Hint: Mammals have 4 chambered hearts and perform double circulation in which oxygenated and deoxygenated blood does not mix up. The SA node is present in the right atrium and is known as the pacemaker. The SA node is responsible for maintaining the heartbeat and pulse rate.
Complete answer: Mammals have a myogenic heart which contracts and relax rhythmically and regulates blood flow. Also, the mammalian heart is four-chambered consisting of two atria and two ventricles. Right atrium has a sinoatrial node or SA node which is also known as the pacemaker of the heart as it generates contraction of the heart and also regulates the heartbeat. The impulse of contraction of the heart begins in the heart itself, as a result, the mammalian heart is called myogenic. It doesn’t need any external stimulus for contraction.
The neurogenic heart is present in lower invertebrates. In this type of heart, the heartbeat is regulated by the ganglion present in the heart. Unlike myogenic heart, the neurogenic heart is not under muscular control. The neurogenic heart is present in annelids, crustaceans, etc.
Hence, the correct answer is option B.
Additional information: Heart of mammals is four-chambered and is located in the thoracic cavity. The SA node is present in the right atrium. It triggers the contraction of the atrium and deoxygenated blood flows from the right atrium to ventricles and from ventricles to the lungs where the blood is oxygenated. Oxygenated blood from the lungs is transported to the left atrium and then to the left ventricle. From the ventricle, blood is transported to body parts.
Note: In myogenic heart, the impulse of contraction is generated by sinoatrial nodes present in the heart itself and in the neurogenic heart, an impulse is generated by nerves present in the heart. Hence, the myogenic heart is under muscular control and neurogenic heart is under neural control.
