blood heart circulation study guide

Functions of the Cardiovascular System

Transport oxygen, nutrients, and hormones. Remove waste products (like CO₂ and urea). Regulate body temperature, pH, and fluid balance. Protect against blood loss (clotting) and infection (immune cells

ABO Blood Type and Rh Factor

ABO = Type A, B, AB, or O based on antigens on red blood cells. Rh factor = + (positive) means you have the Rh antigen; − (negative) means you don't

Type O-

Universal donor (no antigens).

Type AB+

Universal recipient (has all antigens).

blood flow through body

Right atrium → Right ventricle → Lungs → Left atrium → Left ventricle → Body

pulmonary circulation

heart to lungs (oxygenate blood)

systemic circulation

heart to body (deliver oxygen).

Fibrous Skeleton Function

Offers structural support, insulates electrical signals between the atria and ventricles, and anchors heart valves.

Structure of Cardiac Muscle Cells

Branched and striated like skeletal muscle, featuring intercalated discs for communication through gap junctions, and containing a single central nucleus.

Autorhythmic Cells

Specialized cells responsible for generating action potentials without requiring innervation for depolarization, as they possess the ability to self-depolarize. They are located in key areas such as the SA node, AV node, Bundle of His, and Purkinje fibers, with the SA node acting as the fastest natural pacemaker

Cardiac Muscle Action Potential

Involves an influx of Na+, followed by a plateau phase due to Ca²+ influx, and concludes with K+ efflux. Calcium plays a crucial role in triggering contraction by binding to troponin, and the long refractory period prevents tetany, which is a state of constant contraction.

Electrical Pathway Through the Heart

The sSA node to the AV node, followed by the Bundle of His, Bundle branches, and finally the Purkinje fibers. The AV node introduces a delay to allow the ventricles to fill with blood.

ECG Segments

P wave corresponds to atrial depolarization; QRS complex indicates ventricular depolarization; T wave represents ventricular repolarization.

Wigger's Diagram

A diagram that illustrates the relationship between the ECG, heart sounds, pressure changes in the heart chambers, and the movements of the valves

Phases of the Cardiac Cycle

1. Ventricular filling - AV valves are open; 2. Isovolumetric contraction - all valves are closed; 3. Ventricular ejection - semilunar (SL) valves are open; 4. Isovolumetric relaxation - all valves are closed.

Heart Sounds

S1 ('lub') occurs when the AV valves close, and S2 ('dub') happens when the semilunar valves close.

Tunica intima

the innermost layer, smooth in texture

Tunica media

the middle layer, containing muscle tissue and regulated by the autonomic nervous system, particularly sympathetic control

Tunica externa

the outermost layer

arteries

thick and elastic

veins

thinner walls with valves

capillaries

only one cell thick

continuous capillaries

found in muscles and skin

fenestrated capillaries

present in kidneys and intestines

sinusoidal capillaries

located in liver and bone marrow

Why Veins Have Valves

Valves in veins prevent backflow, ensuring unidirectional blood flow toward the heart.

Factors Supporting Venous Return

1. Skeletal muscle pump - muscle contractions help push blood through veins; 2. Respiratory pump - pressure changes during breathing assist blood flow; 3. Sympathetic vasoconstriction - constriction of veins due to sympathetic nervous system activity enhances blood return.

Atrial Fibrillation (AFib)

P waves are not clearly visible, and the rhythm is irregular.

Ventricular Fibrillation (VFib)

chaotic electrical activity, with no distinct QRS complexes.

Heart Block

a prolonged PR interval, showing a delay in electrical signal transmission.

Functions of the Lymphatic System

1. Returns interstitial fluid to the bloodstream; 2. Absorbs fats from the intestines; 3. Aids in immune defense.