L4 Sympathetic nervous system and adrenergic neurotransmission

Most sympathetic post ganglionic nerve endings have ❌ receptors (adrenoceptors), which come in 2 types, ❌. There are subtypes ❌ for both alpha and beta receptors.
Catecholamines act on several R types. Noradrenaline acts on ❌. Adrenaline acts on ❌.

Blood vessels express alpha, beta, dopamine, histamine, and muscarinic receptors. SNS activation releases noradrenaline, adrenaline, and dopamine.
Alpha 1 activation ❌ vessels (arterioles) and ❌ blood flow to unnecessary organs, so more blood can flow to where it's needed. Beta 2 ❌ skeletal muscle beds and decreases overall vascular ❌, increasing ❌ to muscles.

Dopamine (DA) has 3 different concentration-dependent mechanisms:
- Low [DA]: acts at ❌ receptors to dilate renal ❌, and increase ❌.
- Med [DA]: stimulates ❌ receptors to dilate ❌, and decreases systemic vascular ❌
- High [DA]: stimulates ❌ receptors to cause vessel constriction and increase ❌.

All levels of dopamine ❌ kidney perfusion.

Sympathomimetic drugs are drugs that mimic the action of the ❌ nervous system and are adrenergic ❌. They can be ❌ acting, and therefore selective for specific adrenergic receptors(or non-selective). They can also be ❌ acting, by increasing the availability of ❌ to stimulate adrenoceptors.

Adrenergic ❌ are sympatholytics, i.e. they break the effects of the SNS. Many drugs ❌ with the function of the SNS, and affect the ❌ of sympathetically innervated organs. Several of these are important for the treatment of ❌ diseases(e.g. Beta blockers such as ❌.)