BCH201_Blood Pressure

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the average blood pressure maintained by the arteries?

110-120 mmHg

90 mmHg (correct)

140 mmHg

70-80 mmHg

The arteries fluctuate between a state of systole and diastole. In diastole, the recoil of the elastic arteries forces blood out of the arterial system into the capillaries. The pressure in the arteries falls as blood leaves the system. Minimum diastolic pressure is typically 70-80 mmHg. Maximum systolic pressure is typically 110-120 mmHg. There is always pressure in the arteries, never much below ____ mmHg.

70-80

What is the formula for calculating blood pressure?

BP = CO x SVR

Baroreceptors on the aorta and carotid artery respond to rises in blood pressure.

False Signup and view all the answers

Match the antihypertensive drug group with their mechanism of action:

Beta-blockers = Reduce heart's responsiveness to sympathetic activity Angiotensin-II receptor blockers = Bind to and block AT1 receptors to reduce vasoconstrictive effect Calcium-channel blockers = Act on heart's conduction tissue to reduce heart rate, myocardium to reduce stroke volume, and arterioles to reduce systemic vascular resistance Signup and view all the answers

What does an Electrocardiogram (ECG) measure?

Overall electrical activities of the myocardial cells Signup and view all the answers

Match the following components of an electrocardiogram with their causes:

P wave = Atrial depolarization before atrial contraction QRS complex = Ventricular depolarization before contraction T wave = Ventricular repolarization Q wave = Atrial repolarization Signup and view all the answers

Match the following with what an electrocardiogram indicates:

Heart rate & dysrhythmias = Electrocardiogram indicator Cardiac output = Not indicated by electrocardiogram Electrolyte abnormalities = Electrocardiogram indicator Tissue perfusion = Not indicated by electrocardiogram Signup and view all the answers

Match the following figures with their descriptions:

Figure A = Depolarization traveling from left to right Figure B = Depolarization extended over the entire muscle fiber Figure C = Halfway repolarization of the muscle fiber Figure D = Complete repolarization of the muscle fiber Signup and view all the answers

Match the following with what an electrocardiogram does not indicate:

Cardiac output = Not indicated by electrocardiogram Tissue perfusion = Not indicated by electrocardiogram Pacemaker function = Electrocardiogram indicator Electrolyte abnormalities = Electrocardiogram indicator Signup and view all the answers

Match the following with their functions:

Atria = Depolarize before atrial contraction Ventricles = Depolarize before contraction Myocardial cells = Display overall electrical activities Electrodes = Record electrical potentials Signup and view all the answers

Match the following with their effects on the electrocardiogram:

Myocardial ischaemia = Indicated by electrocardiogram Drug toxicity = Indicated by electrocardiogram Pacemaker function = Indicated by electrocardiogram Cardiac output = Not indicated by electrocardiogram Signup and view all the answers

Match the following with their locations in the electrocardiogram:

P wave = Before the QRS complex QRS complex = After the P wave T wave = After the QRS complex Q wave = Before the P wave Signup and view all the answers

Match the following with their effects on the myocardial cells:

Depolarization = Causes muscle contraction Repolarization = Causes muscle relaxation Electrolyte abnormalities = Affects electrocardiogram Pacemaker function = Regulates heart rate Signup and view all the answers

Match the following with what they represent in the electrocardiogram:

Red positive charges = Depolarization inside the muscle fiber Red negative charges = Depolarization outside the muscle fiber Zero baseline = Equal negativity outside the muscle fiber Positivity = Repolarization of the muscle fiber Signup and view all the answers

Match the following with their relationships with the electrocardiogram:

Heart rate = Indicated by electrocardiogram Dysrhythmias = Indicated by electrocardiogram Cardiac output = Not related to electrocardiogram Myocardial ischaemia = Indicated by electrocardiogram Signup and view all the answers

Study Notes

Blood Pressure

A constant flow of blood is necessary to transport oxygen to the cells of the body, and the arteries maintain an average blood pressure of around 90 mmHg to push blood from the arteries into the capillaries.
Blood pressure fluctuates between systole and diastole, with systole increasing pressure as the heart pumps blood and diastole forcing blood out of the arterial system into the capillaries.
The minimum diastolic pressure is typically 70-80 mmHg, and the maximum systolic pressure is typically 110-120 mmHg.
Blood pressure depends on cardiac output (CO) and systemic vascular resistance (SVR), where BP = CO x SVR.
Cardiac output depends on heart rate (HR) and stroke volume (SV), where CO = HR x SV.
The body responds quickly to falls in arterial pressure by increasing cardiac output and systemic vascular resistance through sympathetic activity, vasoconstriction, and increased heart rate and stroke volume.

Role of Baroreceptors and Hormones

Baroreceptors on the aorta and carotid artery respond to falls in blood pressure and send signals to the cardiovascular centre in the brain stem medulla.
The medulla sends signals along the sympathetic nerves to the arterioles and heart, increasing SVR and cardiac output.
Hormones such as angiotensin II and aldosterone play a role in blood pressure regulation, with angiotensin II being a potent vasoconstrictor that increases SVR.

Mechanism of Action of Antihypertensive Drugs

Antihypertensive drugs act on the formula BP = SVR x CO (HR x SV) to reduce blood pressure.
They can reduce SVR, cardiac output, heart rate, or stroke volume to achieve this.
Beta-blockers, angiotensin-II receptor blockers, and calcium-channel blockers are types of antihypertensive drugs that work through different mechanisms to reduce blood pressure.

Electrocardiogram (ECG)

An electrocardiogram is a recording of the electrical potentials generated by the heart's contractions.
It is composed of a P wave, a QRS complex, and a T wave, which represent the electrical activities of the atria and ventricles.
An ECG can display the overall electrical activities of the myocardial cells, including heart rate and dysrhythmias, myocardial ischaemia, pacemaker function, electrolyte abnormalities, and drug toxicity.
However, it does not indicate mechanical performance of the heart, such as cardiac output and tissue perfusion.

Blood Pressure

A constant flow of blood is necessary to transport oxygen to the cells of the body, maintained by an average blood pressure of around 90 mmHg in the arteries.
The arteries fluctuate between systole (increased pressure as the heart pumps blood) and diastole (recoil of elastic arteries forces blood out of the system).
In systole, the pressure in the arteries increases, stretching the elastic walls, which can be felt as a pulse in certain arteries.
In diastole, the pressure in the arteries falls as blood leaves the system, with a minimum diastolic pressure typically around 70-80 mmHg.
Blood pressure depends on cardiac output (CO) and systemic vascular resistance (SVR): BP = CO x SVR.
Cardiac output depends on heart rate (HR) and stroke volume (SV): CO = HR x SV.

Regulation of Blood Pressure

The body responds quickly to falls in arterial pressure by increasing cardiac output (CO) and systemic vascular resistance (SVR).
Sympathetic activity causes vasoconstriction, increasing SVR, and increases heart rate and stroke volume, thereby increasing cardiac output.
Baroreceptors on the aorta and carotid artery respond to falls in BP, sending signals to the cardiovascular center in the brain stem medulla, which then sends signals along the sympathetic nerves to increase SVR and cardiac output.

Mechanism of Action of Antihypertensive Drugs

Antihypertensive drugs act on the formula BP = SVR x CO (HR x SV) to reduce blood pressure.
They act by reducing SVR, cardiac output, heart rate, or stroke volume.
Beta-blockers are beta-adrenoceptor antagonists that bind to and block β1 receptors on the heart, reducing its responsiveness to sympathetic activity.
Angiotensin-II receptor blockers bind to and block the AT1 receptor, reducing the vasoconstrictive effect of angiotensin-II, thereby reducing SVR.
Calcium channel blockers exert their effects by reducing heart rate, stroke volume, and systemic vascular resistance.

Electrocardiogram (ECG)

An electrocardiogram (ECG) is a recording of electrical potentials generated by the heart's electrical activity.
A normal ECG is composed of a P wave, a QRS complex, and a T wave.
The P wave is caused by electrical potentials generated when the atria depolarize before atrial contraction begins.
The QRS complex is caused by potentials generated when the ventricles depolarize before contraction.
An ECG displays the overall electrical activities of the myocardial cells, indicating heart rate and dysrhythmias, myocardial ischemia, pacemaker function, electrolyte abnormalities, and drug toxicity, but not mechanical performance of the heart.