Cardiovascular III

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Questions and Answers

What effect does a decrease in arteriolar diameter have on resistance?

Resistance remains the same

Resistance decreases

Resistance increases (correct)

There is no effect on resistance

Autoregulation allows for control of blood flow to non-critical organs even during changes in pressure.

False

What are the main variables that control blood pressure?

Heart rate, stroke volume, and total peripheral resistance (TPR)

The receptors that sense stretching of the arterial wall are called ______.

baroreceptors Signup and view all the answers

Match the following components of the blood pressure reflex with their functions:

Baroreceptors = Sense stretching of arterial walls Sensory fibers = Transmit signals to the brain Integration center = Compares information to reference value Effectors = Affect heart rate and vessel diameter Signup and view all the answers

Which factor is NOT considered an extrinsic regulator of vascular resistance?

Metabolic regulation Signup and view all the answers

Veins have high resistance to blood flow.

False Signup and view all the answers

What occurs during inspiration that affects venous pressure?

During inspiration, pressure in the thoracic cavity decreases while pressure in the abdominal cavity increases. Signup and view all the answers

The ______ mechanism allows for vasoconstriction in response to sympathetic stimulation.

neuro-hormonal Signup and view all the answers

Which of the following ions is associated with metabolic regulation to increase arteriolar diameter?

K+ Signup and view all the answers

What is the primary determinant of stroke volume?

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

The relationship between preload and stroke volume is directly proportional.

True Signup and view all the answers

What happens during isovolumic contraction?

The ventricles contract without a change in volume as all valves are closed. Signup and view all the answers

The volume of blood remaining in the ventricles after systole is known as _____ .

End-Systolic Volume (ESV) Signup and view all the answers

Match the following terms with their corresponding definitions:

Preload = Volume of blood present in the ventricles at the end of diastole Afterload = Resistance encountered by the ventricles during ejection Stroke Volume = Volume of blood ejected per contraction Cardiac Output = Heart rate times stroke volume Signup and view all the answers

Which factor contributes primarily to venous return?

Pressure difference between veins and the right atrium Signup and view all the answers

Skeletal muscle pump helps increase venous return by pushing blood towards the heart.

True Signup and view all the answers

Describe the effect of increased EDV on stroke volume.

Increased EDV leads to increased stroke volume due to enhanced stretching of cardiac muscle fibers and increased contractility. Signup and view all the answers

The measurement of pressure on the artery wall during systole is called _____ .

Pulse Pressure Signup and view all the answers

Match the cardiovascular concepts to their correct impacts:

Increased heart rate = Increased blood pressure Decreased cardiac output = Decreased blood pressure Increased resistance in arterioles = Increased blood pressure Increased venous return = Increased preload Signup and view all the answers

What aspect of blood vessels is considered the main factor affecting resistance?

Diameter of the vessel Signup and view all the answers

During diastole, the aortic valve is open allowing blood to flow from the ventricles to the aorta.

False Signup and view all the answers

Identify the consequences of low elasticity in arteries.

Low elasticity results in high blood pressure and increased workload on the heart. Signup and view all the answers

The concept that explains the relationship between increased preload and increased contractility is known as _____ law.

Frank-Starling Signup and view all the answers

Study Notes

Cardiac Output

Cardiac output is the volume of blood ejected by the heart per minute.
It can be calculated by multiplying heart rate by stroke volume.
Cardiac output is influenced by sympathetic and parasympathetic nervous systems, contraction strength, and end-diastolic volume.
End-diastolic volume is the volume of blood in the ventricles at the end of diastole.

Heart Rate Regulation

Denervated heart rate is intrinsically dictated by the SA node.
The heart rate is primarily controlled by sympathetic/adrenal medulla and parasympathetic nervous systems.
Sympathetic stimulation and adrenal medulla increase heart rate while parasympathetic stimulation decreases it.

Stroke Volume Regulation

Stroke volume is the volume of blood ejected per heartbeat, determined by the difference between end-diastolic volume (EDV) and end-systolic volume (ESV).
EDV, also known as preload, is the volume of blood in the ventricles at the end of diastole.
ESV, also known as afterload, is the amount of blood remaining in the ventricle after systole.

Effect of End-Diastolic Volume

An increase in EDV leads to an increase in stroke volume.
The Frank-Starling Law of the Heart describes the relationship between preload and contractility.
Increased preload causes increased contractility and stroke volume.
Stretching of the cardiac muscle fibers at the end of diastole improves calcium binding to troponin-C, enhancing contractility.

Factors Affecting Preload

Venous return is the primary determinant of preload (EDV).
Increased venous return leads to increased EDV.
Decreased venous return leads to decreased EDV.

Venous Return

The pressure difference between the large veins and the right atrium drives venous return.
The skeletal muscle pump and respiratory pump contribute to venous return.
Increased blood volume raises venous return.
The autonomic nervous system regulates venous return through sympathetic innervation of smooth muscle in veins.

Factors Affecting Afterload

Afterload is the resistance the ventricles face during ejection.
During exercise, afterload is regulated by sympathetic nervous system-induced increased contractility, resulting in lower ESV.
During rest, arterial vasomotor tone, known as total peripheral resistance (TPR), is the main determinant of afterload.
Blood pressure is a surrogate indicator of afterload.

Blood Vessels

Key properties of blood vessels include diameter, elasticity, and contractility.

Blood Flow

Flow refers to the fluid volume transported per unit time.
Flow is influenced by pressure difference between two points and resistance to flow.
Arteries have higher pressure than veins.
Arterioles serve as the "bottlenecks" and are crucial for pressure and flow regulation due to their abundance of smooth muscle.

Significance of Pressure Difference

The pressure difference between two points, rather than the absolute pressure, is the primary driver of flow.
Initial pressure originates from heart contraction.

Resistance to Flow

Vessel's length contributes to resistance, but is often constant within an individual.
Vessel's radius is the most important factor influencing resistance.
Viscosity of blood, determined by cells and protein concentration, also affects resistance but is not the primary regulator.

Arterial Pressure During a Cardiac Cycle

Aortic valve opening during ventricular contraction results in rapid blood flow, increased arterial pressure, and temporary energy absorption by aorta's elasticity.
Aortic valve closure during diastole stops blood flow from the ventricle, causing stored energy release from aorta and gradual pressure decrease.

Arteries

Arteries are compliant due to their elastic, large diameter walls.
This elasticity limits pressure drop after systole, ensuring more continuous blood flow.

Aortic Blood Pressure Profile

Systolic pressure is high during contraction.
Diastolic pressure is lower during relaxation.
Mean blood pressure (MBP) represents the average pressure over a cardiac cycle.

Factors Influencing Arterial Pressure

Elasticity of arteries: Low elasticity leads to high pressure.
Cardiac output: A higher cardiac output results in increased pressure.
Respiration: Inspiration decreases thoracic pressure and increases abdominal pressure, affecting blood flow. Expiration reverses this effect.
Resistance to flow (TPR): Vasoconstriction of arterioles increases TPR and pressure.
Blood volume: Primarily affects cardiac output (minimal direct effect on pressure due to vein absorption).

Control of Vascular Resistance

smooth muscle in arteriole walls:
- Arterioles possess less elasticity and more smooth muscle fibers.
- Myogenic tone (basal tone) creates a baseline level of constriction, allowing for diameter changes.
- Constriction increases resistance.

Blood Pressure Control: Local vs. Extrinsic

Local (Autoregulation)
- Controls flow to critical organs (heart, brain, liver, kidneys)
- Metabolic regulation: Responses to changes in metabolism, like CO2, pH, K+, and NO, lead to dilation.
- Myogenic regulation: Vessels respond to stretching by adjusting diameter, maintaining flow despite pressure changes.
Extrinsic:
- Regulates systemic pressure.
- Vasoconstrictors: Sympathetic stimulation, angiotensin II, and arginine vasopressin.
- Vasodilators: Parasympathetic stimulation (mainly in penis and clitoris).

Veins and Venous Pressure

Blood pressure is low in the veins (around 10 mm Hg) yet blood continues toward the right atrium due to sufficient pressure difference.
The heart's sucking action during relaxation helps draw blood upwards.
Skeletal muscle activity assists in propelling blood back to the heart.
Veins have smooth muscles but minimal resistance.
High pressure in veins can cause fluid leakage and tissue edema.

Blood Pressure Control Mechanisms

Key variables include:
- Heart rate
- Stroke volume
- TPR (extrinsic regulation)
Blood pressure reflexes involve:
- Baroreceptors
- Sensory fibers
- Integration center
- Motor fibers
- Effectors

Baroreceptors

Stretch receptors in arterial walls (aortic arch and carotid sinus) that sense pressure changes.
Increased stretching causes increased action potential frequency.
Decreased stretching causes decreased action potential frequency.

Sensory Fibers

Transmit signals from baroreceptors via the vagus nerve to the integration center.

Integration Center

Located in the cardiovascular (vasomotor) center in the medulla oblongata.
Compares incoming signals to a reference value.

Motor Fibers

Transmit signals via the autonomic nervous system (both sympathetic and parasympathetic) to effectors.

Effectors

Heart: Regulates heart rate and stroke volume.
Arterioles and veins: Modulate TPR.

Baroreceptor Action

High pressure:
- Increased stretch of baroreceptors
- Increased action potential frequency to integration center
- Integration center triggers parasympathetic nervous system and reduces sympathetic activity
- Decrease heart rate, stroke volume, TPR, and overall blood pressure.
Low pressure:
- Decreased stretch of baroreceptors
- Decreased action potential frequency to integration center
- Integration center triggers sympathetic nervous system and reduces parasympathetic activity
- Increase heart rate, stroke volume, TPR, and overall blood pressure.

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Description

Test your knowledge on cardiac output, heart rate regulation, and stroke volume. This quiz covers essential concepts such as the role of sympathetic and parasympathetic systems and the definitions of key terms like end-diastolic volume. Challenge yourself with questions that explore how these factors interact to influence cardiovascular health.