ventricular systole About 0.3s

ventricular diastole About 0.5s

The primary pumping function of the atrium. The atrium is in a state of relaxation during most of the cardiac cycle. Its main function is to receive and store blood that continuously returns from the veins.

Stroke volume and ejection fraction Ejection fraction is more reflective of ❤ function

Minute output and cardiac index

stroke volume reserve

Heart rate reserve: When the heart rate reaches 160∽180 beats/minute, the cardiac output can be increased to 2∽2.5 times the resting level. However, when the heart rate is >180 beats/min, the diastolic period is too short and the ventricular filling is insufficient, resulting in reduced stroke volume and cardiac output.

Preload is equivalent to the end-diastolic volume of the ventricle, which increases the volume of venous blood return to the heart within a certain range and increases ventricular contractility.

Afterload: Normal aortic pressure is in the range of 80∽170mmHg, and cardiac output generally does not change significantly.

myocardial contractility

atrial myocytes

ventricular myocytes

sinoatrial node cells

Purkinje cells

Vasoconstrictor substances endothelin, thromboxane A2

Vasodilator substances mainly include nitric oxide, hydrogen sulfide, prostacyclin, etc.

Formation conditions "121"

Influencing factors

Central venous pressure refers to the blood pressure in the right atrium and large veins in the chest, about 4∽12mmH2O Its level depends on the heart's ability to eject blood and the amount of blood returned to the heart.

Peripheral venous pressure refers to the venous blood pressure of various organs

venous resistance to blood flow

Factors affecting the amount of venous blood returned to the heart The power of venous return = peripheral venous pressure – central venous pressure

Roundabout pathway: micro-A→posterior micro-A→precapillary sphincter→true capillary network→venule It is the main place for material exchange between blood and tissue fluid, also known as nutritional pathway.

Direct pathway: arterioles→posterior arterioles→blood capillaries→venules Allow part of the blood to quickly enter the veins through this passage to ensure the amount of blood returned to the heart by the veins More common in skeletal muscles

Arteriovenous short circuit: micro A→arteriovenous anastomotic branch→venule Participate in body temperature regulation Commonly seen on the skin and subcutaneous

capillary effective hydrostatic pressure

effective colloid osmotic pressure

capillary wall permeability

lymphatic drainage

innervation of heart

innervation of blood vessels

Carotid sinus and aortic arch baroreceptive reflex: When arterial blood pressure suddenly rises, it can reflexively cause heart rate ↓, ❤ output ↓, vasodilation, peripheral resistance ↓, and blood pressure ↓. This reflex becomes the baroreceptive reflex or antihypertensive reflex . Physiological significance: Rapidly regulate arterial blood pressure in a short period of time and maintain relatively stable arterial blood pressure.

Carotid and aortic body chemoreceptive reflexes

process When sympathetic N↑, renal blood flow ↓ or plasma Na ↓ ▼ Renin secretion↑ ▼ Hydrolyze angiotensinogen to angiotensin I ▼Angiotensin (ACE) continues to be hydrolyzed Angiotensin II (Ang II) ➭ can constrict blood vessels and increase blood pressure ↑ ▼ Continue hydrolysis to Ang III ▼ Aldosterone secretion↑➭water and sodium retention, blood pressure↑

Physiological functions of the main members of the angiotensin family

Adrenaline (E) Strong ability to bind to both a and B (B1 and B2) receptors Can increase cardiac output without increasing or decreasing peripheral resistance

Norepinephrine (NE) Mainly binds to smooth muscle a receptors (weak binding to B2 receptors), and can also bind to ❤ muscle B1 receptors

vasodilator

vasoconstrictor substances