Transcript Nerve activates contraction - e

Chapter 11
The Cardiovascular System
The Cardiovascular System
 A closed system of the
heart and blood
vessels
-heart pumps blood
-blood vessels - circulate
to all parts of body
 Deliver oxygens &
nutrients and to
remove carbon dioxide
& waste products
The Heart
 In thorax between lungs
 Pointed apex toward left hip
 Size of fist
Heart Coverings & Wall Layers
Pericardium – double Three layers
serous membrane
 Visceral - next to heart
 Parietal -
1.Epicardium- Outside
 parietal pericardium
 Connective tissue
outside layer
2.Myocardium- Middle
 Serous fluid fills space
between the layers
 Mostly cardiac muscle
3.Endocardium - Inner
 Endothelium
External Heart Anatomy
Figure 11.2a
The Heart: Chambers
 Right and left act as
separate pumps
 Four chambers
2 Atria - Receiving
- Right atrium
- Left atrium
2 Ventricles - Discharging
- Right ventricle
- Left ventricle
The Heart: Valves
 Allow blood to flow in only one direction
 Four valves
2 Atrioventricular valves – between atria & ventricles
 Bicuspid valve (left)
 Tricuspid valve (right)
2 Semilunar valves - between ventricle & artery
 Pulmonary semilunar valve
 Aortic semilunar valve
 Held in place by chordae
tendineae (“heart strings”)
Operation of Heart Valves
The Heart: Associated Great Vessels
 Aorta - Leaves left
ventricle
 Pulmonary arteries
- Leave right ventricle
 Vena cava - Enters
right atrium
 Pulmonary veins
(four) - Enter left
atrium
Coronary Circulation
 Blood in heart doesn’t
nourish the heart
 Heart’s nourishing
circulatory system
- Coronary arteries
- Cardiac veins
- Blood empties into the
right atrium via the
coronary sinus
The Heart: Conduction System
 Intrinsic conduction system (nodal system)
 Heart muscle cells contract, without nerve impulses, in
a regular, continuous way
- Sinoatrial node – Pacemaker initiates contraction
- Sequential stimulation occurs at other autorhythmic
cells
- Atrioventricular node
- Atrioventricular bundle
- Bundle branches
- Purkinje fibers
The Heart: Cardiac Cycle
 Cardiac cycle – events of one heart beat
 Terms: Systole = contraction
 Atria contract simultaneously
 Atria relax, then ventricles contract
Diastole = relaxation
The Heart: Cardiac Output
Cardiac output (CO)
 Amount of blood pumped by
each side of the heart in one
minute
 CO = (heart rate [HR]) x
(stroke volume [SV])
Stroke volume [SV]
 Volume of blood pumped by
each ventricle in one
contraction
Cardiac Output Regulation
The Heart: Regulation of Heart Rate
 Stroke volume usually remains relatively
constant
- Starling’s law of the heart: the more that
the cardiac muscle is stretched, the
stronger the contraction
 Changing heart rate is the most
common way to change cardiac output
Regulation of Heart Rate
Increased Heart Rate Decreased Heart Rate
1. Sympathetic nervous
system
 Crisis
 Low blood pressure
2. Hormones
 Epinephrine
 Thyroxine
3. Exercise
4. Decreased blood
volume
1. Parasympathetic
nervous system
2. High blood pressure or
blood volume
3. Decreased venous
return