Homeostasis Is a technical term for the process of maintain a constant internal environment despite external changes. The internal environment, compromises; blood, tissue fluid, body cell contents and all the metabolic processes taking place. Constant in this instance is not absolute or fixed it is much more flexible and dynamic as it refers to the physical and chemical composition being kept within a limited range or variables for maximum efficiency, well-being of the whole body and indeed the maintenance of life itself. The limited range of variables is said to be closely regulated.
Negative feedback as a form of regulation
Feedback control systems
This occurs when a n important variable sometimes known as a key variable e.g. pH of blood and tissue fluid, deviates from the accepted range from the accepted range or limits which then triggers responses that return the variable to within the ‘normal range’. Deviation produces a negative response to counteract the deviation. An example of a negative feedback system within the body is the liver when blood glucose levels fall, the glycogen from the liver is converted into glucose in order raise the energy levels in cells which is crucial. Vital organs that help to control the homeostatic mechanisms are the brain and nervous system. These vital organs help use to anticipate when key variables might rise and fall beyond the accepted range, for example; if it has been several hours since you have ate a meal and you are starting to feel tired and cold you will try to eat a warm energy giving meal to counteract these feelings. This can be called ‘feed forward’ as you are taking steps to avoid a low energy state before it has even happened. Negative feedback systems require the following; receptors to detect change, a control centre to receive the information and process the response, and effectors to reverse the change and re-establish the original state.
Most control centres are located in the brain.
Homeostatic mechanisms for regulation of heart rate
The heart is controlled by the autonomic nervous system which has two branches namely the sympathetic nervous system and the parasympathetic nervous system. These two systems act to speed up or slow down the heart quite like a accelerator and brake. The sympathetic nervous system is active when the body is undergoing stress, muscular work or fear. It causes each heartbeat to increase in strength as well as causing an increase in heart rate. The parasympathetic nervous system calms the output of the heart and is active during resting, peace and contentment.rhe main parasympathetic nerve is called the vagus nerve and if this is severed the heart beats faster. The sympathetic nervous system is boosted by the hormone adrenaline during periods of fright, flight and fight. The nerves for this are called the cardiac nerves. The sympathetic and parasympathetic nervous systems supply a special cluster of excitable cells in the upper part of the right atrium of the heart. It is called the sino-atrial node (SA Node) pr in general terms the pacemaker. Impulses from the sympathetic and parasympathetic nerves acting on the SA Node regulate the activity of the heart – to suit the circumstances - minute by minute, hour by hour and day by day. Every few seconds the SA Node sends out a cluster of nerve impulses across the network of muscle fibres that branch of to causes a contraction of the muscle fibres, these impulses are then caught by another group of cells which for the atrio ventricular node (SV Node) and is relayed to a band of conducting tissue, are of large modified muscle cells call the Purkinje fibres.
The transmission of impulses is delayed slightly in the AV Node to enable the atria to complete contraction and the atrio ventricular valves to start to close. Heart valves are located on a fibrous figure of eight between the atrial and ventricular muscle masses and the first part of the conducting...