Autonomic control of the CVS Flashcards
What does the autonomic nervous system control?
Heart rate
Blood pressure
Force of contraction
Peripheral resistance of blood vessels
What are the divisions of the autonomic nervous system?
Parasympathetic
Sympathetic
Where is the parasympathetic input from the heart from?
Vagus nerve
- synapse with SA and AV node
- post ganglionic cells release ACh
Which receptor does the parasympathetic input act on?
M2 receptor
What is the effect of the parasympathetic input?
Decrease heart rate
Decrease AV node conduction velocity
Where is the sympathetic input from the heart from?
Sympathetic trunk
- innverate SA + AV node and myocardium
- release NA
Which receptor does the sympathetic input act on?
β1 adrenoreceptors
What is the effect of the sympathetic input?
Increases heart rate
Increases force of contraction
What is the effect of sympathetic activity on pacemaker potentials?
Increases slope
β1 receptors
GPCRs
Increase cAMP
Speeds up pacemaker potential
What is the effect of parasympathetic activity on pacemaker potentials?
Decreases slope
M2 receptors
GPCRs
Increase K+ conductance
Decrease cAMP
What is the effect of NA on the force of contraction?
Increases force of contraction
How does NA increase force of contraction?
β1 receptors
Increase cAMP
Activate PKA
Phosphorylation of Ca2+ channels - increase Ca2+
Increases uptake of Ca2+ in SR
Increased force of contraction
What innervation does vasculature receive?
Sympathetic
What receptors does vasculature have?
α1 adrenoreceptors
What is vasomotor tone?
The degree of tension of the smooth muscle within the walls of blood vessels
What happens when you increase sympathetic output?
Vasoconstriction
What happens when you decrease sympathetic output?
Vasodilation
What happens when blood vessels have α1 and β2 adrenoreceptors?
Adrenaline has a higher affinity for β2 receptors
At physiological concentration - adrenaline preferentially binds to β2
At higher concentrations - also activates α1
What is the effect of activating β2 adrenoreceptors?
Vasodilation
- increases cAMP
- PKA
- opens K+ channels
- inhibits MLCK
- relaxes smooth muscle
What is the effect of activating α1 adrenoreceptors?
Vasoconstriction
- stimulates IP3 production
- increase in intracellular calcium
- contraction of smooth muscle
What are baroreceptors?
Nerve endings in carotid sinus and aortic arch that are sensitive to stretch
What is the baroreceptor reflex?
Compensates for changes in arterial BP
What drugs can act on the autonomic nervous system?
Sympathomimetics
- α adrenoreceptor agonists
- β adrenoreceptor agonists
Adrenoreceptor antagonists
Cholingerics
- muscarinic agonists
- muscarinic antagonists
What are the uses of sympathomimetics?
Adrenaline - cardiac arrest + anaphylactic shock
Dobutuamine (β1 agonist) - cardiogenic shock
Salbutamol (β2 agonist) - asthma treatment
