Vasoconstriction: Difference between revisions

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Vasoconstriction

File:Cardiovascular system - Vasoconstriction 1 -- Smart-Servier.png

Diagram illustrating vasoconstriction in the cardiovascular system.

Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries and small arterioles. This process is the opposite of vasodilation, which is the widening of blood vessels. Vasoconstriction is a crucial mechanism in the regulation of blood pressure and blood flow.

Mechanism

Vasoconstriction is primarily mediated by the sympathetic nervous system. When the body needs to increase blood pressure or reduce blood flow to certain areas, the sympathetic nervous system releases norepinephrine, which binds to adrenergic receptors on the smooth muscle cells of the blood vessels, causing them to contract. Other factors that can induce vasoconstriction include hormones such as angiotensin II, vasopressin, and endothelin.

Physiological Role

Vasoconstriction plays a vital role in maintaining homeostasis within the body. It helps regulate blood pressure by adjusting the diameter of blood vessels, thus controlling the resistance to blood flow. During cold exposure, vasoconstriction reduces blood flow to the skin to minimize heat loss. In situations of blood loss or dehydration, vasoconstriction helps maintain blood pressure by reducing the volume of the circulatory system.

Pathological Conditions

File:Cardiovascular system - Vasoconstriction 3 -- Smart-Servier.png

Illustration showing the effects of vasoconstriction on blood vessels.

Excessive or prolonged vasoconstriction can lead to hypertension (high blood pressure) and contribute to cardiovascular disease. Conditions such as Raynaud's phenomenon involve abnormal vasoconstriction, leading to reduced blood flow to extremities and causing symptoms like cold fingers and toes.

Pharmacological Agents

Several drugs can induce vasoconstriction, including decongestants like pseudoephedrine and phenylephrine, which are used to relieve nasal congestion by reducing blood flow to the nasal passages. Conversely, vasodilators are used to treat conditions like hypertension by relaxing blood vessels and reducing resistance to blood flow.

Related Pages

References

Guyton, A. C., & Hall, J. E. (2006). Textbook of Medical Physiology. Elsevier Saunders.
Hall, J. E. (2011). Guyton and Hall Textbook of Medical Physiology. Elsevier Health Sciences.

File:Microvessel.jpg

Microvessels, where vasoconstriction can occur.

@@ Line 1: / Line 1: @@
-'''Vasoconstriction''' is the narrowing of the [[blood vessels]] resulting from contraction of the muscular wall of the vessels, particularly the large [[arteries]], small [[arterioles]] and [[veins]]. The process is the opposite of [[vasodilation]], the widening of blood vessels. The process is particularly important in staunching [[hemorrhage]] and acute [[blood loss]].
+== Vasoconstriction ==
-==Mechanism==
+[[File:Cardiovascular_system_-_Vasoconstriction_1_--_Smart-Servier.png|thumb|Diagram illustrating vasoconstriction in the cardiovascular system.]]
-When blood vessels constrict, the flow of blood is restricted or decreased, thus retaining body heat or increasing vascular resistance. This makes the skin turn paler because less blood reaches the surface, reducing the radiation of heat. On a larger level, vasoconstriction is one mechanism by which the body regulates and maintains mean arterial pressure.
-Substances causing vasoconstriction are called [[vasoconstrictor]]s or vasoconstrictive substances. Many vasoconstrictors also cause [[pupil dilation]]. Medications that cause vasoconstriction include: [[antihistamines]], [[decongestants]], and [[stimulants]] used to treat [[ADHD]].
+'''Vasoconstriction''' is the narrowing of the [[blood vessels]] resulting from contraction of the muscular wall of the vessels, particularly the large [[arteries]] and small [[arterioles]]. This process is the opposite of [[vasodilation]], which is the widening of blood vessels. Vasoconstriction is a crucial mechanism in the regulation of [[blood pressure]] and [[blood flow]].
-==Clinical significance==
+== Mechanism ==
-Vasoconstriction can be a contributing factor to [[erectile dysfunction]]. The constriction of blood vessels can also cause full or partial blockage of blood flow to potentially critical organs such as the heart (causing [[myocardial infarction]]) or the brain (causing [[stroke]]).
-==See also==
+Vasoconstriction is primarily mediated by the [[sympathetic nervous system]]. When the body needs to increase blood pressure or reduce blood flow to certain areas, the sympathetic nervous system releases [[norepinephrine]], which binds to [[adrenergic receptors]] on the smooth muscle cells of the blood vessels, causing them to contract. Other factors that can induce vasoconstriction include [[hormones]] such as [[angiotensin II]], [[vasopressin]], and [[endothelin]].
-*[[Vasodilation]]
-*[[Myogenic mechanism]]
-==References==
+== Physiological Role ==
-<references />
+Vasoconstriction plays a vital role in maintaining [[homeostasis]] within the body. It helps regulate blood pressure by adjusting the diameter of blood vessels, thus controlling the resistance to blood flow. During [[cold]] exposure, vasoconstriction reduces blood flow to the skin to minimize heat loss. In situations of [[blood loss]] or [[dehydration]], vasoconstriction helps maintain blood pressure by reducing the volume of the circulatory system.
+== Pathological Conditions ==
+[[File:Cardiovascular_system_-_Vasoconstriction_3_--_Smart-Servier.png|thumb|Illustration showing the effects of vasoconstriction on blood vessels.]]
+Excessive or prolonged vasoconstriction can lead to [[hypertension]] (high blood pressure) and contribute to [[cardiovascular disease]]. Conditions such as [[Raynaud's phenomenon]] involve abnormal vasoconstriction, leading to reduced blood flow to extremities and causing symptoms like [[cold]] fingers and toes.
+== Pharmacological Agents ==
+Several drugs can induce vasoconstriction, including [[decongestants]] like [[pseudoephedrine]] and [[phenylephrine]], which are used to relieve nasal congestion by reducing blood flow to the nasal passages. Conversely, [[vasodilators]] are used to treat conditions like hypertension by relaxing blood vessels and reducing resistance to blood flow.
+== Related Pages ==
+* [[Vasodilation]]
+* [[Blood pressure]]
+* [[Sympathetic nervous system]]
+* [[Hypertension]]
+== References ==
+* Guyton, A. C., & Hall, J. E. (2006). ''Textbook of Medical Physiology''. Elsevier Saunders.
+* Hall, J. E. (2011). ''Guyton and Hall Textbook of Medical Physiology''. Elsevier Health Sciences.
+[[File:Microvessel.jpg|thumb|Microvessels, where vasoconstriction can occur.]]
+{{Cardiovascular physiology}}
-[[Category:Human physiology]]
 [[Category:Cardiovascular physiology]]
-[[Category:Medical terminology]]
-{{stub}}