Activation of autonomic neurons leads to different effects depending on the target organ system. A table consolidating the effect each division of the autonomic nervous system has on specific organ systems is provided below.
- aLess important actions are shown in brackets.
- bSpecific receptor type: α, alpha; β, beta; M, muscarinic.
- cVascular smooth muscle in skeletal muscle has sympathetic cholinergic dilator fibers.
- dProbably through presynaptic inhibition of parasympathetic activity.
- eProbably M1, but M2 may participate in some locations.
- ACh, acetylcholine; NE, norepinephrine.
The above tables that summarize effects of the Autonomic Nervous System on target organs are consolidated into a single table here (link to effects of ANS on organ system table).
"Dually innervated organs such as the iris of the eye and the sinoatrial node of the heart receive both sympathetic and parasympathetic innervation. The pupil has a natural, intrinsic diameter to which it returns when both divisions of the Autonomic Nervous System are blocked. Pharmacologic ganglion blockade, therefore, causes it to move to its intrinsic size. Similarly, the cardiac sinus node pacemaker has an intrinsic rate (about 100–110/min) in the absence of both Autonomic Nervous System inputs. How will these variables change (increase or decrease) if the ganglia are blocked? The answer is predictable if one knows which system is dominant. Normally, both the pupil and, at rest, the sinoatrial node are dominated by the parasympathetic system. Thus, blockade of both systems, with removal of the dominant parasympathetic Autonomic Nervous System and nondominant sympathetic Autonomic Nervous System effects, result in mydriasis and tachycardia."
Question
What effect does the sympathetic nervous system have on cardiac contractility?
Question
Which autonomic nervous system receptors are responsible for the effects of the sympathetic nervous system on contractility?