Blood Pressure Measurement and Regulation 2024

Blood Pressure 2024

• Blood pressure is the pressure inside blood vessels or heart chambers relative to atmospheric pressure. Units are mmHg.
• Indirect measurement of blood pressure using a BP cuff is explained in the topic objectives.
• Systolic, diastolic, mean arterial pressure, and pulse pressure are related by an equation (not shown).
• Differentiate between carotid sinus and aortic baroreceptors in terms if anatomical location and nervous connections.
• Sequence of events to restore blood pressure with acute rise or fall in arterial pressure is detailed.

Topic 5 Objectives

• Explain the rationale behind indirect blood pressure measurement using a blood pressure cuff.
• Relate systolic, diastolic, mean arterial, and pulse pressure in an equation.
• Differentiate between carotid sinus and aortic baroreceptors anatomically and in terms of nervous connections.
• Detail the events that restore blood pressure after an acute rise or fall.

Topic 5 Mini Case

• Sun Wen, a 20-year-old UBC track athlete, measures a resting heart rate (HR) of 45 bpm.
• She begins light stretching, and her HR increases to ~80 bpm.
• During a moderate-intensity stair master workout, her HR rises and stabilizes at 145 bpm.
• During this exercise her blood pressure remained roughly the same.

Blood Pressure Definition

• Blood pressure is the force of blood against the walls of blood vessels.
• Measured in millimeters of mercury (mmHg).

Control of Blood Pressure

• The medulla in the brain controls blood pressure via afferent and efferent nerves containing baroreceptors.
• Baroreceptors are stretch-sensitive nerve endings that detect blood pressure changes.

Baroreceptors

• Carotid sinus baroreceptors are located in the common carotid artery, with afferent nerves through the glossopharyngeal nerve.
• Aortic arch baroreceptors are in the arch of the aorta, with afferent nerves through the vagus nerve.

Acute Increase in Blood Pressure

• Increased baroreceptor stretch triggers increased activity in parasympathetic nerves and decreased activity in sympathetic nerves.
• Consequently, there's a decrease in heart rate (HR), stroke volume (SV), and systemic vascular resistance (SVR).
• Blood pressure is restored to normal.

Acute Decrease in Blood Pressure

• Decreased baroreceptor stretch triggers increased activity in sympathetic nerves and decreased activity in parasympathetic nerves.
• Consequently, there's an increase in heart rate (HR), stroke volume (SV), and systemic vascular resistance (SVR).
• Blood pressure is restored to normal.

Blood Pressure Hormones

• Hormones, such as antidiuretic hormone (AVP) and hormones from the kidney (like Renin-Angiotensin II - Aldosterone system), play in maintaining blood pressure alongside the nervous system.

Hypertension Categories

• Hypertension is categorized clinically based on systolic and diastolic blood pressure values.

Hypertension Medications

• Beta blockers reduce heart rate, cardiac output, and blood pressure.
• Thiazide diuretics reduce blood volume, thus blood pressure.
• ACE inhibitors block Angiotensin II formation from preventing increasing blood pressure.

Hypertension Lifestyle Recommendations

• Healthy eating, salt reduction, and weight management can help control hypertension.
• Avoiding tobacco, managing stress, and following medical prescriptions are recommendations.

Sun Wen's Case - Low Resting HR

• Sun Wen's low resting heart rate is a phenomenon called training-induced or athletic bradycardia.
• Mechanisms include increased vagal tone and reduced SA node activity.
• Increased stroke volume (SV) with no change in cardiac output (CO) can be one contributing factor.
• Changes in beta-receptor desensitization may contribute, though this is controversial.
• Maximum heart rate (HR) for females is approximately 226 - age in years.

Cardiovascular Adaptations to Exercise

• Left ventricle size and wall thickness (hypertrophy) increases with training.
• Stroke volume increases due to volume effects
• Resting and submaximal heart rate decreases with training.
• Blood volume increases with training.
• Blood pressure does not change or slightly decreases with training.
• Cardiac output distribution becomes better to active muscles during exercise with training

Comparison of CV Responses to Exercise

• Trained individuals exhibit lower heart rates and maintain consistent stroke volumes compared to untrained individuals during incremental exercise.

Additional Case Objective

• Describe Sun Wen's cardiovascular status at rest and during exercise.

Office Hours

• Zoom office hours are scheduled for Wednesday, December 11th at 10 am .

This quiz covers key concepts related to blood pressure, including methods of indirect measurement using a BP cuff and the physiological relationships between different types of pressure. You'll also explore the roles of carotid sinus and aortic baroreceptors in blood pressure regulation, as well as the physiological responses to acute changes in arterial pressure.