Test: Circulatory System - 2 - NEET MCQ

The arteries are superficial at some points in the body. In these places, the heart beat is felt as pulses like the radial, brachial pulse.

pH is a measure of the amount of hydrogen ion present in a solution. Thus, a high level of H+ is a low pH (or an acid environment) while a low level of H+ is a high pH (or an alkali or basic environment).

Veins have a slightly lower pH than arteries. This is because the blood circulates through working tissues in our bodies, and drops off oxygen, and picks up carbon dioxide.

Carbon dioxide in water forms a weak acid. In arteries, they carry oxygenated blood, and less carbon dioxide, so the pH is more.

In veins, there is less oxygen and more carbon dioxide which is acidic so the blood in veins has less pH.
So, the correct answer is option B.

Normal blood pressure is below 120/80 mm Hg. If you're an adult and your systolic pressure is 120 to 129, and your diastolic pressure is less than 80, you have elevated blood pressure. High blood pressure is a systolic pressure of 130 or higher,or a diastolic pressure of 80 or higher, that stays high over time.

• The ventricular pressure decreases during the ventricular diastole or when the ventricles relax.
• The tricuspid and bicuspid valves open to allow blood to flow from the atria to the ventricles.

Deoxygenated blood from the upper part of the body returns to the right atrium (RA) via the superior vena cava. On the other hand, deoxygenated blood from the lower portion of the body returns to the RA via the inferior vena cava.

When the RA is full, it contracts which builds up the pressure and opens the tricuspid valve. Blood transfers from the RA into the right ventricle (RV). When the RV is filled, the walls of the ventricle begin to contract and the pressure within the RV rises. The increased pressure closes the tricuspid valve and blood is pumped into the pulmonary artery through the pulmonic valve.

So, the correct answer is option C.

The most important artery running up the side of your neck is called the common carotid artery. It splits into two branches. One of the branches is called the external carotid artery, which supplies your neck and face with oxygenated blood. The other branch of the common carotid artery, which supplies the brain with oxygenated blood, is the internal carotid artery. The internal carotid artery, again, is a branch of the common carotid artery that supplies the brain with oxygenated blood. Each side of your body, more specifically, each side of your neck and head, has one internal carotid artery supplying blood to the brain.

The spleen is the largest lymphatic organ in the body and is positioned in the superior abdomen. The spleen plays important roles in regard to red blood cells and the immune system. It removes old red blood cells and holds a reserve of blood, which can be valuable in case of hemorrhagic shock, blood loss and also recycles iron. It purifies the blood and helps the immune system to recognize and attack foreign antibodies and disease. The spleen is composed of the red and white pulp. The white pulp produces and grows immune cell as well as blood cells. On the other hand, the red pulp is responsible for purifying the blood and removing dead or old blood cells. The spleen has important hematopoietic functions, until the fifth month of gestation. After birth, erythropoietic functions cease, except in some hematologic disorders. As a major lymphoid organ, the spleen retains the ability to produce lymphocytes and, as such, remains an hematopoietic organ.

So, the correct answer is option D.

• We know that the heart beats 70-75 times per minute. It beats approximately 72 times per minute.
• Hence, 72 cardiac cycles take place in one minute.
• Therefore, the duration of one cardiac cycle is 0.8 seconds.

• 72 cardiac cycles take place in one minute.
• The duration of one cardiac cycle is 0.8 seconds.
• During each cardiac cycle, each of the two ventricles pump 70 ml of blood, which is known as the stroke volume.

• Cardiac output is the product of the stroke volume and the heart rate.
• It is the total amount of blood pumped by each ventricle per minute.
• The average cardiac output of a healthy adult is 5000ml.

The first heart sound has slightly greater intensity than the second heart sound. The first heart sound is produced by the closing of the mitral and tricuspid valve leaflets. The second heart sound is produced by the closing of the aortic and pulmonic valve leaflets. The first heart sound, or S₁, forms the "lub" of "lub-dub" and is composed of components M₁ (mitral valve closure) and T₁ (tricuspid valve closure). It is caused by the closure of the atrioventricular valves, i.e. tricuspid and mitral (bicuspid), at the beginning of ventricular contraction, or systole.

• The average cardiac output of a healthy adult is 5000ml or 5 liters.
• This means that if the heart rate is 72 beats per minute and the stroke volume is 70ml, then around 5000ml of blood is pumped by each ventricle in one minute.

The P-wave represents the electrical excitation of depolarisation of the atria which leads to the contraction of both the atria. The T-wave represents the repolarisation of the ventricles.

Purkinje fibres conduct impulse from the AV node to the ventricles. They are situated on the lateral ventricular walls. It allows the heart's conduction system to create synchronized contractions of its ventricles, and are, therefore, essential for maintaining a consistent heart rhythm.

Renal vein contains the least amount of urea. The renal artery enters the kidney as afferent arteriole. It carries the urea loaded blood into the glomerulus of the kidney.

Systemic circulation is the flow of blood from left ventricle of heart to all body parts and return of blood from all body parts to the right auricle. The pathway of systemic circulation can be summarised as:
Pulmonary vein brings oxygenated blood from lungs to the left auricle.
From the left auricle blood passes to left ventricle through bicuspid valve.
From the left ventricle, blood is pumped into aorta.
Aorta divides into many arteries and supply blood to body tissues.
The oxygen in blood is utilised by tissues and deoxygenated blood is collected by veins.
The vena cava brings this deoxygenated blood into the right atrium from where it passes to right ventricle through tricuspid valve.
From the right ventricle, deoxygenated blood is carried to lungs by the pulmonary artery where it is gets oxygenated and returns to left auricle through pulmonary vein.
Hence, in this way, the cycle starts again.

Myogenic contraction refers to a contraction initiated by the myocyte cell itself.

In vertebrates, normal activities of the heart are regulated intrinsically, i.e., auto regulated by specialised muscles (nodal tissue). Hence, the heart is called as myogenic. 

Heart is neurogenic in arthropods.

• The QRS complex represents the depolarisation of the ventricles, which initiate the ventricular contraction.
• The contraction starts shortly after Q and marks the beginning of the systole.

All vertebrates possess a muscular chambered heart. Fishes have a 2-chambered heart with an atrium and a ventricle. 

Amphibians and the reptiles (except crocodiles) have a 3-chambered heart with two atria and a single ventricle, whereas crocodiles, birds and mammals possess a 4-chambered heart with two atria and two ventricles. 

In fishes, the heart pumps out deoxygenated blood, which is oxygenated by the gills and supplied to the body parts from where deoxygenated blood is returned to the heart (single circulation).

Phylum Arthropoda and Mollusca include open circulatory system . Fish is member of phylum Chordata which contain close circulatory system.
Cockroach and scorpion are members of class inscecta phylum Arthropoda.

Angina pectoris is the medical term for chest pain or discomfort due to coronary heart disease. It occurs when the heart muscle doesn't get as much blood as it needs. This usually happens because one or more of the heart's arteries is narrowed or blocked, also called ischemia.

• By counting the number of QRS complexes that occur in a given period, one can determine the heartbeat rate of an individual.
• Any deviation from the shapes of the curve indicates a possible abnormality or a disease.
• Hence, it is of great clinical significance.

Enlargement of auricles is represented by the enlargement of P-wave or sometimes the lengthening of PQ interval also represents the enlargement of auricles by rheumatic fever.

When the heart is not pumping sufficient blood according to the needs of the body organs then it leads to heart failure. Lung congestion is the main symptom of heart failure.

CAD refers to coronary artery disease which is caused by atherosclerosis and arteriosclerosis. Atherosclerosis refers to the deposition of cholesterol, fat, calcium on the walls of coronary arteries while arteriosclerosis refers to the deposition of calcium which leads to the hardening of the arteries.