BCR 1.3 - Control of Blood Pressure and Haemorrhage

What is the main function of elastic arteries?

To act as pressure reservoirs by stretching during systole and recoiling during diastole.

What structural feature allows elastic arteries to function effectively?

High elastin content in the tunica media.

What is the primary function of arterioles?

To regulate blood flow and resistance via smooth muscle contraction.

How does arteriole structure support its function?

They have a narrow lumen and thick muscular walls for controlling resistance.

What happens to compliance with aging?

It decreases, leading to higher systolic blood pressure.

What is compliance in blood vessels?

The ability of a vessel to expand and contract with pressure changes.

How does decreased compliance affect pulse pressure?

It increases pulse pressure.

Where are baroreceptors located?

In the carotid sinus and aortic arch.

What do baroreceptors detect?

Changes in stretch due to blood pressure.

What nerve carries signals from carotid sinus baroreceptors?

Glossopharyngeal nerve (cranial nerve IX).

What nerve carries signals from aortic arch baroreceptors?

Vagus nerve (cranial nerve X).

What happens to baroreceptor firing when blood pressure falls?

It decreases, leading to sympathetic activation.

What is the integrating center for baroreceptor reflexes?

The nucleus tractus solitarius (NTS) in the medulla.

What is the immediate autonomic response to low blood pressure?

Increased sympathetic and decreased parasympathetic activity.

How does sympathetic activation affect the heart?

It increases heart rate and contractility via beta-1 receptors.

Which receptor causes vasoconstriction?

Alpha-1 adrenergic receptor.

What is the effect of beta-1 stimulation on the heart?

Increased heart rate (positive chronotropy) and contractility (positive inotropy).

What is the effect of beta-2 stimulation?

Bronchodilation and vasodilation in skeletal muscle.

What neurotransmitter is released by sympathetic postganglionic neurons?

Noradrenaline (norepinephrine).

What neurotransmitter is released by parasympathetic postganglionic neurons?

Acetylcholine.

Which receptor type is found on parasympathetic target organs?

Muscarinic receptors (e.g., M2 on heart).

What happens to heart rate during parasympathetic activation?

It decreases.

What structure connects pre- and postganglionic autonomic neurons?

Autonomic ganglion.

Which hormone is primarily involved in long-term blood pressure regulation?

Aldosterone.

What triggers renin release from the kidneys?

Decreased blood pressure or sodium delivery to the distal tubule.

What converts angiotensin I to angiotensin II?

Angiotensin-converting enzyme (ACE).

What are the effects of angiotensin II?

Vasoconstriction and stimulation of aldosterone release.

What is the role of aldosterone?

Promotes sodium and water reabsorption in the kidneys.

What hormone causes water retention and vasoconstriction?

Vasopressin (antidiuretic hormone, ADH).

What stimulates ADH release?

Low blood volume, high plasma osmolarity, or angiotensin II.

What is the effect of atrial natriuretic peptide (ANP)?

Promotes sodium excretion and vasodilation.

Where is ANP released from?

Atrial myocytes in response to stretch.

What happens during feedforward control?

A physiological response occurs in anticipation of a stimulus.

Give an example of feedforward control.

Heart rate increases before exercise begins.

What is negative feedback?

A mechanism that reverses deviations from a set point.

Give an example of negative feedback.

Baroreceptor reflex to restore blood pressure.

What is positive feedback?

A mechanism that amplifies a stimulus.

Give an example of positive feedback.

Blood clotting cascade or childbirth.

What is mean arterial pressure (MAP)?

Average pressure driving blood into tissues; MAP = DBP + 1/3(SBP - DBP).

What is pulse pressure?

Difference between systolic and diastolic blood pressure.

What causes orthostatic hypotension?

Failure of sympathetic compensation when standing.

What are symptoms of orthostatic hypotension?

Dizziness, fainting upon standing.

What physiological change occurs when standing up?

Decreased venous return and stroke volume.

What compensatory mechanism prevents fainting when standing?

Sympathetic activation increasing HR and vasoconstriction.

What is the effect of adrenaline on the heart?

Increases heart rate and contractility.

What is the effect of adrenaline on the bronchi?

Bronchodilation via beta-2 receptors.

What is pheochromocytoma?

A catecholamine-secreting tumor of the adrenal medulla.

What lab findings support pheochromocytoma?

High levels of adrenaline, noradrenaline, and metanephrines in urine.

What is the primary receptor type in heart pacemaker cells?

Beta-1 adrenergic receptors (sympathetic), M2 muscarinic (parasympathetic).

What is positive inotropy?

Increased force of cardiac contraction.

What is positive chronotropy?

Increased heart rate.

What is positive dromotropy?

Increased conduction velocity through the AV node.

What is positive lusitropy?

Increased rate of myocardial relaxation.

What kind of receptor is nicotinic?

ACh-gated ion channel on autonomic ganglia and skeletal muscle.

What is the sympathetic neurotransmitter at the adrenal medulla?

Acetylcholine (on nicotinic receptors of chromaffin cells).

What hormones does the adrenal medulla release?

80% adrenaline, 20% noradrenaline.

What part of the ANS is the adrenal medulla part of?

Sympathetic nervous system.

What is the primary effect of alpha-1 activation?

Vasoconstriction of arterioles and increased TPR.

How does total peripheral resistance affect MAP?

↑ TPR = ↑ MAP (if CO is constant).

What does the vasomotor center do?

Regulates sympathetic output to blood vessels.

What receptor is blocked by beta blockers?

Beta-1 adrenergic receptor.

Why are beta blockers used in hypertension?

Reduce HR, contractility, and renin release.

What enzyme initiates the RAAS system?

Renin.

Which organ releases angiotensinogen?

Liver.

Where is ACE primarily located?

Lungs and endothelial cells.

What condition raises set point for BP in vasomotor center?

Essential hypertension.

What causes reduced baroreceptor sensitivity?

Arterial stiffening or atheroma in carotid sinus.

What is the effect of stress on BP?

Chronic stress increases sympathetic tone and BP.

What type of ANS innervation does the heart have?

Dual innervation: sympathetic and parasympathetic.

What type of ANS innervation do most blood vessels have?

Sympathetic only.

What type of receptor is found on vascular smooth muscle?

Alpha-1 adrenergic receptor.

What is the clinical use of adrenaline (EpiPen)?

Treatment of anaphylaxis and acute asthma.

What is tonic activity in the ANS?

Both sympathetic and parasympathetic systems active at rest.

What system dominates at rest?

Parasympathetic nervous system.

What is preload?

The volume of blood in the ventricles before contraction.

What is afterload?

The resistance the heart must overcome to eject blood.

How is cardiac output calculated?

CO = Heart Rate × Stroke Volume.

What happens to CO when HR increases too much?

CO may fall due to reduced filling time.

What increases stroke volume?

Increased preload, contractility, and reduced afterload.

What is the function of the NTS in BP regulation?

Integrates sensory input from baroreceptors.

What causes vasodilation in coronary vessels?

Parasympathetic stimulation and nitric oxide.

What is the role of nitric oxide in vessels?

Causes smooth muscle relaxation and vasodilation.

Where are M3 receptors found?

On endothelial cells of blood vessels.

What happens when M3 receptors are activated in healthy endothelium?

NO release → vasodilation.

What happens when M3 receptors are activated in diseased vessels lacking NO?

Direct vasoconstriction.

What triggers aldosterone release?

Angiotensin II.

What is the effect of aldosterone on kidneys?

Increased Na⁺ and water reabsorption.

Which pressure drives capillary exchange?

Mean arterial pressure.

What receptor subtype becomes more important in heart failure?

Beta-2 adrenergic receptors.

Which muscarinic receptor subtype reduces HR?

M2.

How does ANP counteract RAAS?

Promotes natriuresis and vasodilation.

Which cranial nerves carry baroreceptor signals?

CN IX (glossopharyngeal), CN X (vagus).

Which hormone raises both TPR and blood volume?

Angiotensin II.

What causes an increase in thirst?

Angiotensin II and high plasma osmolarity.

What is the primary mechanism of fast BP regulation?

Autonomic nervous system via baroreflex.

What is the primary mechanism of slow BP regulation?

Hormonal control via RAAS and ADH.

What are Korotkoff sounds?

Sounds heard during BP measurement with a cuff.

What does the first Korotkoff sound indicate?

Systolic blood pressure.

What does the disappearance of Korotkoff sounds indicate?

Diastolic blood pressure.

What is the function of collagen in arterial walls?

To provide tensile strength and resist high pressures.