cardiovascular system

Question 1

What are the functions of the CV system?

Answer 1

1. transport of O2 and nutrients to cells and taking CO2 and waste from cells
2. Regulating temp, pH, & fluid balance
3. protection against blood loss & infection

Question 2

How does blood circulate?

Answer 2

Inferior/Superior vena cava to right atrium to tricuspid valve to right ventricle to pulmonary semilunar valve to pulmonary artery to lungs to pulmonary veins to left atrium to mitral valve to left ventricle to aortic semilunar valve to aorta to arteries to capillaries to veins

Question 3

Conduction process

Answer 3

• Pacemaker cells in SA node have fastest spontaneous rate of depolarization
• Depolarization spreads by intermodal track through right atria and Brachmann’s Bundle through left atria
• Then goes to ventricles by the AV node to bundle of HIS, bundle branches, and to Purkinjie fibers

Question 4

Cellular rates of inherent depolarization

Answer 4

SA Node: 70-80 per min
AV Node: 40-60 per min
Purkinjie Fibers: 15-40 per min

Question 5

ECG Tracing

Answer 5

P Wave: atrial depolarization causing spontaneous contraction
QRS Complex: depolarization of ventricles & atrial repolarization
T Wave: repolarization of ventricles

Question 6

Diastole (relaxation phase)

Answer 6

Ventricular filling period
- both AV valves open so blood enters
- blood volumes in ventricles are greater at end of filling but pressure is lower due to their relaxation

Question 7

Systole (contraction phase)

Answer 7

Isovolumetric contraction Period: AV valves are closed so blood volume remains constant in ventricles but pressure increases
Ventricular ejection period: ventricular pressure is greater than aortic pressure so the semilunar valves open to eject blood

Question 8

Stroke volume and factors influencing it

Answer 8

Volume of blood ejected from ventricles per beat
influenced by:
1. preload
2. contractility
3. afterload

Question 9

What is cardiac output?

Answer 9

amount of blood pumper per min, represents total flow of entire CV system
Qc = SV x HR

Question 10

Aspects of coronary circulation

Answer 10

• myocardial blood flow at rest is 250 ml/min
• At rest 60-70% is extracted by myocardium
• supplied by 2 major coronary arteries:
  - L CA divides into L circumflex A & anterior descending A
  - R CA divides into marginal A & posterior interventricular A
• Venous blood goes to R atrium via coronary sinus

Question 11

Myocardial O2 consumption

Answer 11

Equal to coronary blood flow multiplied by a x vO2 difference
- estimated by: rate pressure product = (SBP x HR)/100
- Influenced by: Increased HR, contraction force, and metabolic products that cause vasodilation & decreased resistance to flow

Question 12

Arteries

Answer 12

Carry blood away from heart and to body
- distend during systole & recoil during diastole
MAP @ rest = PP/3+ DBP
MAP during exercise = PP/2 + DBP

Question 13

Arterioles

Answer 13

“resistance vessels”
- blood flow becomes continuous before capillaries
- smooth muscles allowing for vasodilation & vasoconstriction by sympathetic innervation and metabolic byproducts

Question 14

Capillaries

Answer 14

Exchange gases & nutrients between blood and tissue
- walls are smaller to only allow single file RBC passage
- ANASTOMOSES: wide, connecting channels acting as a shunt b/w arterioles & venues for thermoregulation
- METARTERIOLE: connects arterioles & venues through a capillary bed short cut

Question 15

Venules

Answer 15

Site of nutrient exchange

Question 16

Veins

Answer 16

“capacitance vessels”
- low resistance due to distensibility
- valves don’t allow backflow flow

Question 17

Important aspects of cardiovascular dynamics

Answer 17

1. Flow: destermined by MAP/TPR
2. Resistance: determined by (length x viscosity)/(radius)^4
3. Velocity: inversely related to total cross sectional area

Question 18

What are the central and systemic receptors that can affect control of the cardiovascular system?

Answer 18

Central: cerebral cortex, motor cortex, and temperature
Systemic: baroreceptors, stretch receptors, chemoreceptors, muscle joint receptors

Question 19

Baroreceptors

Answer 19

in carotid A and aortic arch
- respond to increase BP & decreased HR due to increased parasympathetic stimulation & decreased sympathetic stimulation

Question 20

stretch receptors

Answer 20

in right atrium
- respond to increased venous return to heart due to increase sympathetic stimulation & decreased parasympathetic stimulation

Question 21

Chemoreceptors

Answer 21

In aorta & carotid A
- respond to increased PCO2 and H+ ions to vasoconstrict arterioles

Question 22

Muscle Joint receptors

Answer 22

Mechanoreceptors: respond to mechanical movement
Metaboreceptors: respond to metabolic changes, increased HR; vasodilate active muscles & vasoconstrict non active muscles

Question 23

What is the Fick Equation?

Answer 23

Qc = VO2/ (axvO2 difference)
VO2 = Qc x (axvO2 difference)

Question 24

How to measure blood pressure

Answer 24

1. measured by “auscultation”
2. the cuff must inflate to occlude blood flow
3. 1st korotkoff sound corresponds to systolic BP
4. 5th/last korotkoff sound corresponds to diastolic BP