There are two activities in this week’s lab.
Factors that Affect Blood Pressure
For this activity, you will work with a small group of other students in a breakout room, and then return to the main classroom and report back on your findings. Your lab instructor will assign you ONE of the following types of medications to investigate further. Please download the appropriate worksheet when directed to do so. NOTE: you will only complete the worksheet for ONE medication. You do not need to download all four of the files:
Complete the research activities described in the handout. You will need to do outside research to fully answer all questions, but you may also find the information in the text box below helpful.
After you have completed the worksheet, you will create a short (4-5 slides) Google Slides presentation, which will you will then present to the rest of the class. This way, each group of students does in-depth research on only one of the medications, but everyone will be able to learn the details about all four. You may use this template for your presentation: https://docs.google.com/presentation/d/1Ln2r_jPP3mI4KbWtFMGD9yIAgTmvqQcWORWSOvCnFxs/edit?usp=sharing
Please note: You will NOT be able to edit the file I’ve linked above. You must save it to your own Google Drive and edit this copy.
Factors Affecting Arterial Blood Pressure
The importance of Blood Pressure: Arterial pressure is necessary to “push” blood through the circulation so that oxygen and nutrients can be delivered to the tissues. Therefore, if blood pressure is too low, the organs will not be adequately perfused and will show signs of hypoxia (fatigue, confusion, cyanosis, etc.). If blood pressure is too high, it can cause damage to blood vessels (leading to strokes, blindness, kidney failure, heart failure, etc.). Therefore, arterial pressure commonly referred to as blood pressure”) must be carefully regulated. This occurs via several mechanisms, but all mechanisms ultimately affect the “factors” that can affect blood pressure, which are TPR, HR, blood volume, and inotropic state.
The factors that control arterial pressure are cardiac output and vascular resistance. This is often written in equation form, where MAP = mean arterial pressure, which is the average pressure over time in the aorta, and is usually about 100 mmHg, CO = cardiac output, which is normally about 5 liters/minute and TPR = total peripheral resistance, which is determined by the diameters of the arterioles of the body. If the body is going to affect MAP it must do so by affecting either CO or TPR.
MAP = CO x TPR
CO = Heart Rate x Stroke Volume
Heart Rate (normal is 72 bpm). Affected by the sympathetic nervous system. Epinephrine and norepinephrine will bind to β1 receptors to increase HR. Stimulated by the baroreceptor reflex.
Stroke Volume (normal is 65 ml): Amount of blood ejected from the each beat Can be affected by preload and inotropic state (contractility) of the heart. Both of these can be adjusted through different mechanisms.
Preload: Amount of blood in the heart at the end of diastole (end of filling). Indicated by end-diastolic volume. Preload is determined by venous return (amount of blood flowing into the heart) which is usually determined by the amount of blood in the circulation and the tone of venous vessels.
Inotropic State: The strength of the contraction of the heart. Leads to an increase in SV even at the same preload. Affected by epinephrine and norepinephrine binding to β1 receptors on the heart.
Total Peripheral Resistance
Affected by anything that affects the diameter of the arterioles. This includes a variety of neurotransmitters and hormones as well as molecules released during allergies, infections, etc.
Neurotransmitters: Epinephrine and norepinephrine are released as molecules of the sympathetic nervous system. They cause a constriction of arterioles via α1 receptors. These hormones are normally released when blood pressure is low (baroreceptor reflex).
Hormones: Hormones such as angiotensin II and anti-diuretic cause constriction of vessels when they are released/formed at high levels. This normally occurs when blood pressure is very low.
Histamine: Released in large amounts in severe allergic reactions Vasodilates blood vessels after binding to H1 receptor.
Endotoxin: Released from Gram negative cell membranes. Potent vasodilator that can lead to a large decrease in blood pressure (septic shock).
Adapted from a handout by Ron Gerrits, 2007
PhysioEx: Exercise 11: Blood Analysis