When a person changes position from standing to lying down, the following change is seen
When changing position from standing to lying,
Heart rate does not increase. Cerebral flow is unchanged because of autoregulation. 
In lying position apex of the lung is more perfused as the effect of gravity is not much as in standing.  
Venous return to heart increases as pooled blood in lower extremities returns to heart faster.
Heart rate increases
Venous return to heart increases immediately
Cerebral blood flow increases
Blood flow at apices of lung decreases