Why do hormones only affect certain cells in your body?

Draw a flow diagram to show how hormones work. Refer to Cyclic AMP in your answer. Why do hormones only affect certain cells in your body? Refer to the structure of the cell membrane in your answer.
On an outline of a human body draw on and label the major glands of the endocrine system:
a) Pituitary gland
b) Hypothalamus
c) Thyroid and parathyroid gland
d) Pancreas
e) Adrenal medulla
f) Adrenal cortex
g) Gonads and placenta
h) Pineal
i) Gastrointestinal tract
You may wish to use a key system.