Cardiovascular System Quiz

Cardiovascular Physiology

• This study area details the function and structure of the cardiovascular system
• Objectives include: describing cardiac tissues, blood flow through the heart and body, the cardiac conduction system, physiological factors in cardiac output and blood pressure, blood components and their functions, and the clotting process
• Medical terminology relating to the cardiovascular system is critical, including roots, prefixes, and suffixes

Medical Terminology

• Angi/o: Vessel
• Vas/o: Vessel
• Ven/o: Vein
• Phleb/o: Vein
• Aort/o: Aorta
• Arteri/o: Artery
• Ather/o: Thick, fatty
• Atri/o: Atria
• Cardi/o: Heart
• Hem/o: Blood
• Hemat/o: Blood
• Valv/o: Valve
• Valvul/o: Valve
• Thromb/o: Clot
• Vascul/o: Blood vessel
• Ventricul/o: Ventricle
• Scler/o: Hardening

Medical Terminology - Prefixes

• Brady-: Slow
• Ecto-: Out, outside
• En- / Endo-: In, within, inner
• Macro-: Large
• Micro-: Small
• Oligo-: Deficiency, few
• Pre-: Before
• Pro-: Before, forward
• Re-/Retro-: Behind, back
• Tachy-: Rapid

Medical Terminology - Suffixes

• -ary: Pertaining to
• -cyte: Cell
• -dynia: Pain
• -edema: Edema
• -emesis: Vomiting
• -genesis: Creating, producing
• -gram: Record
• -lysis: Destruction
• -megaly: Enlargement
• -oid: Resembling
• -sclerosis: Abnormal hardening
• -stasis: Stopping, cessation

Cardiac Muscle

• Composed of cardiac muscle cells (myocytes)
• Generate their own action potentials and don't need nerve impulses to contract
• Intercalated discs connect cells end-to-end, forming junctions
• Folds in the myocyte membrane create a large surface area between cells, allowing rapid spread of electrical activity

Cardiac Muscle - Functions

• Acts as an endocrine tissue
• Releases atrial natriuretic peptide (ANP) in response to increased atrial pressure or blood volume.
• Decreases the reabsorption of sodium by the kidneys, increasing fluid excretion, relaxing blood vessels (vasodilation), and converting white adipocytes to brown/beige adipocytes to increase fat metabolism and become cardioprotective.

Structure of the Heart

• Located in the mediastinum between the lungs
• Base is superior, behind the sternum; apex is inferior, to the left of the midline
• Enclosed in pericardial membranes
• Fibrous pericardium (outermost layer) is a loose-fitting sac
• Serous pericardium (inner layer) forms a double-layered membrane: parietal (lines fibrous pericardium), and visceral (epicardium)
• Serous fluid reduces friction during heartbeats

Structure of the Heart - Chambers

• Atria (right and left): relatively thin walls, receive blood from the body or lungs
• Ventricles (right and left): thicker walls, pump blood to the lungs or body

Structure of the Heart- Specific Components

• Left atrium (LA): Receives oxygenated blood from lungs via pulmonary veins; produces ANP
• Left ventricle (LV): Pumps oxygenated blood to the body via the aorta
• Right atrium (RA): Receives deoxygenated blood from body via superior and inferior vena cava; produces ANP
• Right ventricle (RV): Pumps deoxygenated blood to the lungs via the pulmonary artery

Valves of the Heart

• Atrioventricular (AV) valves (tricuspid and mitral/bicuspid): Prevent backflow of blood from ventricles to atria during contraction
• Semilunar valves (pulmonary and aortic): Prevents backflow of blood from major arteries to ventricles during relaxation.

Structures & Function of the Heart

• Papillary muscles and chordae tendineae prevent inversion of AV valves during ventricular contraction
• Fibrous skeleton of the heart: anchors the heart valves and separates the myocardium of the atria from that of the ventricles

Coronary Circulation

• Coronary vessels circulate oxygenated blood to the myocardium
• Right and left coronary arteries branch from the aorta, immediately beyond the aortic valve
• Coronary capillaries merge to form coronary veins; coronary veins empty into a large coronary sinus that returns blood to the right atrium

Cardiac Cycle & Heart Sounds

• Cardiac cycle: sequence of events in one heartbeat (simultaneous contraction of atria followed by simultaneous contraction of ventricles)
• Systole: myocardial contraction, increasing pressure in the chamber to eject blood
• Diastole: myocardial relaxation, allowing filling of the chamber
  • Heart sounds (lub-dub)
  • S1 (lub): First sound; caused by closure of AV valves during ventricular contraction
  • S2 (dub): Second sound; caused by the closure of the aortic and pulmonary valves during ventricular relaxation.

Pathways of Circulation

• Pulmonary: Right ventricle pumps blood to the lungs (pulmonary artery, pulmonary capillaries, pulmonary veins) for gas exchange
• Systemic: Left ventricle pumps blood to the body (aorta, systemic arteries, capillaries, systemic veins, superior/inferior vena cava) for gas exchange

Cardiac Conduction System

• The conduction system regulates the cardiac cycle via electrical activity of the myocardium.
• Nerve impulses are not required. Cardiac muscle cells contract spontaneously. Cardiac myocytes generate their own electrical action potentials, and intercalated disks allow propagation of electrical activity quickly through adjacent muscle cells, allowing simultaneous atria contraction followed by simultaneous ventricle contraction.

Conduction Pathway - Specific Components

• Sinoatrial (SA) node: natural pacemaker, initiating the heartbeat
• Atrioventricular (AV) node: located in the interatrial septum; relays impulses from the SA node to the ventricles; causes atrial systole
• AV bundle/bundle of His: only pathway for impulses from the atria to ventricles and is located within the upper ventricular septum
• Bundle branches: receive impulses and travel to the Purkinje fibers to stimulate ventricle systole
• Purkinje fibers: are the terminal fibers of the pathway, transmitting impulses to the rest of the ventricular myocardium

Resting Heart Rate (HR)

• Normal resting HR in healthy adults: 60-80 bpm
• Parasympathetic impulses slow HR; sympathetic impulses increase HR
• Well-conditioned individuals may have resting HR as low as 35 bpm

Heart Rate

• SA node failure: AV node or AV bundle may initiate heartbeat at a slower, but still steady rate.
• Irregular heartbeats (arrhythmias/dysrhythmias) can range from harmless to life-threatening
• Some arrhythmias are common and can be caused by excessive caffeine, nicotine, or alcohol

Cardiac Physiology

• Cardiac output (CO): Volume of blood ejected by a ventricle per minute; CO = stroke volume (SV) x heart rate (HR)
• Stroke volume (SV): Volume of blood pumped out of a ventricle per contraction
• Ejection fraction: Percentage of blood within a ventricle that is pumped out per beat
• Preload: Force stretching cardiac muscle before contraction, related to venous return
• Afterload: Force required to eject blood from ventricles, determined by peripheral resistance

Cardiac Regulation - Physiology

• Starling's Law of the heart: More the cardiac muscle fibers are stretched, the more forcefully they contract
• Increased venous return stretches cardiac tissues resulting in increased stroke volume
• Cardiac reserve: difference between resting cardiac output and maximum cardiac output during exercise

Factors Affecting Cardiac Output

• Sympathetic nervous system, epinephrine, and hormones affect cardiac output
• Venous return, blood volume, and peripheral resistance affect blood pressure

Regulation of Heart Rate & Blood Pressure

• Cardiac control center is located in the medulla oblongata
• Sends signals via autonomic nervous system to alter heart rate and force of contraction
• Baroreceptors and chemoreceptors in the aorta and internal carotid arteries detect and respond to changes in blood pressure and oxygen levels
• These sensory inputs affect the cardiac control center to regulate heart rate and prevent harmful fluctuations

Vascular Physiology

• Blood vessel structure: arteries and arterioles, veins and venules, capillaries
  • Tunica intima (smooth inner lining), tunica media (muscle and elastic tissue), tunica adventitia (outer layer of connective tissue)
• Anastomoses are connections between vessels - providing alternative routes for blood to flow when a vessel is obstructed.
  • Arterial anastomoses: between arteries; venous anastomoses: between veins; these prevent complete blockage of blood flow to an organ

Capillaries

• Capillaries connect arterioles to venules
  • Capillary walls are only one cell thick, allowing rapid nutrient/gas exchange
  • Capillary sphincters (smooth muscles) regulate blood flow into capillary networks

Capillary Exchange

• Diffusion (movement of materials from higher to lower concentration)
  • Gases move passively across the capillary wall
  • Filtration (movement of fluid from higher to lower pressure)
  • Occurs at the arterial end of capillaries; hydrostatic pressure pushes fluid out
  • Osmosis (movement of water from lower to higher solute concentration)
  • Occurs at the venous end of capillaries; colloid osmotic pressure pulls fluid in

Velocity of Blood Flow

• Blood flow velocity is inversely related to cross-sectional area. Capillary beds present the largest cross-sectional area, creating the slowest velocity, allowing for efficient exchange of materials
• As the capillaries merge, the cross-sectional area decreases, and blood flow velocity increases

Components of Blood

• Viscous, slightly thicker than water
• ~ 4–6 liters in an adult
• Composed of formed elements (cells): ~48-62% and plasma (~38-52%).
• Arterial blood is bright red; venous blood is darker, dull red
• Normal pH range is 7.35–7.45; venous blood is slightly lower than arterial, due to higher CO2

Plasma Proteins

• Albumin: most abundant; contributes to plasma colloid osmotic pressure (by pulling fluid into capillaries)
• Globulins: act as carriers, and there are antibodies produced by lymphocytes
• Fibrinogen: aids in blood clotting

Blood Cells

• Erythrocytes (red blood cells): contain hemoglobin to carry oxygen, and are produced in red bone marrow; live for ~120 days
• Leukocytes (white blood cells): part of the immune system, and are produced in red bone marrow
• Thrombocytes (platelets): cell fragments for hemostasis; produced in red bone marrow

Blood Pressure

• Force exerted by blood against vessel walls
• Systolic pressure: pressure generated by ventricular contraction
• Diastolic pressure: sustained pressure when left ventricle relaxes
• Blood pressure is altered by cardiac output, blood volume, and peripheral resistance, which are influenced by multiple factors, as outlined in the slides

Regulation of Blood Pressure

• Hormones (ex. norepinephrine, epinephrine, antidiuretic hormone (ADH), aldosterone, renin-angiotensin-aldosterone system) raise or lower BP

Renin-Angiotensin Mechanism

• Renin-angiotensin mechanism is a compensatory system that regulates blood pressure when blood pressure drops too low
  • Renin secreted by kidneys, leading to the conversion of angiotensin I to angiotensin II, resulting in vasoconstriction and stimulation of aldosterone release by adrenal cortex to reduce Na+/H2O excretion, increasing blood volume and blood pressure

Summary of Hormones in Regulation of Blood Pressure

• Hormones affect blood pressure by acting on the heart, blood vessels, and kidneys, altering blood volume and flow Note: I have combined content where appropriate to create a more concise, coherent treatment of the material.

Test your knowledge of the heart and circulatory system with these questions. Topics include ventricle pressures, heart sounds, blood flow, and cardiac muscle function.