Increase hea rate just before staing exercise is due to?
Ans. is 'c' i.e., Release of adrenaline(Ref As level textbook p.54)Hea rate increase before the sta of exercise , i.e, anticipatory rise in hea rate.It is caused by disease of adrenaline from the adrenal medulla acting directly on the hea and the impact of emotional excitement on the medulla.Hea rate increase fuher rapidly with the sta of exercise.It is due to the following receptors.Proprioceptors (in muscle & joints ) relating to increased motor activity.Chemoreceptors relating to increased CO, /lactic acid and decreased O2.These receptors send messages to cardiac control center causing an increase in hea rate.
Stretch receptors
Proprioceptors
Release of adrenaline
All of the above