Cardio and respiratory Flashcards
Which circulation pumps deoxygenated blood to the lungs?
Pulmonary circulation.
Which circulation distributes oxygenated blood to the body?
Systemic circulation.
What is the full pathway of blood flow through the heart?
Venae cavae → Right Atrium → Tricuspid Valve → Right Ventricle → Pulmonary Valve → Pulmonary Arteries → Lungs → Pulmonary Veins → Left Atrium → Mitral Valve → Left Ventricle → Aortic Valve → Aorta → Systemic circulation.
What is the primary pacemaker of the heart?
The sinoatrial (SA) node.
Name the components of the cardiac conduction system.
SA node, AV node, AV bundle (bundle of His), and Purkinje fibers.
What role does the AV node play in cardiac conduction?
It delays the electrical signal so the atria can contract before the ventricles.
Which nerve mediates parasympathetic control of the heart?
The vagus nerve (cranial nerve X).
What neurotransmitter does the parasympathetic system release to slow heart rate?
Acetylcholine.
How does the sympathetic nervous system affect heart rate and contraction?
It increases heart rate and force of contraction via norepinephrine.
What is the maximum possible heart rate under sympathetic stimulation?
Approximately 250 beats per minute.
— The Vascular System —
What is systolic blood pressure?
The highest arterial pressure during heart contraction (~110-120 mmHg).
What is diastolic blood pressure?
The lowest arterial pressure during heart relaxation (~70-80 mmHg).
How is mean arterial pressure (MAP) calculated?
MAP = (2/3 DBP) + (1/3 SBP).
Which mechanisms provide intrinsic control of blood flow?
Metabolic, endothelial, and myogenic mechanisms.
How do metabolic byproducts affect local blood flow?
They cause vasodilation to increase blood flow.
What endothelial factor promotes vasodilation?
Nitric oxide (NO).
What happens in myogenic control when local pressure increases?
Vessels constrict.
How does the sympathetic nervous system regulate blood flow extrinsically?
By increasing vasoconstriction at the organ level.
What is functional sympatholysis in muscle blood flow?
Local factors reduce sympathetic vasoconstriction during exercise, increasing blood flow to muscles.
What mechanisms assist in returning blood to the heart?
Venoconstriction, the skeletal muscle pump, and the respiratory pump.
What is the role of venous valves in blood return?
They prevent backflow of blood.
Is inspiration an active or passive process?
Active.
Which muscles are primarily responsible for inspiration?
The diaphragm and external intercostals.
What happens to lung volume and intrapulmonary pressure during inspiration?
Lung volume increases and intrapulmonary pressure decreases.
What does Boyle’s law state about pressure and volume during breathing?
Pressure and volume are inversely proportional.
Is expiration usually active or passive?
Usually passive.
What occurs during passive expiration?
Inspiratory muscles relax, lung volume decreases, and intrapulmonary pressure increases, forcing air out.
Which muscles are recruited during active (forced) expiration?
Internal intercostals, latissimus dorsi, quadratus lumborum, and abdominal muscles.
What is the standard atmospheric pressure?
760 mmHg.
What are the approximate percentages of N₂, O₂, and CO₂ in atmospheric air?
79.04% N₂, 20.93% O₂, and 0.03% CO₂.
How is the partial pressure of a gas calculated?
By multiplying the total pressure by the gas’s percentage in air.
What is the approximate partial pressure of O₂ in air?
About 159 mmHg.
What is the typical alveolar PO₂?
Approximately 105 mmHg.
What is the typical pulmonary artery PO₂?
About 40 mmHg.
What is the PO₂ gradient across the alveolar-capillary membrane?
Approximately 65 mmHg.
According to Fick’s law, what factors affect the rate of oxygen diffusion?
Surface area, partial pressure gradient, and tissue thickness.
How does the CO₂ gradient compare to the O₂ gradient in the alveoli?
The CO₂ gradient is much smaller (around 6 mmHg), but CO₂ diffuses easily.
What is the primary function of the respiratory (alveolar-capillary) membrane?
To facilitate gas exchange between alveoli and capillaries.
In oxygen transport, what does hemoglobin saturation refer to?
The percentage of hemoglobin binding sites occupied by oxygen.
What determines blood oxygen-carrying capacity?
The amount of hemoglobin available and its saturation level.
In CO₂ transport, what is the main form in which CO₂ is carried in blood?
As bicarbonate ion.
Name two other ways CO₂ is transported in the blood.
Dissolved in plasma and as carbaminohemoglobin.
What factors regulate pulmonary ventilation?
Neural control, chemical signals (such as CO₂ levels), and mechanical factors.
What is end systolic volume (ESV)?
The volume of blood remaining in a ventricle after contraction.
What is the normal range for resting heart rate (RHR)?
Between 60 and 100 beats per minute.
How does heart rate change during exercise?
It increases significantly to meet metabolic demands.
How does stroke volume change during exercise?
It increases due to enhanced contractility and improved venous return.
Why is stroke volume important for V̇O₂max?
A higher stroke volume increases cardiac output, which is crucial for maximal oxygen uptake.
What mechanisms contribute to an increased stroke volume during exercise?
Enhanced contractility, increased venous return, and reduced end-systolic volume.
How does blood pressure generally change during exercise?
Systolic pressure increases while diastolic pressure remains relatively stable or slightly decreases.
What happens to ventilation during acute exercise?
Ventilation increases to supply more oxygen and remove CO₂.
How does the respiratory system adjust to increased metabolic demands during exercise?
By increasing both the rate and depth of breathing.
What is the ventilatory equivalent for oxygen?
The ratio of ventilation to oxygen uptake.
What is the ventilatory threshold?
The point during exercise when ventilation increases disproportionately to oxygen uptake.
What is the function of heart valves?
They ensure unidirectional blood flow and prevent backflow.
How is stroke volume calculated?
Stroke volume = End-diastolic volume (EDV) minus End-systolic volume (ESV).
What is the main form of CO₂ transport in blood?
Bicarbonate ion.
How is CO₂ also transported in blood besides bicarbonate?
It is dissolved in plasma.
What is carbaminohemoglobin?
CO₂ bound to hemoglobin.
