Hormonal and Neural control of Blood pressure

Question 1

What is blood pressure and how is it calculated?

Answer 1

Blood pressure (BP) is the force exerted by blood on arterial walls.
Equation: BP = CO × TPR
CO (Cardiac Output) = HR × SV
TPR (Total Peripheral Resistance) = Resistance in systemic circulation

Question 2

What factors determine total peripheral resistance (TPR)?

Answer 2

1. Arteriolar smooth muscle tone (Vasoconstriction increases TPR, vasodilation decreases it).
2. Blood viscosity (Thicker blood = more resistance).
3. Blood vessel length (Longer vessels = more resistance).
4. Arterial cross-sectional area (Smaller arteries = higher resistance).

Question 3

Where are baroreceptors located, and what do they detect?

Answer 3

Location:
- Carotid sinus (internal carotid artery, above bifurcation).
- Aortic arch (detects systemic BP changes).
Function:
- Detect arterial stretch, which reflects blood pressure changes.
- Increased stretch = High BP → Increased baroreceptor firing.
- Decreased stretch = Low BP → Reduced baroreceptor firing.

Question 4

What is the neural pathway of the baroreceptor reflex?

Answer 4

1. Baroreceptors (Carotid sinus & Aortic arch) → Nucleus of the Solitary Tract (NTS) in Medulla (receives input).
2. NTS → Rostral Ventrolateral Medulla (RVLM) → Sympathetic Activation (if BP is low).
3. NTS → Nucleus Ambiguus → Parasympathetic (Vagal) Activation (if BP is high).
4. Effect: Modulates vascular tone & heart rate to stabilize BP.

Question 5

What happens in the baroreceptor reflex when blood pressure falls (hypotension)?

Answer 5

1. Less stretch on baroreceptors → Reduced firing rate.
2. NTS signals to the RVLM → Increased sympathetic activity.
3. Effects:
   
   • Arteriolar constriction → ↑ TPR → ↑ BP.
   • Increased heart rate & contractility → ↑ CO → ↑ BP.

Question 6

What happens in the baroreceptor reflex when blood pressure increases (hypertension)?

Answer 6

1. Increased stretch on baroreceptors → Increased firing rate.
2. Inhibits RVLM → Reduced sympathetic activity.
3. Effects:
   
   • Vasodilation → ↓ TPR → ↓ BP.
   • Heart rate decreases (via vagal activation) → ↓ CO → ↓ BP.

Question 7

What are the steps of the RAAS pathway?

Answer 7

1. Renin (Kidneys) converts angiotensinogen (Liver) → Angiotensin I.
2. Angiotensin-Converting Enzyme (ACE) (Lungs) converts Angiotensin I → Angiotensin II.
3. Angiotensin II effects:
   
   • Vasoconstriction → Increases BP.
   • Aldosterone release → Sodium & water retention → Increases BP.
   • ADH release → Water retention → Increases BP.
   • Stimulates thirst → Increases BP.

Question 8

What is the function of aldosterone, and where is it released from?

Answer 8

Function: Increases sodium & water reabsorption in the distal tubule & collecting duct.
Released from: Adrenal cortex.

Question 9

How does antidiuretic hormone (ADH, Vasopressin) regulate blood pressure?

Answer 9

1. Increases water reabsorption in the kidneys.
2. Promotes vasoconstriction to raise BP.
3. Released from the posterior pituitary gland.

Question 10

A 68-year-old woman has severe blood loss. Her BP is 85/50 mmHg, and HR is 120 bpm. What short-term BP regulation system is activated?

Answer 10

Baroreceptor Reflex: Increases HR & vasoconstriction to restore BP.

Question 11

A 75-year-old man experiences dizziness when standing. His BP drops from 120/80 to 90/60 mmHg, and HR increases from 70 to 110 bpm. What condition is he experiencing?

Answer 11

Orthostatic Hypotension – BP drops due to delayed baroreceptor reflex activation.

Question 12

A patient with chronic hypertension is prescribed an ACE inhibitor. How does this medication lower BP?

Answer 12

Blocks Angiotensin-Converting Enzyme (ACE) → Prevents Angiotensin II formation.
No vasoconstriction → BP decreases.

Question 13

How does chronic heart failure affect BP regulation?

Answer 13

1. RAAS is overactivated, leading to fluid retention & increased afterload.
2. Baroreceptor reflex is blunted, causing inappropriate BP regulation.

Question 14

A patient with chronic hypertension is prescribed an ACE inhibitor. How does this medication lower BP?

Answer 14

Blocks Angiotensin-Converting Enzyme (ACE) → Prevents Angiotensin II formation.
No vasoconstriction → BP decreases.

Question 15

How does chronic heart failure affect BP regulation?

Answer 15

RAAS is overactivated, leading to fluid retention & increased afterload.
Baroreceptor reflex is blunted, causing inappropriate BP regulation.