Chapter 19: Functions Of The Blood Vessels

The brachial artery is the most commonly used artery to measure blood pressure. It is located in the upper arm and is easily accessible for measurement using a blood pressure cuff. The brachial artery is preferred because it is close to the heart and provides an accurate reflection of systemic blood pressure. Measuring blood pressure in the carotid artery or femoral artery would require more invasive procedures, while the circle of Willis is a network of arteries in the brain and not typically used for blood pressure measurement.

A sphygmomanometer is a medical device used to measure blood pressure. It consists of an inflatable cuff that is wrapped around the upper arm and a pressure gauge that measures the pressure of the cuff. By inflating the cuff and then slowly releasing the pressure, healthcare professionals can determine the systolic and diastolic blood pressure readings of a patient. Blood pressure is an important indicator of cardiovascular health and can help diagnose conditions such as hypertension. Therefore, the correct answer is blood pressure.

The systolic reading, diastolic reading, and Korotkoff sounds are all related to blood pressure. The systolic reading represents the highest pressure in the arteries when the heart is contracting, while the diastolic reading represents the lowest pressure in the arteries when the heart is at rest. Korotkoff sounds are the sounds heard when measuring blood pressure using a stethoscope. Therefore, blood pressure is the most related to these three elements.

Capillaries have very thin walls, allowing for the exchange of nutrients, gases, and waste products between the blood and surrounding tissues. Their small size and thin walls enable efficient diffusion of substances, making them the primary exchange vessels in the circulatory system. Arterioles, veins, and arteries have thicker walls and different functions.

Dehydration is characterized by poor skin turgor, which means that the skin lacks elasticity and appears to be less firm. When the body is dehydrated, it loses water and electrolytes, causing the skin to lose its normal elasticity. This can be observed by gently pinching the skin and seeing how quickly it returns to its normal position. In cases of dehydration, the skin may take longer to return to its original state or may even remain tented or wrinkled. Therefore, dehydration is the correct answer in this case.

The medulla oblongata is responsible for regulating involuntary functions such as blood pressure, heart rate, and breathing. The baroreceptor reflex is a mechanism that helps maintain blood pressure within a normal range. Baroreceptors located in the walls of blood vessels detect changes in blood pressure and send signals to the medulla oblongata. The medulla oblongata then responds by adjusting heart rate and blood vessel diameter to maintain blood pressure at an optimal level. Therefore, the medulla oblongata participates in the baroreceptor reflex.

The correct answer is the inferior vena cava because it is a large vein that carries deoxygenated blood from the lower body back to the heart. As blood flows from the lower body to the heart, it encounters less resistance compared to the other options mentioned. This results in lower blood pressure in the inferior vena cava compared to the aorta, circle of Willis, and femoral artery.

If the pressure within the pulmonary capillaries increases, it is most likely to result in the development of pulmonary edema. Pulmonary edema occurs when there is an abnormal accumulation of fluid in the lungs, which can be caused by increased pressure in the pulmonary capillaries. This can lead to symptoms such as shortness of breath, coughing, and difficulty breathing.

Pulse pressure is calculated by subtracting the diastolic blood pressure (80 mm Hg) from the systolic blood pressure (120 mm Hg). In this case, the pulse pressure would be 120 - 80 = 40 mm Hg.

When a person takes antihypertensive drugs, these medications work to lower blood pressure by causing vasodilation, which is the widening of blood vessels. Alcohol consumption and sitting in a hot tub can also cause vasodilation. When combined with antihypertensive drugs, this can lead to excessive vasodilation and a drop in blood pressure, resulting in hypotension. Hypotension can cause symptoms such as dizziness, lightheadedness, and fainting. Therefore, it is best for a person taking antihypertensive drugs to avoid alcohol and hot tubs to prevent the risk of vasodilation and hypotension.

Baroreceptors are specialized nerve endings located in the walls of blood vessels, particularly in the carotid sinus and aortic arch. These receptors monitor changes in blood pressure and help regulate it. When blood pressure increases, the baroreceptors send signals to the brain, which then triggers a decrease in heart rate and blood vessel dilation to lower blood pressure. Conversely, when blood pressure decreases, the baroreceptors signal the brain to increase heart rate and constrict blood vessels, raising blood pressure. Therefore, the baroreceptors play a crucial role in maintaining blood pressure homeostasis.

The characteristic of smooth muscle in arterioles allows them to function as resistance vessels. Smooth muscle is capable of contracting and relaxing, which regulates the diameter of the arterioles. When smooth muscle contracts, it narrows the arteriole, increasing resistance to blood flow. This helps regulate blood pressure and control the distribution of blood to different organs and tissues. The ability of smooth muscle to constrict or dilate the arterioles is crucial for maintaining proper blood flow and ensuring that organs receive adequate oxygen and nutrients.

Pulse pressure refers to the difference between the systolic and diastolic blood pressure readings. It is calculated by subtracting the diastolic pressure from the systolic pressure. Pulse pressure provides important information about the health of the cardiovascular system and can indicate conditions such as arterial stiffness or increased risk of cardiovascular events.

Plasma oncotic pressure refers to the pressure exerted by plasma proteins, particularly albumin, in the blood vessels. These proteins are responsible for maintaining the balance of fluids between the blood vessels and the surrounding tissues. Albumin is the most abundant protein in the blood and plays a crucial role in regulating osmotic pressure. It attracts water molecules and helps to prevent excessive fluid leakage from the blood vessels into the tissues. Therefore, plasma proteins, especially albumin, are the primary contributors to plasma oncotic pressure.

The IV infusion of mannitol pulls water out of the interstitium of the brain into the capillaries, thereby relieving edema. This is because mannitol is a hypertonic solution, meaning it has a higher concentration of solutes compared to the surrounding tissue fluid. This creates an osmotic gradient, causing water to move out of the interstitium and into the capillaries. By reducing the amount of fluid in the interstitium, the edema is relieved, which helps decrease intracranial pressure in a head-injured patient.

The patient's complaint of dizziness and loss of consciousness shortly after starting prazosin suggests that the drug has caused a significant decrease in blood pressure, leading to hypotension. This drug is an alpha-1 adrenergic antagonist, which blocks the vasoconstrictive effects of norepinephrine. By inhibiting the sympathetic response, prazosin can cause a sudden drop in blood pressure, resulting in symptoms like dizziness and syncope. This explanation is supported by the fact that the patient's symptoms occurred within an hour of taking the medication.

Vasopressors are substances that constrict blood vessels, leading to an increase in blood pressure. They work by stimulating the smooth muscles in the walls of blood vessels, causing them to narrow. This narrowing results in increased resistance to blood flow, which in turn elevates blood pressure. Diuretics, on the other hand, promote urine production and reduce fluid volume, leading to a decrease in blood pressure. Vasodilators relax and widen blood vessels, also resulting in a decrease in blood pressure. Antihypertensive drugs are a broad category that includes various medications used to lower blood pressure.

When a person stands for a prolonged period, gravity causes an increase in capillary hydrostatic pressure in the blood vessels of the lower extremities. This increased pressure leads to fluid leakage from the capillaries into the surrounding tissues, causing swelling. However, when the woman elevates her feet in the evening, gravity is no longer acting against the blood flow, and the capillary hydrostatic pressure decreases. As a result, the fluid that had leaked into the tissues is reabsorbed back into the capillaries, leading to a decrease in swelling.

Stimulation of the sympathetic nervous system increases vascular resistance, stroke volume, and heart rate. The sympathetic nervous system is responsible for the "fight or flight" response and activates various physiological responses to prepare the body for action. When stimulated, it causes vasoconstriction, which increases vascular resistance. It also increases the force of contraction of the heart, leading to an increase in stroke volume. Additionally, it increases heart rate by stimulating the sinoatrial node, the natural pacemaker of the heart. Therefore, stimulation of the sympathetic nervous system is the correct answer.

Antihypertensive drugs refer to medications that are used to treat high blood pressure. These drugs work by causing vasodilation, which means they relax and widen the blood vessels, reducing vascular resistance. By reducing vascular resistance, antihypertensive drugs help to lower blood pressure. Diuretics, on the other hand, work by increasing urine production and reducing fluid volume in the body. Inotropic drugs affect the force of contraction of the heart, while sympathomimetic drugs mimic the effects of the sympathetic nervous system.

Arterioles have the greatest effect on vascular resistance because they are small blood vessels that regulate blood flow and control the resistance within the circulatory system. By constricting or dilating, arterioles can adjust the amount of blood flowing through the capillaries, thus affecting the overall resistance to blood flow. This ability to regulate resistance is crucial in maintaining blood pressure and ensuring adequate blood supply to various tissues and organs.

If the lymphatic vessels are blocked or surgically removed, the normal drainage of excess fluid from the capillaries is disrupted. This leads to a decrease in plasma oncotic pressure, which is the pressure that keeps fluid inside the capillaries. As a result, fluid and protein start to accumulate in the interstitium, which is the space between cells. This accumulation of fluid and protein causes edema, which is the swelling and fluid retention in the affected area. Therefore, the correct answer is that fluid and protein accumulate in the interstitium, thereby causing edema.

When plasma osmolarity increases, it means that there is a higher concentration of solutes in the plasma. This creates an osmotic pressure gradient between the plasma and the interstitium (the space surrounding the capillary). As a result, fluid is "pulled" into the capillary from the interstitium to equalize the osmotic pressure. This process is known as osmosis. The other options mentioned in the question are not correct because an increase in plasma osmolarity would not cause an increase in filtration rate or the diffusion of plasma proteins out of the capillary into the interstitium.

Capillary hydrostatic pressure is a reflection of blood pressure because it is the pressure exerted by the blood against the walls of the capillaries. This pressure is responsible for pushing fluid out of the capillaries and into the surrounding tissues. Blood pressure is determined by factors such as the force of the heart pumping, the volume of blood in the vessels, and the resistance of the blood vessels. Therefore, blood pressure directly affects the hydrostatic pressure in the capillaries, influencing the movement of fluid and nutrients between the blood and tissues.

Epinephrine and norepinephrine are not steroids, as stated in the first option. They are actually secreted by the adrenal medulla, not the adrenal cortex, as mentioned in the second option. However, both epinephrine and norepinephrine are vasopressors, which means they constrict blood vessels and increase blood pressure, making the fourth option the correct answer.

The given equation, BP=SV*HR*R, is true. BP represents blood pressure, SV is stroke volume (the amount of blood pumped by the heart in one contraction), HR is heart rate (the number of times the heart beats per minute), and R is the total peripheral resistance (the resistance to blood flow in the blood vessels). According to this equation, blood pressure is determined by the product of stroke volume, heart rate, and total peripheral resistance.

Baroreceptors are sensory receptors located in the carotid sinus and aortic arch that detect changes in blood pressure. When blood pressure decreases due to hemorrhage, baroreceptors are activated and initiate a reflex response to increase heart rate (reflex tachycardia) and restore blood pressure. However, baroreceptors are not activated by hypoxemia, which is a low level of oxygen in the blood. Therefore, the statement "activated by hypoxemia" is not true about baroreceptors.

Exertion of pressure over the carotid sinus (tight collar) is most likely to induce a reflex bradycardia. The carotid sinus is located in the neck and is responsible for detecting changes in blood pressure. When pressure is applied to the carotid sinus, it can stimulate the baroreceptors present in the sinus, leading to a reflex response that slows down the heart rate. This reflex response is known as the carotid sinus reflex and is a protective mechanism to prevent a sudden increase in blood pressure.

When the plasma oncotic pressure exceeds the capillary hydrostatic pressure (CHP), it means that the pressure exerted by the plasma proteins in the capillary is higher than the pressure exerted by the fluid in the capillary. This creates an osmotic gradient, causing fluid to move osmotically into the capillary from the interstitium. This movement helps to restore the balance of fluid and maintain the appropriate blood volume.

A sudden rise in blood pressure activates the baroreceptors, which are specialized nerve endings that detect changes in blood pressure. When the baroreceptors are stimulated, they send signals to the brain to decrease heart rate and cardiac output, resulting in bradycardia. This is a protective mechanism to prevent further increases in blood pressure.

Alpha1 adrenergic agonists exert a vasopressor effect. These drugs stimulate the alpha1 adrenergic receptors in blood vessels, causing vasoconstriction and an increase in blood pressure. This can be beneficial in certain medical conditions where increased blood pressure is desired, such as in the treatment of hypotension or shock. Examples of alpha1 adrenergic agonists include phenylephrine and norepinephrine.

When the left ventricle of the heart fails, it is unable to effectively pump blood out to the body. This leads to an increase in pressure in the left atrium and pulmonary veins, causing an increase in capillary hydrostatic pressure in the pulmonary capillaries. The increased pressure forces fluid out of the capillaries and into the lungs, resulting in pulmonary edema. This fluid accumulation in the lungs leads to a decrease in plasma oncotic pressure, as the fluid dilutes the protein concentration in the blood. Therefore, the correct answer is increasing capillary hydrostatic pressure and forcing fluid into the lungs.

A drug that activates alpha1 adrenergic receptors is known to elevate blood pressure. Alpha1 adrenergic receptors are located on smooth muscle cells in blood vessels, and their activation causes vasoconstriction, leading to an increase in blood pressure. Therefore, a drug that activates these receptors would have the effect of elevating blood pressure.

An arteriolar constrictor drug is most likely to increase vascular resistance. Arterioles are small blood vessels that regulate blood flow and resistance in the circulatory system. When these vessels constrict, the diameter decreases, leading to increased resistance to blood flow. This results in an increase in blood pressure and reduced blood flow to the tissues. Therefore, an arteriolar constrictor drug would cause vasoconstriction, leading to increased vascular resistance.

When a patient becomes dehydrated, there is a decrease in the overall fluid volume in the body. This leads to an increase in the concentration of solutes in the plasma, resulting in an increase in plasma osmolarity. Edema, which is the accumulation of excess fluid in the tissues, occurs when there is an imbalance between the hydrostatic pressure and oncotic pressure. In this case, the increase in plasma osmolarity would actually favor the movement of fluid out of the tissues and into the blood vessels, making edema less likely to occur.

Afterload refers to the pressure or resistance that the heart has to overcome in order to pump blood out of the left ventricle and into the aorta. Arteriolar vasoconstriction refers to the narrowing of the arterioles, which increases peripheral vascular resistance and therefore increases afterload. This means that when arteriolar vasoconstriction occurs, the heart has to work harder to pump blood against the increased resistance, leading to an increased afterload. Therefore, arteriolar vasoconstriction is most associated with afterload.

When the capillary hydrostatic pressure (CHP) exceeds the plasma oncotic pressure, it means that the pressure inside the capillary is higher than the pressure exerted by proteins in the plasma. This pressure difference causes fluid to be filtered out of the capillary and into the interstitium, the space between cells. This process is known as filtration and leads to an increase in interstitial fluid volume. Therefore, the correct answer is that fluid is filtered into the interstitium.