1. Cardiovascular system

2. General pattern of blood flow

3. Heart Atria- upper chambers Ventricles- lower chambers
Receive blood returning to the heart
Ventricles- lower chambers
Receive blood from the atria and contract to force blood out of the heart into the arteries
Right ventricle is thinner than the left
Right pumps short distance to the lungs, little resistance
Left must force blood to all other parts of the body, high resistance
Septum- solid, wall like separation between the atrium and the ventricle on the right with those on the left
Blood never mixes with blood from the other side

4. valves
Atrioventricular valve-right tricuspid and left bicuspid ensure one-way blood flow
Tricuspid valve- blood flows from right atrium to right ventricle, prevents back flow
Right ventricle contracts, pressure increases, valve closes
Pulmonary valve- allows blood to leave the right ventricle,prevents back flow
Bicuspid valve- blood passes from left atrium to left ventricle, prevents back flow
Aortic valve-opens when ventricle contracts allows blood to leave
When closed prevents blood from backing up in ventricle

5. Path of blood
Blood low in O2 enters right atrium through vena cavae and coronary sinus
Right atria wall contracts, blood enters right ventricle
Right ventricle wall contracts and blood moves into pulmonary trunk and its branches
From pulmonary arteries blood enters capillaries associated with lungs
Oxygenated blood returns to heart through pulmonary veins through left atrium
Left atrial wall contracts and blood moves into left ventricle, left ventricle contracts blood moves to aorta

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7. Heart blood supply
Coronary arteries supply blood to the heart’s tissue
Cardiac veins drain blood that has passed through the myocardial capillaries
Join coronary sinus on the heart’s posterior surface which empties into the right atrium

8. Cardiac cycle When atria relax blood flows into them
Increases pressure
Most of the blood goes directly to ventricles
Atrial systole– atrial contraction
Forces the rest of the blood into ventricles
Atrial diastole– atrial relaxation

9. Cardiac conduction system
Sinoatrial node (S-A node)-
Can reach threshold on their own
Spread to surrounding myocardium and stimulates fibers
Rhythmic
Referred to as pacemaker
Left and right contact almost simultaneously
Atrioventricular node (A-V node)
Provides normal conduction
Fibers have small diameters that slows the impulse
Allows more time for atria to empty and ventricle fill with blood
Muscles are whorls which cause twisting motion when contract

10. Cardiac conduction system
During ventricular contraction A-V valves remain closed, atrial pressure increases
Ventricles relax- vemtricular diastole
A-V valves open
Blood flows to ventricles
Pressure decreases while filling
Atria contracts increasing pressure in ventricle
When pressure exceeds atrial pressure A-V closes
Pressure increases until valves of pulmonary trunk open and blood flows to arteries

11. Electrocardiogram (ECG)
Recording of the electrical changes in the myocardium during a cardiac cycle
1st change– P wave
Depolarization of atrial fibers will lead to contraction
Fibers reach ventricular fibers and depolarize rapidly
QRS complex– Q wave, R wave, and S wave
Corresponds to depolarization of ventricular fibers just prior to contraction of ventricular walls
T wave
Electrical change as ventricular muscle fibers repolarize
Atrial repolarization is at the same as ventricular fibers depolarize

13. Arteries and arterioles
Artery
Innermost layer helps prevent blood clotting by providing a smooth surface and secreting biochemicals that inhibit platelet aggregation
May also regulate local flow by secreting substances that dilate or constrict blood vessels
Arteries progressively divide into thinner tubes and eventually give rise to arterioles
Walls thin as they near the capillaries

14. Capillaries The smallest diameter of blood vessels
Connect the arterioles and venules
Extensions of the inner linings of arterioles
Area where exchange of materials occurs
Exchange in capillaries
Gas, nutrients, and metabolic by products
The substances exchanged move through capillary walls through diffusion, filtration, and osmosis
Filtration forces molecules through a membrane with hydrostatic pressure

15. Capillary exchange cont.
Blood pressure moves blood through arteries and arterioles
Pressure decreases as the distance from the heart increases
Greater in the arteries than arterioles, arterioles greater than capillaries, etc.
Filtration effect primarily at arteriolar end

16. Veins and Venules
Venules are microscopic vessels that continue from the capillaries and merge to form veins
Veins contain flaplike valves
Valves close if blood begins to back yup in a vein
Aid in returning blood to the heart because they open if blood flow is toward the heart and close if it is in the opposite direction
Also function as blood reservoirs
If a hemorrhage causes a drop in arterial blood pressure, veins are stimulated to constrict and help maintain blood pressure by returning more blood to the heart
Ensures a nearly normal blood flow even when as much as 25% is lost

17. Blood pressure
Blood pressure is the force blood exerts against the inner walls of the blood vessels
Arterial pressure rises and falls in a pattern corresponding to the cardiac cycle
The maximum pressure during ventricular contraction is called the systolic pressure
The lowest pressure that remains in the arteries until the next venticular contraction is diastolic pressure
The alternating expanding and recoiling of the artery wall is felt as the pulse

18. Blood pressure factors
Heart action
Determines how much blood enters the arterial system
Stroke volume-the amount of blood that is discharged from the left ventricle with each contraction
Cardiac output- volume discharged/minute
Stroke volume x heart rate
Blood volume
Equals the sum of formed elements and plasma volumes in vascular system
Varies with age and sex and directly with body size
Normally directly proportional to blood volume
Can fall if fluid balance is upset

19. Factors cont. Peripheral resistance
Produced from friction between blood and vessel walls
Slows blood flow
Contraction of smooth muscles in arteriolar walls increases pressure
Dilation lessens resistance and drops the pressure in response
Blood viscosity
The greater the viscosity, the greater the resistance
Blood cells and plasma proteins increase blood viscosity
Blood pressure increases as viscosity increases and drops as viscosity decreases

20. Control of blood pressure
Two important mechanisms for maintaining normal arterial pressure are:
Regulation of cardiac output
Regulation of peripheral resistance

21. Cardiac output
Volume of blood discharged from the left ventricle and heart rate
Starling’s law of the heart--Greater the length of myocardial fibers the greater the contractional force
Baroreceptors sense changes in pressure
Increases nerve impulse travels to brain, heart rate decreases
Triggers cardioinhibitor reflex—cardiac output falls and blood pressure moves to normal level
Cardioaccelerator reflex triggered by decreasing arterial pressure
Causes heart to beat faster, increases heart rate, and pressure

22. Peripheral resistance
Changes in the arteriole diameters regulate peripheral resistance
Small diameters offer greater resistance to blood flow
Vasomotor center controls impulses sent to arteriole walls
Certain chemicals also influence peripheral resistance by affecting precapillary sphincters and smooth muscle in arteriole walls

23. Venous blood flow
Blood pressure decreases as blood moves through the arterial system and into the capillary networks
Depends on skeletal muscle contraction, breathing movements, and vasoconstriction of veins
Contracting skeletal muscles- thicken and press on nearby vessels squeezing blood inside
Respiratory movements- causes pressure changes in thoracic cavity
Inspiration- pressure decreases in thoracic cavity and rises in abdominal cavity which squeezes blood out of veins

24. Venous blood cont. Vasoconstriction returns venous blood to the heart
Venous pressure is low, sympathetic reflexes stimulate smooth muscle in veins to contract
veins provide blood reservoir that can adapt its capacity to changes in blood volume
If blood is lost and blood pressure falls, venoconstriction can force blood out of reservoir

25. Paths of circulation Two major pathways Pulmonary circuit
Consist of vessels that carry blood from the heart to the lungs and back to the heart
Systemic circuit
Carries blood from the heart to all parts of the body and back again