Homeostasis is the body’s ability to maintain a constant balance between the internal environment and external environment at a constant rate, despite changes which may affect our external environment such as body temperature and the amount of water in our bodies. By keeping this internal balance it allows our bodies to function efficiently. The negative feedback loop is produced when changes to our internal environment changes from its normal range. In this instance the brain and the nervous system help to get our internal environments back to its normal state. An example of this is when an individuals body is too hot and our body begins to sweat in order for us to cool down. Our internal receptors react to make sure that we can return to out normal level. These receptors are needed in the negative feedback loop to help send a message about environmental stimuli to our central nervous system, after this our bodies then send signals to an effector, to respond to the stimuli. By doing all of this our bodies can bring our internal environment back to its normal self. Heart Rate:
The Sino atrial node, which is otherwise known as the heart’s pacemaker is located at the top of the right atrium in the heart. This is what helps to decide what speed our hearts should be beating depending on the situation we are in. When we exercise our sympathetic nerves speed up the heart rate because we would be needing more oxygen in our lungs as we are working harder which means our hearts will then beat at a faster rate, but once we stop the physical activity which we are doing or parasympathetic nerves help to slow down the heart rate as we wouldn’t be needing as much oxygen. Receptors are connected to a control centre, which is the brain. When our brains receive information about a change to our internal environment, it then sends out some signals along nerves that in turn will bring out internal environment back to its normal rate.
As our heart rate is affected by blood pressure, this means that the amount of blood which goes into the heart during circulation, the heart muscle and the muscle fibres all add up to a rate in which our hearts beat at. Baroreceptors are what detects the changes in our blood pressure, and this can either help to increase or decrease our heart rate. For example if we have an increase in blood pressure, baroreceptors will then send a message to our cardiac centre (which is located in an area of the brain called the medulla), once our brain has received the message from chemoreceptor’s, and this will then increase the parasympathetic stimulation and decrease the sympathetic, which will help the heart to contract more slowly. The autonomic nervous system is what controls our heart beat, this connects the brain stem and the spinal cord with internal organs and regulates internal body processes which do not need any conscious effort.
The autonomic nervous system main function is to find a balance between sympathetic and parasympathetic inputs to the hearts. Exercise can lead to an increased heart rate, this is because exercise leads to increased skeletal muscle, body metabolism increases the demand for oxygen. When we exercise, parasympathetic stimulation decreases and sympathetic stimulation increases. When adrenalin rushes through our bodies, our heart beats faster than it normally would, this is because once the adrenergic receptors on cells are stimulated, receptors then pass the fight or flight response onto a protein called G-protein. In turn this stimulates other substances in our cells which set off an alert. This leads on to an increase in the force of a single heart contraction which is why there is an increase in our heart rate.
An increase in temperature would increase heart rate, this is because when our body temperature goes up approximately 10 degrees, a chemical reaction doubles. As our bodies heats up, the vessels near the skin get bigger to release heat which reduces blood pressure so our hearts must beat faster to compensate for this to make sure that blood still reaches all vital organs. For example, if an individual caught a cold, they would also have a fever which will increase our bodies temperature, all chemical processes in our bodes will speed up, even without an increase in physical exercise.