Physiology of Vascular Tone Regulation

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Questions and Answers

Which type of transport requires energy and operates against a concentration gradient?

Passive filtration

Facilitated diffusion

Active transport (correct)

Diffusion

What primarily determines the differences in intensity and selective permeability of capillaries in different vascular areas?

The presence of blood cells within the capillaries

The structural features of the capillaries and their functional states (correct)

The volume of blood flow through the capillaries

The thickness of the vascular wall only

Which process allows for the passage of substances through capillary membranes without requiring energy?

Phagocytosis

Endocytosis

Pinocytosis

Simple diffusion (correct)

What is the term for the transport of substances that occurs through specific protein channels in cell membranes?

Facilitated diffusion Signup and view all the answers

The process of fluid transition through the capillary membrane is known as what?

Filtration Signup and view all the answers

What are the two passive processes involved in the exchange function of capillaries?

Filtration and diffusion Signup and view all the answers

What can limit the permeability of cell membranes to water?

Absence of specific protein channels Signup and view all the answers

Which of the following substances is primarily transported through simple diffusion?

Oxygen Signup and view all the answers

What type of neurogenic regulation controls vasoconstriction through a-adrenergic receptors?

Sympathetic vasoconstrictors Signup and view all the answers

Which mediator is primarily responsible for the action of sympathetic vasodilators?

Adrenalin Signup and view all the answers

Which of the following is a factor that contributes to humoral regulation of vasodilation?

Carbon dioxide Signup and view all the answers

What primarily determines the permeability of capillary vessels and venules?

Endothelium and basal membrane Signup and view all the answers

Which substance is a known vasodilator produced by the endothelium?

Nitric oxide Signup and view all the answers

What are kinins considered in the context of vascular regulation?

Vasodilators Signup and view all the answers

Which of the following is NOT a mediator of sympathetic vasocontraction?

Histamine Signup and view all the answers

What is one of the local factors that can lead to vasodilation?

Carbon dioxide Signup and view all the answers

What primarily causes the increase in arterial hyperemia under pathological conditions?

Depressive influence of nitric oxide (NO) Signup and view all the answers

Which cells are mainly responsible for the large amounts of nitric oxide production during inflammation?

Monocytes and macrophages Signup and view all the answers

What effect does a shift toward acidosis have on vasodilation?

Enhances sensitivity of endotheliocytes to vasodilators Signup and view all the answers

How does increased hydrostatic pressure influence fluid movement in capillaries?

It causes increased fluid movement out of vessels into tissues. Signup and view all the answers

What role do pro-inflammatory factors have in the synthesis of inducible nitric oxide synthase (iNOS)?

They promote the expression of the iNOS gene. Signup and view all the answers

What happens to fluid accumulation in tissues during arterial hyperemia?

Fluid resorption occurs rapidly, preventing accumulation. Signup and view all the answers

What effect does arterial hyperemia have on the oxygenation of tissues?

It significantly improves the oxygenation of tissues. Signup and view all the answers

Which parameter is NOT affected by arterial hyperemia?

Cellular apoptosis rates Signup and view all the answers

What primarily leads to the development of angiospasm?

Activation of neurogenic and dopaminergic mechanisms Signup and view all the answers

Which of the following is considered the most potent vasoconstrictor among the factors mentioned?

Endothelin-1 Signup and view all the answers

What role do prostaglandins play in angiospasm?

They contribute to the process of vasoconstriction. Signup and view all the answers

Which cells produce the biogenic amines that contribute to angiospasm?

Adrenal glands and neuroendocrine cells Signup and view all the answers

What mechanism does endothelin-1 primarily utilize to cause smooth muscle contraction?

Receptor-mediated opening of calcium channels Signup and view all the answers

Which of the following conditions can enhance the synthesis of endothelin-1?

Endothelial damage with oxidized lipoproteins Signup and view all the answers

In which tissue are basophils, a source of histamine, primarily found?

Connective tissue Signup and view all the answers

What is a key characteristic of venous hyperemia?

Cyanosis and swelling in the affected area Signup and view all the answers

What can lead to increased secretion of thromboxane A2 in platelets?

Vascular wall damage Signup and view all the answers

What consequence occurs due to prolonged venous hyperemia?

Atrophy and death of vascular wall elements Signup and view all the answers

Which organ condition is exemplified by venous hyperemia?

Liver cirrhosis Signup and view all the answers

How does venous hyperemia affect fluid dynamics in tissues?

Fluid accumulates in tissues without resorption Signup and view all the answers

What is one of the local effects of oxygen deprivation (hypoxia) due to venous hyperemia?

Disruption of tissue metabolism Signup and view all the answers

What can increase hydrostatic pressure in the venous capillary section by 10 mm Hg?

Violation of venous outflow Signup and view all the answers

What is the definition of ischemia as mentioned in the content?

Violation of peripheral circulation due to reduced arterial blood delivery Signup and view all the answers

What may occur due to clogging of large venous collectors?

General hemodynamic disorders Signup and view all the answers

Study Notes

Mechanisms Regulating Tone of Resistive Vessels

Vasoconstrictors and Vasodilators regulate the tone of resistive vessels, impacting blood flow and pressure.
Neurogenic Regulation:
- Sympathetic Vasoconstrictors: Mediated by adrenalin and nor-adrenalin, acting on α- adrenoreceptors.
- Sympathetic Vasodilators: Mediated by adrenalin acting on β-adrenoreceptors; parasympathetic vasodilators use acetylcholine as a mediator.
Humoral Regulation Via BAS and Hormones:
- Vasoconstrictors: Catecholamines, angiotensin II, vasopressin, endothelin, certain leukotrienes.
- Vasodilators: Kinins, histamine, prostaglandins, leukotrienes.
Humoral Regulation by Vasoactive Products of Tissue Metabolism:
- Vasodilators: Carbon dioxide, local hypoxia, lactic acid, potassium and hydrogen ions, ATP hydrolysis products (especially adenosine), nitric oxide (NO).

Exchange Blood Vessels (Capillaries)

Responsible for exchange of water, electrolytes, gases, nutrients, and metabolites between blood and tissues.
Permeability determined by endothelium and basal membrane.
Transport Mechanisms:
- Active Transport: Requires energy, uses carriers or microvesicles, operates against concentration or electrochemical gradients.
- Passive Transport: Follows concentration or electrochemical gradients, no energy required. Primarily transports water, dissolved gases, and low-molecular substances.
  - Ultrafiltration: Fluid movement through capillary membrane.
  - Diffusion: Exchange of substances dissolved in water.
  - Simple Diffusion: Transport of fat-soluble substances through cell membranes.
  - Facilitated Diffusion: Transport of water and water-soluble substances through specific protein channels in cell membranes.

Arterial Hyperemia

Increased blood flow to an area, often due to inflammation or injury.
NO (Nitric Oxide): Plays a key role in vasodilatation, decreasing calcium sensitivity in smooth muscle cells.
iNOS (Inducible Nitric Oxide Synthase): Synthesized during inflammation, produces large amounts of NO, leading to prolonged arterial congestion and potential cytolysis.
pH Changes: Acidosis promotes vasodilation due to increased sensitivity to vasodilators in endothelial cells and NO in smooth muscle cells.
Filtration and Diffusion: Enhanced at arterial hyperemia due to increased hydrostatic pressure, leading to greater fluid movement from vessels into tissues.
Lymphatic System: Resorptive activity increases, facilitating tissue drainage.

Venous Hyperemia

Clinical Manifestations: Enlargement of affected area, cyanosis, coolness, swelling, increased pressure in veins and capillaries, slowed blood flow, erythrocyte diapedesis.
Prolonged Venous Hyperemia:
- Atrophy and death of vascular wall elements.
- Substitutional proliferation of connective tissue (e.g., cirrhosis in liver due to insufficient cardiac function).
Consequences:
- Decreased fluid filtration and tissue drainage due to increased hydrostatic pressure in venous capillaries.
- Fluid accumulates in tissues, leading to swelling.
- Hypoxia: Tissue oxygen deprivation due to impaired diffusion.
- Tissue metabolism disruption, degenerative changes, connective tissue overgrowth.
General Hemodynamic Disorders:
- Clogging of Large Venous Collectors: Portal vein or inferior vena cava obstruction, leading to blood accumulation, decreased blood pressure, and compromised vital organ blood supply.

Ischemia (Local Anemia)

Decreased or absent arterial blood delivery to a region.
Causes:
- Obstruction of Arteries: Atherosclerosis, thrombosis, embolism.
- Reduced Blood Flow: Vasospasm, hypovolemia, heart failure.
- Increased Tissue Demand: Exercise, cold exposure.

Angiospasm

Vasoconstriction of blood vessels, often contributing to ischemia.
Mechanisms:
- Neurogenic: Activation of sympathetic nervous system.
- Histaminenergic: Release of histamine.
- Serotoninergic: Release of serotonin.
- Dopaminergic: Release of dopamine.
- Prostaglandins: PGF2α and thromboxane A2, particularly released from platelets during adhesion and aggregation.
- Vasoactive Peptides: Vasopressin and angiotensin II.
- Endothelin-1: Released by vascular endothelium, a potent vasoconstrictor.
  - Synthesis Enhanced By: Angiotensin II, catecholamines, thrombin, hypoxia, growth factors, endothelial damage.
  - Mechanism: Opening of calcium channels, Ca2+ release into smooth muscle cells, contraction and proliferation, vascular wall thickening, and narrowing.

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Description

This quiz explores the mechanisms that regulate the tone of resistive blood vessels, focusing on both vasoconstrictors and vasodilators. It covers neurogenic regulation involving sympathetic and parasympathetic responses as well as humoral regulation through hormones and tissue metabolism products. Test your understanding of how these factors influence blood flow and pressure.