Exam 3

What causes the pacemaker potential to gradually depolarize?

Slow Na⁺ influx (through funny channels) and decreased K⁺ permeability.

What ion causes rapid depolarization in pacemaker cells once threshold is reached?

Ca²⁺ influx through voltage-gated calcium channels.

What happens during repolarization in pacemaker cells?

Ca²⁺ channels close and K⁺ channels open, allowing K⁺ to exit.

How does the pacemaker cycle restart after repolarization?

K⁺ channels close, and Na⁺ begins to leak in again.

What is the function of the SA node?

It acts as the primary pacemaker, initiating the heartbeat.

What is the role of the AV node in the conduction system?

It delays the signal to allow the atria to contract before the ventricles.

What does the AV bundle (bundle of His) do?

It conducts the electrical impulse from the AV node to the ventricles.

What is the function of the bundle branches?

They carry the signal down the interventricular septum.

What do Purkinje fibers do?

They distribute the signal throughout the ventricular myocardium for coordinated contraction.

What happens during Phase 4 of a contractile cardiac cell action potential?

Resting potential is maintained by Na⁺/K⁺ ATPase pumps.

What occurs during Phase 0 of cardiac action potential?

Rapid depolarization due to Na⁺ influx through fast voltage-gated Na⁺ channels.

What occurs during Phase 1?

Brief initial repolarization caused by K⁺ efflux.

What is happening during Phase 2 (the plateau phase)?

Ca²⁺ influx and Cl⁻ influx balance K⁺ efflux, creating a plateau.

What completes repolarization during Phase 3?

Ca²⁺ and Cl⁻ channels close while K⁺ efflux continues.

What does the P wave on an ECG represent?

atrial depolarization

What does the QRS complex represent?

Ventricular depolarization and atrial repolarization.

What does the T wave show?

Ventricular repolarization.

What is measured by the PR interval on an ECG?

The time it takes for the impulse to travel from the SA node to the AV node.

What does the QT interval represent?

The total time for ventricular depolarization and repolarization.

What is the order of mechanical events in the cardiac cycle?

Atrial systole → Ventricular systole → Ventricular diastole.

How does blood move through the heart during the cardiac cycle?

It flows from areas of high pressure to low pressure; valves open and close to prevent backflow.

What causes the first heart sound (S1)?

The AV valves closing at the beginning of systole ("lub").

What causes the second heart sound (S2)?

The semilunar valves closing at the beginning of diastole ("dub").

How do pressure and volume change in the ventricles during systole and diastole?

During systole: pressure rises, volume falls.During diastole: pressure falls, volume rises.

What happens to aortic pressure during the cardiac cycle?

Systolic pressure peaks during ejection; diastolic pressure occurs during heart relaxation

What is the formula for cardiac output (CO)?

CO = Stroke Volume (SV) × Heart Rate (HR)

What are the three major branches of the aortic arch (above the heart)?

Brachiocephalic artery, left common carotid artery, and left subclavian artery.

What arteries branch from the external carotid artery?

Superior thyroid, lingual, facial, occipital, posterior auricular, maxillary, and superficial temporal arteries.

What arteries form the Circle of Willis?

Anterior cerebral, anterior communicating, internal carotid, posterior cerebral, and posterior communicating arteries.

What are the branches of the axillary artery?

Superior thoracic, thoracoacromial, lateral thoracic, subscapular, anterior circumflex humeral, and posterior circumflex humeral arteries.

What arteries supply the anterior thorax?

Internal thoracic arteries and their branches.

What arteries supply the posterior thorax?

Posterior intercostal arteries branching from the thoracic aorta.

What are the major branches of the abdominal aorta?

Celiac trunk, superior mesenteric, inferior mesenteric, renal, gonadal, and lumbar arteries.

What are the three branches of the celiac trunk?

Left gastric artery, common hepatic artery, and splenic artery.

What arteries supply the digestive organs?

Celiac trunk supplies the foregut.

Superior mesenteric supplies the midgut.

Inferior mesenteric supplies the hindgut.

What arteries supply the pelvis?

Internal iliac arteries and their branches.

What is the arterial pathway supplying the lower appendage?

External iliac → femoral → popliteal → anterior tibial and posterior tibial arteries.

What is the arterial pathway supplying the upper appendage?

Subclavian → axillary → brachial → radial and ulnar arteries.

What are the major veins above the heart?

Superior vena cava, brachiocephalic veins, subclavian veins, and internal jugular veins.

What veins drain into the internal jugular vein?

Facial, lingual, pharyngeal, superior thyroid, and middle thyroid veins.

What are the superficial veins of the upper appendage?

Cephalic and basilic veins.

What are the deep veins of the upper appendage?

Radial, ulnar, and brachial veins.

What veins drain into the axillary vein?

Brachial, basilic, and cephalic veins.

What veins drain the anterior thorax?

Internal thoracic veins and anterior intercostal veins.

What veins drain the posterior thorax?

Posterior intercostal veins, azygos vein, hemiazygos vein, and accessory hemiazygos vein.

What veins drain directly into the inferior vena cava?

Hepatic, renal, right gonadal, right suprarenal, and lumbar veins.

What veins drain the digestive organs?

Superior mesenteric, inferior mesenteric, and splenic veins, which all drain into the hepatic portal vein.

What vein receives blood from the digestive system before reaching the liver?

The hepatic portal vein.

What vein drains blood from the liver into the inferior vena cava?

The hepatic vein.

What vein drains pelvic organs?

The internal iliac vein and its tributaries.

What are some tributaries of the internal iliac vein?

Vesical, uterine, vaginal, and rectal veins.

What are the superficial veins of the lower appendage?

Great saphenous and small saphenous veins.

What are the deep veins of the lower appendage?

Q15: What are the deep veins of the lower appendage?A15: Anterior tibial, posterior tibial, popliteal, and femoral veins.