How Does Homeostasis Control Heart Rate?
The heart rate is the rate at which the which the heart is working and is described as a number of beats per minute. An adults heart rate at rest will be 60-80 beats per minute and increases during any form of exercise as the body works harder and requires more energy to cope with demands being made on it. Overall fitness determines heart rate during exercise. An athlete's resting heart rate can be as low as 28 to 40 beats per minute because their heart is more conditioned and pumps blood more efficiently. People who are sedentary can have a higher resting pulse of 100 beats per minute, because inadequate exercise causes the heart to work less efficiently.
The brain stem consists of five parts: the thalamus, hypothalamus, midbrain, pons and medulla. 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. During exercise, your muscles send a message through the nervous system to the medulla, which in turn releases epinephrine and norepinephrine. Epinephrine is a hormone also known as adrenaline which increases the heart rate and norepinephrine is a hormone and a transmitter that working with epinephrine gives the body sudden energy. These two chemicals travel along the nervous system to the reach the electrical system of the heart, the sinus node. The sinus mode triggers the heart's contractions. Homeostasis constantly monitors messages coming from the nervous system corresponding between the body's muscles and joints. When you stop exercising, your muscles send along a message to the medulla again, which responds this time by releasing a hormone called acetylcholine. This hormone slows the heart rate, retarding the heart's muscle contractions.
The medulla also relies on information from other parts of the brain to help make decisions for an appropriate response. For instance, the thalamus is the sensory part of the brain. If the thalamus sends the medulla information that the body is under emotional stress, the medulla recognises this as well as information received from the nervous system to harmonize the deviation and trigger the best response. Increasing the heart rate is the body's response to oxygen demand. To prepare and condition the appropriate response, homeostasis may increase the metabolic rate and create a new set point to meet the body's demands.
During any physical activity there is an increased demand from your body to increase the production of muscle cells for oxygen and nutrients and is a state of increased metabolism. Homeostasis is maintained when your heart can provide the rate of blood flow necessary to meet your body's increased metabolic demand for oxygen and nutrients.
Exercise increases the production of cellular wastes such as carbon dioxide and lactic acid. Your cardiovascular system maintains homeostasis between the delivery of oxygen and nutrients and the removal of cellular wastes by increasing your heart rate. Your increased heart rate speeds up delivery of oxygen and nutrient rich blood to your musculoskeletal system while increasing the rate at which blood is taken away from tissues and delivered to the lungs to receive oxygen.
During exercise. To maintain homeostasis, your body redistributes blood flow. During exercise, blood flow to the nervous system, gastrointestinal tract, kidneys, brain and spleen decreases, while blood flow to the musculoskeletal system increases.