Cardiovascular Regulation Mechanisms

Cardiovascular System

• When venous return increases, cardiac muscle fibers stretch, and ventricles pump more forcefully (Starling's law)
• The kidneys play a crucial role in regulating blood pressure through the renin-angiotensin mechanism
• The cardiovascular center is located in the medulla and helps regulate heart rate, stroke volume, blood pressure, and blood flow to specific tissues

Nervous Mechanisms

• The autonomic nervous system, including sympathetic and parasympathetic nerves, regulates heart rate, cardiac output, and blood pressure
• Vasomotor nerves (sympathetic nerves) contract smooth muscle in arterioles, increasing vascular resistance and blood pressure
• Vasomotor nerves also contract smooth muscle in veins, moving blood towards the heart and increasing blood pressure

Arteries

• Arteries carry blood away from the heart and have three layers: external, middle, and inner
• The inner layer, the tunica intima, is in contact with blood and produces nitric oxide, a vasodilator

Arterioles and Veins

• Arterioles are smaller arteries that branch into capillaries
• Veins carry blood back to the heart and have the same three tissue layers as arteries
• The inner layer of veins has smooth endothelium and valves to prevent backflow

Capillaries

• Capillaries carry blood from arterioles to venules and have walls only one cell thick
• Precapillary sphincters regulate blood flow into capillary networks
• Capillaries are the sites of exchange of materials between blood and tissue fluid through diffusion and filtration

Circulatory Routes

• Two main circulatory routes: systemic and pulmonary
• Systemic circulation: oxygenated blood travels from the heart throughout the body, deoxygenating as it goes
• Pulmonary circulation: carries blood from the right side of the heart to the lungs to get oxygen and eliminate CO2
• Hepatic portal circulation: portal vein transports blood from GI organs to the liver

Fetal Circulation

• Specialized for exchange of materials with maternal blood and bypass of lungs
• Umbilical arteries and vein connect to the placenta

Blood Pressure

• Blood pressure is the force blood exerts against blood vessel walls
• Systolic pressure occurs when the left ventricle contracts, and diastolic pressure occurs when it relaxes
• Normal blood pressure range: 90-120 mmHg systolic, 60-80 mmHg diastolic
• Hypertension: consistently higher than normal blood pressure, and hypotension: consistently lower than normal

Maintenance of Systemic Blood Pressure

• Venous return: two mechanisms (skeletal muscle contractions and respiratory pump) help return blood to the heart
• Heart rate and force, peripheral resistance, and elasticity of large arteries all contribute to maintaining systemic blood pressure

Regulation of Blood Pressure

• Intrinsic mechanisms: heart, kidneys, and blood vessels regulate blood pressure internally
• Nervous mechanisms: autonomic nervous system and vasomotor nerves regulate blood pressure through nervous signals