Lab 10: Physiology of the
Circulatory System

• Circulatory System—Made of the Heart, Blood Vessels and
Blood
• Large organisms require a transport system to distribute nutrients and oxygen and to remove wastes and CO2 from cells.

• Open Circulatory System— pumps blood into an internal cavity called a hemocoel (or cavities called sinuses.
• The hemocoel bathes tissues with oxygen- and nutrientcarrying fluid (hemolymph).
• The hemolymph returns to the heart through holes called ostia.
• Insects and most mollusks
• Closed Circulatory System— the oxygen- and nutrientcarrying fluid (blood) is confined to vessels
• Annelids, certain mollusks and vertebrates

• Heart—a 4-chambered organ whose function is to circulate blood by rhythmic contractions
• The heart pumps oxygenated blood from the left ventricle out to the aorta.

• Arteries
• Vessels moving away from the heart
• Branch into smaller vessels, the arterioles, and then into capillaries
• Veins
• Vessels moving toward the heart
• Coming from capillaries, then into larger vessels called venules, then into veins

veins
venules
artery arterioles

▫ blood flows away from heart
▫ thicker walls
 provide strength for high pressure pumping of blood
▫ elastic & stretchable

Blood flows toward heart
▫ blood returns back to heart
▫ thinner-walled
 blood travels back to heart at low speed & pressure
 why low pressure?
 far from heart
Open valve
 blood flows because muscles contract when we move
 squeeze blood through veins
▫ valves in large veins
Closed valve
 in larger veins one-way valves allow blood to flow only toward heart

▫ very thin walls
▫ allows diffusion of materials across capillary
 O
2
, CO
2
, H
2
O, food, waste waste body cell
CO
2
O
2 food

• The cardiac or heart cycle refers to the rhythmic contraction and relaxation of heart muscles.
• http://highered.mcgrawhill.com/sites/0072495855/student
_view0/chapter22/animation__the
_cardiac_cycle__quiz_2_.html
• http://www.youtube.com/watch?v= rguztY8aqpk

• Blood moving through the blood vessels exerts pressure against the vessel walls.
• This blood pressure is highest in the aorta.
• It decreases as the blood moves through the arterioles, capillaries, venules, and veins.

• With each contraction of the heart, you can feel the expansion and recoil of the elastic arteries where they pass near the surface of the skin.
• This is the pulse. When you take your pulse, you measure heart rate—the number of times the heart contracts per minute.

• Two components of Blood
Pressure:
• Systolic Pressure—the pressure in the arteries during the ventricular contraction phase of the heart cycle. The pressure in the vessel is the highest at this time.
• Diastolic Pressure—the pressure in the arteries when the ventricles are relaxed. The pressure is at its lowest point, but it doesn’t drop to zero.

• http://www.phschool.com/sci ence/biology_place/labbench/ lab10/measpr1.html

• Measurement 1: Baseline— take BP after the student has been lying down for 5-10 minutes.
• Measurement 2: Take BP right after standing up. The expected change is that the BP will increase in an effort to overcome the force of gravity that makes the movement of blood through the circulatory system more difficult.
• Measurement 3: Now the pulse rate is taken after standing for a few minutes.
This will provide a baseline to compare the effects of physical challenges on an individual’s pulse.
• Measurement 4: The pulse rate is taken after lying down for 5-
10 minutes. The expected change here is that the pulse rate will decline when lying down just as BP does; the force of gravity is reduced and thus less effort is required to move blood through the system.

• Measurement 5: The pulse rate is taken after standing up again. As with BP, the expected change is that the pulse rate will increase on standing up, owing to gravity.
• Measurement 6: The subject performs some type of exercise and then immediately measures his or her heart rate.
The subject then measures his or her pulse every 30 seconds after the completion of the exercise, until the pulse has returned to the original level from measurement 2.
• The point of the repeated pulse readings in measurement 6 is to determine the “physical fitness” of an individual. The quicker an individual’s heart rate and BP return to normal, the more “fit” that individual is.
• Following that same logic, it takes longer for people who are in better shape to reach their maximum heart rate because their hearts are
“trained” to pump out more volume per beat.

• An ectothermic animal is one whose basic metabolic rate increases in response to increases in temperature.
• Examples of ectothermic animals are: all animals except birds and mammals.
• In contrast, endothermic animals such as birds and mammals have body temperatures that are relatively unaffected by external temperatures.

• In the Cellular Respiration
Lab, you experimented with peas and saw how the rate of oxygen consumption during cellular respiration varied with temperature.
• In that lab, you experimented with peas to see how the rate of oxygen consumption during cellular respiration increased with temperature.

• In animals, an increase in cellular respiration triggers homeostatic mechanisms that increase both breathing and heart rate, resulting in more oxygen being available to cells.
• In the second part of this lab, you will study the relationship between temperature and metabolic activity in an ectothermic animal.
Daphnia magna

• Thermoregulation is is the maintenance of internal temperatures within a range that allows cells to function.
• It may involve both physiological and behavioral adaptations.
• For example, humans thermoregulate by sweating and shivering, dogs by panting, and snakes by basking on sunny rocks.
Because ectotherms' temperature remains close to that of their environment, they face special challenges in thermoregulation.
Ectotherms exhibit a variety of behaviors that allow them to gain or lose heat.

• The rate of metabolism in ectothermic animals increases as the environmental temperature increases.
• This rise occurs because the reactants in the cell have greater thermal energy, and many cellular enzymes are more active as temperature increases.
What is the relationship between metabolic rate and a 10 °C increase in
• This effect is noticeable in a range from approximately 5°C to
35°C; at temperatures much higher than this, enzymes become denatured.
temperature?

• In this experiment, water fleas
(Daphnia), are used to measure the effect of temperature changes on ectothermic animals.
• This experiment requires the establishment of a baseline heart rate for the animal
• After this, the temperature should be raised in 5-degree increments and the heart rate recorded every 5 degrees.
• What would the expected result be?
http://www.youtube.com/watch
?v=HhOUwlOdxkA
Because metabolic rate increases with increasing temperature, ectotherms do not become active until their body has absorbed heat and warmed up. This accounts for the sluggish early morning behavior of ectotherms such as snakes.

10
• The relationship between temperature and metabolic rate is often measured as Q
10
If the metabolic rate doubles
. with a 10°C increase in temperature, then Q
10
= 2.
• http://www.phschool.com/sci ence/biology_place/labbench/ lab10/design2.html