Raise your heart rate
August 11, 2024 10:40 AM Subscribe
What signals the heart to pump faster during exercise? When I search all I can find is "The heart pumps faster to deliver more oxygen and nutrients" or "adrenaline makes it pump faster." But that's not really an answer to the question I'm asking.
Is the heart monitoring the blood coming in for oxygenation and other chemicals, and speeding up when those levels drop? Are the muscles sending chemical signals or neuron signals to the heart? Is something signaling the adrenal glands to excrete adrenaline and that's the only cause of the heart speeding up? Something else?
I'm not interested in the heart rate when you are scared or otherwise excited, only heart rate speed up from exercise. I'm aware there it might be overlap between those two but let's focus on the exercise aspect.
I'm also aware that there might be several signaling pathways and I would be interested in learning about all of them.
Is the heart monitoring the blood coming in for oxygenation and other chemicals, and speeding up when those levels drop? Are the muscles sending chemical signals or neuron signals to the heart? Is something signaling the adrenal glands to excrete adrenaline and that's the only cause of the heart speeding up? Something else?
I'm not interested in the heart rate when you are scared or otherwise excited, only heart rate speed up from exercise. I'm aware there it might be overlap between those two but let's focus on the exercise aspect.
I'm also aware that there might be several signaling pathways and I would be interested in learning about all of them.
Best answer: Your brain has a cardiac center than can directly change the rhythm of your heartbeat via the nerves of the sympathetic and parasympathetic nervous system. The sympathetic nervous system directly innervates the heart and releases epinephrine (aka adrenaline) and norepinephrine as neurotransmitters which bind to receptors in the heart and cause partial depolarization of the heart fibers which makes heart beats propagate faster. The sympathetic nervous system also indirectly speeds up the heart by causing the adrenal glands to release Epi and NE as hormones, which travel through the bloodstream to the heart. The parasympathetic system works via your vagus nerve; when you're at rest it releases acetylcholine which hyperpolarizes the cells of the heart and makes it harder for the heart cells to depolarize/for heart beats to propagate across the heart. (If the heart is left to its own devices it beats around 100 bpm.)
In the case of exercise, the first information that your brain receives that tells it to bump up the heart rate is from proprioreceptors that detect movement in your muscles/limbs. Your cardiac center is like, "OK, gonna need more oxygen soon, better get that heart pumping."
In your aortic arch and carotid arteries you also have chemoreceptors (also present in the medulla oblongata) and baroreceptors (pressure receptors) that keep track of your blood O2, CO2, pH, and pressure, and they work to maintain homeostasis - keeping your pressure and blood chemistry in an acceptable range. So if you're depleting yourself of oxygen that's going to bump your heart rate up higher but if it gets to where your blood pressure is too high, the vagus nerve will come back on and try to reduce your heart rate.
Your heart output also goes up during exercise because muscle movements cause more blood to return to the heart which basically means each stroke has a higher blood volume.
Source: I just finished Anatomy & Physiology II and looked this up in my textbook!
posted by mskyle at 11:39 AM on August 11 [25 favorites]
In the case of exercise, the first information that your brain receives that tells it to bump up the heart rate is from proprioreceptors that detect movement in your muscles/limbs. Your cardiac center is like, "OK, gonna need more oxygen soon, better get that heart pumping."
In your aortic arch and carotid arteries you also have chemoreceptors (also present in the medulla oblongata) and baroreceptors (pressure receptors) that keep track of your blood O2, CO2, pH, and pressure, and they work to maintain homeostasis - keeping your pressure and blood chemistry in an acceptable range. So if you're depleting yourself of oxygen that's going to bump your heart rate up higher but if it gets to where your blood pressure is too high, the vagus nerve will come back on and try to reduce your heart rate.
Your heart output also goes up during exercise because muscle movements cause more blood to return to the heart which basically means each stroke has a higher blood volume.
Source: I just finished Anatomy & Physiology II and looked this up in my textbook!
posted by mskyle at 11:39 AM on August 11 [25 favorites]
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https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4404375/
posted by pullayup at 11:16 AM on August 11 [7 favorites]