The adrenal medulla develops from neural tissue and secretes two hormones, epinephrine and norepinephrine. These two hormones are secreted in response to stimulation by sympathetic nerve, particularly during stressful situations. A lack of hormones from the adrenal medulla produces no significant effects.
Premature ventricular contractions (PVCs, PVC) are premature heartbeats originating from the ventricles of the heart. Premature ventricular contractions are premature because they occur before the regular heartbeat. The heart has four chambers. The upper two chambers are the atria, and the lower two chambers are the ventricles.
Peripheral vascular disease (PVD) can occur when a disease or disorder causes a reduction in blood flow to any part of the circulatory system - outside of the brain or heart. Frequently caused by fatty deposits in arteries, or artheroschlerosis, this is one of the leading causes of disability in adults over 50.