Human Physiology: Blood Flow and Pressure
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Questions and Answers

Which of the following hormones is released by the adrenal medulla in response to sympathetic stimulation?

  • Renin
  • Aldosterone
  • Antidiuretic hormone (ADH)
  • Epinephrine (correct)

    • What is the primary mechanism by which the Renin-Angiotensin-Aldosterone (RAA) system increases blood pressure?

  • Decreased sympathetic nervous system activity
  • Increased production of antidiuretic hormone (ADH)
  • Increased release of atrial natriuretic peptide (ANP)
  • Direct vasoconstriction of blood vessels (correct)

    • Which of the following is NOT a direct effect of Angiotensin II on blood pressure regulation?

  • Direct vasodilation of blood vessels (correct)
  • Increased thirst
  • Stimulation of aldosterone release
  • Vasoconstriction of blood vessels

    • How does Atrial Natriuretic Peptide (ANP) contribute to blood pressure regulation?

    <p>By promoting vasodilation and reducing blood volume (A)</p> Signup and view all the answers

    When the body detects low oxygen levels (hypoxia), what is the immediate physiological response?

    <p>Increased sympathetic nervous system activity (B)</p> Signup and view all the answers

    Which of the following hormones contributes to vasoconstriction and increased blood pressure?

    <p>Antidiuretic Hormone (ADH) (B), Epinephrine (C)</p> Signup and view all the answers

    Which of the following is NOT a key component of the Renin-Angiotensin-Aldosterone (RAA) system?

    <p>Atrial Natriuretic Peptide (ANP) (C)</p> Signup and view all the answers

    What is the primary symptom indicating shock?

    <p>Low blood pressure (D)</p> Signup and view all the answers

    Which hormone is released from the posterior pituitary gland in response to dehydration or decreased blood volume?

    <p>Antidiuretic hormone (ADH) (B)</p> Signup and view all the answers

    What type of shock is caused by a severe allergic reaction?

    <p>Vascular shock (D)</p> Signup and view all the answers

    Which of the following is NOT a homeostatic response to shock?

    <p>Release of local vasodilators (D)</p> Signup and view all the answers

    Which of the following is a consequence of prolonged shock?

    <p>Organ failure (B)</p> Signup and view all the answers

    Which type of shock is caused by a decrease in blood volume?

    <p>Hypovolemic shock (D)</p> Signup and view all the answers

    How does the body respond to shock in terms of heart function?

    <p>Increased heart rate and force of contraction (D)</p> Signup and view all the answers

    What does 'hypoperfusion' refer to in the context of hypotension?

    <p>Insufficient blood flow (C)</p> Signup and view all the answers

    What is the primary goal of treatment for shock?

    <p>Increasing blood flow (B)</p> Signup and view all the answers

    What is the primary reason for the slow velocity of blood flow in capillaries?

    <p>To allow for sufficient time for exchange of materials between blood and interstitial fluid. (A)</p> Signup and view all the answers

    Which of the following is NOT a mechanism of autoregulation of blood flow?

    <p>Hormonal regulation (B)</p> Signup and view all the answers

    Which of the following vessels contribute the most to systemic vascular resistance (SVR)?

    <p>Arterioles, capillaries, and venules (C)</p> Signup and view all the answers

    How do arterioles regulate systemic vascular resistance (SVR)?

    <p>By changing their diameter (D)</p> Signup and view all the answers

    What happens to the blood vessels when the body temperature increases?

    <p>Dilation of both arterioles and capillaries (A)</p> Signup and view all the answers

    What is the relationship between blood flow velocity and cross-sectional area?

    <p>Inversely proportional; as cross-sectional area increases, velocity decreases (D)</p> Signup and view all the answers

    Which of the following is a locally released vasoconstrictor?

    <p>Thromboxanes (C)</p> Signup and view all the answers

    How does the myogenic response regulate blood flow?

    <p>By sensing changes in blood pressure and adjusting vessel diameter accordingly (B)</p> Signup and view all the answers

    Which of the following is NOT a factor that aids venous return?

    <p>Increased blood pressure in the veins (C)</p> Signup and view all the answers

    What is the main function of the skeletal muscle pump?

    <p>Moving blood in one direction through the veins with the help of valves (C)</p> Signup and view all the answers

    What is the primary function of the precapillary sphincters in the metarterioles?

    <p>To regulate the flow of blood into capillaries (A)</p> Signup and view all the answers

    During fight or flight, what happens to the blood flow in skeletal muscles, lungs, and brain?

    <p>Vasodilation in all three organs (A)</p> Signup and view all the answers

    How does the respiratory pump aid venous return?

    <p>By creating pressure gradients that pull blood towards the heart (B)</p> Signup and view all the answers

    Which of the following is NOT a tissue that experiences vasoconstriction during fight or flight?

    <p>Skeletal muscles (B)</p> Signup and view all the answers

    Where is blood flow velocity slowest?

    <p>In the capillaries (C)</p> Signup and view all the answers

    Which of the following is NOT a factor that influences blood flow velocity?

    <p>Heart rate (D)</p> Signup and view all the answers

    Which of these factors directly affects blood flow?

    <p>Pressure difference driving the flow (B), Resistance to blood flow in specific blood vessels (D)</p> Signup and view all the answers

    What is Mean Arterial Pressure (MAP)?

    <p>The average pressure in the arteries (C)</p> Signup and view all the answers

    How can cardiac output (CO) affect mean arterial pressure (MAP)?

    <p>Increasing CO increases MAP if resistance remains constant (D)</p> Signup and view all the answers

    Which of these factors can be readily adjusted by the body to change blood flow?

    <p>Diameter of blood vessels (D)</p> Signup and view all the answers

    What is the relationship between blood flow and pressure in the systemic circulation?

    <p>Blood flow increases as pressure increases (C)</p> Signup and view all the answers

    Which of the following contributes to the relatively low pressure in the venous circulation?

    <p>The large diameter of veins compared to arteries (D)</p> Signup and view all the answers

    What is the effect of 'hardening of the arteries' on the body's ability to regulate blood flow?

    <p>It weakens the body's ability to adjust blood flow (B)</p> Signup and view all the answers

    Which of the following is NOT a factor that affects vascular resistance?

    <p>Blood pressure (A)</p> Signup and view all the answers

    Which of the following is NOT a type of sensory receptor that provides input to the cardiovascular center?

    <p>Thermoreceptors (C)</p> Signup and view all the answers

    What is the primary function of baroreceptors in the cardiovascular system?

    <p>Monitor changes in blood pressure and stretch in blood vessel walls (A)</p> Signup and view all the answers

    Where are the baroreceptors located that are responsible for the carotid sinus reflex?

    <p>Carotid sinus (D)</p> Signup and view all the answers

    What is the effect of decreased baroreceptor activity on the cardiovascular system?

    <p>Decreased parasympathetic and increased sympathetic stimulation (C)</p> Signup and view all the answers

    Which brain region receives input from both higher brain regions and sensory receptors, and plays a crucial role in regulating the cardiovascular system?

    <p>Medulla oblongata (D)</p> Signup and view all the answers

    What type of stimulus triggers the aortic reflex?

    <p>Changes in pressure and stretch in the aortic arch (D)</p> Signup and view all the answers

    Where are chemoreceptors located in the body?

    <p>Both carotid bodies and aortic bodies (A)</p> Signup and view all the answers

    Which of the following is NOT a factor that influences the cardiovascular center in the medulla oblongata?

    <p>Inputs from the endocrine system (D)</p> Signup and view all the answers

    Study Notes

    Blood Flow and Pressure

    • Blood flow is the volume of blood passing through tissue per unit time (mL/min).
    • Cardiac output (CO) is calculated as heart rate (HR) multiplied by stroke volume (SV).
    • Two factors affecting blood flow are:
      • Pressure difference: Blood flows from higher pressure regions to lower pressure regions.
      • Resistance: Resistance to blood flow in specific vessels affects the overall flow.
    • Blood pressure progressively decreases as blood travels farther from the left ventricle.

    Blood Pressure

    • Venous circulation operates at lower pressures than arterial circulation.
    • Small pressure differences (venule - right atrium) – 16 mmHg to 0mmHg, aided by muscle and respiratory pumps–are sufficient for venous return.

    Mean Arterial Pressure (MAP)

    • MAP is the average blood pressure in arteries, roughly one-third of the way between systolic and diastolic pressures.
    • MAP = diastolic BP + 1/3 (systolic BP - diastolic BP).
    • MAP = CO x R (resistance). Blood pressure rises with increasing cardiac output, as long as resistance remains constant.

    Pressure, Flow, and Resistance

    • Vascular resistance depends on factors like lumen size, blood viscosity, and total vessel length.
    • Blood vessel diameter is the factor readily adjusted to change blood flow.
    • Resistance is inversely proportional to the fourth power of blood vessel diameter(R x 1/d^4). Dilation of a vessel reduces its resistance significantly.

    Pressure, Flow, and Resistance

    • "Hardening of the arteries" (loss of elasticity) negatively impacts the body's ability to increase blood flow to meet metabolic demand.
    • Systemic vascular resistance (SVR) refers to the combined resistance of all systemic blood vessels.
    • Smaller blood vessels (arterioles, capillaries, and venules) offer the most resistance.

    Venous Return

    • Venous return, the amount of blood returning to the right atrium, equals the amount pumped into arteries from the left ventricle.
    • Venous return is aided by pressure, venous valves, skeletal muscle pump, and breathing.

    Venous Return

    • Skeletal muscle pump: Muscle contractions assist blood movement.
    • Respiratory pump: Negative pressures in the thoracic and abdominal cavities during breathing move venous blood toward the heart.

    Velocity of Blood Flow

    • Blood flow velocity is inversely related to cross-sectional area.
    • Velocity is slowest where cross-sectional area is largest (capillaries). This slower velocity allows for efficient exchange of materials with interstitial fluid.

    Autoregulation

    • Autoregulation describes how tissues control their own blood flow without outside input from hormones or the nervous system.
    • Factors that cause dilation/constriction include temperature changes and locally released substances (acids, potassium, adenosine, nitric oxide).

    Blood Pressure and Homeostasis

    • The vascular system senses changes in blood pressure and blood flow. Signals are sent to cardiovascular centers in the brain.
    • The heart modifies its rate and force to adjust blood flow.
    • Arterioles and precapillary sphincters adjust blood flow to specific tissue beds, determining which tissues receive blood.

    Blood Pressure and Homeostasis

    • During emergencies, the autonomic nervous system increases blood flow to essential organs (skeletal muscles, lungs, brain) by vasodilation.
    • It reduces blood flow to nonessential organs (skin, GI tract, kidneys) through vasoconstriction.

    The Cardiovascular Center

    • The medulla oblongata receives input from higher brain regions and sensory receptors.
    • Impulse input from cerebral cortex, limbic system, and hypothalamus impacts the cardiovascular center.
    • Types of sensory receptors affecting the CV center include proprioceptors, baroreceptors, and chemoreceptors.

    Blood Pressure and Homeostasis

    • Nerve impulses from higher brain centers, proprioceptors, baroreceptors, and chemoreceptors influence the cardiovascular center.
    • Input to the cardiovascular center influences heart rate (increased rate, decreased rate), heart contractility, and blood vessel vasoconstriction/vasodilation.

    Neural Regulation of Blood Pressure

    • Baroreceptors, located in the arch of the aorta and carotid sinus, are crucial for monitoring blood pressure.
    • The carotid sinus reflex and aortic reflex represent baroreceptor mechanisms maintaining blood pressure.

    Blood Pressure and Homeostasis

    • Carotid sinus reflex (CN IX and X) helps normalize blood pressure in the brain.
    • Aortic reflex (aortic baroreceptors) helps maintain blood pressure.

    Baroreceptors

    • Baroreceptors react to decreasing blood pressure by sensing decreased stretch, which sends signals to the CV center.
    • The cardiovascular center responds with reduced parasympathetic, increased sympathetic stimulation to increase blood pressure.

    Chemoreceptor Reflexes

    • Chemoreceptors located in carotid and aortic bodies monitor oxygen, carbon dioxide, and pH levels, signaling the CV center.
    • When hypoxia, hypercapnia, or acidosis occur, sympathetic stimulation increases heart and respiratory rate, and vessels constrict.

    Hormonal Regulation of Blood Pressure

    • Renin-angiotensin-aldosterone (RAA) system: When blood volume or blood flow decreases, renin converts angiotensinogen to angiotensin II, which stimulates vasoconstriction and aldosterone release.
    • Aldosterone increases retention of water and sodium in the kidneys, thus raising blood volume and pressure.
    • Epinephrine and norepinephrine increase cardiac output via increasing heart rate and contractions.

    Hormonal Regulation of Blood Pressure

    • ADH (antidiuretic hormone) from the posterior pituitary is released in response to dehydration or decreasing blood volume, causing vasoconstriction.
    • ANP (atrial natriuretic peptide) from cardiac atria lowers blood pressure by causing vasodilation and reducing blood volume by promoting loss of salt and water in urine.

    Hormones Summary

    • Epinephrine and norepinephrine cause both vasoconstriction and vasodilation globally increasing blood pressure.
    • Angiotensin II causes vasoconstriction, water retention, and increased blood pressure.
    • Aldosterone increases water and solute reabsorption into the blood.
    • ADH increases water reabsorption.

    Pulse

    • Checking pulse assesses peripheral circulation; the result is the expansion and recoil of elastic arteries.
    • Pulse is strongest closest to heart, weakening distally.
    • Pulse rate usually equals heart rate.

    Measuring Blood Pressure

    • Blood pressure measures the pressure in arteries generated by left ventricle contraction during systole and the pressure remaining when there is a pause between contractions.
    • During measurement : Systolic pressure (first sound heard) measures pressure in arteries during ventricular contraction.
    • Diastolic pressure (last sound heard) measures pressure in arteries during ventricular relaxation.

    Alterations of Blood Pressure

    • Hypertension, abnormally high blood pressure, affects 50 million Americans, contributing to diseases such as atherosclerosis, heart failure, kidney disease, and stroke.
    • Hypertension is defined by elevated systolic (SBP) or diastolic (DBP) blood pressure. Hypertension stages are defined by specific levels of SBP and DBP values.

    Alterations of Blood Pressure

    • Hypotension involves low blood pressure making it hard to deliver nutrients—damaging organs.
    • People with seemingly low BP often are healthy as enough blood flow is delivered to keep healthy organs functioning.

    Shock and Homeostasis

    • Four main types of shock include hypovolemic shock, cardiogenic shock, obstructive shock, and vascular shock.
    • Homeostatic mechanisms, like the RAA system, ADH release, sympathetic nervous system activation, and local vasodilation, occur in response to shock.

    Signs and Symptoms of Shock

    • Shock is characterized by low systolic blood pressure, rapid resting heart rate, weak/rapid pulse, cool/pale skin, altered mental state, reduced urination, thirst, low blood pH.

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