BIOL 465 Unit 6 - Cardiovascular System

What are the two functions of the cardiovascular system?

Transportation and protection

What is transportation?

Delivery of oxygen and nutrients to cells, removal of waste products, transport of hormones, distribution of body heat (via blood)

What is protection?

Defense against disease (leukocytes), distribution of immune cells throughout body

What is the heart?

The pump, muscular, automatic muscle, force generating mechanism

What are blood vessels?

Plumbing, transportation for blood, tubing of different sizes, thicker near the heart, thinner away from heart

What is blood?

Liquid, carrier, generated in bone marrow by hematopoietic cells

What are arteries?

Large, thick-walled elastic tubes, carry blood away from heart (oxygenated)

Why are arteries thick-walled?

They are under high pressure and need to be so they won’t explode

What are arterioles?

Smaller, very muscular tubes, major role in control of blood pressure, surrounded by smooth muscle that responds to stimuli

What are capillaries?

Very small, thin-walled (to allow for gas exchange), exchange gases and nutrients with cells or lungs, (carry both types of blood)

What are venules?

Same size are arterioles, less muscular (no pressure regulation), carry blood towards heart (deoxygenated)

What are veins?

Large, like arteries, thinner walls, carry blood back to heart (deoxygenated)

What is the endocardium?

Thin inner layer of epithelial cells, surrounds inside chambers, sealing blood away

What is the myocardium?

Thick muscular walls of the heart, mostly made of cardiac muscle

What is the epicardium?

Thin outermost layer of connective tissue for protection

What is the pericardium?

Thin connective tissue surrounding the heart, sac

What are features of a fish heart?

1 atrium, 1 ventricle, blood pumps in one direction, gas exchange occurs in gills

What are features of amphibian’s hearts?

2 atria, 2 ventricles, no septum separating ventricles, mixing of deoxygenated and oxygenated blood

What are features of reptile’s hearts?

2 atria, 2 septum, incomplete septum, little bit of mixing of blood

What are features of human hearts?

4 chambers, complete septum, isolated blood makes it efficient as possible for gas exchange

What’s the purpose of the interventricular septum?

Separates sides of the heart (deoxygenated blood from oxygenated blood)

What is the purpose of the atrioventricular valves?

To prevent back flow of blood in the heart (regulation), they open from atria to ventricle

What are the atrioventriuclar valves?

Tricuspid and bicuspid valves

What do the semilunar valves do and what are they?

They open from the ventricles into the great arteries, pulmonary and aortic valves

What is the pathway of the systemic loop?

Left ventricle —> body tissue —> right atrium

What is the major artery in the systemic loop?

Aorta

What are the major veins in the systemic loop?

Superior vena cava and inferior vena cava

Where does the superior vena cava come from?

The head, neck and arms

Where does the inferior vena cava come from?

The lower body

What is the path of the pulmonary loop?

right ventricle —> lungs —> right atria

What are the major arteries in the pulmonary loop?

Pulmonary arteries

What are the major veins in the pulmonary loop?

Pulmonary veins

What is a left-to-right shunt?

Congenital defect in which a portion to the left ventricular output goes back to the lungs instead of going to the systemic loop

What is a septal defect?

Hole in the interventricular septum - promotes mixing of blood

What is patent ductus arteriousus (DA)

The temporary blood vessel that connects the aorta to the pulmonary artery remains open after birth, when it remains open, blood flows from the aorta into the pulmonary artery

True/False - Cardiac cells do not have stem cells so they can’t regenerate

True

What does heart muscle fiber consist of?

One or two nuclei, striated (for sliding filament mechanism), desmosomes, gap junctions

True/False - Muscle cells can not stimulate their own action potential

False

What is the absolute refractory period for heart muscle fiber?

250ms

Is resting potential more negative in heart muscle or skeletal muscle?

Heart muscle

Why is the resting potential in heart muscle more negative than that of skeletal muscle?

There is a higher K+ permeability

What does audtorhythmicity mean?

Adjacent cells can stimulate action potentials in cells not the CNS

What are the types of Ca2+ channels?

Ryanodine, L-type, T-type

What do ryanodine channels do?

Release Ca2+ from the SR

What do L-type Ca2+ channels do?

Larger, long lasting steady current, require strong depolarization to activate

What are T-type Ca2+ channels?

Shorter current, transient, low-voltage activated

What is the process of excitation-contraction in cardiac muscle?

• Na+ enters the cell

• Ca2+ into the cell through L-type channels

• Ca2+ binds to ryanodine receptors to bring more Ca2+ in

  • The cell cannot be permanently contracted — Ca2+ moves out back to the SR via ATPase pump through T-tubules

What causes the rising phase of cardiac muscle cells?

Opening of Na+ channels

What causes the plateau phase?

Initial decrease in K+ permeability and delay in opening of K+ channels, opening of Ca2+ channels in cell membrane and SR

What causes the falling phase?

The opening of K+ channels

What percent of cardiac muscle cells are use for contraction?

99%

What percent of cardiac muscle cells are used for initiation and conducting action potentials?

1%

What is the normal pacemaker of the heart?

The sinoatrial node (SA)

Where is the SA node located?

The upper right atrium

What are pacemaker cells in the SA node specialized for?

Initiation of action potentials

What is pacemaker potential?

Gradual, spontaneous depolarization of cardiac pacemaker cells due to slow leak of Na+ ions —> causes opening of Ca2+ channels —> action potential

What causes cardiac action potential?

The progressive decrease in K+ permeability due to channels still being open (Leaky F-type K+ channels) and the use of L-type channels

What causes SA node action potential?

Na+ leaks in which triggers K+ channels to open causing action potential using T-type channels

What is impulse conduction?

Movement of the impulse down and left to the atria and AV node, pacemaker cells in SA node spontaneously depolarize, impulse spreads

Why it is important that the ventricles are separated from the atria by a nonconducting connective tissue?

The ventricles need to fill with blood before contracting or the blood flow would be messed up, the atria contracts slightly before to move the blood to ventricles then ventricles contract

What is an electrocardiogram?

Recording of electrical activity of the heart

What is the P wave?

Atrial depolarization (atrial excitation is complete)

What is the QRS complex?

Ventricular depolarization (atrial repolarization also happens here)

What is the T wave?

Ventricular repolarization (relaxation)

What is seen in a partial AV block?

Failure of conduction from atria to ventricle, results in skipped beat, extra P wave

What is seen with a complete AV block?

No conduction, more P waves than QRS complexes

What generates pressure changes that result in the movement of blood?

Contraction of the myocardium

Where does blood flow?

From an area of high pressure (heart) to low pressure (cells)

What is the difference between events on the left side of the heart and the right side of the heart?

They are the same but pressures on the right side are lower

Why is pressure on the right side of the heart lower?

Blood here is going to the pulmonary system and increased pressure would explode the capillaries in the lungs

What is systole?

Period of ventricular contraction

What is diastole?

period of relaxation

True/False - Diastole is longer than systole

True

What happens with passive filling?

The atria and ventricle are relaxed - blood can flow into each chamber, no energy is involved, ventricular pressure = 0, AV valves are open *blood is flowing from veins into atria and ventricles*, aortic and pulmonary valves are closed

What happens during atrial contraction?

Late diastole, The SA node depolarizes (reaching all cells), wave of depolarization spreads across both atria, wave reaches AV node then spreads to ventricles—> atria contracts and BP increases in atria, P WAVE HAPPENS,

What is the end-diastolic-volume?

Volume of each ventricle at the end of diastole

What is diastolic blood pressure?

Arterial blood pressure at its lowest point in the cardiac cycle, completion of ventricular filling, end-diastolic-volume ~ 135mL, BP = 80mmHg

What happens during isovolumetric ventricular contraction?

Early systole, ventricular depolarization, action potential conducts through AV node, down bundle of HIS and along Purkinje fibers to innervate all of the ventricle, QRS COMPLEX, ventricles are contracting, increased pressure closes AV valves creating the first heart sound (‘lub’)

What happens during the ejection phase?

Most of systole, ventricular depolarization, aortic and pulmonary valves are open, 2/3 of the blood is ejected from each ventricle, systolic BP = 120mmHg

What is stroke volume (SV)?

Volume of blood ejected by each ventricle in a single beat

What is ejection fraction?

SV/EDV

What is systolic BP?

Arterial BP at its highest point in the cardiac cycle

What happens during isovolumetric ventricular relaxation?

Early diastole, wave of repolarization across ventricles, T WAVE HAPPENS HERE, ventricles relax, semilunar valves close, second heart sound is created (‘dub’)

How long is normal systole?

.3 second

How long is normal diastole?

.5 second

What is systemic arterial BP?

120/80 mmHg

What is pulmonary arterial BP?

25/8 mmHg

What is going on with pressure and force on the left side of the heart?

The same amount of blood is being pumped against higher pressure, stronger contractions, and the myocardial wall here is thicker

What is coronary circulation?

The blood supply to the myocardium, the coronary arteries branch off the base of the aorta, the heart receives 5% of all cardiac output

What is ischemia?

Insufficient blood flow to an organ (blockage of blood flow)

What is myocardial ischemia?

Insufficient blood flow to a part of the myocardium

What is silent ischemia?

Insufficient blood flow to the heart but no symptoms are experienced, no pain, heart rate may be slightly elevated

What is angina pectoris?

Severe pain to chest and left arm, prevented or controlled with nitrates

What do nitrates do?

Lower BP by relaxing the arterioles

What is myocardial infarction?

Heart attack, #1 killer in US, complete blockage of blood flow to a part of the myocardium

What is the most common cause of heart attack?

Atherosclerosis (clots lodging the vessels)

What can a heart attack lead to/cause?

Ventricular fibrillation, weakening the heart muscle which may lead to heart failure

What is an angiogram?

Dye is injected into the coronary circulation to help detect a blockage, seen through x-rays

What is a balloon angioplasty?

A stent is put in to act as scaffolding and keep vessel structure open

What is bypass surgery?

Moving vessels surgically from other part of the body to the heart