1. Heart Muscle

2. Blood Vessels

3. Blood

• The Right Atrium, receives "used blood" from the body. Blood will be pushed through the tricuspid valve to the
• Right Ventricle, the chamber which will pump to the lungs through the pulmonic valve to the
• Pulmonary Arteries, providing blood to both lungs. Blood is circulated through the lungs where carbon dioxide is removed and oxygen added. It returns through the Pulmonary Veins, which empty into the
• Left Atrium, a chamber which will push the Mitral Valve open. Blood then passes into the

  What are the different types of vasculature (vessels)?  What is the function of each and what type of blood does each carry?

a.    Arteries-away from heart, usually high O2

b.    Veins-toward heart, usually low O2

c.    Capillaries-connecting arteries and veins, substances exchanged with body

*a closed system

Valves allow blood blow to be unidirectional. (from atria to ventricles and from heart to arteries) A septum separates L&R and allows no blood flow between them

Why does the systemic circuit require more pressure (and resistance) compared to the pulmonary circuit?

What is the direction of blood flow determined by?

systole-heart contraction

diastole-heart relaxation

Resting HR?

Heart beats every __sec?

diastole every __sec?

systole every __sec?

resting HR-72 bpm

heart beat every 0.8 sec

diastole ~ 0.5 sec

systole ~ 0.3 sec

Different regions contract at different times during heartbeat.

Both atria contract together, there is a slight pause, then contraction of ventricles.

Phase 1: Ventricle Filling

Phase 2:Isovolumetric Contraction

Phase 3:Ventricular ejection

Phase 4:Isovolumetric relaxation

Ventricle Filling

diastole

atria and ventricles fill, AVs open, SLs close

Lub sound

Isovolumetric contraction

systole

increased pressure, AVs and SLs are closed

Lub sound

ventricular ejection

systole

SLs open, blood ejected into pulmonary artery and aorta

dup sound

isovolumetric relaxation

diastole

myocardium relaxes, SLs and AVs closed

Dup sound

pressure changes in atria and vent.

ventricles changes pressure most

1. aorta is a pressure reservoir
2. Aorta diastolic > ventricular diastolic
3. aorta is elastic and very muscular
4. blood flow is roughly constant, no spurts

• no external signals needed for contraction
• originate from autorhythmic cells
• contraction is myogenic, not neurogenic

• make up cardiac conduction system
• pacemaker cells
• conduction fibers

sinoatrial node

atrioventricular node

*both generate APs spontaneously!

1.                                    .    SA node fires, AP passes through atria
2.                                         AV node transmits AP after slight delay
3.                                       AV bundle (bundle of His) conducts through ventricular septum to apex.
4.                                         Right and left bundle branches
5.                                          Purkinje fibers spread AP upward into ventricular myocardium

By gap junctions and desmosomes.

They are concentrated between myocytes at intercalated discs.

• 1st, SA node depolarizes spontaneously (70 bpm)
• Then, AV node can depolarize spontaneously (50 bpm), but is pre-emptied by SA node
• If the SA node fails to fire or there is a conduction block:AV node can initiate AP
• Last, Purkinje fibers fire at 30 - 40 bpm

0. Na+ influx through VGSCs

1. Na+ influx stops, Ca2+ influx rises, through VGCCs

2. Ca2+ influx through VGCCs

3. VGCCs shut off, K+ channels open

4. Resting state - K+ permeability

*have stable resting potentials

• influx of Ca2+ from ECF --> Ca2+ release from SR
• Ca2+ - induced Ca2+ release
• Actin-myosin interactions (like skeletal muscle)
• contraction ceases when Ca2+ is removed

What is an ECG?

How does it work?

1. P wave-atrial depolarization
2. QRS complex-ventricular depolarization
3. T wave-ventricular repolarization

Cardiac Arrhythmias

1. what is it?
2. how is it recorded?
3. does an ecg reveal it?

1. abnormal electrical activity
2. recorded as altered time intervals between waveforms and/or altered waveforms
3. ECG does not reveal mechanical problems (ie bad valves)

leads to altered heart rate

too fast - >100 bpm

too slow - <50 bpm

AV conduction block

(degrees)

1st degree-AV node fires slow, delayed

2nd degree-AV sometimes doesn't fire

3rd degree-no conduction through AV node, ventricles contract IRT Purkinje fibers discharge (30-40 bpm)

Ventricular myocardium contracts in uncoordinated fashion

(difibrilate)

SV=EDV-ESV

70=130-60

EF=SV/EDV

TYPICAL: EF=70 mL/130mL = 0.54

What does Cardiac Output reveal?

What causes change in CO?

CO reveals an industrious organ!

change in HR or SV changes CO

CO=HR x SV

CO= 72 bpm x 0.07 L/beat = 5 L/min

1. neural control
2. hormonal control

*extrinsic

autonomic nervous system, through NTs ACh and NE

• Vagus control of nodes
• cholinergic
• decreases node firing
• slow HR
• mACh
• ACh
• SA and AV

SA, AV, ventricular myocardium

NE:increases node firing and contraction strength

B1

increases HR and SV

innervate nodes and atrial and ventricular myocardium

Why is it advantageous for the systemic circuit to be arranged in parallel capillary beds?

If you arrange the vessels in parallel, such that each organ has its own artery, every organ gets its own blood supply and does not have to wait in line, and organs can regulate their own blood flow based on need.