Cardiovascular System

Heart Actions• Cardiac cycle-heart beat • Atria contract together• Ventricles contract together• Atrial systole-atria contract• Diastole-relaxation of heart• Ventricular systole-ventricles

Cardiac Cycle Steps

High pressure in atria

High pressure in ventricles

Pressure down in ventricles; build in atria

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Atrioventricular valves open and close HOW?

• Contract– Papillary muscles contract– Pull on chordae tendinae– Valves close!– Papillary muscles contract due to stimulation

from purkinje fibers

• Relaxation-no muscle contraction/no pull on chordae tendinae– Valves

Heart Sounds• Open and close of valves • Lubb-ventricular contraction, AV valves

closing• Dupp-ventricles relax, pulmonary and

aortic valves close• Heart murmur-cusps not close enough

and cause blood leak

Cardiac Conduction System • Impulse travels through myocardium

(middle layer of heart)• SA node-pacemaker

– Posterior right atrium– Creates impulse for heart beat– Sends impulse 70-80 times per minute

• Impulse goes to atrial syncytium (mass of merging cells)– Left and right atrium contract

Signal conduction continued• Impulse travels through junctional

fibers– Slows signal down so atria can contract

completely and empty of blood before the impulse goes down to the ventricles

• Goes to AV (atrioventricular node) – Located in septum

• Goes to AV bundle (bundle of His)• Branch into purkinje fibers

– Make connection with papillary muscles– Action squeezes blood out of ventricles

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

F. Electrocardiogram• a recording of the electrical changes

that occur during a cardiac cycle.• P wave,

– depolarization (contraction) of the atria.

• QRS complex – depolarization of ventricles (contraction)

and hides the repolarization (relaxation) of atria.

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• T waves – end the ECG pattern – ventricular repolarization (relaxation)

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

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

1. Atria begin depolarize2. Atria depolarize.

3. Ventricles depolarize at apex; atria repolarize4. Ventricles depolarize

5. Ventricles begin repolarization at apex.6. Ventricles repolarize.

How to read one?

http://www6.district125.k12.il.us/science/secure/wood/anatomy/ch13/ekgtutorial5criteria.mov

Diagnostic Value of ECG

• Abnormalities in conduction pathway

• Myocardial infarction (heart attack)

• Heart enlargement

• Electrolyte and hormone imbalance

• Ischemia-blood supply restriction

Fast heart; chest pain, Shortness of breath, abnormal pacemaker

Heart rate is less than 60 beats

Blood pressure

• Refers to pressure in arteries

• Systolic (pressure in arteries when ventricles contract) over diastolic (pressure in arteries when ventricles are filling up with blood) pressure

• 120/80 is normal

• Pulse (normal is 60 to 100 beats)-expanding and recoiling of arteries

• Many factors influence blood pressure

Heart Action

• This determines how much blood enters the arterial system when the ventricles contract

• Stroke volume-volume of blood leaving LV– About 70 ml in average male

• Cardiac output-volume per minute– Stroke volume x heart rate

• Cardiac output, blood pressure, and stroke volume directly related

Blood volume-Factor that influences this

• Sum of formed elements and plasma volumes in the vascular system

• Blood pressure is directly proportional to blood volume

• Can change due to dehydration (bp drops), blood transfusion, hemorrhage (bp drops)

Control of Blood Pressure• Autonomic nervous system responses

• Peripheral resistance– Pressure between blood and vessel walls

• Temperature change– Higher temp, higher blood pressure

Baroreceptors• Located in aortic arch• Arterial blood increases, basoreceptors send

nerve impulse to medulla oblongata• Sends impulse to SA node

– Cause heart rate to decrease– Blood pressure return to normal

• Arterial blood decreases, sends signal to SA node to increase heart work– Exercise, rise in temp, emotions

Hypertension

• Hypertension-high blood pressure in arteries– Caused by kidney disease, high sodium intake,

obesity, stress, arteriosclerosis– Lead to enlarged heart due to increase pumping

action of LV– Cause embolism, thrombosis, stroke

Vein Control

• Skeletal muscles-pushes blood to the heart

• Breathing movements

• Vasoconstriction-low pressure causes muscles to contract

Sheep Heart Dissection

http://www.youtube.com/watch?v=rI23fdFVRvY