Cardiovascular Regulation: Heart Rate, Blood Volume, and Blood Pressure Control

What controls Heart Rate (HR)?

Sympathetic (↑ HR) and Parasympathetic (↓ HR) nervous systems

What influences Stroke Volume (SV)?

Blood volume and venous compliance

What regulates blood volume?

Fluid intake/loss, kidney function, and venous compliance

How do kidneys regulate blood volume?

By adjusting water and salt retention/excretion

What do α1 receptors do?

Cause vasoconstriction (arteries and veins)

What do β2 receptors do?

Cause vasodilation

What is the effect of sympathetic stimulation on MAP?

Increases MAP via ↑ TPR

Where are baroreceptors located?

Carotid sinus and aortic arch

What happens when BP drops?

↓ Baroreceptor firing → ↑ Sympathetic tone → ↑ HR, contractility, vasoconstriction

What happens when BP rises?

↑ Baroreceptor firing → ↑ Parasympathetic tone → ↓ HR, vasodilation

What evidence supports dual autonomic control at rest?

Metoprolol ↓ HR (blocks sympathetic), Atropine ↑ HR (blocks parasympathetic)

What triggers renin release?

↓ Renal perfusion, ↑ SNS activity, ↓ Na+ in distal tubule

What does Angiotensin II do?

Vasoconstriction, ↑ Aldosterone, ↑ ADH, ↑ SNS activity

What do ACE inhibitors and ARBs do?

Block Ang II formation or action → ↓ BP

What are the effects of ADH?

V1: Vasoconstriction; V2: ↑ Water reabsorption via aquaporins

What triggers ANP release?

↑ Venous volume/stretch

What are ANP's effects?

↑ HR, venodilation, ↓ ADH, ↑ water excretion, ↓ aldosterone

What enhances venous return?

One-way valves, skeletal muscle pump, respiratory pump, sympathetic venoconstriction

What stimulates chemoreceptors?

↑ CO₂, ↓ O₂ (located in carotid bodies)

What is vasovagal syncope?

Emotional trigger → ↑ Parasympathetic + ↓ Sympathetic → Bradycardia + Vasodilation → ↓ MAP

What is the first vital sign change in volume depletion?

Tachycardia (compensatory to maintain CO)

How does renal artery stenosis cause hypertension?

↓ Renal perfusion → ↑ Renin → ↑ Ang II → ↑ BP

What causes edema in heart failure?

↑ Venous pressure (e.g., tricuspid regurgitation)

How do diuretics lower BP?

↓ Blood volume → ↓ MAP

How do beta blockers lower BP?

↓ HR and contractility → ↓ CO → ↓ MAP

How do ACE inhibitors lower BP?

↓ Ang II → ↓ Vasoconstriction and ↓ Aldosterone

What is the top priority of the cardiovascular system?

Maintain MAP to ensure organ perfusion

Why might 'abnormal' vitals be appropriate?

They may reflect compensatory mechanisms