Question

review questions

1. please illustrate regulation of heart output and state its mechanisms.
2. please illustrate the principle of blood pressure formation and its influencing factor.
3. state the factors which can influence venous return.
4. to illustrate the path of microcirculation and its main functions. how to regulate microcirculation?
5. to illustrate the formation of interstitial fluid and influencing factors.

Explanation:

Since there are multiple sub - questions related to the cardiovascular system and related physiological processes, we will use the Answer - Explanation Format (as these are questions about physiological principles in the field of Medicine and Health, which belongs to Natural Science) to answer one of them. Let's choose question 1:

Heart output (cardiac output, CO) is the volume of blood pumped by each ventricle per minute, calculated as \(CO = SV\times HR\) (stroke volume × heart rate).

• Intrinsic regulation (Frank - Starling mechanism): The heart has an inherent ability to adjust SV according to venous return. When venous return increases, the ventricular end - diastolic volume (EDV) increases. According to the Frank - Starling law of the heart, the myocardial contractility increases with the increase of EDV (within a certain range), so SV increases, and thus CO increases.
• Extrinsic regulation:
• Neural regulation: The sympathetic nervous system (SNS) can increase heart rate (HR) and myocardial contractility. Norepinephrine released by SNS acts on β - adrenergic receptors of the heart, increasing the pacemaker activity of the sinoatrial node (increasing HR) and enhancing the contractility of myocardial cells (increasing SV). The parasympathetic nervous system (mainly vagus nerve) can decrease HR by acting on muscarinic receptors of the sinoatrial node, thus decreasing CO.
• Humoral regulation: Epinephrine and norepinephrine (from the adrenal medulla) have similar effects as SNS on the heart, increasing HR and contractility. Thyroid hormones can increase the heart's sensitivity to catecholamines and also directly affect myocardial metabolism to increase HR and contractility in the long - term. Angiotensin II can increase peripheral resistance, and in turn, through the baroreceptor reflex, it can also affect the heart, but its main effect on the heart is to have a positive inotropic effect at higher concentrations.

Answer:

The regulation of heart output (cardiac output) and its mechanisms are as described above (including intrinsic regulation based on the Frank - Starling mechanism and extrinsic regulation involving neural and humoral factors).

If you want answers to other sub - questions, you can provide a specific request, and we will follow the same format to answer.