Cardiovascular System - Control of Cardiac Output

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Questions and Answers

What is the primary formula for calculating cardiac output?

Cardiac Output = Heart Rate x Stroke Volume (correct)

Cardiac Output = Heart Rate + Stroke Volume

Cardiac Output = Stroke Volume - Heart Rate

Cardiac Output = Heart Rate / Stroke Volume

How does stroke volume affect cardiac output during exercise?

Stroke volume decreases, leading to increased cardiac output.

Stroke volume has no impact on cardiac output.

Stroke volume remains constant during exercise.

Stroke volume increases, contributing to increased cardiac output. (correct)

Which factor primarily regulates heart rate?

Blood type

Innervation of the heart (correct)

Oxygen levels in the blood

Body temperature

What effect does increased afterload have on stroke volume?

Decreases stroke volume Signup and view all the answers

During endurance training, how do heart rate and stroke volume in athletes generally compare to the general population at rest?

Athletes have a lower heart rate and higher stroke volume. Signup and view all the answers

What is one key determinant of stroke volume?

Preload Signup and view all the answers

What is the typical resting value for cardiac output in liters per minute?

~5 L/min Signup and view all the answers

How does increased physical activity affect heart rate?

Heart rate increases substantially Signup and view all the answers

What is the formula for calculating cardiac output (CO)?

HR x SV Signup and view all the answers

Which factor influences heart rate through neural regulation?

Chemical signals from the carotid body Signup and view all the answers

What is the primary neurotransmitter involved in reducing heart rate?

Acetylcholine Signup and view all the answers

What occurs during tachycardia?

Pathologically fast heart rate Signup and view all the answers

Which physiological state is associated with an increase in stroke volume?

Exercise Signup and view all the answers

Which center in the medulla oblongata is responsible for increasing heart rate?

Cardioacceleratory center Signup and view all the answers

Which of the following ions is primarily involved in depolarization at the SA Node under sympathetic influence?

Na+ Signup and view all the answers

What is the effect of parasympathetic stimulation on cardiac output?

Reduces cardiac output Signup and view all the answers

At rest, what is a typical stroke volume?

70 ml Signup and view all the answers

Which is a common effect of adrenaline on heart function?

Increases heart rate Signup and view all the answers

Under what condition would heart rate be considered bradycardia?

Below 60 bpm Signup and view all the answers

What is the primary role of baroreceptors in heart function?

Monitor blood pressure Signup and view all the answers

What physiological change occurs during ventricular hypertrophy?

Increase in heart muscle mass Signup and view all the answers

What occurs when there is increased vagal tone?

Decreased heart rate Signup and view all the answers

What is the primary effect of the sympathetic nervous system (SNS) on cardiac muscle function?

Increases force of contraction Signup and view all the answers

Which factor primarily influences stroke volume (SV) through the degree of ventricular stretching?

Preload Signup and view all the answers

Which physiological mechanism aids in increasing venous return during physical activity?

Skeletal muscle pump Signup and view all the answers

What is the effect of increased afterload on stroke volume?

Reduces stroke volume Signup and view all the answers

Which component of the cardiac cycle directly contributes to the force of ejected blood?

End Diastolic Volume (EDV) Signup and view all the answers

Which of the following accurately describes the effect of the parasympathetic nervous system (PNS) on heart function?

Decreases heart rate and contractility Signup and view all the answers

What is a consequence of decreased venous return on cardiac output?

Decreased stroke volume Signup and view all the answers

Which type of effects do hormones like adrenaline have on cardiac muscle?

Positive inotropic effect Signup and view all the answers

What role do valves in veins play in venous return?

Prevent backflow of blood Signup and view all the answers

How do smooth muscle contractions in arteries affect blood flow?

They regulate vascular tone and afterload Signup and view all the answers

Which factor contributes to the autonomic regulation of heart rate?

Chronotropic Effects Signup and view all the answers

What is the relationship between end systolic volume (ESV) and stroke volume (SV)?

SV = EDV - ESV Signup and view all the answers

How does respiratory pressure affect venous return during inhalation?

Increases venous return Signup and view all the answers

What plays a crucial role in the short-term regulation of blood pressure?

Baroreceptors Signup and view all the answers

Which mechanism is involved in the local autoregulation of blood flow?

Nitric oxide production Signup and view all the answers

Which factor primarily influences long-term regulation of blood pressure?

Blood volume regulation Signup and view all the answers

What is the effect of chemoreceptors on blood pressure regulation?

Monitor arterial oxygen levels and influence vascular resistance Signup and view all the answers

What is a key mechanism for blood flow autoregulation in tissues?

Endothelial cell signaling mechanisms Signup and view all the answers

What primarily regulates blood flow in the pulmonary circulation under low oxygen conditions?

Constriction of blood vessels Signup and view all the answers

Which statement accurately describes the response of coronary circulation under sympathetic nervous system activity?

Coronary arteries undergo vasodilation Signup and view all the answers

What is a key characteristic of cerebral circulation during emergencies?

Preservation of blood flow to the brain Signup and view all the answers

What type of pressure regulation is primarily influenced by baroreceptors?

Short-term regulation of blood pressure Signup and view all the answers

In what scenario do blood vessels in most organs exhibit dilation when oxygen levels are low?

Systemic circulation Signup and view all the answers

What does blood pressure primarily depend on?

Total peripheral resistance and cardiac output Signup and view all the answers

What role do vasodilatory metabolites play in blood flow?

They promote the relaxation of blood vessels. Signup and view all the answers

What happens when blood pressure and flow remain insufficient despite autoregulation?

Homeostasis is not restored. Signup and view all the answers

Which factors are involved in short-term regulation of blood pressure?

Neural and hormonal mechanisms Signup and view all the answers

Which of the following substances is NOT a vasodilator that contributes to blood flow regulation?

Acetylcholine (ACh) Signup and view all the answers

How does cardiac output relate to blood pressure?

It influences blood pressure through resistance changes. Signup and view all the answers

What is the effect of increased resistance in arterioles on blood pressure?

It increases blood pressure. Signup and view all the answers

Which type of blood flow regulation is primarily involved in restoring local flow during low perfusion?

Intrinsic control/autoregulation Signup and view all the answers

What is primarily responsible for regulating blood flow to tissues during capillary exchange?

Sympathetic nervous system activity and local metabolic factors Signup and view all the answers

Which of the following factors affects net filtration pressure in capillaries?

Capillary hydrostatic pressure and osmotic pressure Signup and view all the answers

How do capillaries facilitate the exchange of nutrients and wastes?

Through diffusion and filtration processes Signup and view all the answers

What special consideration affects capillary exchange in cerebral circulation?

Maintenance of a stable blood-brain barrier Signup and view all the answers

What effect does sympathetic nervous system activation usually have on blood vessels?

Vasoconstriction and reduced blood flow to non-essential areas Signup and view all the answers

Which physiological change is common in tissues when oxygen levels are low?

Vasodilation in response to hypoxia Signup and view all the answers

What role do vasodilatory metabolites play in blood flow regulation?

They promote vasodilation to improve blood flow to tissues. Signup and view all the answers

What best describes the primary function of capillary beds in the circulatory system?

To facilitate the exchange of nutrients and waste. Signup and view all the answers

How does the structure of capillaries enhance their transport function?

They possess a single layer of endothelial cells. Signup and view all the answers

What factor primarily drives the filtration process in capillaries?

Net hydrostatic pressure. Signup and view all the answers

What defines the net filtration pressure (NFP) in capillary exchange?

The balance of net hydrostatic and net osmotic pressures. Signup and view all the answers

In cases of hypertension, what is the likely effect on net filtration pressure?

It increases, promoting more filtration. Signup and view all the answers

Which type of capillaries are most permeable to solutes and fluids?

Sinusoidal capillaries. Signup and view all the answers

What is the primary mechanism for solute movement across capillary walls during physiological conditions?

Diffusion. Signup and view all the answers

Which component triggers the reabsorption of fluids in capillaries?

Blood colloid osmotic pressure. Signup and view all the answers

How do capillaries contribute to local blood flow autoregulation?

Via feedback mechanisms from local metabolites. Signup and view all the answers

Which of the following pressures typically remains constant along the length of a capillary?

Blood colloid osmotic pressure. Signup and view all the answers

Why does filtration typically exceed reabsorption in capillaries?

Higher capillary hydrostatic pressure. Signup and view all the answers

What is the role of endothelial cells in capillaries?

To act as a barrier while allowing substance exchange. Signup and view all the answers

What mechanism mainly drives the movement of large solutes during transcytosis in capillaries?

Vesicular transport. Signup and view all the answers

What is the effect on net filtration pressure during dehydration at the venous end?

Increased absorption due to high BCOP Signup and view all the answers

Which condition leads to an increase in net filtration pressure at the site of tissue damage?

High capillary hydrostatic pressure Signup and view all the answers

In which situation would fluid potentially leak into the alveoli?

When pulmonary CHP equals 25 mmHg Signup and view all the answers

What is a compensatory mechanism during systole when coronary blood flow is restricted?

Arterial elastic recoil Signup and view all the answers

Which statement accurately describes the dynamic role of capillary exchange in the lungs?

Oxygen exchange increases under lower pulmonary resistance Signup and view all the answers

What primarily determines blood flow regulation in coronary circulation during increased activity?

Local metabolic needs of the myocardium Signup and view all the answers

In which vascular condition does increased interstitial fluid pressure contribute to local swelling?

Increased capillary permeability Signup and view all the answers

How does a decrease in capillary osmotic pressure affect fluid dynamics?

It promotes net filtration out of the capillaries Signup and view all the answers

During intense physical activity, which factor most directly influences blood flow to the heart?

Increased myocardial oxygen demand Signup and view all the answers

What is the primary effect of high blood pressure on capillary function?

Enhanced filtration of fluids into the tissues Signup and view all the answers

Which type of regulation primarily controls blood flow autoregulation during significant metabolic activity?

Local tissue response mechanisms Signup and view all the answers

What happens to cerebral blood flow during a disruption in the vascular supply?

It remains constant due to collateral circulation Signup and view all the answers

What mechanism assists in maintaining adequate oxygen delivery to the heart muscle during low flow conditions?

Capillary network expansion Signup and view all the answers

What physiological response occurs in blood vessels when oxygen levels decrease?

Vasodilation due to elevated CO2 Signup and view all the answers

Study Notes

Cardiovascular System - Lecture 12: Control of Cardiac Output

Cardiac output (CO) is calculated by: CO = Heart Rate (HR) x Stroke Volume (SV)
Typical resting values: CO ~5 L/min, HR 70 bpm, SV 70 ml
During exercise: CO ~20 L/min, HR ~190 bpm, SV ~105 ml
Endurance athletes at rest: CO ~5.5 L/min, HR ~40 bpm, SV ~140 ml, Keely winning ~40 bpm, SV ~ 210 ml, Heart Weight is ~ 500g.
Cardiac output increases during exercise due to an increase in both heart rate and stroke volume.

Objectives

Students should be able to quantify cardiac output, noting its typical values and its regulation within the cardiovascular system (CVS).
Students should be able to describe the heart's innervation and the factors regulating heart rate.
Students should be able to explain how heart rate and the determinants of stroke volume impact cardiac output.

Content

Definition of Cardiac Output
- Cardiac output is the volume of blood ejected by each ventricle per minute.
Heart Rate and Cardiac Output
- Innervation of the heart and control of pacemaker cells.
Stroke Volume and Cardiac Output
- End diastolic and end systolic volumes.
- Preload: degree to which ventricular muscle cells are stretched at the end of diastole. This is directly proportional to EDV and dependent on the rate of venous return and filling time
- Contractility: force produced by ventricular muscle cells during systole at a given preload. Positive inotropic effects increase contractility which reduces ESV. Negative inotropic effects reduce contractility thereby increasing ESV.
- Afterload: the pressure the ventricles need to overcome to open the semilunar valves and eject blood. Increased afterload increases ESV.

Factors Affecting Heart Rate

Chronotropic effects:
- Autonomic innervation (parasympathetic and sympathetic).
- Hormones (e.g., adrenaline)

Neural and Hormonal Regulation of Heart Rate

Medulla oblongata cardioregulatory center.
Sensory nerves feedback to the cardiac reflex.
Parasympathetic (vagus nerve) and sympathetic (sympathetic ganglia) branches to the heart regulate heart rate.
Acetylcholine (ACh) and noradrenaline (NA) are neurotransmitters influencing heart rate and cardiac output
Hormones such as adrenaline and noradrenaline and others (Thyroid, Glucagon)

Autonomic Effects on Heart Rate and Cardiac Output

Parasympathetic:
- Neurotransmitter: Acetylcholine (ACh).
- Chronotropic effect: Negative (lowers heart rate).
- Effect on CO: Reduces CO.
Sympathetic:
- Neurotransmitter: Noradrenaline (NA), Adrenaline.
- Chronotropic effect: Positive (increases heart rate).
- Effect on CO: Increases CO.

Preload and Venous Return

Posture: Blood pools in leg veins when standing due to gravity, reducing venous return.
Skeletal Muscle Pump: Movement of skeletal muscles constricts veins, aiding venous return and preventing backflow.
Respiratory Pump: Inspiration reduces intrathoracic pressure and increases intra-abdominal pressure increasing venous return.
Venous Capacitance: reduced venous compliance and increased central venous pressure increasing venous return.

Determinants of End Diastolic Volume (EDV) and End Systolic Volume (ESV)

Preload: The degree of ventricular stretch at the end of diastole. Increased filling time and venous return increases preload and therefore EDV.
Contractility: Force of ventricular contraction at a given preload. Increased contractility decreases ESV.
Afterload: The pressure the ventricles need to overcome to open the semilunar valves and eject blood. Increased afterload increases ESV.

Increased Afterload

Prolonged elevated afterload can damage the myocardium and lead to heart failure reducing SV and therefore CO.

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Description

This quiz focuses on the control of cardiac output, a key aspect of the cardiovascular system. Students will learn how heart rate and stroke volume contribute to cardiac output, typical values at rest and during exercise, and the factors regulating these parameters. Test your understanding of cardiac function and its importance during different physical states.