Question

Question 1: The pulse wave is created by:

A. the electrical singals of the heart

B. The contraction of the arteries

C. The contraction of the left ventricle

D. The contraction of the bronchioles

Question 2: If the arteries are vasodilated, then the pulse amplitude will be:

a. faster

b. slower

c. higher

d. lower

question 3. venous return of the heart occurs due to pressure created by:

a.respiratory pump only

b. skeletal muscle pump only

c. contraction of the heart

d. skeletal muscle pump and respiratory pump

question 4. A decrease in blood pressure will cause:

a. an increase in the parasympathetic system

b. vascoconstriction

c. vasodilation

d. decreased heart rate

Answer 1

Question 1

The pulse wave is created by:

Answer: C) the contraction of the left ventricle.

Explanation: Pulse wave is created by sudden increase in the blood pressure due to contraction of the left ventricle which pumps the blood into the systemic circulation i.e. the aorta and other systemic arteries. This wave is propagated along the entire arterial system hence a pulse can be measured at different arterial sites in the body. Pulse is used to measure the heart rate and other features of cardiovascular system. It is between the range of 60-100 per minute which is equal to the normal heart rate.

Pulse can be palpated over those systemic arteries which are easily accessible and superficial and close to a body surface. Most commonly used artery to measure the pulse is radial artery at the wrist. Other arteries which can be used to measure the pulse are carotid artery at neck, popliteal artery at kneee, brachial artery at arm, dorsalis pedis artery at foot.

Question 2

If the arteries are vasodilated then the pulse amplitude will be:

Answer: c) higher

Explanation: The degree of expansion of an artery while palpating the pulse is known as the amplitude or volume of the pulse wave. It signifies the pulse pressure (pulse pressure = systolic blood pressure - diastolic blood pressure).

A higher amplitude pulse means that the pulse pressure is higher. It means blood is flowing through the arteries under greater than normal pressure. It can be seen when there is vasodilation. During vasodilatation, the arteries relax which decreases the total peripheral resistance of the systemic circulation. This decrease in the total peripheral resistance causes the left ventricle to pump the blood into the systemic circulation more strongly. This increases the amplitude of the pulse as the pulse pressure in increased. It is seen in conditions like thyrotoxicosis, beri beri, fever, anaemia.

Higher amplitude pulse can also be seen in conditions where the cardiac output and stroke volume is higher like exercise, anxiety.

Question 3

Venous return of the heart occurs due to pressure created by:

Answer: d) skeletal muscle pump and respiratory pump.

Explanation: Blood from all the organs of the body flows back to the heart through a network of veins. This is known as venous return. The capillaries into which carbon dioxide and other metabolic waste products diffuses across the cell membranes, join to form venules which unite together to from veins. All the veins in the body ultimately join into two large veins called superior and inferior vena cavae which opens into the right atrium of the heart.

As veins are low pressure system, they need assistance in carrying the blood to the right atrium of the heart from the entire body. This assistance is provided by skeletal muscle pump and respiratory pump.

Skeletal muscles like gastrocnemius and soleus during motor activities like walking, running, etc. contracts which pumps the blood into the venous system and helps in generating enough pressure to carry this blood to the heart. Hence, these calf muscles like gastrocnemius and soleus are also known as the peripheral heart of the body.

During inspiration, there is negative intrathoracic pressure (leading to air being sucked into the lungs from the atmosphere) and positive abdominal pressure as the diaphragm muscle contracts and pushes the abdominal organs inferiorly. This creates a pressure difference between the supra and infra diaphragmatic part of inferior vena cava which sucks the blood towards the right atrium from the systemic venous circulation.

Question 4

A decrease in blood pressure will cause:

Answer: b) vasoconstriction.

Explanation: When the blood pressure falls, body's compensatory mechanisms gets activated to restore the blood pressure to optimum level. One such mechanism is the vasoconstriction of the arteries which increases the total peripheral resistance which increases the blood pressure. Total peripheral resistance is the resistance in the systemic arteries like aorta against which the left ventricle needs to pump blood during systole. This vasoconstriction and subsequent increase in total peripheral resistance and hence the compensatory increase in blood pressure is caused by increase in sympathetic system signals to restore the falling blood pressure. Sympathetic signals also increase the heart rate which further helps in increasing the falling blood pressure.

The parasympathetic system, decreases the heart rate, causes vasodilatation which further decreases the blood pressure.