Cardiac Physiology Overview

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Questions and Answers

Which of the following best describes the relationship between after-load and stroke volume?

Increased after-load directly increases stroke volume.

Decreased after-load enhances stroke volume.

After-load indirectly decreases stroke volume initially but can increase it over time. (correct)

After-load does not impact stroke volume.

How does pharmacological intervention influence the ventricular function curve?

Only negative inotropic agents shift the curve to the right.

All agents uniformly shift the curve to the left.

The curve remains unchanged regardless of the agent used.

Positive inotropic agents shift the curve to the right indicating increased contractility. (correct)

Which statement about the Frank-Starling relationship is accurate?

It focuses primarily on the effects of negative inotropic agents.

Increased end-diastolic volume leads to increased contractility. (correct)

It describes the effect of arterial pressure on stroke volume.

It is determined solely by external factors affecting muscle length.

Which of the following correctly identifies a characteristic of negative inotropic agents?

They weaken the force of contraction in cardiac muscle. Signup and view all the answers

What mechanism assists in the return of blood to the heart from the venous system?

Skeletal muscle contractions during physical activity. Signup and view all the answers

Which factor primarily influences the preload of the heart?

Ventricular wall thickness Signup and view all the answers

What is the primary mechanism by which the skeletal muscle pump aids in venous return?

Creating pressure gradients through muscle contraction Signup and view all the answers

How does the Frank-Starling Law describe cardiac contractions?

They increase with initial fibre length and stretch. Signup and view all the answers

What effect does reduced ventricular compliance have on preload?

It decreases preload. Signup and view all the answers

What is the typical stroke volume of the heart at rest?

70 ml/beat Signup and view all the answers

Which channel blocker is known to have a direct negative chronotropic effect?

Verapamil Signup and view all the answers

In the context of cardiac output, what does stroke volume represent?

The volume of blood ejected with each ventricular contraction. Signup and view all the answers

Which factor does NOT affect stroke volume?

Capillary permeability Signup and view all the answers

What role do one-way valves play in the venous system?

Prevent backflow of blood toward the extremities Signup and view all the answers

How does skeletal muscle contraction influence venous return?

It compresses veins, promoting blood flow towards the heart Signup and view all the answers

Which factor contributes to the venous return mechanism during respiration?

A decrease in chest cavity pressure during inspiration Signup and view all the answers

What is the primary effect of increased venous return on cardiac output?

Increases end diastolic volume Signup and view all the answers

What happens to the valves in the veins during calf muscle contraction?

They open to allow blood to flow back to the heart Signup and view all the answers

What is affected by the skeletal muscle pump mechanism?

Blood flow dynamics in the venous system Signup and view all the answers

Which statement about venous return is accurate?

It is unidirectional due to venous valves Signup and view all the answers

How does cardiac output relate to venous return?

Higher venous return typically increases cardiac output Signup and view all the answers

Match the terms with their definitions related to venous return:

O2 poor blood = Blood that is rich in carbon dioxide (CO2) O2 rich blood = Blood that has high levels of oxygen (O2) Cardiac Output = Volume of blood pumped out per minute Stroke Volume = Volume of blood pumped out of the heart in one contraction Signup and view all the answers

Match the mechanisms affecting venous return:

One-way valves = Prevent backflow of blood in veins Skeletal muscle contractions = Aid in the compression of large veins Respiration = Acts like a pump during chest cavity pressure changes Calf muscle contraction = Can open and close venous valves during movement Signup and view all the answers

Match the blood types with their oxygen and carbon dioxide levels:

O2 poor blood = CO2 rich blood O2 rich blood = CO2 poor blood Systemic blood = Transports oxygen to body tissues Pulmonary blood = Carries carbon dioxide to lungs for exhalation Signup and view all the answers

Match the terms with their relationship to venous return:

End Diastolic Volume = Volume of blood in ventricles before contraction Pulmonary Venous Return = The flow of oxygenated blood back to heart from lungs Valves in veins = Prevent backflow and ensure unidirectional flow of blood Compression of veins = Facilitated by surrounding muscle contraction Signup and view all the answers

Match the following factors with their effects on venous return:

Chest cavity pressure = 5 mmHg less during inspiration aids venous return Skeletal muscle pump = Enhances blood flow back to the heart One-way valves = Essential for maintaining direction of venous blood flow Calf muscle action = Compresses veins aiding in venous return Signup and view all the answers

Match the components of venous return with their characteristics:

Blood flow caused by muscle contraction = Facilitates the return of blood to the heart Valves prevent backflow = Essential for maintaining venous return efficiency Respiratory pump = Influences pressure gradient during breathing One-way valves in veins = Act as gates controlling blood flow direction Signup and view all the answers

Match the physiological processes with their influences on venous return:

Contraction of calf muscles = Helps to compress veins Inspiration = Creates negative pressure in thorax enhancing venous return Valves in veins = Prevent backflow during venous return Skeletal muscle activity = Increases effectiveness of venous return Signup and view all the answers

Match the following terms with their correct definitions:

Pre-load = Myocardial sarcomere length before contraction Stroke Volume = Volume of blood ejected in each ventricular contraction End Diastolic Volume (EDV) = Volume of the ventricle when relaxed End Systolic Volume (ESV) = Volume of the ventricle when fully contracted Signup and view all the answers

Match the following terms with their related muscle type:

Skeletal muscle = Contains both thick and thin filaments Cardiac muscle = Contraction by sliding of filaments Both muscle types = Use myosin and actin Cardiac muscle only = Exhibits no descending limb in length-tension Signup and view all the answers

Match the following cardiac mechanisms with their descriptions:

Frank-Starling Law = Strength of cardiac contraction based on initial fibre length Negative chronotropic effect = Slows heart rate Positive inotropic effect = Increases strength of heart contractions Ventricular compliance = Ability to stretch and accommodate blood volume Signup and view all the answers

Match the following physiological concepts with their implications:

Increased venous return = Enhances stroke volume Reduced compliance = Decreases pre-load Hypertrophy = Reduces pre-load due to wall thickening Cardiac activation = Variable and affects stroke volume Signup and view all the answers

Match the following heart conditions with contributing factors:

Heart failure = Not due to excessive stretch Increased EDV = Improves stroke volume Altered Ca2+ sensitivity = Influences contraction strength Pericardial compliance = Affects pre-load readings Signup and view all the answers

Match the following cardiac output components with their equations:

Stroke Volume = $EDV - ESV$ Cardiac Output = $Heart Rate \times Stroke Volume$ Total blood volume = Affects preload indirectly Ventricular filling = Influences EDV Signup and view all the answers

Match the following drugs or mechanisms to their effects:

Atenolol = Beta-blocker that slows heart rate Calcium channel blockers = Direct negative chronotropic effect Increased blood volume = Enhances pre-load Decreased respiration = Reduces intra-thoracic pressure Signup and view all the answers

Match the following agents with their category:

Digitalis = Cardiac Glycosides Epinephrine = Catecholamines Diltiazem = Calcium channel blockers Beta blockers = Negative inotropic agents Signup and view all the answers

Match the following neurotransmitters to their sympathetic or parasympathetic roles:

ACh = Parasympathetic NE = Sympathetic Epinephrine = Sympathetic Dopamine = Parasympathetic Signup and view all the answers

Match the following receptors with their corresponding signaling pathways:

b1 = Increases cAMP M2 = Decreases cAMP Calcium channels = Facilitates calcium influx K-ACh channels = Inhibits pacemaker activity Signup and view all the answers

Match the following terms with their correct definitions related to cardiac contractility:

Positive inotropes = Increase myocardial contractility Negative inotropes = Decrease myocardial contractility Calcium Pump = Regulates intracellular Ca levels cAMP = Mediates effects of beta-adrenergic stimulation Signup and view all the answers

Match the following terms to their effects on cardiac function:

Increase in intracellular Ca = Enhances contractility Activation of PKA = Increases phosphorylated proteins Beta receptor activation = Increases heart rate Calcium channel blockade = Decreases contractility Signup and view all the answers

Match the following vascular terms with their correct descriptions:

Vasoconstriction = Narrowing of blood vessels due to smooth muscle contraction Vasodilation = Widening of blood vessels due to smooth muscle relaxation Hydrostatic Pressure = Pressure exerted by fluid at rest Oncotic Pressure = Pressure that draws fluid into the capillaries Signup and view all the answers

Match the following types of blood vessels with their primary function:

Arterioles = Regulate blood flow to capillary beds Capillaries = Site of exchange between blood and tissues Venules = Collect blood from capillaries to form veins Lymphatic vessels = Transport lymph fluid back to circulation Signup and view all the answers

Match the following terms related to capillaries with their characteristics:

Metarterioles = Connect arterioles to capillaries Pre-capillary sphincters = Control blood flow into capillaries Thoroughfare channel = Direct pathway from arterial to venous system Interstitial fluid = Fluid between blood plasma and tissue cells Signup and view all the answers

Match the following pressures with their impact on fluid movement:

NFP = +10 mmHg = Fluid filtration out of capillaries NFP = 0 mmHg = No net fluid movement NFP = -7 mmHg = Fluid reabsorption into capillaries CHP > BCOP = Fluid movement out of capillaries Signup and view all the answers

Match the following components of the circulatory system with their roles:

Aorta = Largest artery carrying blood from the heart Medium Arteries = Distribute blood to specific organs Large Veins = Return blood to the heart Arterioles = Control blood flow and pressure Signup and view all the answers

Match the following fluid dynamics terms with their definitions:

Bulk flow = Movement of fluid due to pressure differences Filtration Pressure = Net pressure determining movement out of capillaries Colloid Osmotic Pressure = Pressure due to proteins in blood plasma Hydrostatic Pressure = Pressure from fluid within the capillaries Signup and view all the answers

Match the following types of fluid to their characteristics:

Lymph = Fluid that circulates in the lymphatic system Plasma = Liquid component of blood containing proteins and electrolytes Interstitial fluid = Fluid surrounding tissue cells Blood = Fluid connective tissue that transports nutrients and gases Signup and view all the answers

Match the following physiological processes with their descriptions:

Perfusion = Supply of blood to tissues Filtration = Movement of fluid out of capillaries Reabsorption = Movement of fluid back into capillaries Drainage = Return of excess interstitial fluid via lymphatic vessels Signup and view all the answers

Match the following blood supply routes with their descriptions:

Arterioles = Main regulators of blood flow to capillary beds Capillaries = Microscopic vessels where exchange occurs Venules = Small vessels that gather blood from capillaries Lymphatic vessels = Return excess fluid to the bloodstream Signup and view all the answers

Match the following terms related to vascular structure with their definitions:

Smooth muscle = Layer responsible for contraction and regulation of blood pressure Endothelial cells = Line the interior of blood vessels Elastic fibers = Allow blood vessels to stretch and recoil Basement membrane = Supportive layer beneath endothelial cells Signup and view all the answers

Match the following components to their roles in blood flow regulation:

Pre-capillary sphincters = Regulate blood entry into capillary beds Arterioles = Control resistance to blood flow Capillary walls = Facilitate exchange of substances Venules = Begin the collection of deoxygenated blood Signup and view all the answers

Match the following aspects of lymphatic function with their roles:

Lymphatic drainage = Removes excess interstitial fluid Immune response = Filters pathogens via lymph nodes Nutrient absorption = Transports lipids from the digestive tract Fluid balance = Maintains homeostasis between blood and interstitial fluid Signup and view all the answers

Match the following terms related to pressure gradients in capillaries:

CHP = Capillary hydrostatic pressure BCOP = Blood colloid osmotic pressure NFP = Net filtration pressure Effective filtration pressure = Determines fluid movement across capillary walls Signup and view all the answers

Match the following processes with their descriptions:

Venoconstriction = Activation of smooth muscle in veins Cardiac suction = Atrial pressure drops during ventricular contraction Skeletal muscle pump = Compression of veins aiding blood return Respiratory pump = Pressure variation in the chest during breathing Signup and view all the answers

Match the components of cardiac output with their definitions:

Stroke Volume (SV) = Amount of blood pumped per heartbeat Heart Rate (HR) = Number of beats per minute Cardiac Output (CO) = Total blood flow from the heart per minute mmHg = Unit of measurement for blood pressure Signup and view all the answers

Match the types of blood vessels with their characteristics:

Arteries = Carry blood away from the heart Veins = Contain one-way valves to prevent backflow Capillaries = Main site for fluid exchange Arterioles = Regulate blood flow to tissues Signup and view all the answers

Match the autonomic nervous system effects with their functions:

Sympathetic activation = Increases heart rate and force of contraction Parasympathetic activation = Decreases heart rate Vasoconstriction = Constriction of blood vessels for increased pressure Vasodilation = Dilation of blood vessels to enhance blood flow Signup and view all the answers

Match the elements of blood pressure regulation with their functions:

Baroreceptor reflexes = Detect changes in blood pressure Chemoreceptor reflexes = Monitor oxygen and carbon dioxide levels Adrenaline release = Increases heart rate and blood pressure Long-term regulation = Involves kidney function and fluid balance Signup and view all the answers

Match the features of veins with their functions:

One-way valves = Prevent backflow of blood Smooth muscle innervation = Controlled by the sympathetic nervous system Larger lumen = Facilitates easy blood return to the heart Compliance = Ability to stretch and accommodate varying volumes Signup and view all the answers

Match the mechanisms of venous return with their descriptions:

Muscle contractions = Compress veins to push blood Respiration = Creates a pressure gradient aiding return Venoconstriction = Reduces vein diameter to push blood back Cardiac suction = Helps draw blood into the heart with negative pressure Signup and view all the answers

Match the components of vascular anatomy with their corresponding types:

Aorta = Largest artery in the body Small arteries = Distribute blood to capillaries Capillaries = Exchange sites for nutrients and waste Venules = Collect blood from capillaries back to veins Signup and view all the answers

Study Notes

Heart Rate & Contractility

Atenolol is a beta-blocker that slows down heart rate.
Calcium channel blockers like verapamil have a direct negative chronotropic effect, meaning they decrease heart rate.

Stroke Volume

Stroke volume (SV) is the amount of blood ejected from the heart during each contraction.
SV = End Diastolic Volume (EDV) - End Systolic Volume (ESV).
Resting SV is typically around 70 ml/beat.

Cardiac Length-Tension Relationship

Cardiac muscle contraction is caused by the sliding of thick (myosin) and thin (actin) filaments, similar to skeletal muscle.
Key difference: there is no descending limb on the length-tension curve for cardiac muscle.

Factors Affecting Stroke Volume

Pre-load: Refers to the myocardial sarcomere length before contraction.
- Approximated by EDV (end diastolic volume).
- Influenced by:
  - Ventricular filling: affected by intra-thoracic pressure, respiration, and blood volume.
  - Ventricular and pericardial compliance: reduced compliance decreases pre-load.
  - Ventricular wall thickness: hypertrophy decreases pre-load.
After-load: The force the ventricles must overcome to eject blood.
- Sum of elastic and kinetic forces.
- Primary forces opposing ejection are arterial blood pressure and vascular tone.
- Increased arterial resistance initially decreases stroke volume, but compensatory mechanisms increase it over time.
Contractility: Influences the inherent strength of heart muscle contraction during systole.
- Pharmacological agents can affect contractility.
  - Negative inotropic agents weaken contraction.
  - Positive inotropic agents strengthen contraction.
  - The F-S curve shifts to the right with negative inotropy and to the left with positive inotropy.
  - The dashed line on the F-S curve indicates where maximal contractility has been exceeded.

Venous Return

Venous return is the flow of blood back to the heart through the veins.
Directly affects:
- End Diastolic Volume (EDV): Volume of blood in the ventricles before contraction.
- Stroke Volume: Volume of blood pumped out with each beat.
- Cardiac Output: Volume of blood pumped out per minute.

Mechanisms of Venous Return

One-way valves prevent backflow.
Compression of large veins: Facilitated by skeletal muscle contractions.
Respiration: Acts as a pump, creating a pressure difference between the chest and atmosphere during inspiration, pulling blood back to the heart.

Venous Return in the Legs

One-way valves and skeletal muscle contractions in the calves are crucial for returning blood back to the heart.
Valve opens during calf muscle contraction, squeezing blood upwards and preventing backflow when muscle relaxes.

The Vasculature

The vasculature consists of blood vessels, including arteries, arterioles, capillaries, venules, and veins.
Arteries transport oxygenated blood away from the heart, while veins return deoxygenated blood to the heart.
Arterioles are the smallest arteries, responsible for controlling blood flow to capillaries.
Capillaries are the smallest blood vessels, facilitating gas exchange between blood and tissues.
Venules are small veins collecting blood from capillaries.

Circulation and Lymph

Blood flow is driven by blood pressure.
Arteries and arterioles regulate blood pressure, directing blood flow to specific tissues.
Capillaries facilitate fluid exchange between blood and the interstitial fluid.
Lymphatic vessels collect excess interstitial fluid and return it to the circulatory system.
The venous system returns deoxygenated blood to the heart.

Blood Pressure Regulation

Blood pressure is regulated by cardiac output and peripheral resistance.
Cardiac output is the volume of blood pumped by the heart per minute.
Stroke volume is the volume of blood ejected by the ventricle during each contraction.
Baroreceptors and chemoreceptors detect changes in blood pressure and blood chemistry, sending signals to the autonomic nervous system to adjust heart rate and blood vessel diameter.
Long-term blood pressure regulation involves hormonal mechanisms and renal mechanisms.
Hypertension is high blood pressure, often caused by dysfunction of the cardiovascular system.

Cardiac Output

Cardiac output (CO) is calculated using the formula: CO = SV x HR.
CO represents the amount of blood pumped by the heart per minute.
SV is the volume of blood ejected during each heart beat.
HR is the number of heart beats per minute.

Autonomic Nervous System Regulation of Cardiac Output

The sympathetic nervous system increases heart rate and force of contraction.
The parasympathetic nervous system decreases heart rate and force of contraction.
The sympathetic nervous system causes vasoconstriction, while the parasympathetic nervous system causes vasodilation in most blood vessels (excluding the penis and clitoris).
The adrenal medulla releases adrenaline and noradrenaline, further increasing heart rate and force of contraction.

Heart Rate

Heart rate is the number of ventricular contractions per minute.
Certain drugs, like atenolol and calcium channel blockers, have a negative chronotropic effect on heart rate.

Cardiac Output: Stroke Volume

Stroke volume (SV) is the volume of blood ejected from the ventricle during each contraction.
SV is calculated as the difference between end-diastolic volume and end-systolic volume.
The Frank-Starling Law of the heart states that the strength of cardiac contraction is directly proportional to the initial length of the cardiac muscle fibers.

Stroke Volume (Factors influencing)

Preload: myocardial sarcomere length just prior to contraction. Affected by:
- Ventricular filling: Influenced by intra-thoracic pressure, respiration, and blood volume.
- Ventricular and pericardial compliance: Reduced compliance decreases preload.
- Ventricular wall thickness: Hypertrophy decreases preload.

Factors Affecting Cardiac Contractility

Intracellular calcium concentration determines myocardial contractility.
Factors influencing intracellular calcium levels affect contractility.
Positive inotropic agents increase contractility:
- Cardiac glycosides (digitalis): Block Na-K ATPase.
- Catecholamines (epinephrine, norepinephrine, isoproterenol): Activate beta-adrenergic receptors.
Negative inotropic agents decrease contractility:
- Beta-blockers: Block beta-adrenergic receptors.
- Diltiazem and verapamil: Block DHPR Ca channels.

Autonomic Regulation of Cardiac Contractility

The sympathetic nervous system increases myocardial contractility through norepinephrine and beta-1 receptors.
The parasympathetic nervous system decreases myocardial contractility through acetylcholine and M2 receptors.

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Description

This quiz covers fundamental concepts of cardiac physiology, focusing on heart rate, stroke volume, and the cardiac length-tension relationship. It examines the effects of various medications like Atenolol and calcium channel blockers, as well as factors influencing stroke volume.