This makes the skin turn paler because less blood reaches the surface, reducing the radiation of heat.

[1] The mechanism that leads to vasoconstriction results from the increased concentration of calcium (Ca2+ ions) within vascular smooth muscle cells.

Smooth muscle cells are capable of generating action potentials, but this mechanism is rarely utilized for contraction in the vasculature.

The rise in intracellular calcium complexes with calmodulin, which in turn activates myosin light-chain kinase.

Examples of endogenous factors include the autonomic nervous system, circulating hormones, and intrinsic mechanisms inherent to the vasculature itself (also referred to as the myogenic response).

Several factors contribute to vasoconstriction, including the release of vasoconstrictor substances such as endothelin and angiotensin II, both of which play crucial roles in the modulation of vascular tone.

[16] Additionally, sympathetic nervous system activation, triggered by stress or other stimuli, prompts the release of norepinephrine, a neurotransmitter that induces vasoconstriction by binding to alpha-adrenergic receptors on smooth muscle cells.

Chronic vasoconstriction is associated with hypertension, a major risk factor for cardiovascular diseases such as heart attack and stroke.

Moreover, impaired blood flow resulting from abnormal vasoconstriction may contribute to tissue ischemia, which can be observed in conditions like Raynaud's disease.

Understanding the pathology of vasoconstriction is crucial for developing targeted therapeutic strategies to manage conditions associated with abnormal vascular tone.