[CVS] Q.17) What are the factors affecting heart rate?

Ans.

(1) Higher centre: Stimulation of post group of hypothalamic nucleus increase heart rate. Middle group decrease heart rate. Stimulations of area-13 of frontal lobe cause tachycardia.

(2) Cardio-vascular reflexes:

(a) Baroreceptor reflex→ (stimulate) of Baroreceptor→decrease HR

(b) Brain Bridge reflex→ (stimulate) of Brain Bridge reflex →increase HR

(3) Respiration:

Heart rate increase during inspiration particularly in children.

Heart rate decrease during expiration.

(4) Temperature:

Increase Temp. →increase HR by (stimulated) the SA node

(5) Muscular exercise:

Exercise increase HR

(6) Age: from infant to old age HR progressively decrease

(7) Sex: female have slightly faster HR than male

(8) Surface area: HR 1/∞ Surface area

(9) Hormones:

Adrenaline –increase HR

Thyroxin – increase HR