Autonomic Nervous Control Flashcards
The ANS is broken into what 2 sections?
Sympathetic and parasympathetic
The ANS exerts control over what?
Vascular and visceral smooth muscle, exocrine section, rate and force of contraction in the heart
Where does the sympathetic ANS exit the spine?
Thoracic, lumbar spine
Where does the parasympathetic ANS exit the spine?
Medullary, sacral
Detail the neurotransmitters and receptors involved in the autonomic nervous system
PARA: muscarinic M1, M2, M3, pre = ACh nAChR, post = Ach mAChR.
SYM: adrenergic α1, α2, β1, β2 pre = ACh nAChR, post = NA adrenoceptors
How does the PNS control heart rate and force of contraction in the normal heart?
Para, 10th cranial nerve = vagus, synapse with SA and AV postganglionic cells = release Ach – acts on M2 = decrease chronotropy, decrease inotropy, also decrease AV conduction velocity
How does the SNS control heart rate and force of contraction in the normal heart?
Sym, postganglionic fibres from sympathetic trunk, innervate SA, AV and myocardium = release NA – acts on β1 adrenoceptors = increase chronotropy, increase inotropy
What are baroreceptors?
Found in aortic arch and carotid sinus (located in the base of the internal carotid)
specialized nerve ending = sensitive to stretch = allows medullary centre in brain to sense blood flow and BP
What is the baroreceptor reflex?
body’s homeostatic mechanisms, helps to maintain BP at nearly constant levels = increase in mean arterial pressure, detected by baroreceptors, afferent pathway to medulla, efferent pathway to heart/vessels = bradycardia and vasodilation
What sets the rhythm of the heart?
SA node firing an AP
What is the effect of SNS on pacemaker AP?
Increase rate to threshold = β1 GPCR, increase cAMP, faster opening Na+ channels = faster HR
What is the effect of PNS on pacemaker AP?
Decreases rate to threshold = M1 GPCR, decreases cAMP, slower opening Na+ channels = slows HR
How does NA increase inotrophy?
NA acting on β1 in myocardium = increase cAMP = increase PKA = increase phosphorylation Ca2+ channels = higher [Ca2+], increased Ca2+ stores, increased sensitivity
Outline vasodilation of vascular smooth muscle cells
NA activating β2 = increased cAMP = increased PKA = opens K+ channels = inhibits MLCK = relaxation of smooth muscle
also metabolites (K+, H+) = vasodilation
What is the role of local metabolites in regards to tissue perfusion?
Strong vasodilator effect
Adenosine, K+, H+
