1. Do Now 3/31 PALLIATE (PAL ee ayt) v.
to make seem less serious; to mitigate
Christopher was given aspirin to PALLIATE his headache.
After Alex’s goldfish died, his mother bought him a puppy to PALLIATE his grief.
The nurse PALLIATED the patient’s burns by applying cold, wet bandages to the sensitive area.

2. The mammalian heart
Ch 9

3. Heart Made of cardiac muscle filled with blood
Coronary arteries deliver blood to the walls of the heart itself

5. The cardiac cycle Heart beats ~70x/min in continuous cycle
‘Begin’ with heart filled with blood and muscles in atrial walls contract: called atrial systole
Not very high in pressure b/c walls of atria are thin
Forces blood through atrioventricular valves into ventricles

6. The cardiac cycle
~0.1 second after atrial systole is ventricular systole
Generates great pressure (~120mmHg)
Pushed blood through semilunar valves
Last for ~0.3 seconds

7. The cardiac cycle
When ventricles relax it is called ventricular diastole
As muscle relaxes, pressure in ventricles drops
Semilunar valves prevent backflow

8. Cardiac cycle Ventricle walls much thicker than atria walls
Generates higher blood pressure in ventricles than atria
Left ventricle thicker than right

9. Control of the heart beat
Cardiac muscle is myogenic, meaning it naturally contracts and relaxes without nerve impulses
However, individual cells do not (and cannot) contract on their own individual rhythm, it needs to be cyclical with all other heart cells

10. Control of the cardiac cycle
The heart has its own built-in controlling and coordinating system to regulate cardiac muscle contractions
Cardiac cycle begins specialized patch of al muscle in the right atrium called the sinoatrial node (SAN) aka pacemaker

11. Control of the cardiac cycle
Muscle cells of the SAN set rhythm for all other heart cells
Their natural rhythm is slightly faster than all other muscle cells
They set up a wave of electrical activity which spreads rapidly over the walls of the atria
Cardiac muscle responds to this electrical excitation by contracting

12. Control of the cardiac cycle
Band of fibers between atria and ventricles prevent electrical signal from exciting ventricles to contract at the same time and atria
Electric signal must then be passed through conducting fibers in the septum, known as the atrioventricular node (AVN)

13. Control of the cardiac cycle
The AVN picks up the electrical wave as it spreads out across the atria and passes it on to a bunch of conducting fibers known as the Purkyne tissues (Purkinjie fibers)
Transmits excitation to base of septum where it spreads upwards through ventricle walls, causing ventricles to contract from the bottom up

14. Improper cardiac coordination
If ventricles fail to contract from bottom up, the coordination of the contraction can go wrong and cause chaotic excitation
Small sections of cardiac muscle contract while other relax, resulting in fibrillation, in which the heart wall simply flutters instead of contracting as a whole
Almost always fatal unless treated instantly

15. Electrocardiograms (ECGS)
Relatively easy to detect and record waves of excitation flowing through the heart muscle
Electrodes are placed on the skin over opposite sides of the heart
Result is a graph of voltage over time
P= wave of excitation over atrial waves
Q, R, S = wave of excitation over
ventricle walls
T = recovery of ventricle walls