Anatomy & Physiology
P5, M2 & D2: Explain the concept of homeostasis and discuss the probable homeostatic responses to changes in the internal environment during exercise
In this assignment the concept of homeostasis will be explained and the probable homeostatic responses to changes in the internal environment during exercise will be discussed. Homeostasis is simply how the body keeps conditions inside the same. It is described as the maintenance of a constant internal environment. Generally, the body is in homeostasis when its needs are met and it’s functioning properly. Every organ in the body contributes to homeostasis. A complex set of chemical, thermal, and neural factors interact in complex ways, both helping the body while it works to maintain homeostasis. In homeostasis there is the concept of Negative feedback which ensures that, in any control system, changes are reversed and returned back to the set level. There are four different homeostatic mechanisms for regulation these four are the heart rate, breathing rate, body temperature and blood glucose levels. Negative feedback system is made out of 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. (Anatomy & Physiology, 2013) The autonomic nervous system controls the heart and has two branches; the sympathetic nervous system and the parasympathetic nervous system. When the body is undergoing muscular work, fear or stress the sympathetic nervous system will be active. When the sympathetic nervous system is active it will cause every heartbeat to increase in strength and heart rate. During resting, peace and contentment the parasympathetic nervous system is active and it calms the heart output. During periods of fright, flight and fight the sympathetic nervous system is boosted by the hormone; adrenaline. The nerves of the adrenaline are the cardiac nerves. A special cluster of excitable cells are supplied by the sympathetic and parasympathetic nervous system in the upper part of the right atrium. We call this ‘the peacemaker’ in general terms. A connection of impulses from the sympathetic and parasympathetic nerves acting on the sino-atrial (‘the pacemaker’) regulates the activity of the heart to suit situations from minute to minute, hour to hour and day to day. The sino-atrial node sends out a cluster of nerve impulses every few seconds around the branching network of atrial muscle fibres to cause contraction. The impulses are caught by a different group of cells forming the atrioventricular node and relayed to a band of leading tissue made of big, modified muscle cells called Purkinje fibres. In the atrioventricular node the transmission of impulses is delayed slightly to enable the atria to complete their contractions and the atrioventricular valves to start to close. The location of heart valves is on a fibrous figure-of-eight between the atrial and ventricular muscle masses.(Aldworth and Billingham, 2010) The lowest part of the brain is the medulla and is located above the spinal cord and is often known as the ‘brain stem’. The two important centres for control of the heart rate are located in the brain stem. These are called the cardiac centres. The sympathetic fibres descend through the spinal cord from the vasomotor centre while the cardio-inhibitory centre is in charge of the origins of the parasympathetic fibres of the vagus nerve reaching the sino-atrial node. (Aldworth and Billingham, 2010) Baroreceptors are found in the walls of the aorta and they detect changes in blood pressure. If in the arteries a small upward change in blood pressure happens it often indicates that extra blood has been pumped out by the ventricles as result of the extra blood that enters the heart on the venous or right side. When the baroreceptors detect the change they relay the information in nerve impulses to the cardiac...
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