cardiac function overview

major functions of cardiovascular system

• transport + delivery

• hemostatic regulation

• protection

• blood recondition

major functions: transport + delivery

• O2 (hemoglobin) and CO2 (byproduct of metabolism)

• nutrients

• waste products like lactic acid and CO2

• hormones

major functions: hemostatic reg

• fluid balance

• temp

• BP

• pH balance

major functions: protection

• blood loss via hemostatic mechanism

• prevent infection (WBC + lymphatics)

major functions: blood recondition

• lungs with O2 and CO2 exchange

• kidneys (fluid)

what percentage of blood sits in the systemic circulation?

84%

the CV system is what type of system?

closed system

what percentage of blood is in the heart?

7%

what percentage of blood is in the pulmonary?

9%

pulmonary and systemic circulation are in what kind of arrangement?

in series

parallel arrangement (what most organs are arranged in)

prevents blood flow changes in one organ from affecting blood flow to other organs, allowing independent control of blood flow

what is the fundamental principle behind excitation-contraction coupling in cardiac muscle?

direct mechanical coupling between electrical and contractile proteins

what is the primary function of hemoglobin in the blood?

to transport oxygen and carbon dioxide

what is the role of WBCs in the blood?

to prevent infection as part of the body’s protective mechanisms

what is the difference between systemic and pulmonary circulation?

systemic involves high pressure and carries blood away from the heart to the body

pulmonary involves low pressure and carries blood to the lungs for gas exchange

what is the significance of the portal circulation?

it carries about 70% of hepatic blood flow from the portal vein, allowing deoxygenated blood to transport digestion products directly to the liver for processing

what is a disadvantage of the portal circulation?

downstream tissues receive partially deoxygenated blood at reduced pressure, making them vulnerable to hypotension

how does the heart contribute to blood circulation?

it generates pressure to push blood throughout the circulatory system

what is the blood volume distribution in terms of cardiac output and oxygen consumption?

different organs have varying ratios of Q to VO2, indicating their metabolic demands

what is the relationship between BF and vascular resistance?

a decrease in total vascular resistance can enhance BF to organs

what does the term “hemostatic regulation” refer to?

the mechanisms that prevent blood loss through clotting and other processes

how does the body maintain pH balance in the blood?

through buffers such as hemoglobin and other physiological mechanisms

what is the primary function of the kidneys in the context of blood?

to regulate fluid balance and filter waste products from the blood

what is the role of the pulmonary arteries and veins?

carry deoxygenated blood to the lungs and return oxygenated blood to the heart

what is the impact of blood distribution on organ function?

organs receive blood with nearly identical composition, ensuring they function optimally

what is the clinical implication of differing Q/VO2 ratios in various organs?

it indicates varying metabolic demands and can inform medical assessments and interventions

what is the term for the area where the heart is surrounded by a sac?

pericardium

what are the two layers of the serous pericardium?

visceral and parietal

what is the pericardial space and how much fluid does it typically contain?

pericardial space lies in between the visceral and parietal layer…15-50 mL of fluid

what is the impact of intrapericardial pressure during inspiration and expiration?

inspiration = -5 mmHg

expiration = +5mmHg

what effect does decreased thoracic cavity pressure have on venous return?

increases venous return

what is PMI in relation to cardiac anatomy?

point of maximum impulse AKA the apical pulse or apex beat

what is the windkessel effect?

aorta distends during systole (when the heart pumps blood out) and recoils during diastole (when the heart relaxes), storing some of the ejected blood and releasing it later

what are the major branches of the left coronary artery?

left anterior descending artery (LAD) and left circumflex artery

what is the function of arterial anastomoses?

they provide interconnections between arteries to reduce the chance of blood flow reductions with disease

what is the significance of the aortic arch in cardiac anatomy?

it’s the section of the aorta that curves between the ascending and descending aorta, giving rise to major arteries supplying the head, neck, and arms

what is the role of the coronary sinus?

collects deoxygenated blood from the heart muscle and drains it into the right atrium

what are physiological end arteries?

arteries that do not have significant anastomoses and supply a specific area of tissue

what is the anatomical position of the descending aorta?

it is divided into thoracic and abdominal sections

what is the significance of the great vessels in relation to the heart?

they are major arteries and veins that transport blood to and from the heart

what is the significance of the aortic knob in cardiac anatomy?

it serves as a radiological landmark indicating the position of the aorta

what are the two main types of coronary artery anastomoses?

inter coronary anastomosis and extracardiac anastomosis

what is the purpose of the pericardial reflection?

it allows the pericardium to reflect back on itself at the great vessels, providing a space for movement

what are the two arteries that branch from the internal thoracic artery related to the pericardium?

pericardiacophrenic and musculophrenic arteries

how does rapid occlusion relate to collateral circulation effectiveness?

it leads to ineffective anastomoses

how does gradual occlusion relate to collateral circulation effectiveness?

allows anastomoses to enlarge and maintain adequate circulation

what is koch’s triangle?

anatomical area in the heart that is significant for its relation to the AV node

what are the components of the cardiac conduction system?

SA node, internodal pathways, AV node, AV bundle (bundle of HIS), bundle branches (left and right), and terminal purkinje fibers

what is the resting membrane potential of cardiac cells?

approximately -60 mV for nodal cells and -90 mV for non-pacemaker cells

what is automaticity in cardiac physiology?

refers to the heart’s ability to generate spontaneous rhythmic impulses without external stimulation

what is the role of SERCA pumps in cardiac muscle cells?

they help to remove calcium ions from the cytoplasm to allow the heart muscle to relax

what are the phases of the action potential in nodal (pacemaker) cells?

phase 0: Ca2+ channels open; phase 3: K+ out, Phase 4: slow Na+ influx (funny channels)

what is the effect of parasympathetic stimulation on heart rate?

parasympathetic stimulation decreases heart rate (negative chronotropic effect)

what is the effect of sympathetic stimulation on heart contractility?

sympathetic stimulation increases contractility (positive inotropic effect) and heart rate (positive chronotropic effect) » funny channels are activated here; sodium permeability increases

what are the phases of the action potential in non-pacemaker cells?

phase 0: fast Na+ channels open; phase 1: inactivation of Na+ channels and gated K+ out; phase 2: Ca2+ in and K+ out; phase 3: inactivation of Ca2+ channels and K+ out; phase 4: Na+/K+ ATPase pumps restore RMP

what is the significance of the concentration gradient in cardiac action potentials?

the concentration gradient drives the movement of ions across the membrane, and this is crucial for generating action potentials

what is the role of the Na+/Ca2+ exchanger in cardiac cells?

helps to regulate intracellular calcium levels, which is important for cardiac muscle contraction and relaxation

what happens during the threshold potential in cardiac cells?

sufficient depolarization occurs to trigger an action potential

what is the role of the autonomic nervous system in cardiac action potentials?

the ANS modulates heart rate and contractility through sympathetic and parasympathetic pathways

what is the significance of the electrical force in cardiac action potentials?

the electrical force influences ion movement across the membrane, contributing to the depolarization and depolarization phases of the action potential

what is the primary ion responsible for depolarization in cardiac pacemaker cells?

calcium ions (Ca2+) are primarily responsible for depolarization in pacemaker cells

what is the effect of calcium on cardiac muscle contraction?

calcium ions are essential for initiating contraction in cardiac muscle cells

what is the difference between nodal and contractile action potentials?

nodal action potentials have a slower depolarization phase and rely on Ca2+ influx while contractile action potentials have a rapid depolarization phase due to Na+ influx

what is the importance of the refractory period in cardiac physiology?

it prevents the heart from undergoing tetany and ensures proper timing of contractions

what is the function of internal pathways in the cardiac conduction system?

they facilitate the rapid conduction of impulses from the SA node to the AV node

what determines the ability of fast Na+ channels to reopen during cardiac action potential?

the percentage of fast Na+ channels that have recovered from the inactive state

what is the absolute refractory period in cardiac physiology?

the period during which the heart is unexcitable to a new stimulus

what is the effective refractory period (ERP)?

a period where a stimulus can produce a localized action potential but is not strong enough to propagate

what characterizes the relative refractory period?

a stimulus can trigger a conducted action potential but the rate of rise is less than normal

what is the supranormal period in cardiac physiology?

period during which a less than normal stimulus can trigger an action potential

what is the function of the cardiac skeleton?

• attaches atrial and ventricular myocardium

• provides a foundation for heart valves

• prevents overstretching of heart valves

• electrically separates upper and lower chambers

typical weight range of human heart

300-350 grams (0.55-0.77 lbs)

what is the pathway of blood flow from the inferior/superior vena cava to the aorta?

IVC/SVC, RA, tricuspid valve, RV, pulmonic valve, pulmonary artery, lungs, pulmonary veins, LA, mitral valve, LV, aortic valve, ascending aorta

what is the formula for calculating BF in relation to pressure and resistance?

Q = deltaP / R, where Q is blood flow, deltaP is the difference between arterial and venous pressure, R is resistance

what drives organ blood flow in the body?

the pressure gradient

what is the resting cardiac output range for adults?

3-6 L/min

what are the two types of devices that aid in enhancing venous return?

muscle pump and device aids such as impella

what is the function of valves in veins?

they ensure unidirectional blood flow

what are the three layers of the heart wall?

endocardium, myocardium, epicardium

what is the role of the pericardium?

provides protection and support to the heart

what are intercalated discs and their function?

they contain gap junctions and desmosomes, allowing for coordinated contraction of cardiac muscle cells

what are the characteristics of cardiac muscle cells?

automaticity, excitability, conductivity, and contractility

what is the function of T-tubules in cardiac muscle cells?

they facilitate comms from outside to inside of cell, signaling the SR to release calcium

what is excitation-contraction coupling? (ECC)

the process by which an electrical signal triggers muscle contraction involving calcium release

what is the role of calcium in cardiac muscle contraction?

calcium induces calcium release, which is crucial for muscle contraction

what is the significance of costameres in cardiac cells?

they tie into the ECM, providing mechanical support and facilitating lateral force transmission

what is electroporation in the context of cardiac cells?

a method using ultra-rapid electrical pulses to destabilize cell membranes, leading to apoptosis

what is the mechanism of action (MOA) of pulsed field ablation (PFA)?

it destabilizes the cell membrane by forming nanoscale pores through ultra-rapid electrical pulses

what is the formula for stroke volume?

end diastolic volume minus end systolic volume

what is torsional contraction in the heart?

a contraction mechanism that decreases end systolic volume

what is dynamic relaxation in cardiac physiology?

a contraction mechanism that increases end diastolic volume

what is the significance of the sarcomere in cardiac muscle?

it’s the contractile unit containing proteins like actin and myosin essential for muscle contraction

what are the two types of cardiac muscle cells?

nodal (non-contractile, pacemaker) and non-nodal (contractile) cells

what is the role of ATPase in cardiac muscle cells?

breaks ATP down to use for energy to get rid of calcium through the active exchange channels

what is the impact of substrate stiffness on cardiomyocyte fate?

influence the mechanical properties and behavior of cardiomyocytes

what is the cardiac cycle composed of?

systole (contraction) and diastole (relax)

what is EDV?

volume of blood in V at the end of diastole

what is ESV?

volume of blood in V at end of systole

what is the primary function of the blood?

transport of gases, hormones, metabolic substrates, and other substances

what are the components of blood volume?

plasma volume (55%) and formed elements (45%)