ch 17

Simple squamous epithelium ; blood flows against (touches) this layer; continuous with blood vessels

• Transports blood from heart to pulmonary trunk/arteries to lung capillaries and back to heart pulmonary veins.

• RIGHT side of heart

• Transports blood from Aorta of the heart to body capillaries and back to the superior and inferior vena cava of the heart

• LEFT side of heart

blood pressure stretches aorta, when it snaps back blood is forced into systemic capillaries and left and right coronary arteries

• insufficient blood flow generates new anastomoses for alternate blood flow

• prevents heart attack (MI)

• MI, Heart attack

• obstructs blood flow to Myocardium tissue and tissue dies (infarct)

1. Pacemaker cells (1%)

2. Contractile cells (99%)

hold cells together

allow ions (action potentials) to pass from one cell to another)

1. SA node generates an AP which spreads to atrial cells and the AV node

2. After the AV node delay, the action potential is conducted to the AV bundle and then to the R and L bundle branches

3. the AP spreads from the bundle branches along the Purkinje fibers to the contractile cells of the ventricles

1. slow depolarization phase: HCN channels open, Na+ enters cell, -60mv to -40mv

2. Full Depolarization phase: Ca+ enters -40mv to +10mv

3. Repolarization phase: K+ exits +10mv to -60mv

4. minimum potential phase: cell hyperpolarizes which opens HCN channels. no true resting membrane potential

1. Rapid depolarization phase: pacemaker action potentials open Na+ gates (-85mv to 20-30mv)

2. Initial repolarization phase: Na+ gates close and K+ exits (20-30mv to less pos)

3. Plateau phase: Ca2+ enter (20mv to 0mv) relatively long period where contraction occurs

4. Repolarization: K+ exits (0mv to -85mv)

• atrial depolarization

• Na+ & Ca2+ enter atrial contractile cells

• Ventricular depolarization (masking atrial repolarization)

• Na+ & Ca2+ enter ventricular contractile cells

• Ventricular Repolarization

• K+ exit ventricular contractile cells

• Duration of an action potential across the heart

• time of one cardiac cyle

• the number of R-R intervals in one minute measures Heart Rate

• AV valve closes

• vibrations of ventricles and blood vessel walls create sound

Semilunar valves close

blood flows into ventricles

blood finished draining from atria to ventricles, typically due to stiff or enlarged ventricle

sequence of events from one heart beat to next

1. Ventricular Filling phase

2. Isovolumetric Contraction phase *S1

3. Ventricular Ejection phase

4. Isovolumetric Relaxtion phase *S2

• Ventricles fill with blood and are in diastole

• Atrioventricular (tricuspid and mitral valves are open)

• Atrial systole occurs

• Semilunar valves are closed

• Ventricular systole begins

• AV valves close when enough pressure builds in the ventricles

• Semilunar valves remain closed

• Atrial diastole begins

  *S1 OCCURS

• Ventricular systole continues

• AV valves still closed

• Atrial diastole continues

• Pressure opens SL valves, and blood is ejected into the pulmonary artery and aorta

• Ventricular diastole begins

• AV valves still closed

• Atrial diastole continues

• SL valves close

*S2 OCCURS

• increase heart rate

• sympathetic nervous system, certain hormones, elevated body temperature

• decrease heart rate

• parasympathetic nervous system, decreased body temperature

ventricular blood volume at end of ventricular diastole

volume that remains in each ventricle after ventricles contract

• amount of blood ejected from each ventricle

• SV=EDV-ESV

• Percentage of blood ejected w/ each ventricular systole

• ejection fraction = SV/EDV

• normal value 50-60%

• Preload

• Contractility

• Afterload

Stretch of ventricular sarcomeres due to the blood; increased preload increases contractility and SV

• Ventricular filling time-

  extremely high HR decreases filling time and decreases preload

• Venous return -

  amount of blood returning to right ventricle

• Frank-Sterling Law-

  increased ventricular stretch results in forceful contraction and increased SV

• Heart's ability to generate tension (force of contraction)

• increased contractility increases SV

• agents that affect contractility

• sympathetic nervous system increases contractility

• The force ventricles must overcome to eject blood

• Increased afterload decreased SV

• The amount of blood pumped into the systemic circuit each minute

• CO= HRxSV (EDV-ESV)

• increases entry of calcium ions

• increases contractility

• Vagus Nerve

• Acetylcholine-decreases HR

• Adrenal Medulla

• thyroid hormone and glucagon

• Aldosterone and antidiuretic hormone (increase blood volume and pre load and increase CO)

• Atrial Natriuretic peptide (decreases blood volume and preload, and decreases CO)

Coronary Sinus

• Receives blood from Great cardiac, small cardiac, and middle cardiac veins

Into the atria from the ventricles

Opening in the interatrial septum of the fetal heart that connects the right and left atrium

the atria and ventricles to depolarize and contract separately

Plateau phase

Q-T interval

cardiac muscle

• hormone secreted by the atria of the heart

• decreases cardiac output by decreasing blood volume and preload

70 ml

Stroke volume (SV)