Control of heart beat:

The rate of heart beat is controlled both by nervous & endocrine system.

 Nervous control: SA (sino-atrial node) receives 2 sets of nerve fibers from brain. 

1) Sympathetic nerve fibres:- That stimulates the SA node & starts heart beat.

2) Parasympathetic nerve fibres:- That stimulates the SA node & stops heart beat.

Hormonal (Endocrine) control: Hormones from medulla oblongata (Epinephrine & nor epinephrine) starts heart beat at emergency.