How does norepinephrine increase our heart rate

Norepinephrine

Norepinephrines,Arterenol, norepinephrine, levarterenol, 1- (3,4-dihydroxyphenyl)-2-aminoethanol, Abbr. N / A, E.norepinephrine, catecholamine synthesized from the amino acid tyrosine via dopa and dopamine in vertebrates and humans. Places of formation are the adrenal medulla (adrenal gland), parts of the brain stem and the synapses of postganglionic sympathetic nerve fibers. The main synthesis area of ​​noradrenaline in the central nervous system is the locus coeruleus. Axons of this core area project to the diencephalon (thalamus, hypothalamus), into the limbic system (especially to septo-hippocampal structures) and into the entire neocortex. Noradrenergic activation of the diencephalon and limbic-hippocampal structures leads to an increase in the signal-to-noise ratio of neuronal activity in these structures. In addition, norepinephrine increases attention (attention). Via projections to vegetative centers of the spinal cord, brain stem and hypothalamus, norepinephrine increases sympathetic activation. In the periphery of the body, norepinephrine causes blood pressure to rise and the heart rate to rise. The increase in blood pressure leads via vagal reflexes (stimulation of baroreceptors) to a compensatory, central nervous-mediated inhibition of sympathetic activation and thus, in the long term, to a reduction in heart rate. Preganglionic release of acetylcholine causes the hormone to be secreted directly in the adrenal medulla and indirectly in the sympathetic nerve cells by triggering an action potential. At rest, the norepinephrine level in the blood is 2-3 times higher than the adrenaline level and precedes the rise in adrenaline when motor activity begins. The organ and effect specificity is achieved through different receptor systems (adrenergic receptors) (alpha, beta receptors). Central nervous effects of noradrenaline can be mimicked by β-receptor agonists, but by α2-Inhibit receptor agonists. The α2-Adrenoceptors are located presynaptically in this case and mediate autoinhibition of noradrenergic activation in the locus coeruleus. In the body periphery, β-receptors mediate vasoconstriction and an increase in heart rate. - The breakdown of noradrenaline (see fig.) Takes place through monoamine oxidase (MAO) and through catechol-O-methyl-transferase (COMT), primarily to 3-methoxy-4-hydroxymandelic acid (vanillin-mandelic acid). The inhibition of breakdown by MAO inhibitors leads to an increase in the norepinephrine level and its discharge. This effect is apparently the basis of the antidepressant effect of MAO inhibitors (antidepressants). Inhibition of COMT by pyrogallol, on the other hand, does not show any significant functional effects. The elimination of noradrenaline from the synaptic cleft after release takes place predominantly through re-uptake into the noradrenergic terminal, which can be inhibited by numerous amines and by tricyclic antidepressants, whereby the noradrenaline concentration in the cleft increases. Their antidepressant effect is attributed to this effect. Norepinephrine is also released at the axonal varicosities and then reaches the adrenergic receptors of the surrounding postsynaptic nerve cells by diffusion. This form of adrenergic neurotransmission is more likely to serve to convey general system states in the context of unspecific activations or inhibitions. Catecholamines, hormones, neurotransmitters, synapses.



Norepinephrine

Breakdown (inactivation) of norepinephrine:
The effect of noradrenaline is 90% through resumption of varicosity and partial degradation by the MAO (monoamine oxidases) in the mitochondria (uptake I), otherwise through uptake in the effector cell and other surrounding cells (uptake II) and degradation by the cytoplasmic COMT (catechol-O-methyl transferase) and the mitochondrial MAO terminated. The breakdown products get into the blood. Traces of norepinephrine are also transported via the bloodstream to the liver, where they are broken down by the MAO and COMT.