Which 2 major mechanisms are involved in the increase of heart rate during exerc

Question

Which 2 major mechanisms are involved in the increase of heart rate during exercise?

I've already explained one major mechanism:

Increased levels of carbon dioxide is detected by chemoreceptors in the aorta and carotid arteries, and the body responds by dilating veins, which enables more blood to be delivered to the heart. With more blood inside, the heart muscles are stretched, and the pressure is raised. Baroreceptors that are also located on the aorta and carotid arteries, signal the cardioacceleratory center of the medulla oblongata to stimulate the Sinoatrial node (the pacemaker of the heart) by the sympathetic nervous system. The stimulation of the SA node increases heart rate and the force of contraction.

I'm confused about what the other mechanism is. I'm pretty sure it's an endocrine mechanism involving the adrenal medulla and the release of epinephrine and norepinephrine, but where I'm confused is because I would have thought that the medulla oblongata's stimulation of the sympathetic nervous system is one in the same with the release of adrenaline.

Could somebody please clearly explain another mechanism that increases heart rate during exercise BESIDES the one that I explained?

Thank you very much!

Explanation / Answer

When u start exercising or encounter some physically dangerous situation then your body prepares itself for flight and fight reaction which orginates in HYPOTHALAMUS .

This triggers the release of ADRENALINE( STRESS HORMONE) from adrenal.gland.which increses the heart rate and blood pressure.

Adrenaline acts on heart via beta 2 receptor( G- protein coupled receptor) leading to increase in calcium influx and fast and better contractaction of heart muscle leading to increase in heart rate.

Adrenaline also acts on alpha 2 receptor on blood vessel Leading to vasoconstriction of vessel and increases the blood pressure.

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