Cardiovascular Physiology Quiz

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Questions and Answers

What physiological response occurs to maintain a constant Mean Arterial Pressure (MAP) when cardiac output decreases?

End-diastolic volume decreases dramatically

Total Peripheral Resistance must increase (correct)

Heart rate must decrease to balance the system

Vasodilation decreases Total Peripheral Resistance (TPR)

How does the body primarily regulate blood pressure during exercise?

By maintaining constant blood volume

By increasing heart rate alone

By adjusting vessel diameter to change resistance (correct)

By decreasing stroke volume

In terms of myocardial oxygen utilization during exercise, what primarily influences the heart's energy needs?

Total Peripheral Resistance alone

Vasodilation of coronary vessels

Only heart rate changes

Cardiac Output and stroke volume (correct)

What is the effect of arterioles relaxing on blood flow and blood pressure?

Blood pressure decreases as blood flows freely Signup and view all the answers

What happens to Total Peripheral Resistance when there is an increase in stroke volume during exercise?

It can increase if MAP is to be maintained Signup and view all the answers

With respect to the Rate Pressure Product, which factor would most likely increase it during intense physical activity?

An increase in both heart rate and systolic blood pressure Signup and view all the answers

What role does vasoconstriction play in blood pressure regulation?

It increases Total Peripheral Resistance and raises blood pressure Signup and view all the answers

How does body position affect cardiovascular response during upper body versus lower body exercise?

Upper body exercise causes a greater increase in heart rate than lower body Signup and view all the answers

What is the role of baroreceptors in blood pressure regulation during standing?

They monitor the mechanical strain on arterial walls to adjust blood pressure. Signup and view all the answers

How does resistance training primarily affect myocardial oxygen utilization compared to aerobic exercises?

It reduces myocardial oxygen utilization due to lower cardiac output. Signup and view all the answers

What primarily differentiates blood pressure responses in upper body versus lower body exercises?

Lower body exercises cause more vasodilation in active muscle compared to upper body exercises. Signup and view all the answers

What physiological changes characterize hypotensive recovery after intense exercise?

Baroreceptors inhibit the cardioacceleratory center to decrease heart rate. Signup and view all the answers

How is Rate Pressure Product (RPP) affected during exercise?

RPP increases due to elevated heart rate and blood pressure. Signup and view all the answers

How does increased stroke volume affect mean arterial pressure (MAP)?

It increases MAP by enhancing cardiac output. Signup and view all the answers

What is the primary reason that the blood pressure gradient decreases from arteries to veins?

Distance from the heart and vessel resistance. Signup and view all the answers

During exercise, how is myocardial oxygen utilization primarily affected?

It increases due to higher cardiac output. Signup and view all the answers

Which of the following describes the hypotensive recovery response after exercise?

Gradual decrease in blood pressure post-exercise. Signup and view all the answers

What is the significance of the Rate Pressure Product (RPP) during physical exertion?

It indicates the heart's oxygen consumption requirements. Signup and view all the answers

Which of the following factors contributing to arterial blood pressure is least affected by exercise?

Total peripheral resistance. Signup and view all the answers

In terms of blood pressure response, what distinguishes upper body exercise from lower body exercise?

Upper body exercise always results in higher systolic pressure. Signup and view all the answers

What physiological response is most likely to occur during isovolumetric contraction?

Increased ventricular pressure without a change in volume. Signup and view all the answers

How does blood viscosity influence mean arterial pressure in the context of increased exercise intensity?

Higher viscosity during intense exercise can raise MAP. Signup and view all the answers

What potential complication can venous pooling cause during prolonged inactivity or after intense exercise?

Fainting due to insufficient cerebral blood supply. Signup and view all the answers

What is the physiological response of the heart during vigorous exercise in terms of coronary blood flow?

Coronary blood flow increases by 4-6 times above resting levels. Signup and view all the answers

What is the primary determinant of the Rate Pressure Product (RPP)?

Systolic blood pressure and heart rate. Signup and view all the answers

How does sympathetic stimulation affect heart rate during exercise?

It increases heart rate by accelerating SA node depolarization. Signup and view all the answers

What is the most accurate relationship between myocardial oxygen utilization at rest compared to other tissues?

Myocardium extracts 70-80% of oxygen from blood. Signup and view all the answers

During the recovery phase after exercise, which mechanism is primarily responsible for returning heart rate to baseline levels?

Increased parasympathetic influence. Signup and view all the answers

Which process is primarily activated to supply adequate oxygen to the myocardium during high-intensity exercise?

Elevated coronary blood flow. Signup and view all the answers

What condition arises when blood flow to coronary muscles is compromised?

Angina pectoris. Signup and view all the answers

What is the heart rate change range during intense exercise due to extrinsic control?

60-220 BPM. Signup and view all the answers

Which of the following areas of the heart has the slowest intrinsic rhythm for initiating heart contractions?

Ventricular tissue. Signup and view all the answers

During exercise, what immediate cardiovascular change is expected due to anticipatory responses?

Increased sympathetic activity with decreased parasympathetic tone. Signup and view all the answers

What happens to systemic vascular resistance (SVR) during graded exercise as intensity increases?

SVR decreases due to vasodilation in active muscles. Signup and view all the answers

How does upper body exercise compare to lower body exercise in terms of physiological strain?

Upper body exercise involves more muscle mass and higher physiological strain. Signup and view all the answers

What is the effect of maximal exercise on systolic blood pressure (SBP) in individuals with a high aerobic capacity?

SBP may exceed 200 mmHg despite a decrease in total peripheral resistance. Signup and view all the answers

What physiological response typically occurs during the hypotensive recovery phase after exercise?

Blood pressure dips below pre-exercise levels for several hours. Signup and view all the answers

In the context of myocardial oxygen utilization, how does lower body exercise compare to upper body exercise at maximal effort?

Upper body exercise has a VO2 max that is 20-30% below that of lower body exercise. Signup and view all the answers

Which statement about blood pressure response to resistance exercise is true?

Resistance exercise causes an increase in SBP due to muscle contractions compressing blood vessels. Signup and view all the answers

What defines the Rate Pressure Product (RPP) during exercise?

Systolic blood pressure multiplied by heart rate. Signup and view all the answers

During steady-rate exercise, what is the primary reason for the initial increase in systolic blood pressure (SBP)?

Increased cardiac output due to elevated heart rate and stroke volume. Signup and view all the answers

What best defines Total Peripheral Resistance (TPR) at rest with given values of DBP, SBP, and CO?

TPR is calculated by dividing the difference in blood pressure (DBP to SBP) by cardiac output. Signup and view all the answers

What is the primary function of the cardiovascular system?

To deliver oxygen and nutrients to active tissues Signup and view all the answers

Which of the following describes systemic circulation?

Carries oxygenated blood away from the heart to the body Signup and view all the answers

What type of muscle is primarily responsible for heart contraction?

Cardiac muscle Signup and view all the answers

What is the term for the volume of blood in the heart at rest?

End Diastolic Volume Signup and view all the answers

Which type of valves are the tricuspid and bicuspid valves classified as?

Atrioventricular valves Signup and view all the answers

What is the brief period called when all heart valves are shut and the ventricular volume remains the same?

Isovolumetric contraction Signup and view all the answers

What characteristic differentiates cardiac muscle fibers from skeletal muscle fibers?

Cardiac muscle fibers are branched. Signup and view all the answers

Which circulation has a higher pressure, systemic or pulmonary?

Systemic circulation Signup and view all the answers

Which of the following statements accurately describes the role of arteries in the circulatory system?

Arteries carry blood away from the heart but may contain deoxygenated blood. Signup and view all the answers

What distinguishes the pulmonary circulation from systemic circulation?

Pulmonary circulation conducts blood to and from the lungs. Signup and view all the answers

What is the term for the volume of blood present in the heart at the end of diastole?

End Diastolic Volume Signup and view all the answers

In which phase of the heart cycle do all heart valves remain closed while ventricular pressure rises?

Isovolumetric Contraction Signup and view all the answers

Which type of muscle fibers are found in cardiac muscle?

Striated branched and uninucleated Signup and view all the answers

What characterizes the stroke volume, calculated by the formula EDV - ESV?

The volume of blood ejected per heartbeat Signup and view all the answers

Which of the following describes the function of the atrioventricular valves?

They prevent backflow of blood into the atria during ventricular contraction. Signup and view all the answers

What type of muscle control is characterized as involuntary in the heart?

Cardiac muscle contraction Signup and view all the answers

What is the main difference in pressure between systemic circulation and pulmonary circulation?

Systemic circulation has a higher pressure than pulmonary circulation. Signup and view all the answers

Which structural feature is unique to cardiac muscle compared to skeletal muscle?

Cardiac muscle fibers are branched and interconnected. Signup and view all the answers

Study Notes

Mean Arterial Pressure (MAP)

MAP is the average pressure in the arteries during one cardiac cycle, calculated as: MAP = DBP + [⅓(SBP-DBP)]
MAP is the perfusion pressure of organs; insufficient blood flow can lead to ischemia if MAP is below 60 mmHg for a long period.
The body can adjust resistance at the ends of vessels to maintain a constant MAP.
If cardiac output decreases, total peripheral resistance (TPR) must increase to maintain MAP.

Total Peripheral Resistance (TPR)

Blood vessel diameter is used to regulate blood pressure.
Nerves control the muscles that cause vessels to contract (vasoconstriction) or dilate (vasodilation).
TPR is influenced by vessel diameter, length, and viscosity.
Vessel length remains constant after adulthood; changes in TPR are primarily due to changes in vessel diameter.

Cardiac Output (CO)

The amount of blood ejected by one ventricle in one minute.
At rest, CO is approximately 5 L/min.
CO can be increased by increasing heart rate (HR), stroke volume (SV), or both.
Increased CO leads to increased MAP.

Steady Rate Exercise

During the first few minutes of exercise, increased blood flow (CO) rapidly increases systolic blood pressure (SBP).
Vasodilation in active muscles decreases TPR, increasing blood flow to the peripheral vasculature.
As exercise continues, SBP gradually decreases due to continued vasodilation and decreased TPR.
Muscle contraction and relaxation enhance venous return.

Graded Exercise

SBP increases rapidly at the start of exercise and increases linearly with exercise intensity.
Diastolic blood pressure (DBP) may remain unchanged or decrease slightly.
Maximum SBP may exceed 200 mmHg despite reduced TPR.
This high SBP reflects the heart's increased CO during maximal exercise in individuals with high aerobic capacity.

Blood Pressure Response to Resistance Exercise

Concentric contractions compress peripheral vasculature, increasing resistance.
The magnitude of increase in SBP is related to exercise intensity and muscle mass used.

Submaximal Upper Body Exercise (UBE)

UBE requires greater oxygen consumption than lower body exercise at any submaximal power output due to lower mechanical efficiency, recruitment of stabilizing muscles, and greater physiological strain.
UBE leads to higher heart rate (HR), ventilation (Ve), blood pressure (BP), and ratings of perceived exertion (RPE).

Maximal Upper Body Exercise

VO2 values are typically 20-30% lower than lower body exercise.
Lower maximum HR and pulmonary ventilation due to smaller musculature activated.

Hypotensive Recovery Response

SBP temporarily decreases below pre-exercise levels for up to 12 hours after sustained light to moderate exercise in both normal and hypertensive individuals.
This is due to blood pooling in skeletal muscle vascular beds during recovery.

Clinical Significance of Exaggerated BP Response

Increased risk for hypertension, cardiovascular mortality, and cardiovascular events.
Presence of cardiac hypertrophy.

The Heart's Blood Supply

The heart chambers do not receive nutrients from the blood they contain.
Coronary circulation supplies the heart muscle with approximately 5% (250ml) of total cardiac output.
Right and left coronary arteries originate from the aorta behind the aortic valve and divide into dense capillary networks that feed the myocardium.
Coronary sinus and anterior cardiac veins collect blood and empty directly into the right atrium.

Myocardial Oxygen Utilization

At rest, the myocardium extracts 70-80% of the oxygen from the blood flowing in coronary vessels.
During vigorous exercise, coronary blood flow increases 4-6 times above resting levels.
Impaired coronary blood supply causes chest pain (angina pectoris).

Impaired Coronary Blood Supply

Coronary muscle is purely aerobic.
Exercise increases energy requirements, making it a diagnostic tool for myocardial ischemia.
A blood clot in the coronary vessels can result in myocardial infarction.
Ischemia: Restriction in blood supply to tissues.
Hypoxia: A region of the body is deprived of adequate oxygen supply.
Infarction: Tissue death caused by a local lack of oxygen.

Rate Pressure Product (RPP)

Provides a non-invasive estimation of myocardial workload (myocardial oxygen uptake).
RPP = SBP x HR.
RPP has a linear relationship with exercise intensity.
Chronic exposure to higher myocardial workload can lead to cardiac hypertrophy.

Cardiovascular Regulation and Integration

Cardiac muscle is autorhythmic, meaning it can maintain its own rhythm (heart rate).
The intrinsic heart rate is approximately 100 BPM.
Extrinsic control via neurohumoral factors can adjust heart rate from 40 BPM at rest to 220 BPM at peak exercise.

Autorhythmic/Automaticity

The heart can beat independently without exogenous commands.

Intrinsic Regulation of Heart Rate

Heart rate originates in the sinoatrial (SA) node, propagating outwards.
The SA node initiates depolarization, which travels through the atrioventricular (AV) node to the Purkinje fibers and bundle of HIS.
The signal then travels up the walls of the ventricle.
The AV node delays the electrical signal for 0.10 seconds, allowing atrial contraction before ventricular filling.
Ventricular contraction occurs 0.06 seconds after stimulation.

Electrocardiogram (ECG/EKG)

Records the electrical activity of the heart.
P-wave: Atrial depolarization.
QRS complex: Ventricular depolarization and atrial repolarization occurring simultaneously.
T-wave: Ventricular repolarization.
ECG abnormalities can indicate coronary heart disease.

Relationship Between Pressure Changes and ECG

Atrial depolarization leads to atrial contraction, a slight increase in blood volume, and a minimal increase in ventricular pressure.
Ventricular depolarization leads to ventricular contraction, generating maximum pressure, and signaling ventricular repolarization.

Areas of the Heart that can Initiate a Rhythm and Intrinsic Rate

Sinus node: 60-100 BPM.
Atrial tissue: 60-100 BPM.
AV node: 40-60 BPM.
Ventricular tissue: 20-40 BPM.

Extrinsic Heart Rate Regulation

Neural influences superimpose on the inherent rhythm of the myocardium.
This regulation adjusts heart rate in anticipation of exercise and as exercise intensity changes.
The range of heart rate regulated by neural influences is 20-200 BPM (dependent on physical fitness).

Sympathetic and Parasympathetic Control

Sympathetic stimulation: - Catecholamines (NE/Epinephrine). - Results in tachycardia (increased heart rate). - Increases SA node depolarization. - Enhances contractility.
Parasympathetic influence: - Acetylcholine (vagal influence). - Results in bradycardia (decreased heart rate). - Slows SA node depolarization.

Exercise and Blood Flow

Parasympathetic Neural Control:
- Peripheral effects include excitation of the iris, gallbladder, and coronary arteries.
- Inhibition of gut sphincters, intestines, and skin vasculature.
- During the onset of exercise, heart rate increases by inhibiting the parasympathetic nervous system (PNS).

Sympathetic Control on Blood Flow

Mechanism involves NE via adrenergic fibers located in the smooth muscles of small arteries, arterioles, and precapillary sphincters.
Inactive tissue (vasoconstriction):
- Renal, splanchnic, and inactive skeletal muscle.
- Produces systemic vasoconstriction of inactive muscle.
Active tissue (vasodilation):
- Active muscle.
- Decreases sympathetic nervous system (SNS) activity.

Neural Response During Exercise

Anticipatory response:
- Decreased parasympathetic activity.
- Increased sympathetic activity.
Exercise: - Parasympathetic inhibition (early). - Sympathetic stimulation (more intense).
Results: - Increased heart rate and contractility. - Increased arterial blood pressure. - Vasodilation of active skeletal muscles. - Vasoconstriction of skin, gut, spleen, etc. - Vasoconstriction increases venous return.

Functional Sympatholysis

Sympathetic neural activity normally causes vasoconstriction.
Local changes in muscle metabolites and other substances reduce vascular responsiveness to alpha-adrenergic receptor activation, allowing for vasodilation in active tissues.

Peripheral Input Control of CV Response

The initial signal for cardiovascular system activation originates in higher brain centers.
This signal is fine-tuned by feedback from:
- Chemoreceptors (sensitive to blood oxygen, carbon dioxide, and pH levels).
- Baroreceptors (sensitive to changes in arterial blood pressure).
- Muscle mechanoreceptors (heart, skin, joints; sensitive to force and speed of muscle movement).
- Metaboreflex muscle chemoreceptors (sensitive to muscle metabolites like potassium and lactic acid).

BP Response to Standing

Gravity-induced drop in BP due to blood pooling in the legs is detected by baroreceptors in the carotid arteries and aorta.
Baroreceptors signal the brain, activating the sympathetic nervous system.
This increases heart rate, contractility, and cardiac output.
Blood vessels constrict via alpha-1 receptors to increase blood volume.

Baroreceptors

Located in the aortic arch and common carotid arteries.
When blood pressure is too high:
- Baroreceptors are stimulated and signal the brain.
- The cardioacceleratory center is inhibited, and the cardioinhibitory center is stimulated.
- This decreases heart rate, cardiac output, and vasoconstriction.
- Arterial vasodilation occurs, reducing blood pressure.

Chemoreceptors

Sensitive to oxygen, carbon dioxide, and pH levels.
When homeostasis is disturbed (decreased oxygen and pH, increased carbon dioxide):
- Chemoreceptors are stimulated and signal reflex responses.
- The cardioinhibitory center is inhibited, and the cardioacceleratory center is stimulated.
- Cardiac output increases.
- The respiratory center is stimulated, increasing respiratory rate.

Blood Flow Regulation

Blood Flow = Pressure x Resistance.
TPR is influenced by physical characteristics of the blood (viscosity) and the size of individual vessels (length and diameter).

Poiseuille’s Law

Quantifies blood flow resistance.
Flow = pressure gradient x vessel radius^4 / vessel length x viscosity.
Vessel diameter is the most significant factor in influencing blood flow resistance.
Vessel length and blood viscosity have less of an impact because they remain relatively constant.

Exercise and Blood Flow

Nerve and local metabolites cause dilation of arterioles in active muscle beds.
Vasoconstriction in visceral organs and the muscle pump bring blood to central circulation.
Example:
- Kidneys:
  - Rest = 1100 ml/minute (20% of CO).
  - Exercise = 250 ml/minute (1% of CO).

Active Muscle

At rest, only 1 out of 40 capillaries in active muscle are open.
Opening dormant capillaries during exercise:
- Increases muscle blood flow.
- Allows for a large blood volume with minimal increase in blood flow velocity.
- Increases the surface area for gas and nutrient exchange between blood and muscle fibers.
Local factors (autoregulatory mechanisms) involved in capillary opening:
- Decreased pH, increased PCO2, increased ADP, increased Ca++, increased temperature.

Key Functions of the Cardiovascular System

Delivers oxygen and nutrients to active tissues.
Returns deoxygenated blood to the lungs.
Transports heat (byproduct of cellular metabolism) and hormones.

Circulatory System

Also known as Cardiovascular System.
The heart functions as a dual pump.
Two blood flow circuits exist:
- Systemic circulation: Circulates blood between the heart and the body (excluding the lungs).
- Pulmonary circulation: Circulates blood between the heart and the lungs.
Some differences between the circuits:
- Pulmonary circuit blood flow travels shorter distances.
- Systemic circulation has higher pressure.
Arteries carry blood away from the heart, but this blood may not always be oxygenated.
Systemic circulation is responsible for carrying oxygenated blood away from the heart towards the body and returning deoxygenated blood back to the heart.

Heart Cell Types

Two types of cells exist in the heart:
- Electrical cells: Responsible for conducting electrical signals.
- Contractile cells: Responsible for the mechanical contraction of the heart.

Heart Structure and Function

Skeletal muscle:
- Striated, tubular fibers containing multiple nuclei.
- Voluntary control (consciously controlled).
- Usually attached to the skeleton.
Cardiac muscle:
- Striated, branched fibers with only one nucleus per fiber.
- Involuntary control (not consciously controlled).
- Found solely within the heart walls.

Anatomy of the Heart

Four chambers:
- Right atrium: Receives deoxygenated blood from the body.
- Right ventricle: Pumps deoxygenated blood to the lungs.
- Left atrium: Receives oxygenated blood from the lungs.
- Left ventricle: Pumps oxygenated blood to the body.
Four valves:
- Atrioventricular valves:
  - Tricuspid (right): Controls blood flow between the right atrium and right ventricle.
  - Bicuspid/mitral (left): Controls blood flow between the left atrium and the left ventricle.
- Semilunar valves:
  - Pulmonary: Prevents blood from flowing back into the right ventricle from the pulmonary artery.
  - Aortic: Prevents blood from flowing back into the left ventricle from the aorta.

Terms and Definitions for Heart Contraction

Diastole: The resting phase of the heart.
- End Diastolic Volume (EDV): The volume of blood in the heart during diastole (rest).
Systole: The contracting phase of the heart.
- End Systolic Volume (ESV): The volume of blood remaining in the heart after contraction.
Stroke Volume (SV): The amount of blood ejected with each heartbeat (calculated as EDV-ESV).
Isovolumetric: Refers to a period of constant volume.
- Isovolumetric contraction: A brief period (0.02-0.06 seconds) during which all four heart valves are closed, and ventricular pressure rises rapidly.

Key Functions of the Cardiovascular System

Delivers oxygen and nutrients to active tissues.
Returns deoxygenated blood to the lungs
Transports heat (byproduct of cellular metabolism) and hormones.

Circulatory System

Also known as the Cardiovascular system.
The heart acts as a dual pump.
Consists of two blood flow circuits:
- Systemic Circulation: Heart and system; includes all parts of the body besides the lungs.
- Pulmonary Circulation: Heart and lungs.
The blood flow in the pulmonary circuit is shorter than in the systemic circuit, so the blood doesn't need to travel as far.
Systemic circulation has higher pressure compared to pulmonary circulation.
Arteries carry blood away from the heart but may not always be oxygenated.
Systemic circulation carries oxygenated blood away from the heart to the body and returns deoxygenated blood back to the heart.

Heart Cell Types

Two types of cells in the heart:
- Electrical: Responsible for the electrical pathway in the heart.
- Contractile: Responsible for the mechanical function (contractions) of the Heart.

Cardiac Muscle

Cardiac muscle has striations, branches, and is uninucleated.
It is involuntary and only covers the walls of the heart.
Unlike skeletal muscle, which is voluntary, striated, tubular, and multinucleated while also being attached to the skeleton, cardiac muscle is involuntary.

Anatomy of the Heart

Consists of four chambers:
- Right Atrium
- Right Ventricle
- Left Atrium
- Left Ventricle
Consists of four valves:
- Atrioventricular Valves:
  - Tricuspid (Right)
  - Bicuspid/Mitral (Left)
- Semilunar Valves:
  - Pulmonary
  - Aortic

Terms and Definitions for Heart Contraction

Diastole: The resting phase of the heart.
- End Diastolic Volume (EDV): Volume of blood in the heart during diastole (rest).
Systole: The contraction phase of the heart.
- End Systolic Volume (ESV): Volume of blood in the heart during systole (contraction).
Stroke Volume (SV): The amount of blood ejected with each heartbeat. Calculated as EDV - ESV.
Isovolumetric: Means "same volume"
- Isovolumetric Contraction: A brief period (0.02-0.06 seconds) when all heart valves remain closed, and ventricular pressure rises, resulting in the first heart sound.

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Description

Test your knowledge on Mean Arterial Pressure (MAP), Total Peripheral Resistance (TPR), and Cardiac Output (CO). This quiz covers the calculations, physiological significance, and regulatory mechanisms involved in cardiovascular functioning. Assess your understanding of how these concepts interplay to maintain blood flow and pressure.