Vasomotor refers to actions upon a

blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...

which alter its diameter. More specifically, it can refer to vasodilator action and

vasoconstrictor Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vess ...

action.

Control

Sympathetic innervation

Sympathetic nerve fibers travel around the

tunica media The tunica media (New Latin "middle coat"), or media for short, is the middle tunica (layer) of an artery or vein. It lies between the tunica intima on the inside and the tunica externa on the outside. Artery Tunica media is made up of smooth ...

of the artery, secrete

neurotransmitters A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell. Neurot ...

such as

norepinephrine Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad' ...

into the

extracellular fluid In cell biology, extracellular fluid (ECF) denotes all body fluid outside the cells of any multicellular organism. Total body water in healthy adults is about 60% (range 45 to 75%) of total body weight; women and the obese typically have a low ...

surrounding the smooth muscle (tunica media) from the terminal knob of the axon. The smooth muscle cell membranes have α and β-adrenergic receptors for these neurotransmitters. Activation of α-adrenergic receptors promotes vasoconstriction, while the activation of β-adrenergic receptors mediates the relaxation of muscle cells, resulting in vasodilation. Normally, α-adrenergic receptors predominates in smooth muscle of resistance vessels.Robert C. Ward et al. (2002). In
Foundations for osteopathic medicine
'. Lippincott Williams & Wilkins. 2nd edition. p. 98. . Google Book Search. Retrieved on 5 December 2010.

Endothelium derived chemicals

Endothelin Endothelins are peptides with receptors and effects in many body organs. Endothelin constricts blood vessels and raises blood pressure. The endothelins are normally kept in balance by other mechanisms, but when overexpressed, they contribute ...

, and

angiotensin Angiotensin is a peptide hormone that causes vasoconstriction and an increase in blood pressure. It is part of the renin–angiotensin system, which regulates blood pressure. Angiotensin also stimulates the release of aldosterone from the adren ...

are the vasoconstrictors of smooth muscles while nitric oxide and prostacyclin are vasodilators of the smooth muscles.

Pathology

Some vasoactive chemicals such as vasodilator acetylcholine are known for causing reduced/increased blood flow in the tumours by vasomotor changes. Inadequate blood supply to the tumour cells can cause the cells to be radio-resistant and resulted in reduced accessibility to

chemotherapeutic Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothera ...

agents. Injuries to nerves of the lower trunk of the

brachial plexus The brachial plexus is a network () of nerves formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in t ...

( Klumpke's paralysis) and compression of

median nerve The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus. The median nerve originates from the lateral and medial cords of the brachial plexus, and has cont ...

at the

flexor retinaculum of the hand The flexor retinaculum (transverse carpal ligament, or anterior annular ligament) is a fibrous band on the palmar side of the hand near the wrist. It arches over the carpal bones of the hands, covering them and forming the carpal tunnel. Structur ...

(

Carpal Tunnel Syndrome Carpal tunnel syndrome (CTS) is the collection of symptoms and signs associated with median neuropathy at the carpal tunnel. Most CTS is related to idiopathic An idiopathic disease is any disease with an unknown cause or mechanism of apparen ...

) can cause vasomotor changes at the areas innervated by the nerves. This area of the skin will become warmer because of vasodilation (loss of vasoconstriction). Depression of the

vasomotor center The vasomotor center (VMC) is a portion of the medulla oblongata. Together with the cardiovascular center and respiratory center, it regulates blood pressure. It also has a more minor role in other homeostatic processes. Upon increase in carbon ...

of the brain can cause the loss of

vasomotor tone Vascular resistance is the resistance that must be overcome to push blood through the circulatory system and create flow. The resistance offered by the systemic circulation is known as the systemic vascular resistance (SVR) or may sometimes be ca ...

of blood vessels, resulting in massive dilatation of veins. This will result in a condition called as

neurogenic shock Neurogenic shock is a distributive type of shock resulting in hypotension (low blood pressure), often with bradycardia (slowed heart rate), caused by disruption of autonomic nervous system pathways. It can occur after damage to the central nerv ...

References

{{Reflist, 30em Medical terminology

Control

Sympathetic innervation

Endothelium derived chemicals

Pathology

See also

References