How does the carotid sinus reflex work in terms of the autonomic nervous system pathways?
starting with the medulla oblongata
- John TLv 54 years agoFavorite Answer
During a carotid sinus reflex, when someone pinches/applies pressure on the carotid arteries, the carotid arteries detect more stretch/more pressure and send an increased frequency of action potentials to the medulla vasomotor center (mVMC). As a result, there is parasympathetic correction/override. Blood vessels vasodilate and TPR decreases. As a result, so does blood pressure. In addition, there is increased cardioinhibitory/vagal activity which causes increased release of acetylcholine which decreases chronotropy. However, there is also decreased cardioacceletory activity which decreases epinephrine release on the heart, which decreases chronotropy and inotropy. Because Heart Rate and Stroke Volume are both decreased, so is Cardiac Output. With decreased cardiac output, less blood is pumped to the periphery, and thus, this also contributes to the decrease in blood pressure.
If you want more specifics, you can say that the vagus nerve releases acetylcholine onto its postganglionic nerve, which also releases acetylcholine, but this time on the heart. This acetylcholine binds muscarinic Ach receptors on the heart tissue, in particular, the pacemaker nodes (SA and AV) and decreases heart rate. With less epinephrine released from the sympathetic postganglionic nerve onto the Beta 2 receptors of the myocardium, there is also less contractile force of the myocardium.Source(s): Physiology tutor