BIOLOGY 2 Marks Questions

Heart is called myogenic because all the normal activities of the heart are regulated intrinsically or the activities are auto regulated by specialised muscles known as nodal tissues without the need for an external stimulus to be delivered by the nervous system.

Two prominent sounds are produced during each cardiac cycle. The first heart sound (lub) is associated with the closure of the tricuspid and bicuspid valves whereas the second heart sound (dub) is associated with the closure of the semilunar valves. These sounds are of clinical diagnostic significance.

Hepatic portal vein is the unique vascular connection between digestive tract and the liver. Significance: It brings blood from intestine to the liver, before it is delivered to the systemic circulation due to which the liver gets its nutrients.

S. No	Auricles	ventricles
(a)	They are the receiving chambers.	They are the pumping chambers.
(b)	They are thin-walled.	They are thick-walled.
(c)	Their systole always precedes ventricular systole.	Their systole always follows auricular systole.

1. Bone marrow.
2. Sinoatrial node (SA node).
3. Reptiles have three-chambered heart except crocodile, which has four chambered heart.

During one cardiac cycle or one heart beat the volume of blood pumped by the heart is called stroke volume. This is normally 70mL. In one minute the heart beats about 72 times and the amount of blood pumped per minute is called cardiac output. This is usually 4900ml - 5 litres.

In electrocardiography, P-Q interval (also called PR interval) is the time taken by the impulse to travel through atria, AV node and the rest of the conducting tissues. The normal PR interval lasts for about 0.16s. The ST interval is the representation of time between the end of the spread of impulse through ventricles and its repolarisation.

Fig.: Diagrammatic representation of standard ECG.

S.No.	column I	S.No.	column II
(A)	SA node	(ii)	Right auricle
(B)	Right AV aperture	(iii)	Tricuspid valve
(C)	Interstitial	(iv)	Intercellular spaces
(D)	Single circulation	(i)	Fishes

When the blood supply to myocardium of the heart is greatly reduced, then the cardiac muscle fibres die. This reduced blood supply can be due to the blockage of the coronary muscles by the thrombus (blood clot formed in the coronary artery).

• Sympathetic nerves increase the rate of heart beat, the strength of ventricular contraction and thereby the cardiac output.
• Parasympathetic neural signals decrease the rate of heart beat, speed of conduction of action potential and thereby the cardiac output.

2. We should work tirelessly to attain our goal.

Explanation:
We should avoid taking oily food and should also avoid taking too much of carbohydrate in our diet. Excess fat in the diet changes into harmful cholesterol. Even excess carbohydrate is changed into fat and stored in the body. Excess fat in the body changes into cholesterol. Cholesterol gets deposited in arteries and clogs them. This results in increased workload on the heart and manifests as different diseases of the heart. We should take lot of fruits and green vegetables in our food. We should develop a habit of eating light.

Individuals with blood group O are called universal donors. These individuals do not have either A or B antigens on the surface of their RBCs, but their blood serum contains antibodies against both A and B antigens. Therefore, group individuals can only receive blood from a group O individual, but they can donate blood to individuals of any ABO blood group (i.e., A, B, O or AB).

At the start of the ventricular systole, the mitral valve closes to prevent the flow of blood back into the atrium. As systole continues, blood from the right ventricle enters the pulmonary artery and blood from the left ventricle enters the aorta.

Anemia: It is due to the less amount, of haemoglobin. It may be caused by loss of blood (haemorrhage), destruction of RBCs (haemolysis or faulty formation of blood).

If a patient's ECG reveals an abnormally long delay between P-wave and the QRS deflection, it suggests that there is a delay of conduction from the atria to the ventricles. Hence, the stimulation from SA nodes are conducting stimuli to the ventricles very slowly.

The tricuspid valves are present between right atrium and ventricle. Bicuspid valves are present between the wall of left atrium and left ventricle. The semilunar valves are present in the inner wall of aorta.

S. No	Blood Group	Antigens on RBCs	Antibodies in Plasma	Donor's Group
(a)	A	A	Anti- B	A, O
(b)	B	B	Anti- A	B, O
(c)	AB	A, B	NIL	AB, A, B, O
(d)	O	NIL	Anti- A, B	O

Differentiate between basophils and eosinophils are as follows.

Basophils	Eosinophils
These possess 3 lobed nucleus, with less number of coarse granules. These take basic stain. These are normally 0-1% is the blood.	These possess bilobed nucleus and coarse granules in cytoplasm These take acidic stain These are 1-6% is the blood.

• The volume of blood pumped by each ventricle during one cardiac cycle, is known as stroke volume.
• It is about 70ml.

The closed circulatory system considerably enhances the speed, precision and efficiency of circulation. The blood flows far more rapidly, it takes less time to circulate through the closed system and return to the heart. This fastens the supply and removal of materials to and from the tissues by the blood.

We can hear with a stethoscope, the two main heart sounds (i.e., lubb and dupp), which repeat rhythmically. These sounds result from the closure of the heart valves. The first sound (lubb), which is of longer duration (0.16-0.90s) and a louder one is created by the closure of the atrioventricular valves immediately after the start of the ventricular systole. The second sound is of shorter duration (0.10s) and is created by the closure of the semilunar valve at the end of the ventricular systole.

Causes of high blood pressure are as follows:

1. A diet full of oily and greasy products, increase cholesterol level, which can cause thickening of the arteries due to which BP may rise.
2. Tobacco smoking also speeds up the heart rate and contracts blood vessels.
3. Mental tension is also one of the main causes of hypertension.

The oxygenated blood entering the aorta is carried by a network of arteries, arterioles and capillaries to the tissues from where the deoxygenated blood is collected by a system of venules, veins and vena cava and emptied into the right atrium. This is the systemic circulation. The systemic circulation provides nutrients, O, and other essential substances to the tissues and takes co, and other harmful substances away for elimination.

S. No	Column I	S. No	Column II
(a)	Basophils	3.	0.5-1.0%
(b)	Lymphocytes	4.	20-25%
(c)	Neutrophils	2.	60-65%
(d)	Monocytes	1.	6-8%

Reptiles have 3-chambered heart (2 atria and 1 ventricle) with exception of crocodiles, which have four chambered heart (2 atria and 2 ventricles) like birds and mammals which does not allow mixing of oxygenated and deoxygenated blood due to the presence of inter atrial and inter ventricular septum between atria and ventricles respectively.

Differences:

S. No	Monocytes	Eosinophils
(a)	They are agranulocytes.	They are granulocytes.
(b)	They are phagocytic.	They are not phagocytic.
(c)	They destroy the foreign microbes by phagocytosing them.	They are involved in allergic reactions and also resist infections.
(d)	They constitute about 6-8 percent of leucocytes.	They constitute about 2-3 percent of leucocytes.

1. Arteries do not have valves, but the veins are provided with valves all along their length.
2. Arteries (except pulmonary artery) carry oxygenated blood from the heart and veins (except pulmonary vein) carry deoxygenated blood towards the heart.

• The single atrium receives deoxygenated blood from all parts of the body.
• It is pumped into the ventricle from where it is pumped to the gills for oxygenation. The oxygenated blood flows from the gills to various parts.

• B-lymphocytes and T-lymphocytes.
• B-lymphocytes produce antibodies and provide humoral immunity.
• T-lymphocytes provide cell-mediated immunity.

S. No	Column I	S. No	Column II
(a)	Neutrophils	3.	Phagocytosis.
(b)	Erythrocytes	4.	Transport of oxygen.
(c)	Basophils	2.	Inflammatory reactions.
(d)	Eosinophils	1.	Allergic reactions.

Differentiate between blood and lymph are as follows.

Blood	Lymph
Blood is a connective tissue which has erythrocytes leucocytes and platelet present in fluid called plasma. It-flows in all blood vessels.	Lymph is also a connective tissue which, is devoid of RBC but has large number of WBC (leucocytes) in plasma. It flows only in lymphatic system and is also found extracelluarly inside the tissue.

Angina pectoris: It is also called angina. It causes chest pain. In this disease enough oxygen does not reach the heart muscles and the patient experiences heart pain usually in front of the chest. It is more common among the middle aged and elderly people.

Heart Attack	Heart Failure
It is the condition where the heart muscle is suddenly damaged due to inadequate blood supply.	It is the condition heart is not pumping effectively enough blood to meet the needs of the body.

• Bicuspid valve guards the opening in the atrio ventricular septum between the left atrium and left ventricle.
• Tricuspid valve guards the opening in the atrio ventricular septum between the right atrium and right ventricle.

Differences between sinoatrial node and atrio-ventricular node are:

	Sinoatrial node	Atrioventricular node
(i)	It is present in the right atrium near the opening of superior vena cava.	It is also present in the right atrium but near the base of the inter atrial septum.
(ii)	It is called pacemaker.	It is called pacesetter.
(iii)	Impulse of cantraction is intiated and activated by SA node.	Impulse initated by SA node is transmitted to all parts of ventricles by AV node.
(iv)	It is regulated by the cardiac centres present in the medulla oblongata of the brain.	It is stimulated by cardiac impulses originated in the SA node.

Differentiate between tricuspid valve and bicuspid valve are as follows.

Tricuspid Valve	Bicuspid Valve
This valve separates the right atria from right ventricle. It is made of 3 cusps or flaps. This is also known as right atrio ventricular valve.	This valve separates the left atria from left ventricle. It has 2 cups or flaps. This is also called mitral valve or left atrio ventricular valve.

His WBC count may show an increase from the normal range. As pathogens may be present in his body so the body is producing more WBCs to fight against those pathogens. WBC count is a good tool to asses presence of infection in a sick person.

Phases of blood pressure are:

1. Systolic blood pressure: It is seen during the contraction of left ventricle.
2. Diastolic blood pressure: It is seen during the relaxation of left ventricle.

The time gap in the passage of action potential from sinoatrial node to the ventricles allows ventricles to relax. The ventricular pressure falls, causing the closure of semilunar valves, this prevents the back flow of blood into the ventricles.

1.  

• RBCs have an average life span of 120 days.
• Spleen is their graveyard.

2. Their main function is transport of respiratory gases, i.e. oxygen and carbon dioxide.

Incomplete double circulation is the phenomenon in which the atria of the heart of an animal receives oxygenated blood and deoxygenated blood separately, but the two get mixed up in the ventricle, which pumps out the mixed blood. e.g., Amphibians and reptiles except crocodile.

• Neutrophils and monocytes are phagocytic and protect the body from infections.
• Basophils are involved in inflammatory reactions.
• Eosinophils resist infections and are associated with allergic reactions.
• Lymphocytes are responsible for the immune response.

Heart Failure	Cardiac Arrest
It is the sate of the heart, when it is not pumping effectively enough blood to meet the needs of the body.	It is the state, when the heart stops beating completely death ensues.

Open and closed system of circulation.

	Open system	closed system
(i)	In this system, blood is pumped by the heart, through large vessels, into body cavities called sinuses.	In this system, blood is pumped by the heart, throuth a closed netwoek of vessels.
(ii)	The body tissues are in direct contact with blood.	The body tissues are in indirect contact with blood.
(iii)	Blood flows at low pressure.	Blood flows at high pressure.
(iv)	Blood flow cannot be regulated.	Blood flow can be regulated.
(v)	This is present in arthroponds and molluscs.	This is present in annelids, echinoderms, and vertebrates.

• Interstitial fluid is the fluid (water along with many substances dissolved in it) that comes out of the blood capillaries as the blood flows through them.
• Exchange of materials like nutrients respiratory gases, etc. between the blood and the tissues occurs through this fluid only.

• During joint diastole, blood enters the right atrium through superior and inferior vena cavae; blood also enters the left atrium through pulmonary veins.
• 70% of the blood enters the ventricles from the respective atria, through the open atrio-ventricular valves.
• The semilunar valves are closed during the joint diastole.

The Heart is divided into four chambers namely two upper Atria and two lower Ventricle. The atria have comparatively thinner walls than the ventricles because atria only receive blood from the upper parts of the body, i.e., head, etc. and the ventricles have to pump the blood to the farthermost parts of the body, for example, the toes to up to head, i.e., against gravity.

S. No	Neutrophils	Lymphocytes
(a)	They are granulocytes.	They are agranulocytes.
(b)	They constitute about 60-65 percent of leucocytes.	They constitute about 20-25 percent of leucocytes.
(c)	They are phagocytic.	They are not phagocytic.
(d)	They destroy the foreign organisms/ antigens entering the body.	They are responsible for the immune response of the body.