summer studying lecutre 13 a/b/c/d

What are the general characteristics of the cardiovascular system?

Consists of heart and blood vessels

What is the heart?

Hollow, cone-shaped muscular pump; generates force to transport respiratory gases, nutrients, and wastes through body

What are blood vessels?

Transport blood throughout body

• consists of arteries, veins, capillaries

What are arteries?

Transport blood away from ventricles of heart

What are veins?

Receive blood from venules and carry it back to atria of heart

What are capillaries?

Transport blood between arteries and veins, perform nutrient, gas, and waste exchange

What is the pericardium (pericardial sac)?

Covering over heart and proximal ends of large blood vessels

• consists of fibrous, parietal, visceral pericardium

  • consists of pericardial cavity

What is fibrous pericardium?

Tough outer layer that surrounds double-layered serous membrane

What is the parietal pericardium?

Deep to fibrous pericardium; outer layer of serous membrane

What is the visceral pericardium?

Inner layer of serous membrane; attached to surface of heart

• aka epicardium

• reduces friction

What is the pericardial cavity?

Space between visceral and parietal layers of serous pericardium

What are the 3 layers of the heart?

1. epicardium

2. myocardium

3. endocardium

What is the myocardium?

Middle layer of heart; thickest layer

• composed of cardiac muscle tissue

What is the endocardium?

Innermost layer of heart; thin

• forms inner lining of all heart chambers

What are the 9 steps to the path of blood flow to the heart?

1. right atrium receives blood from superior and inferior venae cavae and coronary sinus

2. blood flowers from right atrium through open tricuspid (right AV) valve into right ventricle

3. Pulmonary valve is pushed open when right ventricle contracts, allowing blood to enter pulmonary trunk

4. blood travels with right and left pulmonary arteries to alveolar capillaries in lungs, where CO2 is unloaded and O2 is loaded

5. blood travels within right and left pulmonary veins from lungs to left atrium

6. Blood in left atrium flows through open mitral (left AV) valve into left ventricle

7. aortic valve is pushed open when left ventricle contracts, allowing blood to enter aorta

8. blood flows from aorta to systemic capillaries where O2 is unloaded and CO2 is loaded

9. blood returns to right atrium from body tissues and myocardium (via venae cavae and coronary sinus)

What is the pulmonary circuit?

Portion of circulatory system that carries deoxygenated blood from heart to the lungs for oxygenation and returns oxygen-rich blood back to heart

What is the blood flow pathway of the pulmonary circuit?

1. starts in Right Atrium and goes through tricuspid valve, to the right ventricle, and to the pulmonary valve

2. Blood flows into pulmonary trunk, where it flows to both the left and right pulmonary arteries

3. The left blood supply will flow to alveolar capillaries in left lung; the right blood supply will flow to alveolar capillaries in right lung (now oxygenated)

4. Both blood flows will respectively go to left/right pulmonary veins

5. both veins will flow into left atrium

6. from the left atrium, blood flows to the mitral valve, into the left ventricle, to the aortic valve

7. Finally arrives at the aorta

What do the right and left coronary arteries do?

Supply heart with oxygenated blood

What is the systemic circuit?

Part of circulatory system that carries oxygen-rich blood from left ventricle to aorta, to all tissues, then returns oxygen-depleted blood to the right atrium via venae cavae

What is the blood flow pathway of the systemic circuit?

1. begins in left ventricle, where blood travels to the aortic valve, then into the aorta

2. From the aorta, systemic capillaries in the upper body tissues, myocardium, and lower body tissues receive blood

3. deoxygenated blood then flows back into the superior vena cava, coronary sinus, and inferior vena cava

4. all of the cava/sinuses then flow back into the right atrium, where it is then carried through the tricuspid valve, right ventricle, into the pulmonary valve

5. blood finally arrives at the pulmonary trunk

Where does the systemic capillaries of the upper body tissues flow?

Superior vena cava

Where does the systemic capillaries of the myocardium flow into?

Coronary sinus

Where does the systemic capillaries of the lower body tissues flow into?

inferior vena cava

What are the actions of the heart?

1. systole

2. diastole

   1. both contribute to the cardiac cycle

What is systole?

contraction of a heart chamber

What is diastole?

relaxation of a heart chamber

What is the cardiac cycle?

1. atria contract (atrial systole) while the ventricles relax (ventricular diastole)

2. Then ventricles contract (ventricular systole) while atria relax (atrial diastole)

3. Then both chambers relax briefly

What is a heart transplant?

Replacement of most of a failing heart w/ a donor heart

What is an LVAD?

Left Ventricular Assist Device

• mechanical half-heart, used in some cases temporarily until donor heart is available

What is an implantable replacement heart?

Titanium and plastic artificial heart, used in people that cannot have a heart transplant, and do not have long to live

What is stem cell technology?

Cardiac muscle tissue can be cultured from altered somatic cells; may allow stem cell heart patches in the future

• need to match up intercalated discs for action potentials to travel

What is the cardiac conduction system?

Specialized group of cardiac muscle cells, which initiate and distribute cardiac action potentials through myocardium

What are the major components of the cardiac conduction system?

1. Sinoatrial Node

2. Internodal Atrial Muscle (atrial syncytium)

3. Junctional Fibers

4. Atrioventricular Node

5. Atrioventricular Bundle (of His)

6. Left and Right Bundle Branches

7. Purkinje Fibers

8. Ventricular syncytium

What is the Sinoatrial Node?

Pacemaker, initiates rhythmic contractions of the heart

What is the internodal atrial muscle?

Conducts impulses from SA node to atria

What are junctional fibers?

Conduct impulses from SA node to atria

What is the Atrioventricular Node?

Conducts impulses to AV bundles; delays impulse, so atria finish contracting before ventricles contract

What is the Atrioventricular Bundle (of His)?

Conduct impulses rapidly between SA node and bundle branches

What are the left and right Bundle Branches?

Split off from AV Bundle, conduct impulse to Purkinje fibers on both sides of heart

What are the Purkinje Fibers?

Large fibers that conduct impulses to ventricular myocardium; conduct impulses to apex first

• whorled pattern of muscle in ventricles contract w/ twisting motion

What is an electrocardiogram (ECG, EKG)?

A recording of electrical charges that occur in myocardium during cardiac cycle

• used to assess ability of heart to conduct impulses

• includes P wave, QRS complex, and T wave

What is the P wave?

Atrial depolarization; occurs just prior to atrial contraction

What is the QRS complex?

3 waves→ ventricular depolarization that occurs just prior to ventricular contraction

• record of atrial repolarization is hidden in large QRS complex as ventricular depolarization is much larger

What is the T wave?

Ventricular repolarization that occurs just prior to ventricular relaxation

What is the ECG Pattern?

1. initial impulse from SA node

2. then contraction in right atria into septum to left atria→ by end of P wave, electrical impulse has moved across into AV node

3. Signal then moves from AV node to AV bundle into bundle branches→ signal moves back to myocardium of ventricles

4. QRS complex then finishes when impulse has made its way through all muscle

5. T wave then starts and brings ventricular repolarization

6. 
   

What does a prolonged QRS complex indicate?

Indicates disruption of ventricle→ AV bundle damage

What does an absent P wave indicate?

SA node issue

What does an absent T wave indicate?

Issue with repolarization in ventricles

• issue w/ myocardium in ventricle

What are the properties of pressure and volume changes during cardiac cycle?

Pressure in heart chambers rises and falls

• pressure changes open and close the valves

What happens to pressure/volume in ventricular diastole?

1. ventricular pressure is lower than atrial pressure

2. atria and ventricles are relaxed

3. AV valves open, and semilunar valves are closed

4. about 70% of blood flows passively from atria into ventricles

What happens to pressure/volume during atrial systole and ventricular diastole?

1. Atria contract and ventricles are relaxed

2. AV valves open and semilunar valves close

3. Atrial systole pushes remaining 30% of blood into ventricles, causing ventricular pressure to increase

What happens to pressure/volume during ventricular systole and atrial diastole?

1. when ventricular pressure rises above atrial pressure, AV valves close

2. chordae tendineae prevents cusps of valves from bulging too far backward into atria

3. atria relax

4. blood flows into atria from venae cavae and pulmonary veins

5. ventricular pressure continues to increase, and opens semilunar valves

6. blood flows into pulmonary trunk and aorta

What regulates the cardiac cycle?

Cardiac center in medulla oblongata performs neural regulation of heart

• SA node (pacemaker) normally controls heart rate→ heart rate changes occur due to factors that influence SA node

• sympathetic/parasympathetic fibers modify heart rate in response to physical exercise, body temp, fight-or-flight, concentration of K+ and Ca2+

How do the parasympathetic impulses influence the heart rate?

Reach heart via vagus nerves

• lower SA node rate of 100 beats/min to 60/80 beats/min

• decrease heartrate (due to influence on SA and AV nodes)

How do the sympathetic impulses influence the heart?

Reach heart on accelerator nerves

• increases heartrate due to influence on SA and AV nodes, atrial and ventricular myocardium

What are the baroreceptor reflexes?

Involve cardiac control center medulla oblongata

• balance inhibitory/excitatory effects of parasympathetic and sympathetic fibers

• contains cardio-inhibitor reflex and cardio-accelerator reflex

What are the characteristics of the baroreceptor reflex?

A rapid negative feedback loop where elevated blood pressure causes heartrate and blood pressure to decrease

• a decrease in blood pressure leads to an increased heart rate→ returning blood pressure to normal levels

What are the steps to the baroreceptor reflex?

1. stretch receptors located in the wall of the aortic arch and carotid sinus will sense stretch caused by inc blood pressure

2. sensation will trigger baroreceptors to fire action potentials at higher than normal rate

3. Inc activity is sent via vagus and glossopharyngeal nerves to nucleus of tractus solitarius (NTS) in brainstem

4. NTS activates the parasympathetic system and inhibits the sympathetic system→ allows same direction to maximize blood pressure reduction

5. PSNS releases ACh which impacts pacemaker cells of SA node

6. Inhibition of SNS causes vasodilation, decreased HR and stroke volume

7. If blood pressure is decreased, NTS will inhibit PSNS and activate SNS

8. SNS will release norepinephrine, which accelerates HR and BP via SA node

What happens to blood pressure when standing up from sitting?

Decrease in blood pressure is sensed by baroreceptors as decrease in tension

• baroreceptors fire at a lower than normal rate and info is transmitted to NTS

• NTS then inhibits PSNS and activates SNS

• SNS will then release Norepinephrine which acts on SA node to inc heart rate and blood pressure, and vasoconstriction

What parts of the SA node are impacted by norepinephrine and acetylcholine?

cardiomyocytes, smooth muscle cells of blood vessels

What are arrhythmias?

Altered heart rhythms

• consists of 4 types

  • Tachycardia

  • fibrillation

  • bradycardia

  • flutter

What is fibrillation?

Uncoordinated, chaotic contraction of small areas of myocardium

• atrial fibrillation not life-threatening; ventricular fibrillation is often fatal

What is tachycardia?

Abnormally fast heartbeat

>100 bpm at rest

What is bradycardia?

abnormally slow heartbeat

>60 bpm at rest

What is a flutter?

Rapid, regular contraction of a heart chamber

250-350 bpm

What is premature beat?

beat that occurs before expected in normal cardiac cycle; often originates from ectopic regions of heart (other than SA node)

What is the ectopic pacemaker?

Damage to SA node may lead to AV node taking over→ acts as secondary pacemaker

• 40-60bpm

What is an artificial pacemaker?

Device used to treat disorders of cardiac conduction system; implantable and battery-powered

What does a ventricular fibrillation look like?

WRS complex is absent

• P wave are present

• ventricles not contracting

What does tachycardia look like?

QRS complexes present

• R to R is much smaller than normal pace

What does bradycardia look like?

QRS complexes present

• R to R is much bigger than normal pace

What does an atrial flutter look like?

Lots of P waves are present (continuous stimulation)

• QRS firing prematurely or long period of nonfiring

What are venules?

receive blood from capillaries and conduct it back to veins

What are arterioles?

Receive blood from arteries, carry it back to capillaries

What is angiogenesis?

formation of new blood vessels

• mainly controlled Vascular Endothelial Growth Factor (VEGF)

• Regulated in the body since excess, deficient, or inappropriate blood vessel formation can cause common diseases

how is angiogenesis promoted?

Body secretes VEGF in response to blocked coronary artery

• if not sufficient, VEGF may be able to be delivered in time-release capsules or gene therapy→ delivers genes encoding VEGF to area that lacks oxygen

How is angiogenesis prevented?

Tumor secrete VEGF to nourish themselves→ antiangiogenesis drugs are used to treat cancer and age-related macular degeneration

What percent of blood is in systemic veins?

60-70% at any time

What percent of blood is in the lungs?

10-12% at any time

What percent of blood is in the heart?

8-11% at any time

What percent of blood is in systemic arteries?

10-12% at any time (arteries)

What percent of blood is in capillaries?

4-5% at any time

What is atherosclerosis?

Deposits of cholesterol plaque form in inner lining of walls of arteries and arterioles

What is an aneurysm?

A bulge in the wall of an artery, formed when blood pressure dilates a weakened area of the vessel; can burst wall of artery

What is phlebitis?

Inflammation of a vein, very common

What are varicose veins?

Abnormal and irregular dilations in superficial veins; most common in legs

What is blood pressure?

The fource the blood exerts against the innner walls of the blood vessels

• circulates the blood

• usually refers to pressure of systemic arteries

• exists throughotu tthe vascular system

• blood moves from higher to lower presure throughout the system

What is arterial blood pressure?

Rises when ventricles contract; fals when ventricles relax

What is arterial systolic pressure (SP)?

The maximum pressuer reached during ventricular contraction

What is arterial diastolic pressure (DP)?

The minimum pressure remaining before next ventricular contraction

What is the blood pressure format?

SP/DP

What is Pulse Pressure (PP)?

Difference between systolic and diastolic blood pressures

• SP-DP

What is Mean Arterial Pressure (MAP)?

Avereage pressure in arterial system; representst average force driving blood to the tissues

• (2DP+SP)/3

What is stroke volume (SV)?

Volume of blood that enters the arteries w/ each ventricular contraction (70mL/beat)

• 1.85xPP (pulse pressure)

What is cardiac output (CO)?

volume of blood discharged from a ventricle each minute; blood pressuer varies w/ cardiac output

• CO= SV*HR

What does an increase in SV (stroke volume) imply?

HR (heart rate) is increased, which increases CO (cardiac output)→ inc blood pressure (BP)

What is peripheral resistance (PR)?

Force of friction between blood and wals of blood vessels

• measured as Total Peripheral Resistance (TPR)=MAP/CO

• blood pressure must overcome PR in order to flow

• factors that change PR also change BP

What does vasoconstriction do to arterioles?

Increases peripheral resistance, which increases BP

How does blood go against PR (peripheral resistance)?

When blood is pumped out of ventircles, arteries swell

• rapid elastic recoil sends blood through arteries, against PR in arterioles and capillaries

How does viscosity impact the cardiovascular system?

Difficulty w/ which molecules of fluid flow past each other

• greater the viscosity, greater the resistance Etonian blood flow

• blood cells and plasma proteins inc the viscosity of blood

• any facter that alters conc of blood cells or plasma proteins also alters blood viscosity