Vasoconstriction

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Vasoconstriction

Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, arterioles and veins. The process is the opposite of vasodilation

Vasodilation

Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins....
, the widening of blood vessels. When blood vessels constrict, the flow of blood is restricted or decreased, thus, retaining body heat or increasing vascular resistance

Vascular resistance

Vascular resistance is a term used to define the resistance to flow that must be overcome to push blood through the circulatory system. The resistance offered by the peripheral circulation is known as the systemic vascular resistance , while the resistance offered by the vasculature of the lungs is known as the pulmonary vascular re...
. Cutaneously

Skin

The skin is the outer covering of the body, also known as the epidermis. It is the largest organ of the integumentary system made up of multiple layers of epithelial biological tissue, and guards the underlying muscles, bones, ligaments and organ s....
, this makes the skin turn paler because less blood reaches the surface, preventing the radiation of heat.

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Vasodilation

Vascular resistance

Skin

Mean arterial pressure

The mean arterial pressure is a term used in medicine to describe a notional average blood pressure in an individual. It is defined as the average arterial pressure during a single cardiac cycle....
.

Substances causing vasoconstriction are called vasoconstrictors or vasopressors. Generalized vasoconstriction usually results in an increase in systemic blood pressure, but it may also occur in specific tissues causing a localized reduction in blood flow. The extent of vasoconstriction may be slight or severe depending on the substance or circumstance. Many vasoconstrictors also cause pupil dilation

Pupillary response

Pupillary response or dilation of the pupil is a physiological response that varies the size of the pupil of the eye via the iris dilator muscle....
. Medications that cause vasoconstriction include antihistamines, decongestants and stimulants used to treat ADHD.

General mechanism

The mechanism that leads to vasoconstriction results from the increased concentration of calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft grey alkaline earth metal, and is the fifth most abundant element by mass in the earth's Crust ....
(Ca²⁺ ions) within vascular smooth muscle cells. However, the specific mechanisms for generating an increased intracellular concentration of calcium depends on the vasoconstrictor. Smooth muscle cells are capable of generating action potentials, but this mechanism is rarely utilized for contraction in the vasculature. Hormonal or pharmokinetic components are more physiologically relevant. Two common stimuli for eliciting smooth muscle contraction is circulating epinephrine

Epinephrine

Epinephrine is a hormone and neurotransmitter.Epinephrine increases the "fight or flight" response of the Sympathetic nervous system of the autonomic nervous system....
and activation of the sympathetic nervous system

Sympathetic nervous system

The Sympathetic Nervous System is a branch of the autonomic nervous system along with the enteric nervous system and parasympathetic nervous system....
(through release of norepinephrine

Norepinephrine

Norepinephrine or noradrenaline is a catecholamine with dual roles as a hormone and a neurotransmitter.As a stress hormone, norepinephrine affects parts of the brain where attention and responding actions are controlled....
) that directly innervates the muscle. These compounds interact with cell surface adrenergic receptors. Such stimuli result in a signal transduction

Signal transduction

In biology, 'signal transduction' refers to any process by which a cell converts one kind of signal or stimulus into another. Most processes of signal transduction involve ordered sequences of biochemistry chemical reaction inside the cell, which are carried out by enzymes, activated by Second messenger systems, resulting in a signal tran...
cascade that leads to increased intracellular calcium from the sarcoplasmic reticulum through IP3

Inositol triphosphate

Inositol trisphosphate or inositol 1,4,5-trisphosphate , together with diglyceride, is a secondary messenger molecule used in signal transduction in cell s....
mediated calcium release, as well as enhanced calcium entry across the sarcolemma

Sarcolemma

The sarcolemma is the cell membrane of a muscle cell. It consists of a true cell membrane, called the plasma membrane, and an outer coat made up of a thin layer of polysaccharide material that contains numerous thin collagen fibrils....
through calcium channels. The rise in intracellular calcium complexes with calmodulin

Calmodulin

Calmodulin is a calcium-binding protein expressed in all eukaryotic cells. It can bind to and regulate a number of different protein targets, thereby affecting many different cellular functions....
, which in turn activates myosin light chain kinase. This enzyme is responsible for phosphorylating

Phosphorylation

Phosphorylation is the addition of a phosphate group to a protein or other organic molecule. Protein phosphorylation in particular plays a significant role in a wide range of cellular processes....
the light chain of myosin

Myosin

Myosins are a large family of motor proteins found in eukaryotic Biological tissue. They are responsible for actin-based motility.Following the discovery, by Pollard and Korn, of enzymes with myosin-like function in Acanthamoeba, a large number of divergent myosin genes have been discovered throughout eukaryotes....
to stimulate cross bridge cycling.

Once elevated, the intracellular calcium concentration is returned to its basal level through a variety of protein pumps and calcium exchangers located on the plasma membrane and sarcoplasmic reticulum. This reduction in calcium removes the stimulus necessary for contraction allowing for a return to baseline.

Factors and individual mechanisms

Factors that trigger vasoconstriction can be of exogenous or endogenous original. Ambient temperature is an example of the former. Cutaneous vasoconstriction will occur because of the body's exposure to the severe cold. Examples of endongeous factors include the autonomic nervous system

Autonomic nervous system

The autonomic nervous system is the part of the peripheral nervous system that acts as a control system, maintaining human homeostasis in the body....
, circulating hormones and intrinsic mechanisms inherent to the vasculature itself (also referred to as the myogenic

Myogenic

Myogenic contraction refers to a myocyte contraction that originates from a property of the myocyte itself. I.e. the contraction is initiated by the cell itself, not an outside occurrence or stimulus such as nerve innervation....
response).

Exogenous medications

Examples include amphetamine

Amphetamine

Amphetamine and related drugs such as methamphetamine are a group of drugs that act by increasing levels of norepinephrine, serotonin, and dopamine in the brain....
s, antihistamine

Antihistamine

An H1 antagonist is a histamine antagonist of the histamine H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergy....
s and cocaine

Cocaine

Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine....
. Many are used in medicine to treat hypotension

Hypotension

In physiology and medicine, hypotension refers to an abnormally low blood pressure. This is best understood as a physiologic state, rather than a disease....
and as topical decongestant

Topical decongestant

Topical decongestants are decongestants applied directly to the nasal cavity. By applying them directly to the site of action, topical decongestants relieve nasal congestion while reducing the side effects associated with systemically-acting decongestants, such as high blood pressure....
s. Vasoconstrictors are also used clinically to increase blood pressure

Blood pressure

Blood pressure is the pressure exerted by circulating blood on the walls of blood vessels, and constitutes one of the principal vital signs. The pressure of the circulating blood decreases as it moves away from the heart through artery and capillary, and toward the heart through veins....
or to reduce local blood flow.

The routes of administration varies. They may be both systemic and topical. For example, pseudoephedrine

Pseudoephedrine

Pseudoephedrine is a sympathomimetic amine amine commonly used as a decongestant. The salts pseudoephedrine hydrochloride and pseudoephedrine sulfate are found in many Over-the-counter drug preparations either as single-ingredient preparations, or more commonly in combination with antihistamines, paracetamol and/or ibuprofen....
is available systemic (i.e. orally ingested tablets like Sudafed

Sudafed

Sudafed is a brand name and registered trademark for a family of over-the-counter substance decongestants manufactured by Johnson & Johnson for sale in the United States, the United Kingdom, Australia and Canada....
), and topical (such as nose sprays like phenylephrine Neo-synephrine, and eye drops for pupil dilation purposes)

Examples include:

Vasoconstrictor	Receptor (↑ = opens. ↓ = closes)	Transduction (↑ = increases. ↓ = decreases)
Amphetamine Amphetamine Amphetamine and related drugs such as methamphetamine are a group of drugs that act by increasing levels of norepinephrine, serotonin, and dopamine in the brain.... s
antihistamines
Cocaine Cocaine Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine....
LSD LSD Lysergic acid diethylamide, LSD, LSD-25, or acid, is a semisynthetic psychedelic drug of the ergoline family. Its unusual psychological effects, which include visuals of colored patterns behind the eyes in the mind, a sense of time distorting, and crawling geometric patterns, have made it one of the most widely known psyched...
LSA Ergine LSA, also known as d-lysergic acid amide, d-lysergamide, ergine, and LA-111, is an alkaloid of the ergoline family that occurs in various species of vines of the Convolvulaceae and some species of fungi....
Methylphenidate Methylphenidate Methylphenidate is the most commonly medical prescription psychostimulant and is indicated in the treatment of attention-deficit hyperactivity disorder and narcolepsy, although off-label uses include treating lethargy, depression, neural insult and obesity....
Oxymetazoline Oxymetazoline Oxymetazoline is a selective alpha-1 agonist and partial alpha-2 agonist topical decongestant, used in the form of Oxymetazoline hydrochloride, in products such as Afrin , Dristan, Nasivin, Vicks Sinex, Visine L.R., Sudafed OM, and Zicam....
Phenylephrine Phenylephrine Phenylephrine or Neo-Synephrine is an Alpha-1_adrenergic_receptor agonist used primarily as a decongestant, as an agent to dilate the pupil and to increase blood pressure....
Pseudoephedrine Pseudoephedrine Pseudoephedrine is a sympathomimetic amine amine commonly used as a decongestant. The salts pseudoephedrine hydrochloride and pseudoephedrine sulfate are found in many Over-the-counter drug preparations either as single-ingredient preparations, or more commonly in combination with antihistamines, paracetamol and/or ibuprofen....
Stimulant Stimulant Stimulant drugs are drugs that temporarily increase alertness and awareness. They usually have increased side-effects with increased effectiveness, and the more powerful variants are therefore often prescription medicines or illegal drugs.... s
Tetrahydrozoline hydrochloride Tetrahydrozoline Tetrahydrozoline is a derivative of imidazoline, which is found in over-the-counter eye drops and nasal sprays. Other derivatives include naphazoline, oxymetazoline, and xylometazoline.... (in eye drops)
Psilocybin Psilocybin Psilocybin is a psychedelic drug indole of the tryptamine family, found in psilocybin mushrooms. It is present in List of Psilocybin mushrooms of fungi, including those of the genus Psilocybe, such as Psilocybe cubensis and liberty cap , but also reportedly isolated from a dozen or so other genera....

Endogenous

Vasoconstriction is a procedure of the body that avoids orthostatic hypotension

Orthostatic hypotension

Orthostatic hypotension is a form of hypotension in which there is a sudden fall in blood pressure, typically greater than 20/10 mm Hg, that occurs when a person assumes a standing , usually after a prolonged period of rest....
. It is a part of a body negative feed back loop in which the body tries to restore homeostasis.

For example, vasoconstriction is a hypothermic preventative in which the blood vessels constrict and blood must move at a higher pressure to actively avoid a hypoxic reaction. ATP

Adenosine triphosphate

This article is about the chemical used by cells as an energy carrier. For other uses, see ATP .Adenosine-5'-triphosphate is a multifunctional nucleotide, and plays an important role in cell biology as a coenzyme that is the "molecule unit of currency" of intracellular energy transfer....
is used as a form of energy to increase this pressure to heat the body. Once homeostasis is restored the blood pressure and ATP production regulates.

Vasoconstriction also occurs in superficial blood vessels of warm-blooded

Warm-blooded

In biology, a warm-blooded animal species is one whose members maintain thermal homeostasis; that is, they keep their body temperature at a roughly constant level, regardless of the ambient temperature....
animals when their ambient environment is cold; this process diverts the flow of heated blood to the center of the animal, preventing the loss of heat.

>

Vasoconstrictor	Receptor (↑ = opens. ↓ = closes)	Transduction (↑ = increases. ↓ = decreases)
Stretch	↑Stretch-activated ion channel Stretch-activated ion channel Stretch-activated or stretch-gated ion channels are ion channels which open their pores in response to mechanical deformation of a neuron's plasma membrane.... s	depolarization Depolarization In biology, depolarization is a decrease in the absolute value of a cell's membrane potential. Thus, changes in membrane voltage in which the membrane potential becomes less positive or less negative are both depolarizations.... --> open VDCC Voltage-dependent calcium channel Voltage-dependent calcium channels are a group of voltage-gated ion channel ion channels found in excitable cells with a Permeability to the ion calcium.... s (primarily) --> ↑intracellular Ca²⁺ ↑Voltage-gated Na⁺ channels --> more depolarization --> open VDCC Voltage-dependent calcium channel Voltage-dependent calcium channels are a group of voltage-gated ion channel ion channels found in excitable cells with a Permeability to the ion calcium.... s --> ↑intracellular Ca²⁺ ↓Na⁺-Ca²⁺ exchanger Sodium-calcium exchanger The sodium-calcium exchanger is an antiporter membrane protein which removes calcium from cells. It uses the energy that is stored in the electrochemical gradient of sodium by allowing Na+ to flow down its gradient across the plasma membrane in exchange for the countertransport of calcium in biology ions .... activity --> ↑intracellular Ca²⁺
ATP Adenosine triphosphate This article is about the chemical used by cells as an energy carrier. For other uses, see ATP .Adenosine-5'-triphosphate is a multifunctional nucleotide, and plays an important role in cell biology as a coenzyme that is the "molecule unit of currency" of intracellular energy transfer.... (intracellular)	↓ATP-sensitive K⁺ channel
muscarinic agonists e.g. acetylcholine Acetylcholine The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including homo sapiens....	↑muscarinic receptor M₂ Muscarinic acetylcholine receptor M2 The muscarinic acetylcholine receptor M2, also known as the cholinergic receptor, muscarinic 2, is a muscarinic acetylcholine receptor....	Activation of G_i Gi alpha subunit Gi alpha subunit is a heterotrimeric G protein subunit which inhibits the production of Cyclic_adenosine_monophosphate from Adenosine triphosphate.... --> ↓cAMP Cyclic adenosine monophosphate Cyclic adenosine monophosphate is a second messenger that is important in many biological processes. cAMP is derived from adenosine triphosphate and used for intracellular signal transduction in many different organisms.... --> ↓PKA activity --> ↓phosphorylation Phosphorylation Phosphorylation is the addition of a phosphate group to a protein or other organic molecule. Protein phosphorylation in particular plays a significant role in a wide range of cellular processes.... of MLCK --> ↑MLCK activity --> ↑phosphorylation of MLC (calcium-independent)
NPY Neuropeptide Y Neuropeptide Y is a 36 amino acid peptide neurotransmitter found in the brain and autonomic nervous system.NPY has been associated with a number of physiologic processes in the brain, including the regulation of energy balance, memory and learning, and epilepsy....	NPY receptor
adrenergic agonists e.g. norepinephrine Norepinephrine Norepinephrine or noradrenaline is a catecholamine with dual roles as a hormone and a neurotransmitter.As a stress hormone, norepinephrine affects parts of the brain where attention and responding actions are controlled....	↑a₁ adrenergic receptor Alpha-1 adrenergic receptor The alpha-1 adrenergic receptor is an adrenergic receptor with the primary effect of vasoconstriction....	Activation of G_q Gq alpha subunit Gq protein or Gq/11 is a heterotrimeric G protein subunit that activates phospholipase C . PLC in turn hydrolyzes phosphatidylinositol to diacyl glycerol and inositol triphosphate signal transduction Metabolic pathway.... --> ↑PLC Phospholipase C Phosphoinositide phospholipase C is a family of eukaryotic intracellular enzymes that play an important role in signal transduction processes.... activity --> ↑IP₃ Inositol triphosphate Inositol trisphosphate or inositol 1,4,5-trisphosphate , together with diglyceride, is a secondary messenger molecule used in signal transduction in cell s.... and DAG --> activation of IP₃ receptor Inositol triphosphate receptor Inositol triphosphate receptor is a membrane glycoprotein complex acting as calcium channel activated by inositol triphosphate . The IP3 receptor was first purified from rat cerebellum.... in SR --> ↑intracellular Ca²⁺
thromboxane Thromboxane Thromboxane is a member of the family of lipids known as eicosanoids. The two major thromboxanes are thromboxane A2 and thromboxane B2.Thromboxane is named for its role in clot formation ....	↑thromboxane receptor Thromboxane receptor The thromboxane receptor is a protein on the surface of cell s in the endothelium of blood vessels and in the placenta which interacts with the eicosanoid lipid thromboxane....
endothelin Endothelin Endothelins are proteins that constrict blood vessels and raise blood pressure. They are normally kept in balance by other mechanisms, but when they are over-expressed, they contribute to high blood pressure and heart disease....	↑endothelin receptor Endothelin receptor There are at least three known endothelin receptors, ETA, ETB1 and ETB2, all of which are G protein-coupled receptors whose activation result in elevation of intracellular-free calcium.... ET_A
angiotensin II	↑Angiotensin receptor 1	Activation of G_q Gq alpha subunit Gq protein or Gq/11 is a heterotrimeric G protein subunit that activates phospholipase C . PLC in turn hydrolyzes phosphatidylinositol to diacyl glycerol and inositol triphosphate signal transduction Metabolic pathway.... --> ↑PLC Phospholipase C Phosphoinositide phospholipase C is a family of eukaryotic intracellular enzymes that play an important role in signal transduction processes.... activity --> ↑IP₃ Inositol triphosphate Inositol trisphosphate or inositol 1,4,5-trisphosphate , together with diglyceride, is a secondary messenger molecule used in signal transduction in cell s.... and DAG --> activation of IP₃ receptor Inositol triphosphate receptor Inositol triphosphate receptor is a membrane glycoprotein complex acting as calcium channel activated by inositol triphosphate . The IP3 receptor was first purified from rat cerebellum.... in SR --> ↑intracellular Ca²⁺
angiotensin II		open VDCC Voltage-dependent calcium channel Voltage-dependent calcium channels are a group of voltage-gated ion channel ion channels found in excitable cells with a Permeability to the ion calcium.... s --> ↑intracellular Ca²⁺
ATP Adenosine triphosphate This article is about the chemical used by cells as an energy carrier. For other uses, see ATP .Adenosine-5'-triphosphate is a multifunctional nucleotide, and plays an important role in cell biology as a coenzyme that is the "molecule unit of currency" of intracellular energy transfer.... (extracellular)	↑P2X receptor P2X Receptor P2X receptors are a family of cation-permeable ligand-gated ion channel that open in response to the binding of extracellular adenosine 5'-triphosphate ....	↑Ca²⁺
moderately high levels of stress Stress (medicine) Stress is a biological term which refers to the consequences of the failure of a human or animal body to respond appropriately to emotional or body threats to the organism, whether actual or imagined....	-	release of adrenergic agonists
Asymmetric dimethylarginine Asymmetric dimethylarginine Asymmetric dimethylarginine is a naturally occurring chemical found in blood plasma. It is a metabolism by-product of continual protein modification processes in the cytoplasm of all human cells....
Antidiuretic hormone (ADH or Vasopressin) Vasopressin Arginine vasopressin , also known as vasopressin, argipressin or antidiuretic hormone , is a hormone found in most mammals, including humans....	Arginine vasopressin receptor 1 (V1) on vascular smooth muscle	Activation of G_q Gq alpha subunit Gq protein or Gq/11 is a heterotrimeric G protein subunit that activates phospholipase C . PLC in turn hydrolyzes phosphatidylinositol to diacyl glycerol and inositol triphosphate signal transduction Metabolic pathway.... --> ↑PLC Phospholipase C Phosphoinositide phospholipase C is a family of eukaryotic intracellular enzymes that play an important role in signal transduction processes.... activity --> ↑IP₃ Inositol triphosphate Inositol trisphosphate or inositol 1,4,5-trisphosphate , together with diglyceride, is a secondary messenger molecule used in signal transduction in cell s.... and DAG --> activation of IP₃ receptor Inositol triphosphate receptor Inositol triphosphate receptor is a membrane glycoprotein complex acting as calcium channel activated by inositol triphosphate . The IP3 receptor was first purified from rat cerebellum.... in SR --> ↑intracellular Ca²⁺

Pathology

Vasoconstriction can be a contributing factor to erectile dysfunction

Erectile dysfunction

Erectile dysfunction is a sexual dysfunction characterized by the inability to develop or maintain an erection of the penis sufficient for satisfactory sexual performance....
. An increase in blood flow to the penis causes an erection, however, if the mechanism is perturbed the blood vessels allow less blood to pool. This does not necessarily mean that the person in question is not aroused, it is a lapse in judgment between the Central Nervous System and the Peripheral Nervous System. When blood pools in the penis the body reacts to the excessive heat to cool it, resulting in vasoconstriction.

Improper vasoconstriction may also play a role in secondary hypertension

Hypertension

Hypertension, also referred to as high blood pressure, HTN or HPN, is a medical condition in which the blood pressure is chronically elevated....
.

Vasoconstriction

General mechanism

Factors and individual mechanisms

Exogenous medications

Endogenous

Pathology

See also

External links