Subject:
Chapter 45 Hormone Chemical signal that is secreted into the extracellular fluid Carried by circulatory system Communicates regulatory messages within the body Can reach all parts of body but only target cells respond Nervous System Coveys high-speed electrical signals along specialized cells called neurons These messages control the movement of body parts in response to sudden environmental changes Endocrine System All hormone-secreting cells make up the endocrine system. Endocrine glands are hormone-secreting organs. Endocrine glands are referred to as ductless glands since they secrete their messengers directly into extracellular fluid, which then diffuse into the circulation. Overlap between endocrine and nervous regulation Lines between two systems unclear
