Circulatory System

is located in the thoracic cavity behind the sternum

it is about the size of your fist

It uses up 15% of the bodies O2 and food supply

it is surrounded by a fluid-filled membrane called the pericardium which prevents friction

cardiac muscle is very strong

a layer of fat protects and cushions the heart

the coronary artery supplies the heart with blood

The heart has 4 chambers 2 atria (L&R) 2 ventricles (L&R)

The Septum is a wall of muscle separates the right and left sides of the heart

Septum

atria act like holding chambers for blood entering the heart

blood from the pulmonary system enters the left atrium

blood from the systemic system enters the right atrium

ventricles are strong muscular chambers that pump blood away from the heart

Your Assignment: Heart Diagram – label the structures (see page 320)

aorta left pulmonary arteryseptum left pulmonary veinright atrium right pulmonary arteryleft atrium right pulmonary veinright ventricle 2 semilunar valvesleft ventricle 2 atrioventricular (AV) valvessuperior vena cava inferior vena cavachordae tendonae (draw this in)

pulmonary circulation = blood vessels that carry blood to and from lungs

systemic circulation = blood vessels that carry blood to and from body

Superior vena cava = carries deoxygenated blood from your head to your heart

Inferior vena cava = carries deoxygenated blood from your body to your heart 

Veins carry blood to the heart deoxygenated blood reaches the heart

through inferior and superior vena cava and empties into the right atrium

blood moves through atrioventricular or (AV) valve into right ventricle

(***note: these are supported by bands of tendons called chordae tendinae)

Blood is pumped through semilunar valve into the left and right pulmonary arteries

(***note: these are the only arteries that carry deoxygenated blood)

In lungs, oxygen diffuses into the blood

Oxygenated blood enters pulmonary veins which take it back to the heart

(***note: these are the only veins that carry oxygenated blood)

Blood enters left atrium then moves through atrioventricular or (AV) valve into the left ventricle

oxygenated blood is pumped through semilunar valve into the aorta (largest artery) where it travels to body tissues

(*** note: these valves prevent the backflow of blood from the artery into a ventricle)

tissues use oxygen/nutrients/fluids that is in blood

then deoxygenated blood moves through vein system into inferior and superior vena cava

coronary arteries supply the heart muscle cells with O2 and nutrients

Is chest pain (angina) that occurs when too little O2 reaches the heart

it could be but not always caused by a blockage

if it is a blockage, then the blockage can be bypassed by using veins from other parts of the body …these are grafted into the heart

Your Assignment: Draw red (oxygenated) and blue (deoxygenated) arrows on heart diagram to show blood flow into and out of heart

Your Assignment: Page 320, 1-4

http://www.pbs.org/wgbh/nova/sciencenow/3209/05.html

It is a technique used to detect coronary artery blockage

A catheter (small thin hollow tube) is passed into an artery in the groin

The catheter is then pushed up through the aorta and into the heat

A dye is then injected into the catheter

The dye travels through the blood vessels while its image is traced by a fluoroscope

An area of restricted blood flow pinpoints the region of blockage Figure 5 Page 323

Blood samples can also be taken to determine how much O2 is in the blood in different chambers of the heart

Cardiac muscle tissue is the only muscle that can contract without external nerve stimulation

Muscle with this ability is called myogenic muscle

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

The heart's tempo is set by the sinoatrial or (SA) node

This is a bundle of specialized nerves and muscle located in the upper right atrium

The SA nodes acts as a pacemaker, and sets a rhythm of about 70 beats/min

The contraction is generated in the SA node

electrical impulses pass on to both atria, causing them to simultaneously contract

The impulses then move to the atrioventricular node (AV node)

(which acts like a conductor passing the nerve impulses)

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

It is then sent to the Perkinje Fibres

The result is both ventricles are now stimulated to contract at the same time

Monitor the concentration of chemicals in the blood and blood pressure:

baroreceptors detects blood pressure in the aorta and carotid artery

chemoreceptors detects amount of CO2

or O2 in blood

these receptors signal the medulla oblongata

the medulla oblongata responds by stimulating the autonomic nervous system

Consists of the: parasympathetic and sympathetic

nervous system

regulates equilibrium

its nerve impulses can affect heart rate

parasympathetic nervous system: tells heart to beat at a normal rate

sympathetic nervous system: tells heart to increase heart rate

sympathetic nerves send impulses to the pacemaker to increase heart rate

this increases blood flow to the tissues

Heart rate exceeding 100 beats/minute = tachychardia

E.g. exercise, drugs (cocaine, caffeine)

parasympathetic nerves are stimulated

A nerve impulse is sent to the pacemaker to slow the heart down

Low heart rate = bradycardia 

an electrocardiogram (ECG) measures the electrical activity of the heart

changes in the electrical current reveal normal or abnormal events in the cardiac cycle

Pwave = atrial contraction

QRS = ventricular contraction

T = ventricles relaxedElectrical Current (mV)

Time (s)

By comparing electrocardiograph tracings doctors can determine areas of the heart that are having problems

Case study Page 324 (Diagnosing Heart Conditions)

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

The "lubb-dubb" sound we hear is caused by the opening and closing of heart valves

lubb is the closing of the AV valves (ventricles pumping)

dubb is the closing of the semilunar valves (atria pumping)

The period of contraction is called systole 

The heart also has a period of relaxation = diastole (both atria and ventricles are relaxed)

1.The atria are relaxed and fill with blood (diastole)

2.the atria contract and AV valves open

3.blood flows and fills the ventricles

4.the ventricles contract – (systole)

5.the pressure causes the AV valves to close (lubb sound heard)

6.blood pushes through the semilunar valves and into the ateries

7.semilunar valves close (dubb sound heard)

8.ventricular relaxation (filling with blood again) – (diastole)

occur when blood leaks past a closed heart valve

People with heart murmurs must make up for decrease O2 by having the heart beat faster

1. The heart can beat faster2. The cardiac muscle can stretch….. more

than normal

the atrium accepts the normal volume of blood plus some from the ventricle (this stretches the atrium)

blood is driven to the ventricle with force which causes it to contract with force…. thus more blood to tissues

Beta blockers: are often used to treat irregular heartbeats

and high blood pressure

They slow heart rate down

Epinephrine, a stress hormone, binds to receptors on heart cells and blood vessels

This increases heart rate and narrows blood vessels (both increase blood pressure)

Beta blockers work by binding to the receptor site on the cell so epinephrine can’t bind

Result = heart is slowed….individuals may feel dizzy because of low blood pressure

Your Assignment: page 327, 1-12