Hi Keira,

1) Acetylcholine and Epinephrine do regulate our heart rate as necessary, however, this questions speaks to how our SA node has parasympathetic innervation on a day to day basis in order to maintain our resting HR around 60-80 bpm. Our intrinsic HR is actually quite high so we have a constant vagal tone (vagus nerve innervation, acetylcholine) to reduce it to our working resting HR.

2) Ligand-gated channels require ligand binding (via neurotransmitters for example) to open channels whereas voltage-gated channels require a change in voltage (specific to the channel) to open and close it. VG-channels are typically found throughout the axon and LG-channels are found in the dendrites/axon terminal.

Hope this helps!