Cardiovascular and Nervous System

Autorhythmicity is a property of electrically active cells, that show rhythmic activity without being driven by the rhythmic external stimulation, e.g., heart muscle cells or neurons.
Thus, the correct answer is option (C), 'Heart'.

The central nervous system includes brain and spinal cord. It integrates and stores the sensory information from external and internal sense organs and commands different organs to respond accordingly. This makes option A incorrect. Peripheral nervous system lies outside the central nervous system. It serves to carry the sensory information from external sensory receptors to CNS and motor signals from CNS to skeletal muscles via its somatic division (the voluntary actions). The autonomous division of peripheral nervous system controls the cardiac and smooth muscles and glands, thereby the functioning of internal organs, without our conscious control (the involuntary actions). This makes option B incorrect and option C correct. The 12 pairs of cranial nerves are part of peripheral nervous system and are mostly concerned with head, neck and facial region of the body (vagus nerve X being the part of autonomous division serves as an exception). Option D is incorrect.  Correct answer is C. 

The parasympathetic nervous system is responsible for the rest and digest response, which includes slowing down the heart rate.

The sympathetic nervous system prepares the body for stress by increasing heart rate. It typically inhibits digestive secretions like saliva.

The sympathetic nervous system mediates the fight or flight response, which causes physiological changes like increased heart rate and dry mouth during stressful situations like watching a horror movie.

The autonomous nervous system control the heart beat rate via cardio regulatory centre in medulla oblongata. The emergency conditions activate the sympathetic motor nerve and make the adrenal medulla to release epinephrine and nor-epinephrine which in turn increase the heart beat rate.  Thus, the correct answer is C. The central nervous system (Central NS) includes brain and spinal cord. It integrates and stores the sensory information from external and internal sense organs and commands different organs to respond accordingly. Peripheral nervous system (PNS) lies outside the central nervous system and is further divided into somatic and autonomic nervous system. It serves to carry the sensory information from external sensory receptors to CNS and motor signals from CNS to skeletal muscles via its somatic division (the voluntary actions). The autonomic division of peripheral nervous system controls the cardiac and smooth muscles and glands, thereby the functioning of internal organs, without our conscious control (the involuntary actions). On the other hand, vagus nerve conducts the parasympathetic motor impulses which in turn slow down the hearth beat rate by effect of acetylcholine; a neurotransmitter released by parasympathetic nervous system. 

The semilunar valves are present inbetween the aorta and the left ventricle (aortic semilunar valve) and between the right ventricle and the pulmonary artery (pulmonary semilunar valve). The aortic semilunar valve functions to pevent backflow of blood into the ventricle. Damage to chordae tendinae of the aortic semilunar valve will therefore cause backflow of blood to the left ventricle. The first heart sound is produced by the closure of the mitral and the tricuspid valve, that are the atrioventricular valves. 

Hypertension is caused due to an elevation in the pressure applied during the blood flow in the blood vessels. Blood pressure is expressed by two measurements, the systolic and diastolic pressures, which are the maximum and minimum pressures, respectively, in the arterial system. The systolic pressure occurs when the left ventricle is most contracted, the diastolic pressure occurs when the left ventricle is most relaxed prior to the next contraction. Normal blood pressure at rest is within the range of 100–140 millimeters mercury (mmHg) systolic and 60–90 mmHg diastolic. Hypertension is present if the blood pressure is persistently at or above 140/90 mmHg for most adults. 

S.A node called as pacemaker ,node of keith and  flack heart , brain of heart ,pulsation centre. 

When irregularity in the heart rhythm occurs, normal heart rhythm can be reared and maintained by surgically implanting an artificial pace maker, a device that sends out small electrical current to stimulate the heart to contract.

Congenital heart disease refers to the problem in the structure of the heart that is present at birth. It can be related to the wall of the heart, the valves of the heart and the arteries and veins associated with the heart. Patent Foramen Ovale is the example of congenital heart disease in which the septal wall between the right and the left atrium is not formed.

The events of a heart attack can be put in a sequence of I, IV, II, III.

A heart attack occurs when one of the heart's coronary arteries is blocked suddenly or has extremely slow blood flow. A heart attack also is called a myocardial infarction. The usual cause of sudden blockage in a coronary artery is the formation of a blood clot.

Angina pectoris - It is the sensation of chest pain as a result of myocardial ischemia, caused by an imbalance between myocardial blood supply and oxygen demand. It is a common symptom among patients with coronary artery disease (CAD).
Myocardial infarction - commonly known as a heart attack, occurs when blood stops flowing properly to a part of the heart, and the heart muscle is injured because it is not receiving enough oxygen. Usually, this is because one of the coronary arteries that supplies blood to the heart develops a blockage due to an unstable buildup of white blood cells, cholesterol and fat.
Cardiomegaly - is a medical condition, which refers to the enlargement of heart.