Homeostasis
The conditions inside the body must be controlled within narrow limits. This is called homeostasis. These conditions include water content, ion content, and body temperature and blood glucose concentration.
Homeostasis aims for normal functions and values from the body, such as temperature and blood glucose levels. When those values are either lower or higher than normal, homeostasis brings the functions back within normal values.
Internal environment
Concept of negative feedback
Homeostatic Mechanisms for regulation of the Heart Rate
Heart Rate
The medulla controls the heart rate. It sends and receives messages in the form of chemicals or hormones from the thousands of nerves running through the medulla, in an area called the medullary pyramids. The medulla constantly receives messages from the nerves, which are communication pathways from muscles, organs and other parts of the body.
Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute (bpm). Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep.
The measurement of heart rate is used by medical professionals to assist in the diagnosis and tracking of medical conditions. It is also used by individuals, such as athletes, who are interested in monitoring their heart rate to gain maximum efficiency from their training
The beating frequency (heart rate) is controlled by the balance of stimulation coming from the sympathetic and parasympathetic branches of the autonomic nervous system. Both nervous inputs to the heart converge on a small area of tissue on the right atrium.
Roles of Internal Receptors

Autonomic Nervous System
Two major divisions * Sympathetic; activated in response to challenge- * Parasympathetic; active in the absence of challenges * Both