Cardiovascular System: Blood Cells, Heart, and Vascular Anatomy
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95 Terms
Which WBC increases during bacterial infections?
Neutrophils
Which WBC increases during viral infections?
Lymphocytes
Which WBC increases during chronic inflammation or chronic infection?
Monocytes
Which WBC increases during parasitic infections and chronic allergic reactions?
Eosinophils
Which WBC is associated with histamine release and early allergic reactions?
Basophils
Why is the heart considered unique?
It generates its own electrical impulses and functions as an electrical pump.
What ion causes depolarization in skeletal muscle?
Sodium (Na⁺)
What ion causes repolarization in skeletal muscle?
Potassium (K⁺)
What are the stages of a skeletal muscle action potential?
Depolarization → Repolarization → Hyperpolarization
What occurs during depolarization in cardiac muscle?
Na⁺ channels open.
What occurs during early repolarization?
Some K⁺ channels open.
What occurs during the plateau phase?
Ca²⁺ channels open.
What occurs during repolarization?
K⁺ channels open.
What ion makes cardiac muscle action potentials different from skeletal muscle action potentials?
Calcium (Ca²⁺)
Why is the plateau phase important?
It allows sustained contraction of cardiac muscle.
What is the correct flow of blood through the heart?
Venae cavae → Right atrium → Tricuspid valve → Right ventricle → Pulmonary semilunar valve → Pulmonary trunk/arteries → Lungs → Pulmonary veins → Left atrium → Mitral (bicuspid) valve → Left ventricle → Aortic semilunar valve → Aorta → Body → Venae cavae
What is the normal electrical conduction pathway of the heart?
SA node → AV node → Bundle branches → Purkinje fibers
Which structure is the heart's natural pacemaker?
SA node
What is sinus rhythm?
A normal heartbeat initiated by the SA node.
Why are electrolytes important for heart function?
They control electrical activity, contraction, pumping, and perfusion.
What happens when electrolytes become abnormal?
Electrical activity becomes abnormal, causing abnormal contraction, pumping, and perfusion.
What is sodium's main role in cardiac cells?
Depolarization.
What happens when sodium enters a cell?
The inside becomes more positive and the cell fires.
What happens if sodium is insufficient?
Electrical signaling slows.
What phrase should you remember for sodium?
Sodium starts the signal.
What is potassium's main role?
Repolarization/resetting the cell.
What happens when potassium leaves a cell?
Repolarization occurs.
Why is potassium called the reset button?
It prepares the cell for the next heartbeat.
What phrase should you remember for potassium?
Potassium resets the signal.
What is calcium's main role?
Contraction.
What is the sequence involving calcium and contraction?
Electrical signal → Calcium enters → Muscle contracts.
What phrase should you remember for calcium?
Calcium creates the squeeze.
What does Na⁺ do?
Starts depolarization.
What does K⁺ do?
Repolarization/reset.
What does Ca²⁺ do?
Contraction.
What is the consequence of abnormal electrolytes?
Abnormal electrical activity → abnormal pumping.
What is hyperkalemia?
Too much potassium.
How does hyperkalemia affect cardiac cells?
Cells become harder to reset properly.
What does hyperkalemia cause?
Abnormal conduction and arrhythmias.
What life-threatening conditions can hyperkalemia lead to?
Ventricular fibrillation or asystole.
Can hyperkalemia stop the heart?
Yes.
What is hypokalemia?
Too little potassium.
What happens to repolarization during hypokalemia?
It becomes difficult.
What develops with hypokalemia?
Electrical instability and arrhythmias.
Can hypokalemia be fatal?
Yes.
Why must patients taking Lasix often receive potassium supplements?
Lasix causes potassium loss in urine.
Why are potassium levels monitored closely?
Abnormal potassium levels can cause lethal arrhythmias.
Why do calcium channel blockers affect the heart?
They reduce calcium entry into cardiac muscle.
What happens when less calcium enters cardiac muscle?
Weaker contraction.
What is the result of weaker contractions?
Reduced cardiac workload and lower blood pressure.
List the vessel types from largest artery to largest vein.
Elastic artery → Muscular artery → Arteriole → Capillary → Venule → Medium vein → Large vein
What is the primary function of capillaries?
Exchange.
What moves across capillary walls?
Materials between blood and interstitial fluid.
What structures make up a capillary wall?
Endothelium and basement membrane.
Do capillaries have tunica media?
No.
Do capillaries have tunica externa?
No.
How large is a capillary's diameter?
Similar to a red blood cell.
What characterizes continuous capillaries?
Complete endothelial lining with tight junctions.
What can pass through continuous capillaries?
Water and small solutes.
What is blocked by continuous capillaries?
Blood cells and plasma proteins.
What cells contain contractile proteins in continuous capillaries?
Pericytes.
What special feature do fenestrated capillaries possess?
Filtration pores (fenestrations).
What is the function if Fenestrated Capillaries?
Rapid exchange of water.
Where are fenestrated capillaries found?
Kidneys, endocrine organs, intestinal tract, choroid plexus.
What makes sinusoids unique?
Large gaps between endothelial cells.
Where are sinusoids found?
Liver, spleen, bone marrow.
What can pass through sinusoids?
Water, albumin, clotting factors, and blood cells.
Which capillary type is most permeable?
Sinusoids.
What does a capillary bed connect?
One arteriole and one venule.
What controls blood entry into capillaries?
Precapillary sphincters.
What do precapillary sphincters do?
Open and close, causing blood flow in pulses.
Why are veins called capacitance vessels?
They can hold large volumes of blood.
What happens to veins when empty?
They collapse.
How does blood flow in veins compare to arteries?
Veins have steady flow; arteries have pulsatile flow.
What is the average venous pressure?
About 10 mm Hg.
What is the most common route of blood flow?
Heart → Arteries → Arterioles → Capillaries → Venules → Veins
Why do alternate circulatory routes exist?
To provide backup pathways for blood flow.
What are the benefits of alternate routes?
Maintain perfusion, protect tissues, meet metabolic demands, reduce effects of blockages.
Why is relying on a single blood pathway dangerous?
Blood flow is too important to depend on only one route.
What is blood pressure?
The force blood exerts against vessel walls.
Where is blood pressure commonly measured?
Brachial artery.
What device measures blood pressure?
Sphygmomanometer.
What is systolic pressure?
Peak arterial pressure during ventricular contraction.
What is diastolic pressure?
Minimum arterial pressure during ventricular relaxation.
What is a normal blood pressure for a young adult?
120/80 mm Hg.
What do the numbers 120/80 represent?
Systolic pressure/Diastolic pressure.
What is pulse pressure?
Systolic pressure − Diastolic pressure.
Calculate pulse pressure for 120/80 mm Hg.
40 mm Hg.
Which ion starts the signal?
Sodium.
Which ion resets the signal?
Potassium.
Which ion creates contraction?
Calcium.
Which capillary type is least permeable?
Continuous capillaries.
What is the normal cardiac conduction pathway?
SA → AV → Bundle branches → Purkinje.
What is the normal blood pressure value to memorize?
120/80 mm Hg.
What is the average venous pressure to memorize?
10 mm Hg.