[PHYSIOL - LE 2 ] CARDIAC

what are the layers of the heart and their description

1.  Epicardium: the most superficial (outer) layer the visceral layer of the serous pericardium

2.  Myocardium: The middle layer of the heart muscle composed of cardiac muscle and forms the bulk of the heart mass. This is the layer that contracts.

3. Endocardium: The inner layer ; is of endothelium which rests on a thin layer of connective tissue. It is continuous with the lining of the blood vessels entering and leaving the heart.

What is a platelet plug and how is it formed?

A platelet plug forms around the site of vessel damage

What is vascular spasm and when does it occur?

Vascular spasm is the immediate constriction of an injured blood vessel's smooth muscle

what is the 3 step process in the coagulation cascade

1. Vascular spasm (vasoconstriction)

2. formation of platelet plug

3. blood coagulation

What role do endothelial cells play during vascular spasm, what do they release ?

Endothelial cells release vasoconstrictors such as endothelin to help constrict the smooth muscle of the blood vessel.

What is the role of von Willebrand factor (vWF) in platelet adhesion?

vWF acts as a bridge between platelets and collagen seen in formation of the platelet plug

What does the enzyme ADAMTS13 prevent in platelet plug formation?

ADAMTS13 cleaves ultra-large vWF multimers to prevent excessive clotting while allowing normal platelet adhesion.

what is the whole process (including the enzymes ) in the process of hemostasis

1. vascular spasm

   > vessel damage > smooth muscle constrict reflex > release of endothelin > waits for 2-30 mins for other process

2. platelet plug formation

   > platelets stick to exposed collagen fiber > vWF bridges platlet and collagen > ADAMTS13 stops vWF from over clotting > platelets undergo change and release TxA2 > platlet aggregation and further vasoconstriction

3. Blood coagulation

   >thrombin turns fibrinogen > IIa and IIb binds fibrinogen and fibrinogen turns to insoluable fibrin

What is the role of thromboxane A₂ in hemostasis?

Thromboxane A₂ promotes platelet aggregation and vasoconstriction

what is the order of intrinsic pathway in blood coagulation

vessel damage > exposed collagen > 12 turns to 12a > cleaves 11 and turns into 11a > cleaves 9 and turns into 9a and then works with 8 and turns into 8a > cleaves factor 10 and turns it into 10a > 10 a cleaves prothrombin into thrombin

12 , 11 , 9, 10

what is the order of extrinsic pathway in blood coagulation

vessel damage > subendothelial cells exposed to blood > tissue factor (factor 3) gets alarmed > factor 7 cleaves factor 9 and turns into 9 and cleaves > factor 10 and turns into 10a and cleaves prothrombin to thrombin

3, 7,9, 10

What is the role of thrombin in the coagulation cascade?

Thrombin converts fibrinogen into fibrin

What is the significance of glycoprotein IIb/IIIa (GPIIb/IIIa) receptors in platelet aggregation?

GPIIb/IIIa receptors bind fibrinogen and  acts like glue to hold the platelets together.

What is the role of phospholipase A₂ in platelet function?

Phospholipase A₂ catalyzes the formation of thromboxane A₂ from arachidonic acid

What is the overall purpose of hemostasis?

Hemostasis prevents excessive bleeding when a blood vessel is injured.

What is the importance of maintaining blood pressure during hemostasis?

to ensure adequate blood flow and prevent shock during the clotting process.

What is the role of ADAMTS13 in hemostasis?

ADAMTS13 controls a protein called vWF and prevents dangerous small blood clots

How is Factor XII activated and from pathway?

Factor XII (Hageman factor) gets activated when it touches exposed collagen from an injury. intrinsic pathway

What is the function of thrombin in the coagulation process?

Thrombin converts soluble fibrinogen into insoluble fibrin threads

What is the role of Factor Xa in the coagulation cascade?

Converts prothrombin to thrombin (common pathway)

How does Factor XIIa contribute to clot stability?

Initiates intrinsic pathwaY

What are the two primary pathways of the coagulation cascade?

The intrinsic pathway (slower but stable) and extrinsic pathway (immediate)

What is the function of plasminogen activators?

Plasminogen activators help break down blood clots by converting plasminogen (an inactive protein in the blood) into plasmin (an active enzyme).

What is the function of phospholipase A₂ in hemostasis?

Phospholipase A₂ produces thromboxane A₂ for platelet aggregation

What is hemophilia?

Hemophilia is a genetic disorder caused by deficiency of a specific coagulation factor. a genetic X-linked disorders seen primarily in men because xy since only 1 x that x might be defective and be copied unlike women na may extra 

What is von Willebrand's disease?

Von Willebrand's disease is characterized by reduced levels of vWF

• less platelet plug formation and easier to bleed 

• Decreases platelet plug formation

How do vitamin K deficiencies affect coagulation?

Vitamin K deficiencies lead to decreased synthesis of clotting factors. SINCE ALL FACTORS ARE K-DEPENDENT

What is the role of plasmin in hemostasis?

Plasmin breaks down the fibrin mesh during fibrinolysis.

How is unbound thrombin inactivated?

Unbound thrombin is inactivated by Antithrombin III and protein C.

What is heparin and where is it found?

Heparin is an anticoagulant found in mast cells

 inhibits thrombin by enhancing Antithrombin Ill and clotting by inhibiting the intrinsic pathway

What role do endothelial cells play in the circulatory system?

Endothelial cells are normally smooth and intact and prevent platelets from adhering, but inappropriate clotting causes serious problems including stroke, heart attacks, tissue ischemia and death.

What is the role of aspirin in clot prevention?

Aspirin is an antiprostaglandin that inhibits the formation of TxA2. clinically to prevent clots.

What are thromboembolic disorders?

disorders that result from inappropriate clot formation

What is an embolus?

An embolus is a clot that is free-floating in the bloodstream and can wedge in a vessel.

What is thrombocytopenia?

Thrombocytopenia is characterized by a lack of platelets which causes spontaneous bleeding in small blood vessels.

What can cause thrombocytopenia?

can be caused by anything that affects bone marrow

What treatment is available for thrombocytopenia?

The only treatment is platelet transfusions.

How does impaired liver function affect clotting?

Impaired liver function causes a lack of procoagulants

What treatment can be given for vitamin K deficiency?

Vitamin K shots can be administered if there is a deficiency.

What is the circulatory pathway through the body?

The pathway is: Aorta > arterioles > capillaries > venules > veins > vena cava > right atrium > tricuspid valve > right ventricle > pulmonary valve > pulmonary artery > pulmonary arterioles > pulmonary capillaries > pulmonary venules > pulmonary vein > left atrium > bicuspid/mitral valve > left ventricle > aortic valve > aorta.

What are the main types of blood vessels?

Blood vessels can be divided into arteries (away from heart), veins (back to heart) and capillaries (facilitate exchange of waste and contents)

What is the exception to the general rule about arteries and veins?

The exception is that pulmonary arteries carry deoxygenated blood to the lungs

What are the types of hemophilia and their associated factors?

• Hemophilia A or classical hemophilia is a lack of factor VIII

• Hemophilia B is a lack of factor IX.

•  Hemophilia C seen in both sexes and is mild,  a lack of factor XI

What factors affect blood resistance?

1. Blood viscosity: increased viscosity increases resistance;

2. Total blood vessel length: longer vessels increase resistance;

3. Blood vessel diameter: narrower vessels increase resistance.

What is the coronary sinus?

The coronary sinus is where most cardiac veins drain into and it empties into the right atrium.

What is the role of the SA node in the heart?

The SA node is known as the heart's natural pacemaker ,include both beta-adrenergic receptors and muscarinic cholinergic receptors to regulate heart contractility

What is the function of gap junctions in the heart?

Gap junctions allow direct electrical contact between cardiac muscle cells

What is the role of the AV node?

The AV node is located between the atria and ventricles and delays the electrical signal from SA node by about 0.1 seconds.

This delay gives the atria time to fully contract and fill the ventricles with blood before the ventricles themselves contract

What is atrial natriuretic peptide (ANP)?

ANP is a peptide hormone secreted by the atria that helps regulate sodium levels in the blood and body fluids.

• When sodium is lost in kidney to urine, water follows it, helping to reduce blood volume and blood pressure.

What is the significance of the left side of the heart?

The left side of the heart has more pressure and requires more stability to pump blood effectively.

What is resistance in the cardiovascular system?

Resistance is the difficulty for blood to flow between two points at a given pressure difference

What is the composition of the endocardium?

The endocardium is composed of endothelium resting on a thin layer of connective tissue and is continuous with the lining of blood vessels.

What is the sequence of excitation in the heart starting from the SA node?

1. SA node fires → atria contract → blood moves into ventricles. 2. Delay at AV node. 3. Signal moves through Bundle of His → Purkinje fibers → ventricles contract from the bottom up. 4. Contraction pushes blood out of the heart.

What is the role of the Bundle of His in the cardiac conduction system?

It conducts the electrical impulse from the AV node to the Purkinje fibers.

How do Purkinje fibers contribute to heart function?

They spread the electrical signal quickly throughout the ventricles from the down up

What is the function of coronary arteries?

They supply blood to the myocardium and branch from the aorta

What does the P wave represent in an ECG?

Atrial depolarization, atrial systole

What does the QRS complex represent in an ECG?

Ventricular depolarization and atrial repolarization, ventricular systole

What does the T wave represent in an ECG?

Ventricular repolarization, ventricular diastole

What is the significance of the PR interval in an ECG?

It reflects the time taken for the electrical impulse to travel from the atria to the ventricles.

What does the QT interval indicate in an ECG?

It reflects the time from the start of ventricular depolarization to the end of ventricular repolarization.

What are arrhythmias?

Uncoordinated atrial and ventricular contractions caused by a defect in the conduction system.

What is the difference between atrial fibrillation and ventricular fibrillation?

Atrial fibrillation can cause clotting and inefficient filling of the ventricles, while ventricular fibrillation ventricles pump without filling and if the rhythm is not rapidly reestablished then circulation stops and brain death occurs.

What is defibrillation?

The application of an electrical stimulus to shock the heart back into a normal rhythm.

What is cardiac output (CO)?

The amount of blood pumped out of each ventricle in one minute

What happens during systole?

It is the contraction phase of the cardiac cycle.

What happens during diastole?

It is the relaxation phase of the cardiac cycle.

What role does extracellular calcium play in cardiac action potential?

It enters the cell through L-type calcium channels during the plateau phase and triggers the release of more calcium., cardiac muscle relies on this extracellular calcium

What is the function of a pacemaker in the heart?

It delivers electrical stimuli to regulate heart rhythm when the SA node is not functioning properly.

What is considered normal blood pressure?

About 120/80 mm Hg.

What is the role of the right atrium?

Receives deoxygenated blood from the body and gives it to the ventricle to the triscuspid valve

What does the right ventricle do?

Pumps blood to the lungs and goes out through pulmonary valve

What is the function of the left atrium?

Receives oxygenated blood from the lungs. and transfers to ventricle by mitral valve

What does the left ventricle do?

Pumps oxygen-rich blood to the body through the aortic valve .

What factors regulate blood pressure?

• Heart rate.

• Blood vessel diameter (vasoconstriction/dilation).

• Blood volume.

What is the formula for cardiac output?

CO = Heart Rate x Stroke Volume.

What is the pathway of blood from the heart to the body?

Left ventricle → Aorta → Arteries → Arterioles → Capillaries → Venules → Veins → Superior/Inferior vena cava → Right atrium.

What is the pathway of blood from the heart to the lungs?

Right ventricle → Pulmonary artery → Pulmonary capillaries → Pulmonary veins → Left atrium.

What is the pathway for lymphatic fluid return to the blood circulation?

Excess tissue fluid → Lymph capillaries → Larger lymphatic vessels → Thoracic duct/right lymphatic duct → Subclavian veins.

Where is the highest pressure found in the cardiovascular system?

In the arteries

What happens to blood pressure as blood moves through arterioles and capillaries?

Blood pressure drops to allow for exchange.

Where is the lowest pressure found in the cardiovascular system?

In the veins

Which vessel carries oxygenated blood from the lungs to the heart?

Pulmonary vein.

What is the role of pulmonary circulation?

To exchange gases in the alveoli and return oxygenated blood to the heart.

In which vessel is blood pressure highest?

Aorta.

How does blood flow from the left ventricle to the rest of the body?

Through the aorta.

Which vessels have the lowest blood pressure?

Veins.

What helps return deoxygenated blood from the body back to the right atrium?

Veins (deoxygenated)

What is preload in the context of heart function?

The initial stretching of the cardiac muscle fibers in the ventricle just before contraction.

What determines preload?

The volume of blood that fills the ventricle at the end of diastole (end-diastolic volume).

What is the physiological significance of afterload?

It refers to the pressure the heart must work against to eject blood.

What does an increase in preload result from?

Greater venous return

What factors influence preload?

Venous return and respiratory or positional changes affecting blood flow into the heart.

What is the function of the pericardium?

The pericardium is the sac that protects the heart.

What is the Frank-Starling mechanism?

The Frank-Starling mechanism states that increased preload enhances the strength of cardiac contraction.

What does the pressure-volume (P-V) loop represent?

The P-V loop shows how the pressure in the heart's ventricle changes as it fills with blood and contracts to pump blood out.

What is the effect of vagal (parasympathetic) nerves on heart rate?

Vagal nerves decrease heart rate.

What is the effect of sympathetic nerves on heart function?

Sympathetic nerves increase heart rate and contractile strength.

What is the role of potassium (K+) in cardiac function?

Excessive K+ can depress cardiac activity

What is the significance of calcium (Ca2+) in cardiac muscle contraction?

Calcium is critical for contraction; increases in extracellular calcium strengthen contractions.