Heart rate at rest. Bradycardia is a slow heart rate, defined as below 60 bpm at rest. During sleep a slow heartbeat with rates around 40–50 bpm is common and is considered normal. When the heart is not beating in a regular pattern, this is referred to as an arrhythmia. Abnormalities of heart rate sometimes indicate disease. While heart rhythm is regulated entirely by the sinoatrial node under normal conditions, heart rate is regulated by sympathetic and parasympathetic input to the sinoatrial node. The accelerans nerve provides sympathetic input to the heart by releasing norepinephrine onto the cells of the sinoatrial node
Lymph node and fixed macrophages. The subcapsular sinus has clinical importance as it is the most likely location where the earliest manifestations of a metastatic carcinoma in a lymph node would be found. The cortex of the lymph node is the outer portion of the node, underneath the capsule and the subcapsular sinus. It has an outer superficial part and a deeper part known as the paracortex. The subcapsular sinus drains to the trabecular sinuses, and then the lymph flows into the medullary sinuses. The outer cortex consists mainly of the B cells arranged as follicles, which may develop a germinal center