Download Chapter 12, Part 2 – The Heart The Heart is a Double Pump

Chapter 12, Part 2 – The Heart!
Chapter 12, Part 2 – The Heart!
Right side
of heart!
Left side
of heart!
Anterior view!
1!
The Heart is a Double Pump!
Right heart:!
Powers pulmonary circuit!
Pumps blood to and from!
lungs!
Receives blood from systemic!
circuit!
Left heart:!
Powers systemic circuit!
Pumps blood to and from rest of body!
Receives blood from pulmonary circuit!
2!
1!
Chapter 12, Part 2 – The Heart!
Heart Wall!
Pericardium!
•  Has two layers and a fluid-filled space
(pericardial cavity) between them!
•  Creates low-friction environment for heart to
beat in!
Myocardium = heart muscle!
" "Cardiac muscle!
Endocardium!
" "Smooth, thin endothelial lining!
3!
Pericardium and Pericardial Space!
Pericardial
cavity!
4!
2!
Chapter 12, Part 2 – The Heart!
Cardiac Muscle Tissue!
Adjacent cells are connected by intercalated
discs (identified in lab)"
Gap junctions electrically connect cells!
Electrical syncytium: a group of cells
synchronized to work together to as a single
giant cell!
One atrial syncytium!
If one atrial cell depolarizes, all depolarize!
One ventricular syncytium!
If one ventricular cell depolarizes, all
depolarize!
Cardiac Muscle Tissue "
"
"
5!
Figure 4.3!
Intercalated!
discs!
6!
3!
Chapter 12, Part 2 – The Heart!
Cardiac Anatomy "
"
"
"
Figure 12.7!
7!
Pressure Differences and Heart Function!
Pressure is the key to blood flow patterns and to
the opening and closing of the valves.!
•  Blood moves from an area of higher pressure to
an area of lower pressure.!
•  Valves open and close in response to pressure
gradients.!
•  Ventricular and atrial contraction (systole) and
relaxation (diastole) must be coordinated to
produce the proper pressure gradients.!
8!
4!
Chapter 12, Part 2 – The Heart!
Overall Heart Function - (Download this)!
Three words:"
•  Pressure"
•  Pressure"
•  Pressure"
Know the path
blood takes
through the
heart!!"
9!
Heart Valves!
Right AV = tricuspid!
Left AV = mitral or bicuspid!
Aortic Semilunar Valve!
Pulmonary SLV!
10!
5!
Chapter 12, Part 2 – The Heart!
Path of Blood Through Heart!
Right and left ventricles pump the same amount
of blood each minute.!
Left ventricular wall is thicker and develops
higher pressures. (Why does this make
sense?)!
All valves open and close in response to
pressure.!
Papillary muscle and chordae tendineae prevent
eversion (“blowback”) of AV valves. They DO
NOT open or close valves.!
11!
Coronary Circulation!
Do not memorize these
vessels. Simply gain an
appreciation for the
coronary vasculature.!
12!
6!
Chapter 12, Part 2 – The Heart!
Cardiac Conducting System!
a.k.a. Nodal System!
A system of specialized cardiac muscle cells!
•  Specialized to generate and conduct the
contraction signal rather than for contraction!
•  Contraction involves spontaneous
depolarization of sinoatrial (SA) node!
A.K.A. Autorhythmicity or automaticity!
Neural or hormonal input is not required
for the heart to beat!!
13!
Conduction System
"
"
" Figure 12.12 !
!
NOTE errors in text!
!
Insulation!
AV bundle (of His)!
R. and L. bundle
branches!
Purkinje !
fibers!
14!
7!
Chapter 12, Part 2 – The Heart!
1. Sinoatrial Node (SA node)!
Found in R. atrium near superior vena cava
opening!
Fastest rate of spontaneous depolarization!
•  Called “cardiac pacemaker” because it
normally initiates the contraction signal!
•  Intrinsic rate = 80 - 100 depolarizations/min!
!
Resting heart rate is normally slower!
Parasympathetic input slows HR!
15!
2. Atrioventricular (AV) Node!
Found in R. atrium near opening of coronary sinus!
!
Delays conduction of contraction signal from atria
to ventricles!
!
Allows for coordinated heart beat!
•  Atria contract together first, then ventricles!
•  This is obviously important!!
16!
8!
Chapter 12, Part 2 – The Heart!
3. Conducting Cells Transmit the Signal!
AV bundle (of His)!
•  AV node → bundle branches!
Bundle branches (Right and Left)!
•  Bundle branches → Purkinje fibers!
Purkinje fibers"
•  Innervate ventricular myocardium!
•  Cause ventricles to contract from apex to
base!
17!
Impulse Conduction
"Deleted from 4th edition!
Electrical events!
•  SA node fires! Atria!
•  Atria depolarize! contract!
•  Delay at AV node!
Ventricles!
•  Conduction down!
contract!
AV bundle and bundle!
branches to Purkinje!
fibers!
18!
9!
Chapter 12, Part 2 – The Heart!
The Cardiac Cycle "
"
"
Start!
Figure 12.11!
Blood flow!
19!
Electrocardiogram (ECG or EKG)!
Records electrical activity in body fluids!
•  Does not record muscle contraction!
!
ECG waves!
Record electrical changes from baseline (0 mV)!
P wave = atrial depolarization!
QRS complex = ventricular depolarization!
" "
"(Atrial repolarization is hidden)!
T wave = ventricular repolarization!
20!
10!
Chapter 12, Part 2 – The Heart!
An Electrocardiogram!
Know significance of:!
•  P wave!
•  QRS complex!
•  T wave!
21!
Cardiac Output (CO)!
CO = the volume of blood pumped by a ventricle
in one minute (e.g. ml/min or l/min)!
CO = HR X SV !
"
"
" CO = heart rate x stroke volume!
" CO = beat/min x ml/beat = ml/min!
!
For example:!
"75 beat/min x 80 ml/beat = 6000 ml/min !
" "
"
"
"
" = 6 l/min!
22!
11!
Chapter 12, Part 2 – The Heart!
The Frank-Starling Principle!
a.k.a. Starling’s Law of the Heart!
•  Within physiological limits, the more the heart
is filled during diastole, the greater the force
of contraction and the more blood the
ventricle will pump.!
•  Or…“more in = more out”!
!
More venous return → more vigorous
contractions → more blood pumped by
ventricle!
23!
Exercise and Cardiac Output!
Resting CO:!
HR ≈ 75 beat/min!
SV ≈ 70 ml/beat!
CO ≈ 5.25 l/min!
Mild exercise CO:!
HR ≈ 100 beat/min!
SV ≈ 100 ml/beat!
CO ≈ 10 l/min!
Intense exercise CO:!
HR ≈ 150 beat/min!
SV ≈ 130 ml/beat!
CO ≈ 19.5 l/min!
24!
12!