Tag: heart, blood vessels and cardiac cycle

All vertebrates possess a muscular chambered heart. Fishes have a 2-chambered heart with an atrium and a ventricle. In fishes, the blood transports nutrients when the heart pumps blood throughout the body. Animals like hydra and sponges do not possess any circulatory system. The water in which they live brings food and nutrients as it enters their body. The water carries waste materials and carbon dioxide as it moves out. Hence In animals like hydra and sponges, there is no blood for transport of nutrients.

• The amount of blood pumped by the heart per minute is called the cardiac output.
• The heart of a normal person beats 72 times per minute. This is called the heart rate. During each and every heartbeat, the ventricles pump about 70 ml of blood.
• This is known as stroke volume. This means heart pumps 72 x 70 ml = 5040 ml or approximately 5 liters of blood per minute.
  
  Thus the correct answer is option C.

The pulse rate is the number of times one can feel a pulse in one minute. The radial artery is present on the thumb side of the wrist. To measure the pulse rate place two fingers between the bone and the tendon over your radial artery. Count the number of beats in 15 seconds, multiply this with four you will get the pulse rate. Therefore The pulse rate can be determined from the arteries.

• This sequential event in the heart that 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 number of heartbeats per minute in resting person is called a normal heart rate. 
• The normal heart rate is about 72 beats per minute. Hence the unit of measurement of the heartbeat is Beats per minute.

• Lubb is the first sound which has a low pitch and produced by the closure of tricuspid and bicuspid valves (collectively called atrioventricular valves) at the beginning of ventricular systole.
• Dup is the second sound which is sharp and has a high pitch. It is produced by closure of semilunar valves by the end of ventricular systole.

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. Hence pulse rate can be measured in the arteries of the neck and arteries of the wrist.

The heart is located in the mediastinum, but the apex of the heart, which is formed by the left ventricle, is directed toward the left side of the chest, making the heartbeat more audible there.

The sympathetic nervous system is responsible for the fight or flight response. This response includes increasing the heart rate to prepare the body for physical activity.

Adrenaline (epinephrine) is the primary hormone released during stress that stimulates the heart to beat faster and with more force. Thyroxine also affects heart rate, but adrenaline is the classic stimulator for immediate heart rate increases.