Unit 8 Notes

Cardiac Muscle

• Cardiac muscle can contract spontaneously and independently, even if all nervous connections are severed

• Different muscle cells in different areas have different rhythms

– Atrial cells: 60 beats/min

– Ventricular cells: 20-40 beats/min• Because of this, we need a controlling system to

regulate & coordinate contractions!

What controls the heart beating?

• 2 controlling systems

– Nerves of Autonomic Nervous System

• Acts like “brakes” and “accelerators”

– Intrinsic Conduction System

• AKA nodal system

• Enforces a contraction rate to keep everything together

Parts of Intrinsic Conduction System

• Sinoatrial Node (SA node) - the pacemaker; where the action potential originates, starting each heartbeat

• As action potential moves, contraction of atria is stimulated

• Atrioventricular Node (AV node) - receives action potential from SA node and sends along to…

Parts of Intrinsic Conduction System• Atrioventricular Bundle

(Bundle of His) – branches off into right and left bundle branches, and then sends action potential along to…

• Purkinje Fibers – action potential received begins ventricular contraction at apex and continues contraction back up toward atria, helping to eject blood into pulmonary trunk or aortic arch

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__conducting_system_of_the_heart.html

The Cardiac Cycle

• Refers to one complete heartbeat

• Systole – heart contraction

• Diastole – heart relaxation

• Since most of pumping done by ventricles, terms usually refer to ventricles (unless otherwise stated)

• Normal length of cycle: 0.8 seconds– Translates into 75 beats/min (average)

The Cardiac Cycle• First heart sound or “lub”

– Atrioventricular valves close at beginning of ventricular systole

• Second heart sound or “dub”– Aortic and pulmonary semilunar valves close at

beginning of ventricular diastole

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__the_cardiac_cycle__quiz_1_.html

Electrocardiogram

• Electrodes placed on the surface of the body

• Action potentials through myocardium during cardiac cycle produces electric currents that can be measured

• http://video.about.com/heartdisease/Electrocardiogram.htm

Electrocardiogram• Pattern

– P wave

• Impulse moves across atria (depolarization/contraction)

– QRS complex

• Spread of impulse to ventricles (depolarization/ contraction)

• Atria repolarization/ relaxation

– T wave:

• Ventricle repolarization/ relaxation

• End of electrical activity

Cardiac Arrhythmias

• When any electrical activity of the heart is irregular

Types of Cardiac Arrhythmias

• Heart Block – AV node damaged– Ventricles beat at their own

rate (slower)– Slower heart beat can lead to

ischemia: lack of blood flow to heart

– Leads to fibrillation: rapid, uncoordinated movement of heart muscle (= cardiac arrest, death)

– Artificial pacemakers usually implanted to correct problem

Types of Cardiac Arrhythmias

• Tachycardia– Resting heart rate above 100 bpm

• Bradycardia– Resting heart rate below 60 bpm

• Heart Palpitations– Premature Atrial Contractions

• Misshapen “P” Wave

– Premature Ventricular Contractions• Misshapen “QRS” Complex / T Wave

Heart Murmurs

• Heart Murmurs: unusual sounds from heart (besides normal “lub-dub”)– Often indicate valve problems– If valve does not close, “swishing” sound from

blood flowing back– If valve is narrowed (stenosed), “rushing”

sound

Heart Murmurs

• Doctors will listen at different locations on your chest to see if valves are functioning properly

Now, let’s talk about blood flow in the rest of the body!!!

The Vascular System:

Taking Blood to the Body and Back

The Vascular System

• Arteries – carry blood away from the heart – Branch into Arterioles– Pulmonary Arteries - carry deoxygenated blood– Systemic Arteries – carry oxygenated blood

• Capillaries- exchange– One cell layer thick!– Oxygen and nutrients cross to cells– Carbon dioxide and wastes cross into blood

• Veins – carry blood back to the heart– Branch into Venules– Pulmonary Veins – carry oxygenated blood– Systemic Veins – carry deoxygenated blood– Has valves internally!

Vascular System Anatomy

• Veins & Arteries have three layers (tunics)– Tunic interna– Tunic media– Tunic externa

• Opening through which blood flows is called lumen

Vascular System Anatomy

Arteries Veins

Direction of flow

Blood Away from Heart

Blood to Heart

Pressure Higher Lower

Walls Thicker Thinner

Wall Layers

Tunica media thicker than tunica externa

Tunica externa thicker than tunica media

Lumen Smaller Larger

Valves No valves Valves

Vital Signs

Vital Signs

• Pulse

• Blood Pressure

• Respiratory Rate

• Body Temperature

• All indicate the efficiency of the system

Pulse• Pulse – pressure

wave of blood

• Monitored at “pressure points” where pulse is easily felt

• Measured on arteries because pressure is strong enough to be felt

Pulse

• Radial pulse and Carotid pulse most common (helps to have the artery close to the surface & hard surface to press it on)

• Average pulse is 65-80 beats per minute

• Pulse influenced by activity, postural changes, and emotions… stress… tests… homework… you know

• Pressure points can also be used as compression point if trying to stop blood flow

Blood Pressure

• Measurements by health professionals are made on the pressure in large arteries (usually the brachial artery)

• Pressure in blood vessels decreases as the distance away from the heart increases (not feeling the pressure created by the left ventricle as much!)

Blood Pressure

• Systolic Pressure (heart ventricles contract)

• Diastolic Pressure (heart ventricles relax)

• Blood Pressure= systolic/diastolic

• Normal= 120/80

Measuring Arterial Blood PressureMeasuring Arterial Blood Pressure

Changing Blood Pressure

• Temperature– Heat has a vasodilation effect– Cold has a vasoconstricting effect

• Chemicals– Various substances can cause increases or

decreases

• Diet

Blood

Blood Facts

• Only fluid tissue in human body

• Blood heavier than water and 5 times thicker

• Slightly basic – pH approximately 7.4

• Temperature slightly higher than body temperature (100.4°F)

• Approximately 6 quarts (1.5 gallons) in adult

•

Blood Facts

• Blood stays in a closed system except…– White blood cells travel in and out of the blood

stream (lymphatic system)– Water and solutes (ions, nutrients, etc) travel

in and out of the blood stream

Blood Functions Include…

• Distribution & Transport– Respiratory Gases– Nutrients– Wastes– Bacteria, Viruses, Toxins, etc.

• Regulation and Maintenance– Hormonal Regulation– pH balance (blood is a buffer!)– Temperature

Blood Functions Include…

• Protection– Clotting– Immunity

Composition of Blood

• Plasma – 55% of blood– Mostly water (90%)– Plasma proteins

• Albumin – pH• Clotting Proteins• Antibodies - defense

– Salts (electrolytes)– Nutrients– Waste Products– Hormones– Gases

Composition of Blood• Formed Elements -

45% of blood– Erythrocytes (Red

Blood Cells)– Leukocytes (White

Blood Cells)– Plateletes

Formed Elements

• Erythrocytes (RBC)– No nucleus, very few

organelles– Contains hemoglobin

• Iron-containing protein that helps transport oxygen

– Biconcave disk• Increases surface area for

gas transport

– Outnumber WBC 1000 to 1

– Formed by red bone marrow

Formed Elements

• Leukocytes (WBC)– Only complete blood cell; contain nucleus and

organelles– Needed for defense– Can slip in and out of blood vessels where

needed for immune response– Also created in bone marrow– Types of WBC…

Formed Elements

• Types of WBC– Granulocytes: contain granules

• Neutrophils: most common WBC, active phagocytes (destroy harmful particles or cells)

• Eosinophils: kill parasitic worms, allergies• Basophils: contain histamine (vasodilator)

Neutrophil & Eosinophil

Basophil

Formed Elements

• Types of WBC– Agranulocytes: no

granules• Lymphocytes:

produce antibodies, fighting tumors & viruses

• Monocytes: largest WBC, fight chronic infections

Monocyte Lymphocyte

Formed Elements

• Platelets– Not cells, but rather fragments– Important in blood clotting

Steps to Blood Clotting

• 1. Vessel damage, blood loss; collagen fibers exposed

• 2. Vascular spasm to decrease blood loss; Platelets become “sticky” and cling to fibers

Steps to Blood Clotting

• 3. Anchored platelets signal to attract more platelets; Platelet plug forms

• 4. Coagulation; fibers reformhttp://health.howstuffworks.com/human-body/systems/circulatory/blood3.htm

Blood Transfusions

• Body can only compensate for a certain amount of blood loss– Loss of 15-30% of blood: weakness– Loss of over 30%: severe shock, usually fatal

• Therefore, we need to replace the blood when it is lost!– Blood treated with an anticoagulant (prevents

clotting) can be refrigerated at 4°C for about 35 days

Blood Transfusions

• However, blood must be compatible with your body!– All plasma membranes of RBC bear certain

proteins (antigens) which are unique– We also have antibodies looking for antigens– We can tolerate our own antigens, but if we

get different antigens from another person, antibodies will attack RBC!

– This causes RBC’s to clump (agglutination)

Blood Transfusions

• Agglutination is bad because…– Small blood vessels will clot– Oxygen won’t get delivered to tissues– Kidney tubules will block and cause kidney

failure

• While there are 30 common RBC antigens in humans, some antigens cause a worse reaction than others

ABO Blood Groups

• Based on if type A antigen or type B antigen is inherited

• Lack of either of these antigens is called type O

• When blood is transfused, only receive antigens (not antibodies) from donor

Blood that can be

received

A, O B, O A, B, AB, O (Universal Recipient)

O (Universal

Donor)

In Summary…

• O can give to all • A can give to A and AB • B can give to B and AB • AB can give to AB only

• O can receive from O only • B can receive from B and O • A can receive from A and O • AB can receive from all

Rh Blood Typing

• Named because of the presence or absence of Rh antigens (originally studied in Rhesus monkeys)– Rh+: have antigen– Rh-: don’t have antigen

• Rh antibodies are not automatically formed in Rh- individuals; blood must be exposed to Rh+ blood to develop antibodies against it

Rh Blood Typing

• Rh+ person can get either + or – blood because they have no antibodies!

• However, if Rh– person receives Rh+ blood, antibodies can form– Okay for first transfusion, but in 2nd

transfusion, antibodies will attack new Rh+ blood = bad.

• In summary:– Rh+ can get Rh+ or Rh– blood– Rh– should only get Rh– blood

Rh Blood Typing

• Also, if Rh- woman becomes pregnant with Rh+ baby, she can develop antibodies– The antibodies would

then attack the blood of a second Rh+ baby = BAD!

– Mom can be treated so that this doesn’t happen

Erythroblastosis fetalis

Cardiovascular Conditions

Review of some terms…

• Ischemia: lack of blood flow to the heart

• Fibrillation: rapid, uncoordinated movement of the heart muscle due to ischemia

• Cardiac Arrest: blood flow to body ceases, leads to death

Conditions

• Arteriosclerosis– Any hardening of

arteries, which leads to narrowing of artery lumen, and so insufficient blood supply to the organ it feeds

• Atherosclerosis– Hardening specifically

due to plaque buildup

• A Balloon Angioplasty or a Stent can be used to treat the previous conditions

• http://www.nhlbi.nih.gov/health/dci/Diseases/Angioplasty/Angioplasty_All.html

Conditions

• Thrombosis: blood clot in an intact blood vessel – Can happen in arteries or veins– Most common in veins of the legs– Compression stocking and anticoagulants can

help

Conditions

• Embolism: occurs when a thrombosis migrates from one part of the body to another (via circulation) and causes a blockage

Conditions

• Pulmonary Embolism: when an embolism blocks the pulmonary arteries specifically

• http://video.about.com/quitsmoking/Pulmonary-Embolism.htm

Conditions

• Varicose Veins: veins have become enlarged and twisted– Can happen as blood pressure in

veins increases and gets blocked around the valves

– More common in women; linked with heredity; becomes worse with obesity and prolonged standing

– http://video.about.com/seniorhealth/Varicose-Veins.htm

Conditions

• Hypertension: high blood pressure– Systolic above 140 and diastolic above 90– Can indicate other issues– http://video.about.com/highbloodpressure/

Blood-Pressure.htm

• Your chances of developing high blood pressure are also higher if you:

– Are overweight

– Are a man over the age of 45 / woman over 55

– Have a family history of high blood pressure

• Other things that can raise blood pressure include:

– Eating too much salt

– Drinking too much alcohol

– Not getting enough potassium in your diet

– Not doing enough physical activity

– Taking certain medicines

– Having long-lasting stress

– Smoking

Conditions

• Coronary Heart/Artery Disease (CHD)– End result of plaques within the walls of the

arteries that supply the myocardium with oxygen

– #1 killer in the US– Often leads to myocardial infarction– Angina (heart pains) can indicate CHD

Conditions

• Myocardial Infarction– AKA Heart Attack– A coronary artery is blocked, and so the heart

muscle itself is starves of oxygen– ischemia fibrillation cardiac arrest

death– If the person survives, their muscle tissue can

be severely damaged

For your information…

• 1.5 million heart attacks suffered in the United States each year

• 500,000 will be fatal

• The total direct and indirect cost of cardiovascular disease (CVD) and stroke in the United States for 2008 is an estimated $448.5 Billion. By comparison, in 2007, the estimated cost of all cancer related costs, both benign and malignant was only $219 billion.

• http://video.about.com/heartdisease/Heart-Attack.htm

• http://video.about.com/heartdisease/Heart-Bypass.htm

• http://video.about.com/heartdisease/LV-Assist-Device.htm

Conditions

• Congestive Heart Failure– The heart muscle is weakened (due to CHD,

myocardial infarctions, hypertension, viral infections, or stresses such as childbirth & chemo/radiation)

– Decline in pumping efficiency– Inadequate circulation in body – leading to

cyanosis and swelling of limbs/abdomen– Because blood not being pumped to body, can get

backed up in lungs, causing shortness of breath

• http://video.about.com/heartdisease/Congestive-Heart-Failure.htm

Conditions

• Aneurysm– Blood filled bulge of blood

vessel– Usually an artery– Caused by disease or weak

vessel wall– Base of brain and aorta most

common places to happen– When it bursts = BAD.

Conditions

• Heart Block– AV Node is damaged, which means ventricles

beat at their own rate, which is slower than normal

– ischemia fibrillation cardiac arrest death

– Pacemaker can be implemented

Conditions

• Hemophilia– The body’s ability to control

blood clotting is impaired, as missing factors prevent fibrin formation in a clot

– Sex-linked, x-chromosome disorder; usually shows up in males, but inherited from the mother

– Patients can be regularly infused with clotting factor

• Hemophilia in European royalty is featured prominently and thus is sometimes known as "the royal disease". Queen Victoria passed the mutation to her son Leopold and, through several of her daughters, to various royals across the continent, including the royal families of Spain, Germany, and Russia.

Conditions

• Anemia– Blood has abnormally low oxygen-

carrying capacity– Different types include…

• Aplastic anemia – destruction or inhibition of red bone marrow

• Hemorrhagic anemia – result of acute or chronic loss of blood

• Sickle-Cell anemia – cells take on abnormal shape, which decreases the cell’s flexibility and oxygen capacity