Transcript Cardiovascular System

Cardiovascular System
 Heart Actions
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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
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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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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)
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hw/hhw_electrical.html
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1. Atria begin depolarize
2. Atria depolarize.
3. Ventricles depolarize at apex; atria repolarize
4. Ventricles depolarize
5. Ventricles begin repolarization at apex.
6. Ventricles repolarize.
How to read one?
http://www6.district125.k12.il.us/science/secu
re/wood/anatomy/ch13/ekgtutorial5criteria.
mov
Diagnostic Value of ECG
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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=rI
23fdFVRvY