycardia.

Sex Differences

• Typical resting heart rates show differences between the sexes (Men 65-75 bpm, Women 75-85 bpm)

Exercise Heart Rate

• Heart rate increases with increased exercise intensity.
• During exercise, there is a sympathetic outflow and parasympathetic withdrawal.

Anticipatory Response

• This response is an early increase in heart rate in preparation for an activity.

Steady State

• A steady state of elevated heart rate during exercise is often achieved around 2-3 minutes into an activity.

HR Recovery

• Fast heart rate recovery is a sign of a strong cardiovascular system.

Incremental Exercise

• Used to assess maximum oxygen consumption (VO2max). HR and VO2 are compared to identify a critical heart rate threshold.

Impact of Training

• Training improves cardiovascular efficiency and leads to a lower maximal heart rate.

Heart Rate Variability (HRV)

• The differences and timing between heartbeats fluctuates slightly with changes in various factors. High HRV is associated with low stress, easy responses and recovery.

Summary of Stroke Volume (SV) Regulation

• SV is regulated by factors:
  • Preload (end-diastolic volume - EDV): determined by the stretch on the cardiac cells and related to the Starling law of the heart
  • Contractility: influenced by extrinsic neural stimulation, and blood catecholamines, and is largely independent of preload
  • Afterload: resistance to ejection and is a function of afterload as well as peripheral vascular resistance and the pressure difference between the ventricles and the arteries.

Stroke Volume (SV) During Exercise

• SV increases linearly with workload in trained individuals till it plateaus.
• SV may not plateau or increases beyond the %40 mark in well-trained and seasoned athletes.
• Stroke volume increases with exercise intensity in untrained individuals but often plateaus at approximately 40% of maximum workload.

Cardiac Output (Q) During Exercise

• Cardiac output increases significantly with exercise in both trained and untrained individuals.
• Increased cardiac output is essential to meet increased demand for oxygen delivery.

Left Ventricular Adaptations

• Endurance training can lead to eccentric hypertrophy (increased chamber size).
• Resistance training can induce concentric hypertrophy (increased wall thickness).

Pathologic Hypertrophy

• Characterized by increased thickness of ventricle walls but with decreased overall size of the heart.

Ventricular Hypertrophy: Summary

• Different types of hypertrophy (eccentric, concentric, and pathologic) show varying effects on ventricular volume and wall thickness.

Oxygen Delivery During Exercise

• The cardiovascular system increases cardiac output (5-6 times higher than at rest) to supply oxygen to exercising tissues.
• Blood is redirected away from non-active organs to exercising organs.

Functional Sympatholysis

• Mechanisms the cardiovascular system uses to preferentially direct blood flow towards exercising tissues.
• Blood flow is redistributed from non-exercising organs to exercising organs.

Blood Pressure Responses to Exercise

• Systolic blood pressure (SBP) typically increases with increasing intensity of exercise.
• Diastolic blood pressure (DBP) can remain constant or only slightly increase with exercise intensity.

BP Response Chart

• Shows that various types of exercise (e.g., aerobic, 2-arm curl, 2-leg press) can impact blood pressure.

Blood Pressure - MacDougall 1985

• Chart data shows a significant increase in blood pressure during resistance exercise (especially with the double leg press) at 80% of 1RM (one repetition max).

This quiz explores the cardiovascular responses during exercise, focusing on the role of the sympathetic nervous system, blood flow distribution, and heart rate changes. Test your knowledge on how exercise intensity affects blood pressure and heart rate recovery in individuals. Ideal for students of exercise physiology and fitness enthusiasts!