What are the factors affecting the rate of heart beat?

The factors which affect the rate of pace-maker potential also influence the rate of heart beat.
The main factors are:

1. Temperature : The velocity of the conduction of action potential and level of resting membrane potential are directly related to the temperature.

2. Neural signals through the sympathetic nerves increase the hearbeat rate. 
3. A special nerve centre in the medulla oblangata can effect the heart beat rate. 

3. Chemical transmitters and hormones.

(i) Acetylcholine tends to reduce the rate of heart beat.

(ii) Norepinepherine liberated from sympathetic nerveous system, increases the rate of heartbeat per minute.

(iii) Hormone adrenaline, secreted from adrenal cortex, also increases the heart beat rate.