The Normal Control of Heart Rate - Essay Example

The heart is a specialized organ developed to control the blood flow of the whole body. It is known as the pumping organ of the body as it has the capability to pump blood to all the vital organs and tissues in the body. And thus to fulfill the heart of its function has the capability to generate its own impulses which further maintain or control the heart rate. This heart rate is maintained at a steady rate of seventy-two beats per minute. However, it is not necessary that heart rate is maintained at this steady rate in all conditions. This rate may not be effective enough when the person is requiring a huge amount of blood in the body. Thus it is vital for the heart to alter its rate as per the conditions.
It is very important for the heart to alter its rate because this steady rate pumps only a specific amount of blood in the resting state. But this blood would not be enough when the person is exercising or going through any other trauma of blood loss. This trauma or hypoxia would result in increased demands of blood to the tissues and hence it is necessary for the heart to reply in the same manner so as to satisfy the needs of the body. Thus homeostasis is playing important role in controlling the heart which is essential for the survival of life. Because of this homeostasis, the internal environment of the body is continuously maintained.
The heart is a complex organ whose rate is maintained by a set of physiological processes. It has a self excitatory node that normally passes the impulses in the heart to help it maintain a normal rate. Normally it is the sinoatrial node that develops such impulses in the heart. And in developing such impulses the sa node has its own resting membrane potential which is about sixty mV. But this node also has leaky sodium channels which allow the influx of sodium ions and help it to reach a threshold level of 40mV where the calcium channels open and create an action potential. The heart is contracted and relaxed due to the spread of action potential in the heart. the action potential in the heart is created by the sinus node present in the right atrium of the human heart. The depolarization wave produced by the sinus node enters the atrial muscle fibres and the atria contract. Also, the wave is carried through internodal pathways to the atrioventricular node which transmits it to the ventricles after a delay. After passing through the A-V node, the impulse is transmitted by Purkinje fibres to the left and right ventricles which make them contract. And following this repolarization occurs in the ventricles which helps them to relax. All these events in heart take place in a proper manner. The atrial systole occurs when the pressure changes develop in between the atria and the ventricles. The pressure in the atria should be greater than that of the ventricles so that blood can be moved from the area of higher pressure to lower pressure. Following this, the filling of the ventricle occurs which is completed in three phases. During the first phase of filling the stored blood of the atria is passed into the ventricles whereas during the second phase the blood of the veins directly enters the ventricles through the atria. This phase is also known as diapedesis. And lastly, the atria contract themselves to release the left blood into the ventricles. This filling of ventricles is then followed by ventricular systole. However ventricular systole takes longer than the atrial systole as it has to build a high pressure of blood inside so that the blood can be passed into the arteries. Because of this systole, the ventricles are able to pump blood into the arteries. Following this, the ventricular diastole occurs during which the ventricles relax. After this relaxation, the phase of the filling of ventricles can begin once again. Moreover, the heart rate is maintained by two complex systems known as the sympathetic and parasympathetic systems respectively. Sympathetic helps to increase the heart rate in times the body is in need of more blood whereas parasympathetic has an opposite action in which it decreases the heart rate of the heart rate in response to a stimulus. The sympathetic nervous system helps by working in cooperation with epinephrine and norepinephrine. Parasympathetic on the other hand works in cooperation with the vagus nerves by secreting acetylcholine.
Measuring pulse is an important way in the world nowadays to determine the normal functioning of the heart. In measuring the pulse several measures can be used which involve the usage of the new scientific methods. The patient would first be told as to how the pulse is measured. He would be told that the way his heart functions can be calculated with the help of his pulse. There are several sites for measuring the pulse but the most common site for measuring pulse is the radial artery. Read More