The HeartCARDIAC CIRCULATION

Objectives1.Identify the structures of the heart.2.Describe the path of blood through the heart.3.Describe the pulmonary and systemic circuits

THREE CIRCULATORY SYSTEMS

- There are 3 circulatory systems in your body

1) Systemic- delivers blood between the heart and body cells (we have covered this… Describe..)

2) Cardiac-circulation of blood in the heart

3) Pulmonary- blood goes to the lungs to be oxygenated- delivers blood between the heart and the lungs

heart oxygenated blood

artery

arterioles

capillaries (half blue) gas exchange

venuoles deoxygenated blood

veins

heart

Systemic circulation:

This section of the system including the right side of the heart, deals with the deoxygenated blood.

This section of the system including the left side of the heart, deals with the oxygenated blood.

Lungs

Body cells

• The mammalian heart is a double pump, separated by a wall of muscles called a septum

The interior of the heart has:•4 chambers – two atria (top chambers)

- two ventricles (bottom chambers)•4 valves – two atrio-ventricular valves - two semi–lunar valves•Septum – a wall

Each side of the heart is divided into two chambers: an upper atrium and a lower ventricle (four chambers in total)

• It is used to push blood through the body and provides a connection between our pulmonary and systemic circulatory systems

• The heart is supplied by blood via the coronary arteries (come off main aorta)

Refer to your heart diagram as we move through the lesson….

You should be able to label it by the end!

The two top chambers are called the right atrium and the left atrium. Atria are thin-walled and flexible allowing for easy filling or collecting of blood

The two bottom chambers are called the right ventricle and the left ventricle. Ventricles are thick-walled and strong enough to pump blood out of the heart. The left ventricle is the most muscular chamber of the heart.

The two atrio-ventricular valves lie between the atria and the ventricles. R◦ Right it is called the tricuspid valve ◦ Left it is called the bicuspid valve.

The two semi-lunar valves lie between the ventricles and their attached vessels. They are called the right and left semi-lunar valves.

A wall that separates the heart into a right side and a left side. This ensures that blood in each side of the heart stays in that side of the heart.

Two Pumps

The right pump on the right side of the heart, collects or fills with deoxygenated blood coming back from the body by way of veins and then pumps it to the lungs

The left pump on the left side of the heart, collects or fills with oxygenated blood coming from the lungs and pumps it into the body by way of arteries

  There are 4 main vessels that are responsible for

bringing blood into the heart and out of the heart

Right Side – the superior and inferior vena cava bring deoxygenated blood from the body into the right atrium; two pulmonary arteries carry this deoxygenated blood away from the heart and into the right and left lung.

Left Side – the pulmonary veins carry oxygenated blood from the right and left lung towards the left atrium of the heart; the aorta carries this oxygenated blood away from the left ventricle of the heart to the body  

• http://www.fed.cuhk.edu.hk/~johnson/teaching/transport/animations/HyperHeart.swf

• http://www.mayoclinic.com/health/circulatory-system/MM00636

• http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_pumping.html

Your Task

1. Label your diagram of the heart. This could appear on the test.

2. On your second heart, trace the path of blood as it enters the heart on its way to the lungs and then back from the lungs to the body.

1. Use colour to represent oxygenated and deoxygenated blood.

3. Answer questions 1-4 on page 258 of your text.

OVERALL CARDIAC CIRCULATION

deoxygenated blood is collected

from your upper body through the superior vena cava

from your lower body through the inferior vena cava

right atrium

(through atrioventricular tricuspid valve)

right ventricle

(through semilunar valve)

right pulmonary artery left pulmonary artery

right lung left lung

capillaries -> CO2 exchanged for O2 through simple diffusion

pulmonary veins

left atrium

(through atrioventricular bicuspid valve)

left ventricle

(through semilunar valve)

aortaarteries

arterioles

veins

venules

capillaries (O2 is dropped off, CO2 is picked up)

Pulmonary Circuit

Plenary

1. Trace the path of blood through the heart.

2. What is the function of A-V and Semi lunar valves

3. What is different about the pulmonary arteries and veins

Control of the Heartbeat

Objectives:1.Describe the sequence of events involved in the heart contracting.2.Explain what intrinsic and extrinsic control is3.Explain what pulse and blood pressure is and how it is measured.

• Each heartbeat is called a cardiac cycle

• On average the heart beats 72 b/minute

• Each heartbeat lasts 0.85 seconds

• Systole refers to the contraction of the heart

• Diastole refers to the relaxation of the heart

• One heartbeat consists of the following:

• Two atria contract

• Two ventricles contract

• Four chambers relax

Heart Beat

• These are sounds produced by the heart caused mainly by the vibrations produced when the heart valves close and the blood bounces back against the walls of the ventricles or blood vessels

Heart Sounds

First Heart Sound◦ is the beginning of systole◦ the sound is a longer and lower pitched ‘lub’◦ it is caused by vibrations occurring when the A-V

valves close due to the pressure of the ventricles filling with blood from atria

 Second Heart Sound

◦ this sound occurs at the end of systole and the beginning of diastole

◦ the sound produced is a shorter and sharper pitched ‘dub’◦ Atria are relaxed and fill with blood◦ it is caused by vibrations occurring when the semi-

lunar valves close preventing blood from re-entering the ventricles 

Stethoscope is a diagnostic tool used to help determine heart sounds of systole and diastole (TRY LISTENING to your partners heart!!)

‘‘LUB – DUB’LUB – DUB’

HEART MURMUR

• Slush sound after the ‘lub’ heart sound that may be caused by faulty valves, in particular the A-V valves, allowing blood to back flow into the atria from the ventricles.

• Rheumatic fever may be a cause of faulty valves

• faulty valves can be surgically corrected

Intrinsic Control– internal (inside) control of the heartbeat

  The intrinsic conduction system of the heart is responsible for

the rhythmical contraction of the heart There are four structures that form this system. They are:

i) SA nodeii) AV nodeiii) AV bundleiv) Purkinje fibres

  Nodal tissue is a unique muscle tissue of the heart It has properties of both muscle and nervous tissue Nodal tissue is located in two areas of the heart: i) the upper dorsal (back) wall of the right atrium (SA

node)ii) the base of the right atrium near the septum (AV node)

 

INTRINSIC Control of the Heartbeat

SA NODE

• Sinoatrial node sets the heart’s tempo or beat rate

• Also called the pacemaker

• Initiates the heartbeat and automatically sends out an excitation impulse every 0.85 seconds causing atria to contract

• NOTE: when the SA node malfunctions the heart still beats due to AV nodal tissue but the beat is slower. This is corrected by inserting an artificial pacemaker.

A-V NODE

• Atrio-ventricular node

• Upon completion of contraction of the atria the A-V node sends an impulse through the A-V bundle which then passes the impulse onto Purkinje fibres found throughout the periphery of the ventricles causing them to contract.

SA and AV nodes

1. SA node initiates an impulse causing both atria to contract

2. Both atria contract forcing blood into each ventricle3. AV node sends impulse onto A-V bundle to the

Purkinje fibres triggering the contraction of both ventricles

4. Both ventricles contract and force blood into both arteries (on the right side of the heart the pulmonary arteries receive the blood and on the left side of the heart the aorta receives the blood)

5. Heart relaxes allowing the atria to fill with blood

Sequence of Contraction

SA and AV nodes

There are two factors involved in outside control of the heart. They are the medulla oblongata in the brainstem and hormones

The autonomic nervous system has 2 divisions, the sympathetic and parasympathetic

The sympathetic system, when activated, increases the heart rate as directed by the medulla oblongata

The parasympathetic system, when activated, decreases the heart rate as directed by the medulla oblongata

The hormones epinephrine and norepinephrine, released by the adrenal medulla, will also increase heart rate.

EXTRINSIC Control of the Heartbeat

The medulla contains cardiac and respiratory centers that play a role in involuntary functions, such as breathing, heart rate and blood pressure.

The hormones epinephrine and norepinephrine, released by the adrenal medulla, will also increase heart rate.Epinephrine and norepinephrine also produce fight or flight responses such as increasing heart rate and increasing blood flow to skeleton muscles … to run away.

P wave – occurs just prior to atrial contractionQRS wave – occurs just prior to ventricular contractionT wave – occurs when the ventricles are recovering from contraction

The purpose of an ECG is to detect various types of abnormalities in the beating of the heart

ECG is a recording of electrical changes that occur in myocardium during a cardiac cycle (one heartbeat)

Your Task1. Read the handouts on the Circulatory System

and Blood Vessels and answer the questions.

Plenary1. What does systole and diastole mean?2. What causes the ‘Lub’ ‘Dub’ sounds your

heart makes?3. What is the ‘pacemaker’ of your heart and why

is it called this?4. Describe the sequence of events involved in

the heart contracting.5. Explain what intrinsic and extrinsic control is6. What is a heart murmur.7. What happens during systole and diastole?

Measuring Pulse and Blood Pressure

Objectives

is caused by the rhythmical expansion and recoil of the arterial walls as blood passes through the artery

it can be felt (palpated) in any artery close to the body’s surface

the two most common sites to check for a pulse are the radial artery and the carotid artery

the pulse is used in place of a direct measurement of heart rate. It is an estimation of heart rate

Pulse Points

Is the pressure or force that blood exerts against the wall of a vessel

The aorta is under the highest pressure of all the vessels and BP is lowest in the vena cava

Blood pressure is the greatest in arteries, less in capillaries and negligible in veins

The further away form the heart the vessel is, the less pressure the vessel is under

Systolic pressure is the highest arterial pressure reached during ejection of blood from the heart (ventricular contraction)

Diastolic pressure is the lowest arterial pressure measured while the heart ventricles are relaxing

Normal resting BP is 120/80 mmHg at the site of the brachial artery

BP in venules and veins is negligible

Venous return of blood is dependent upon the following three factors:

Skeletal muscle contraction Valves in the veins Respiratory movements

Skeletal muscle contraction moving blood in veins

SPHYGMOMANOMETER is a blood pressure cuff is a diagnostic tool for measuring BP usually used to measure BP at the brachial

artery

HYPERTENSION Is a condition that occurs when arterial BP is

significantly above average most of the time (at least 140/90 mmHg)

If not treated it can cause cerebral hemorrhage (stroke) or heart failure

Blood pressure accounts for the flow of blood in the arteries and the arterioles

Skeletal muscle contraction, valves in veins and respiratory movements account for the flow of blood in the venules and the veins

Blood velocity gradually decreases further away from the heart as blood pressure decreases

Blood velocity is greatest in arteries, less in arterioles, very slow in capillaries, increases slightly in venules and veins

1. Answer Questions2. P.263 #1,2,3, 5, 6,73. H/W Read about Disorders of the

Circulatory System.4. Make study notes to help you remember at

least …• 1 disorder that is associated with the heart• 1 disorder that is associated with the blood• 1 disorder that is associated with the blood

vessels.

1. Explain what pulse and blood pressure is and how it is measured.

2. What factors affect heart rate and blood pressure?

3. How can we determine if these factors are having an effect on heart rate and blood pressure?

4. When designing an experiment, why is it important to only change one variable?

5. How can you ensure that your investigation is a fair test?