FAQ on Blood Pressure

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Explain how blood pressure and resistance determine volume of blood flow:

The higher the BP, the more the blood flow. The higher the resistance, the lower the blood flow.

What is systolic blood pressure? Diastolic blood pressure? Mean arterial blood pressure?

Systolic pressure is the pressure exerted during ventricular systole ~ 120 mm Hg. Diastolic pressure is the recoil pressure exerted by the aorta ~ 80 mm Hg.

MABP = DBP + 1/3 x [SBP - DBP]

Summarize the factors that affect blood pressure:

Blood pressure depends on cardiac output and resistance.

Describe the hormonal regulation of blood pressure:

Hormones that regulate blood pressure are:

Renin-angiotensin-aldosterone (RAA) system: Quantity in direct proportion to blood pressure.

Epinephrine and Norepinephrine: Quantity in direct proportion to blood pressure.

Antidiuretic hormone (ADH): Quantity in direct proportion to blood pressure.

Atrial nautriuretic peptide (ANP): Quantity in inverse proportion to blood pressure.

Describe the operation of the carotid sinus and aortic reflexes:

Baroreceptors located in the walls of the carotid sinus initiate the carotid sinus reflexes. When blood pressure is higher than normal, baroreceptors become activated and propagate nerve impulses over axons of CN IX to medulla oblongata.

Baroreceptors located in the wall of ascending aorta and arch of aorta initiate the aortic reflex which regulate systemic blood pressure. Impulses reach the brain over the CN X.

What is autoregulation? Explain how it occurs through physical and chemical changes in the blood:

Autoregulation is the automatic adjustment of blood flow and blood volume for an organ or tissue. This is seen during exercise, etc.

What mechanisms , apart from cardiac contraction, act as pumps to boost venous return?

Two other mechanisms are the skeletal muscle pump and the respiratory pump.

Skeletal muscle pump: Venous return in the skeletal muscles is enhanced by the compression and uncompression of the valves due to muscle movement.

Respiratory pump: The pressures in the thoracic and abdominal cavities vary due to diaphragmatic movements, and this enhances venous return.

How does the cardiovascular system respond to changes in blood pressure?

This is when the Cardiovascular Center of the brain comes into play. The CV center receives inputs from various proprioceptors and baroreceptors distributed throughout the body. Proprioceptors monitor the movements of joints and muscles and control blood pressure accordingly, while baroreceptors monitor blood pressure in various parts of the body.

As an example, take sudden blood loss. What would happen to the filling pressure of the heart?

During blood loss, filling pressure would drop and shock would persist.

What would happen to cardiac output and blood pressure because of this?

Since Cardiac Output = Stroke Volume x Heart Rate, CO would decrease and blood pressure would also decrease.

How does the body compensate for this within seconds?

We’re talking about a sudden decrease in blood volume, or hypovolemic shock. When this happens, the body’s initial response is vasoconstriction, that is, blood flow is reduced and volume is conserved. The skin becomes pale in color.

How does it compensate over minutes to hours?

The negative feedback systems come into play: The Renin-angiotensin-aldosterone system is activated and Antidiuretic hormone is released, the sympathetic division of ANS is activated and local vasodilators are released.

Additional Reading:

Basic Pathology

1. Cell Injury
2. Inflammation and Repair
3. Immunopathology
4. Water, Electrolyte, Acid-Base, Hemodynamic Disorders
5. Genetic and Developmental Disorders
6. Environmental Pathology
7. Nutritional Disorders
8. Neoplasia
9. Vascular Disorders
10. Heart Disorders
11. Red Blood Cell Disorders
12. White Blood Cell Disorders
13. Lymphoid Tissue Disorders
14. Hemostasis Disorders
15. Blood Banking and Transfusion Disorders
16. Upper and Lower Respiratory Disorders
17. Gastrointestinal Disorders
18. Hepatobiliary and Pancreatic Disorders
19. Kidney Disorders
20. Lower Urinary Tract and Male Reproductive Disorders
21. Female Reproductive and Breast Disorders
22. Endocrine Disorders
23. Musculoskeletal Disorders
24. Skin Disorders
25. Nervous System Disorders
26. Notes on Tissue Regeneration
27. A Table of Bleeding Disorders
28. FAQ on Structure and Function of Red Blood Cells
29. FAQ on Components of Blood
30. Notes on Hemostatic Mechanisms
31. What is Fever?
32. What is Edema?
33. FAQ on Blood Pressure
34. FAQ on principles of fluid and flow dynamics of Blood
35. Causes of Thrombocytopenia
36. Squamous cell carcinoma of head and neck mucosa
37. Four tumors which never metastasize to the brain
38. What is caustic injury?
39. What causes Peripheral Edema?

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