Biology 20 - Patricia Schwandt Courses



Biology 20

Circulatory System

General Outcome 2 – Students will explain the role of the circulatory and defence systems in maintaining an internal equilibrium.

A. Functions of the Circulatory System

• Circulatory systems can be either open or closed. Open systems do not have the blood contained to vessels – insects. Closed systems have all of the blood moving through the body via vessels – humans. Closed systems are more efficient at transporting material than open systems.

• On average, your body has about 5 liters of blood continually traveling through it by way of the circulatory system.

• The heart, lungs, and blood vessels work together to form the circle part of the circulatory system. The pumping of the heart forces the blood on its journey.

• Our circulatory system has several functions:

1. Carries nutrients to cells

2. Carries wastes away from cells

3. Transports chemical messengers to all parts of the body (hormones)

4. Distributes heat

5. Houses immune system cells

The body’s circulatory system has three distinct parts:

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• 1. Pulmonary circulation – blood to the lungs

• 2. Coronary circulation – blood to the heart

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• 3. Systemic circulation – blood to the rest of the body

• Systemic circulatory system supplies nourishment to all the tissues located throughout the body, with the exception of the heart and lungs because they have their own systems.

• The systemic circulatory system is an intensive network of blood vessels.

B. Blood Vessels

The human body has three types of blood vessels.

• Arteries

• Capillaries

• Veins

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a) Arteries

• High pressure blood vessels that carry blood away from the heart.

• Composed of three distinct layers.

• The outer and inner layers are rigid connective tissue, whereas the middle layer is made up of muscle fibers.

Real-life Applications

• Aneurysm – fluid-filled bulge in a weakened wall.

• Atherosclerosis – buildup of fat deposits in inner wall of the artery.

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b) Arterioles

• Fine branches from the arteries. The middle layer is composed of elastic fibers and smooth muscle. The diameter of the arterioles is regulated by the nerves from the autonomic nervous system (unconscious control = involuntary).

• Vasoconstriction – contraction of smooth muscle in the arterioles, reducing the diameter of the blood vessel. This reduces blood flow to an area.

• Vasodilation – relaxation of smooth muscle in the arterioles, increasing the diameter of the blood vessel. This increase blood flow to that area, thereby, increasing the delivery of nutrients to tissues, and increasing the capacity of the cells in that localized area to perform energy-consuming tasks.

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Real-life Applications

• Blushing

• Paleness due to being frightened or sick

c) Capillaries

• Single layer of cells – site of fluid and gas exchange between the blood and the body cells. The single layer is ideal for diffusion; however the capillary beds are easily destroyed. High blood pressure or any impact can rupture the thin layered capillary.

Real-life Application

• Bruising – rupture the capillary beds, which allows for blood to flow into the interstitial spaces

d) Venules

• Small veins that lead away from the tissues (capillaries) to begin the journey back to the heart.

e) Veins

• Carry blood back to the heart. Large vessels with thin walls – there is no muscle fibers located here.

• Contains one-way valves to help pull the blood back towards the heart against the force of gravity. Contraction of skeletal muscles surrounding the veins will also help to pump the blood back towards the heart. The one-way valves will open when pressure increases inside the vein.

• Veins act as blood reservoir – as much as 50% of your total blood volume can be found in the veins at any one time.

Real-life Application

• Varicose (Spider) Veins – large volumes of blood can distend the veins. When this pooling of blood occurs over a long period of time the one-way valves are damaged.

Worksheet – Blood Vessels

1. Label the following diagram

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2. Use blue and red to indicate whether the vessel carries oxygenated blood (red), deoxygenated blood (blue) or both.

3. Compare the structure and function of the three types of blood vessels.

|Blood Vessel Type |Structure Description |Function |

|Artery | | |

| | | |

|Vein | | |

| | | |

|Capillary | | |

| | | |

Heart → Arteries → Arterioles → Capillaries → Venules → Veins → Heart → Lungs

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C. Heart Structure/Function

Define the following terms:

|Aorta | |

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|Septum | |

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|Right atrium | |

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|Left atrium | |

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|Right ventricle | |

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|Left ventricle | |

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|Superior vena cava | |

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|Inferior vena | |

|Cava | |

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|Chordae tendonae | |

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|Left pulmonary artery | |

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|Left pulmonary vein | |

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|Right pulmonary artery | |

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|Right pulmonary vein | |

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|Semilunar valves | |

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|Atrioventricular valves | |

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|Tricuspid valve | |

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|Bicuspid valve | |

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D. Blood Flow and the Heart

Pulmonary Circulation – blood vessels that carry blood to and from the lungs.

Systemic Circulation – blood vessels that carry blood to and from the body.

Blood Flow:

1. Deoxygenated blood reaches the heart through the inferior and superior vena cava and empties into the right atrium.

2. Blood moves through the AV valve into the right ventricle.

3. Blood is pumped through the semilunar valve into the right and left pulmonary arteries (**these are the only arteries that carry deoxygenated blood**)

4. Oxygen diffuses into the blood in the lungs.

5. Oxygenated blood now enters the pulmonary veins which take the blood back to the heart (**these are the only veins that carry oxygenated blood**)

6. Blood enters the left atrium and moves through the AV valve into the left ventricle.

7. Oxygenated blood is pumped out through the semilunar valve into the aorta where it will travel to the body tissues.

8. Tissues use the oxygen/nutrients/fluids in the blood, then the deoxygenated blood moves through the venous system back towards the inferior and superior vena cava.

Worksheet - Flow of Blood Through the Heart

1. Using blue and red pencils or pens, diagram the pathway of blood through the heart using arrows. Use blue to represent deoxygenated blood and red for oxygenated blood.

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2. Using the above diagram as a reference, fill in the missing terms in the sentences below.

a) Blood enters the right atrium through the _______________________.

b) Blood flows from the right atrium into the right ventricle through the _________________.

c) Blood is pumped from the right ventricle into the pulmonary trunk that splits into the right and left _____________________.

d) Blood returns from the lungs by way of the right and left ____________________.

e) Blood enters the ____________________ when it returns from the lungs.

f) Blood flows past the ________________________ as it enters the left ventricle.

g) The left ventricle pumps out past the ______________________ into the aorta.

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E. Nervous Control of the Heart

Receptors in the body monitor the concentration of chemicals in the blood and the blood pressure.

1. Baroreceptors – monitor pressure in the aorta and carotid artery

2. Chemoreceptors – monitor amount of CO2 in the blood.

These receptors send signals to a specialized area in the brain called the medulla oblongata. The medulla responds by stimulating one of two nerves:

1. Parasympathetic nerve – tells the heart to beat at a normal rate.

2. Sympathetic nerve – tells the heart to increase the heart rate.

These nerve control the heart by stimulating a specialized area in the right atrium called the sinoatrial node (SA node).

The SA node is the pacemaker…. It causes the heart to beat approximately 70 times each minute. The following sequence of events outlines the nervous control of the heart:

1. The beat (contraction) is generated in the SA node.

2. Electrical impulses pass on to both atria, causing them to simultaneously contract.

3. The impulses then move on to a second node called the atrioventricular node (AV node).

4. The message to contract is then relayed quickly down special nerves in the septum called the Bundle of His.

5. The message is sent into extensions of nerves in the ventricle walls called the Perkinje Fibres.

6. Both ventricles are now stimulated to contract at the same time.

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F. Electrical Conductivity of the Heart

The electrical activity of the heart can be monitored by using an electrocardiogram (ECG).

Changes in the electrical current reveal normal or abnormal events in the cardiac cycle.

Pwave – atrial contraction

QRS – ventricular contraction

T – ventricles relaxed

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G. Heart Sounds

The sounds of the heart are referred to as lub and dub.

Lub is the closing of the AV valves (ventricles pumping).

Dub is the closing of the semilunar valves (atria pumping).

The Cycle

1. AV valves open.

2. Ventricular contraction – systole

3. AV valves close

4. Lub sound heart

5. Semilunar valves close

6. Dub sound heard

7. Ventricular relaxation (filling with blood again) – diastole

Heart rate – the number of beats per minute (around 72 bpm)

Stroke volume is the amount of blood passing through the heart with each beat (about 80mL)

Cardiac output is the amount of blood pumped each minute.

Cardiac output = heart rate x stroke volume

= 72bpm x 80mL/beat

= 5760 mL/beat

Thought Lab - How Much Blood Does Your Heart Pump?

Investigate the relationship between cardiac output and heart rate

Cardiac output is the volume of blood pumped by each ventricle per minute. Because humans have a closed circulatory system, the cardiac output is the same as the volume of blood that traverses the systemic or pulmonary circulations per minute. It is calculated by multiplying the heart rate by the stroke volume. Stroke volume is the volume of blood ejected by each ventricle per beat.

A healthy heart with a normal cardiac output pumps about 5 to 6 litres of blood every minute when a person is at rest. The heart pumps about 75 mL each time it beats, and it beats an average of 70 times each minute.

Cardiac output = stroke volume × heart rate

Cardiac output = 75 mL × 70 beats per minute

Cardiac output = 5.3 litres per minute

Cardiac output increases during exercise because of an increase in heart rate and stroke volume. When exercise begins, the heart rate increases up to about 100 beats per minute. As exercise becomes more intense, skeletal muscles squeeze on veins more vigorously, returning blood to the heart more rapidly. In addition, the ventricles contract more strongly, so they empty more completely with each beat.

During exercise, the cardiac output increases to a maximum of about 25 litres per minute in an average young adult. Although the cardiac output has increased by five times, not all organs receive five times the blood flow; some receive more, others less. This is because the arterioles in some organs, such as those in the digestive system, constrict, while arterioles in the muscles that are working and in the heart (another muscle) dilate. Vasodilation greatly increases blood flow; vasoconstriction greatly decreases blood flow.

What to do

1. Determine your heart rate by taking your pulse.

2. Multiply your pulse rate by the stoke volume (75 mL). Assume for the purposes of this activity that the stroke volume remains constant.

3. Do this for different levels of activity (sitting at rest, lying on the floor, running on the spot), and compare your results.

Answer the questions below

|Type of Activity |Pulse rate per minute |Stroke volume |Cardiac Output (L) |

| | |(mL) | |

| | | | |

|Sitting, at rest | | | |

| | | | |

|Lying on the floor | | | |

|After 2 minutes of running on | | | |

|the spot | | | |

1. Define the terms “cardiac output” and “stroke volume.”

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2. DID YOUR CARDIAC OUTPUT INCREASE OR DECREASE DURING THE 2 MINUTES OF EXERCISE? EXPLAIN WHY.

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3. EXPLAIN WHY SOME OF YOUR ARTERIOLES DILATE WHILE OTHERS CONSTRICT WHEN YOU EXERCISE.

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4. YOUR BODY CONTAINS APPROXIMATELY 5 LITRES OF BLOOD. HOW LONG DOES IT TAKE FOR THE ENTIRE VOLUME OF BLOOD TO PUMP THROUGH YOUR HEART WHEN YOU ARE SITTING?

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H. BLOOD PRESSURE

Blood pressure is the pressure exerted on the walls of the blood vessels. Constant blood pressure is needed to maintain the proper functioning of all other systems. Blood pressure is measured in the arteries.

Diastolic (relaxation) pressure is about 35% lower than systolic (contraction) pressure.

Normal blood pressure for an adult at rest is 120/80 mmHg (systolic/diastolic)

Blood pressure is measured using a sphygmomanometer.

Blood pressure readings can vary depending where in the body it is being measured.

1. Highest in left ventricle – needs to pump blood to the entire body.

2. High in systemic circulation – body

3. Lower in pulmonary circulation – lungs

4. Lowest in the right side of the heart – only has to pump blood to the lungs.

Regulation of Blood Pressure

Blood pressure is regulated by special receptors called baroreceptors, the medulla oblongata, and nerves called the sympathetic and parasympathetic.

High Blood Pressure

Baroreceptors in the aorta and carotid artery signal the medulla. This in turn is going to increase parasympathetic nerve function and decrease sympathetic nerve function in order to decrease blood pressure.

Arterioles dilate which makes the stroke volume decrease and therefore, the blood pressure will also decrease.

Low Blood Pressure

Baroreceptors in the aorta and carotid artery signal the medulla. The medulla increases sympathetic nervous system function and decreases parasympathetic nervous system function.

Arterioles constrict which makes the stroke volume increase and therefore, increasing the blood pressure.

Stress and Exercise

Sympathetic nerve stimulates the adrenal gland which then secretes adrenalin (epinephrine). Adrenalin has three functions:

1. Releases red blood cells from the spleen to increase O2 delivery.

2. Vasodilation of arterioles in heart, brain, muscles.

3. Vasoconstriction of arterioles in kidneys, stomach, intestines.

Most active tissues get the priority – fight or flight response.

Lab – Factors Affecting Heart Rate and Blood Pressure

Hypothesis

Make and record a hypothesis about the effects of at least two different factors on heart rate and blood pressure.

Safety Precautions

Do not over-inflate the blood pressure cuff. Students with circulatory or blood pressure problems should not be test subjects.

Materials

• blood pressure cuff

• watch with a second hand or a digital display of seconds

Experimental Plan

1. Working in a group, prepare a list of ideas for testing your hypothesis, using the materials available in your classroom.

2. Decide on one idea you can use to design an experiment that can be conducted in your classroom.

3. What will be your manipulated variable? What will be your responding variable(s)? What will be your control variable(s)? How many trials will you run? Remember that you should test one variable at a time. Plan to collect quantitative data.

4. Outline, step-by-step, a procedure for your experiment. Assemble the materials you will require.

5. Design a table for collecting your data.

6. Obtain your teacher’s approval before starting your experiment.

Data and Observations

7. Conduct your experiment, and record your results. Prepare a graph or chart to help you communicate your findings to other groups in the class.

Analysis

1. What was the resting blood pressure and heart rate for each test subject?

2. How did the blood pressure change as a result of the factor you were testing? How did the heart rate change as a result of the variable you were testing?

3. How long did each change last after termination of the testing factor?

Conclusions

4. Compare your results with the results of other groups in the class. Explain any differences.

5. What is the adaptive advantage of a temporary increase in blood pressure? What is the adaptive advantage of a temporary increase in heart rate?

Extension

6. High blood pressure is a common problem in North America. Fortunately, many different treatments are available. Some examples include treatments used in Western medicine, traditional Aboriginal medicine, traditional Chinese medicine, Ayurvedic medicine, naturopathy, homeopathy, massage therapy, and yoga. Research three different treatments for high blood pressure, and prepare a brief report to compare the main features of these treatments. If someone wanted to receive treatment for high blood pressure, which would you recommend? Justify your choice.

7. If possible, obtain two types of blood pressure cuffs. Newer cuffs give digital readings, while older cuffs require the use of a stethoscope to listen to the sounds of blood moving through the vessels. Use both types of blood pressure cuff to measure a partner’s blood pressure. Compare the readings you got, and describe the differences in your experiences with the two cuffs.

I. Capillary Fluid Exchange

Every cell in the body is within 0.1mm of a capillary. Capillaries serve very important functions:

1. Provides cells with nutrients and gases (glucose and O2).

2. Takes away cell wastes (CO2).

3. Maintains a constant fluid level.

4. Exchanges fluid between blood and extracellular fluid (ECF).

A. Filtration

Occurs in the arteriole end of the capillary. Water and small ions move out f the capillary into the ECF. This movement is the result of a pressure gradient. The water and ions move from an area of high pressure to an area of low pressure.

B. Absorption

Occurs in the venule end of the capillary. Water moves from ECF into the capillary – large proteins in the capillary makes the concentration of H2O greater in the ECF. This movement is the result of an osmotic gradient – going from an area of high water concentration to an area of low water concentration.

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| |Cause |Effect |

|Hemorrhage | | |

| | | |

| | | |

|Edema | | |

| | | |

| | | |

|Allergic Reaction | | |

| | | |

| | | |

J. Lymphatic System

1. • a noncircular system of vessels that takes fluids from tissues to the bloodstream

2. • vessels are similar to veins…they use one-way valves and muscular contractions to move the fluids

3. • lymph is any fluids and proteins that collect in the ECF (mostly water)

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4. • large lymphatic ducts collect the lymph…the main duct is called the thoracic duct

5. • lymph nodes are located along the vessels (mainly in neck, groin and armpits)

6. • these nodes manufacture and house immune system cells that filter bacteria and debris from the lymph

7. • blocking of lymphatic ducts can cause severe edema

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Worksheet – The Lymphatic System

1. Label the human lymphatic system diagram below. Use green to indicate the lymphatic vessels.

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2.

A) WHERE DOES LYMPH COME FROM?

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B) HOW IS LYMPH RETURNED TO THE CARDIOVASCULAR SYSTEM?

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C) WHAT FEATURE DO LYMPHATIC VESSELS SHARE WITH VEINS TO ENSURE ONE-WAY FLOW?

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D) WHAT IS THE KEY DIFFERENCE IN THE CIRCULATION SYSTEMS OF BLOOD AND LYMPH?

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3. LABEL THE DIAGRAM BELOW.

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4. Another function of the lymphatic system is to help fight infection.

A) HOW DOES THE LYMPHATIC SYSTEM FIGHT INFECTION?

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B) WHY DO YOUR LYMPH NODES SWELL WHEN YOU ARE ILL?

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K. BLOOD FUNCTIONS

1. • our blood has five main functions

1. 1. transportation – nutrients, wastes, hormones, etc.

2. 2. water balance

3. 3. pH balance

4. 4. maintain body temperature

5. 5. house immune system cells

L. Blood Composition

1. • blood is made up of a variety of blood cells

2. • all blood cells come from stem cells in bone marrow…the stem cells differentiate to become the different blood cells

3. • 1 L of blood contains 200 mL of O2 which is carried by hemoglobin

***blood carries 70X more O2 with hemoglobin (you can live ~ 5 minutes without O2 but without hemoglobin you would live 4.5 seconds!)

|Component (%) |Structure |Function |Other |

|Plasma | | | |

|(~55 %) |• 90 % water |• maintains blood volume |• proteins – globulin,|

| |• 10 % glucose, proteins, |• proteins for homeostasis |albumin, fibrinogen |

| |vitamins/minerals, wastes, gases |• carries O2 and CO2 | |

|RBC’s | | | |

|(~45 %) |• contains hemoglobin…280 million |• carry oxygen |• anemia is a ↓ in |

| |on one RBC (heme is pigment, globin|• hemoglobin + O2 forms oxyhemoglobin|RBC’s |

| |is protein) | |• injury ↓ RBC’s |

| |• no nucleus |• also carries CO2 |• high altitude – need|

| |• biconcave disks |• hemoglobin + CO2 forms |more RBC’s because |

| |• live ~ 120 days |carbaminohemoglobin |less O2 |

| |• produced in bone marrow | | |

|WBC’s | | | |

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