Tag: circulation of blood

Smaller organisms have a higher surface-area-to-volume ratio, leading to faster heat loss and higher metabolic rates. The heart rate comparison is a valid physiological example of this trend.

This sequential event in the heart which is cyclically repeated is called the cardiac cycle. Each cardiac cycle consists of systole and diastole of both the atria and ventricles. Each cardiac cycle represents one heartbeat. The normal heart rate is about 72 beats per minute. The heart rate is same as pulse rate because the pumping action of the heart causes an increase in blood pressure in arteries that leads to noticeable pulse. Hence the pulse rate per minute describes the heartbeat.

The entire heart is made of cardiac muscles. A specialized cardiac musculature called the nodal tissue is also distributed in the heart i.e sino-atrial node (SAN- A patch of this tissue is present in the right upper corner of the right atrium )and atrioventricular node (AVN- mass of this tissue is seen in the lower left corner of the right atrium close to the atrioventricular septum). The nodal musculature has the ability to generate action potentials without any external stimuli, i.e., it is autoexcitable. Hence, the rhythmic beating of the heart is due to the action of muscles in the atria and ventricle.

Pulse pressure is defined as the difference between the systolic blood pressure and the diastolic blood pressure.

Atrial natriuretic factor (ANF) is a hormone secreted by the atrial cells of the heart in response to high blood pressure to help lower it.

• Human heart is a four chambered structure where t he upper 2 chambers are the atria and the lower 2 chambers are the ventricle.
• Atria are the chambers of the heart that receive the blood from various organs of the body. Right atria receives deoxygenated blood from the body organs other than lungs through the vena cana, where as the left atria receives blood that is oxygenated from the lungs via pulmonary vein.
• The blood from both the atria is to be transferred to the respective ventricles and for that the valves that guard the atrio ventricular opening should be opened and closed after the blood is transferred from one chamber to the other so as to prevent the backward flow of the blood.
• For this opening and closing of the valve and also for the systole and dystole movement of the chambers stimulus is required which is provided by the sino atrial node that is present at the upper right corner of the right atria.
• This node generates the action potential which travels from the SA node to the atrio ventricular node that is AV node which is present at the lower left corner if the right atria. From the AV node the potential travels along the Purkenej fibers in the wall of atrio ventricular septum and the potential then spreads to the cardiac muscle of the heart.
• Therefore the whole functioning of the heart is dependent upon the action potential that is generated from the SA node in the atria.
• Therefore the answer 'Action mentioned in Statement 1 is dependent on action mentioned in Statement 2' is correct.
  

The numeric difference between systolic and diastolic blood pressure is called pulse pressure. For example, if the resting blood pressure is 120/80 millimeters of mercury (mm Hg), pulse pressure is 40 which is considered a normal and healthy pulse pressure.

There are four heart sounds, each corresponding to a particular event in the cardiac cycle. The first two are most easily distinguished, and sound through the stethoscope like 'lubb dup'. The first sound, 'lubb', is fairly loud and is due to the closure of the atrioventricular valves. This closure corresponds with the start of the Ventricular systole.