1. Overview: Cardiovascular System and the Heart
Circulatory System = heart, BVs, and blood
Cardiovascular System = passageways for blood = heart, arteries veins, etc.
Two Hearts:
Pulmonary Circuit (right side) - takes blood to lungs for gas exchange
Systemic circuit (left side)- takes oxygen rich blood to the organs and oxygen poor blood back to the heart

2. Right side of heart gets O2 poor blood
Pulmonary artery takes it away from heart to lungs
Pulmonary veins bring it back O2 rich
Left side of heart serves systemic system
Aorta takes O2 rich blood out to organs
Superior vena cava brings it back from head, neck, upper limbs
Inferior vena cava brings it back from organs below diaphragm.

3. Pericardium Double walled sac enclosing heart
In the pericardial cavity is pericardial fluid that allows the heart to beat without friction
Pericarditis is the pain caused by friction when the membranes are dry

4. Heart wall Epicardium outer layer fatty Myocardium thickest layer
cardiac muscle that pulls against a fibrous skeleton of fibers
focuses the movement of electricity
Endocardium
Smooth inner lining

5. Chambers Right and left atria receive returning blood
have an easier workload
Right and left ventricles eject blood

6. Heart Valves Ensure one way flow Made of flaps called cusps
Open & close as a result of pressure changes
When ventricles relax, valves are open
Full ventricles contract pressure pushes valves shut
AV valves = between atria + ventricles
Right AV – tricuspid valve
Left AV – bicuspid valve (aka,
mitral valve)
Semilunar valves = bet. ventricles +
the great arteries

7. Coronary Circulation Getting blood to your heart
~3 billion beats over an 80 year life span
Heart needs 5% of body’s O2
delivered by coronary arteries
Myocardial Infarction: fat deposits blocking arteries leading to necrosis of tissue
Anastomoses: our body’s defense
Two arteries covering the same area
If the damage is extensive, the
heart beat becomes inefficient
- coronary bypass may be necesssary

8. Cardiac Muscle and The Cardiac Conduction System
Cardiocytes: short, thick branched cells
-mononucleated, striated
-myogenic –will beat rythmically
w/o CNS stimulation
-inherent contractile activity controlled
by the ANS
• Intercalated discs join cells end to end
Gap junctions allow ions to flow between cells, keep electrical current flowing from one cell to the next
The action potential travels thru all cells connected together forming a functional syncytium

9. Cardiac conduction system
Our brain can modify the heartbeat, but not create it. Disembodied hearts can beat for hours.
Sinoatrial (SA) node = the pacemaker
-initiates heart beat and determines heart rate
-damage to SA node results in slower heart rate – implant an artificial pacemaker
Atrioventricular node = sends signals to the ventricles
Purkinje fibers arise from bundle branches near the apex and then spread throughout the myocardium.

10. Control of Heart Rate
Without nervous system control, the heart would beat about 100 times per minute
Both sympathetic and parasympathetic nerves innervate the SA node
When you are relaxed, your parasympathetic nervous system (via the vagus nerve) sets a resting heart beat rate at about 70 beats/min
When exercising or anxious, the sympathetic nervous system ↑ heart beat via hormones like adrenaline – this ↑ flow of O2 blood to muscles
Average maximum heart rate is 220 minus your age

11. Electrical & Contractile Activity
Contraction = systole
Relaxation = diastole
These can apply to parts (e.g., atrial systole), or just to the ventricles
Sinus rhythm = normal beat triggered by SA node
Can have ectopic focus (alternate source of beat, instead of SA node) called nodal rhythm
Arrhythmia = abnormal rhythm

12. Physiology of the SA node
The nerves of the SA node are always slowly moving toward an action potential
As soon as the heart beats it’s already starting toward another beat
Avg. ~75 beats per minute
Cardiac muscle has a sustained contraction, and a longer refractory period
This prevents tetanus: continual contraction
Membrane potential starts around -60mV.
Pacemaker potential is a gradual drift
upward (slow inflow of Na+ w/o outflow
of K+).
Fast calcium channels – inflow of Ca+.

13. Electrocardiogram (ECG/EKG)
Composite reading of many action potentials
P wave: atria contract
QRS complex: AV node fires, ventricles start to contract
T wave: ventricles repolarizing
U wave: not always seen – repolarization of papillary muscles or Perkinje fibers

14. Electrocardiogram

15. Cardiac cycle “Lub-dub” sounds are made when the heart valves that
separate the chambers of
the heart open and close in
sequence.

16. Now, you can… Identify the chambers and valves of the heart
Trace the flow of blood through the heart chambers
Contrast cardiac vs. skeletal muscle
Describe the physiological properties of cardiac muscle
Describe the heart’s electrical conduction system
Describe the physiological mechanism of control of rate of heart beat