Lecture 5.2 - Controls of blood pressure

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Questions and Answers

What is the primary mechanism of action of diuretics in managing hypertension?

Slowing the heart rate

Removing excess volume from the bloodstream (correct)

Dilating blood vessels

Inhibiting angiotensin production

A patient's blood pressure reading is 125/85 mmHg. Which stage of hypertension does this fall under?

Elevated blood pressure (correct)

Hypertension stage 2

Normal blood pressure

Hypertension stage 1

What is the primary characteristic of essential hypertension?

A high sodium intake

No single, reversible cause can be readily identified (correct)

An underlying, identifiable cause

A high caloric intake

Which of the following medications is not typically used to manage hypertension?

Anticoagulants Signup and view all the answers

What is the primary mechanism of action of angiotensin inhibitors in managing hypertension?

Inhibiting the production of angiotensin Signup and view all the answers

What is the estimated percentage of adults with hypertension that have primary or essential hypertension?

85-90% Signup and view all the answers

What is the primary purpose of tightly controlling blood pressure in the body?

To ensure adequate blood flow to organs throughout the body Signup and view all the answers

Where are arterial baroreceptors typically located in the body?

In the carotid sinus and aortic arch Signup and view all the answers

What happens to the firing frequency of action potentials generated by baroreceptors when arterial pressure suddenly rises?

It increases due to passive expansion of the arterial walls Signup and view all the answers

What is the result of decreased stretch of the arterial walls on baroreceptor firing frequency?

Decreased firing frequency due to decreased stretch of the arterial walls Signup and view all the answers

What is the normal blood pressure range in a healthy adult?

120/80 mmHg Signup and view all the answers

What is the location of the highest pressure in the arterial system?

Aortic arch Signup and view all the answers

What is the purpose of the negative feedback system incorporating pressure sensors in the arterial system?

To decrease blood pressure in response to increased stretch of the arterial walls Signup and view all the answers

What happens to the walls of the vessels containing baroreceptors when arterial pressure suddenly rises?

They passively expand, increasing the firing frequency of action potentials Signup and view all the answers

What is the primary function of the nucleus of tractus solitarius (NTS) in the medulla?

To control cardiac accelerator and inhibitory centres Signup and view all the answers

Which of the following neurotransmitters is involved in the vasodilation mechanism in hypertension?

Acetylcholine Signup and view all the answers

What is the primary difference between short-term and long-term compensation mechanisms in hypotension?

Short-term compensation involves the nervous system, while long-term compensation involves the kidneys Signup and view all the answers

What is the primary function of aldosterone in the renin-angiotensin-aldosterone system?

To increase the reabsorption of sodium and water in the kidneys Signup and view all the answers

Which of the following drugs is used to manage blood pressure by inhibiting sympathetic activity?

Sympatholytic drugs Signup and view all the answers

What is the primary effect of atrial natriuretic peptide (ANP) on blood pressure?

It decreases blood pressure by increasing vasodilation and reducing sodium reabsorption Signup and view all the answers

Which of the following is a characteristic of hypertension?

Increased heart rate and increased total peripheral resistance Signup and view all the answers

What is the primary function of the cardio inhibitory centre in the medulla?

To inhibit the heart rate and decrease blood pressure Signup and view all the answers

Which of the following is a stage of hypertension?

Compensatory stage Signup and view all the answers

What is the primary mechanism of action of angiotensin II in the renin-angiotensin-aldosterone system?

It stimulates the release of aldosterone and increases sodium reabsorption Signup and view all the answers

Study Notes

Hypotension

Baroreceptors in carotid and aortic sinus sense low blood pressure and send signals to medulla in brain via sensory afferent fibers of CN X and CN IX.
Information from CN X and CN IX is transmitted to Nucleus of tractus solitarius (NTS) in medulla, which has control over cardiac acceleratory centre and inhibitory centre.
To compensate for low blood pressure, the body increases cardiac output (CO) or total peripheral resistance (TPR), which can be achieved by increasing stroke volume and heart rate.

Hypotension - Compensation Mechanisms

Nucleus of tractus solitarius stimulates cardiac acceleratory centre and inhibits the inhibitory centre, leading to:
- Increased heart rate and contractility via sympathetic fibres and norepinephrine.
- Vasoconstriction and increased total peripheral resistance via sympathetic fibres and alpha-1 adrenoceptors.
- Release of epinephrine and norepinephrine from chromaffin cells in adrenal medulla, leading to increased heart rate, contractility, and total peripheral resistance.

Hypotension - Long-term Compensation

Kidneys detect low blood pressure and release renin, which converts angiotensinogen to angiotensin I.
Angiotensin I is converted to angiotensin II by angiotensin converting enzyme (ACE) in the lungs.
Angiotensin II stimulates zona glomerulosa cells in adrenal cortex to release aldosterone, leading to:
- Increased fluid absorption and blood volume.
- Increased stroke volume and cardiac output.
- Vasoconstriction and increased total peripheral resistance.

Hypertension - Compensation Mechanisms

Hypertension is compensated by decreasing cardiac output (CO) and total peripheral resistance (TPR), as well as stroke volume and heart rate.
Nucleus of tractus solitarius stimulates cardio inhibitory centre and inhibits the cardio acceleratory centre, leading to:
- Decreased heart rate and contractility via vagus nerve and parasympathetic branch of nervous system.
- Vasodilation and decreased total peripheral resistance.

Hypertension - Long-term Compensation

Increased blood pressure leads to increased atrial pressure, which secretes atrial natriuretic peptide (ANP).
ANP has vasodilator effects, leading to:
- Venodilation and decreased central venous pressure.
- Arterial vasodilation and decreased total peripheral resistance.
- Inhibition of renin-angiotensin-aldosterone system (RAAS) and decreased aldosterone and ADH synthesis.

Drugs Used to Manage Blood Pressure

Sympatholytic drugs inhibit sympathetic activity.
Angiotensin inhibitors inhibit angiotensin.
Diuretics remove volume.
Vasodilators.

Stages of Hypertension

Normal: SBP 120 mmHg and DBP 80 mmHg.
Elevated BP: SBP 120-129 mmHg and DBP less than 80 mmHg.
Hypertension stage 1: SBP 130-139 mmHg or DBP 80-89 mmHg.
Hypertension stage 2: SBP greater than or equal to 140 mmHg or DBP greater than or equal to 90 mmHg.

Classification

Essential hypertension: no single, reversible cause can be identified; risk factors include lower levels of physical activity, high sodium intake, and high caloric intake.
Secondary hypertension: due to underlying, identifiable cause; treatment of the underlying cause can potentially reverse hypertension.

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Description

This quiz covers the regulation and compensation mechanisms of hypotension, including the role of baroreceptors, cranial nerves, and the brain's medulla.