Is a doctor chosen by the patient who is the first doctor the patient sees responsible for making referrals for further treatment by a specialist or for hospitalization?

If the doctor believes treatment by a specialist or hospitalization is necessary, yes, he is responsible for making those recommendations to the patient. The patient is ultimately the one who will either accept or reject those recommendations, and could seek a second opinion from another doctor if he or she chooses. If the patient accepts the advice of the first doctor, the doctor will make the referrals.