Download Outline Chapters 15-16 - Mead`s Fabulous Weebly

Lap 6: Cardiovascular System
Mead Anatomy and Physiology
15.1 The Heart: Structure
A. Location and Coverings
 Location: btwn 2 lungs in thoracic cavity; 2/3 of mass is to the left of midline
 Pericardium
◦ Membrane that surrounds and protects the heart
◦ 2 layers
1. Outer
 Tough layer, inelastic
 Prevents overstretching, protects, anchors in chest
2. Inner
 Thin layer
 Holds pericardial fluid to reduce friction during beats
B. Heart wall: 3 layers
 Epicardium
◦ Thin, transparent, outer layer
 Myocardium
◦ Cardiac muscle layer, pumping action
◦ Bulk of heart tissue
 Endocardium
◦ Thin layer, inside heart
◦ Covers valves and tendons attached to valves
◦ Continuous with epithelial lining of large blood vessels
C. 4 Chambers of Heart Wall
 Atria: 2 upper chambers
◦ Left and right atrium
◦ Receive blood from veins
 Ventricles: 2 lower chambers
◦ Left and right ventricles
◦ Pump blood out to body via the arteries
 Interventricular septum
◦ Divide the left and right sides of the heart
 Auricle
◦ Anterior surface of the atrium
◦ Increases capacity of atrium, increases blood volume
D. Valves of Heart
 Def: dense, connective tissue that is covered by endothelium; prevents blood from
flowing backward
 Chordae tendonae: connect valves to muscle wall
 Open and close due to changes in pressure
 Atrioventricular valves (AV)
◦ Btwn atrium and ventricles
◦ Tricuspid: right side
◦ Bicuspid or mitral: left side
 Semilunar valves
◦ Btwn ventricles and blood vessels (veins) leaving the heart
◦ Pulmonary semilunar valve: between right ventricle and pulmonary artery
◦ Aortic semilunar valve: between left ventricle and aorta
E. Blood flow through heart (fig 15.5)
1. Blood enters right atrium, low oxygen
2. Through tricuspid valve to right ventricle, low oxygen
3. Through pulmonary semilunar valve to pulmonary artery, low oxygen
4. Lung, oxygen enters blood (low to high)
5. Pulmonary vein back to heart, high oxygen
6. Enters left atrium, high oxygen
7. Through biscupsid valve to left ventricle, high oxygen
8. Through aortic semilunar valve to aorta, high oxygen
9. Body, oxygen leaves blood (high to low)
10. Superior/inferior vena cava back to heart, low oxygen
F. Blood supply to heart
 Heart muscle needs a separate supply of blood for oxygen and nutrients
 Cannot get from the blood inside the chambers
 Coronary circulation provides blood to nourish muscle tissue
 Principle vessels: left and right coronary arteries
15.2 Heart Function
A. Conduction system of heart (fig 15.6 or handodut)
1. Cardiac “excitement” begins at Sinoatrial Node (SA node)
 In right atrial wall
 Below superior vena cava
 Action potential generates here
 Spreads through atria
 Atria contract
2. Signal reaches Atrioventricular Node (AV Node)
 In interatrial spetum
 Slows down signal
 Allows atria to empty blood
3. Signal enters AV Bundle
 Also called Bundle of His
 In interventricular septum
 Passes signal from atria to
ventricles
4. Signal moves along left and right Bundle branches
 Through Interventricular septum
 Twd apex of heart
5. Purkinjie Fibers carry signal
 Move throughout ventricles
 Ventricles contract
B. Electrocardiogram (ECG or EKG)
 Def: recording of electrical signals of heart during cardiac cycle
 3 waves
1. P = Atrial depolarization
◦ Signal spreads from Sa node to atria; Atria contract
2. QRS Complex = Ventricle depolarization
◦ Signal spreads through ventricles; Soon after, ventricles contract
3. T = Ventricle repolarization : Ventricles relax
C. Cardiac Cycle: 3 phases
1. Relaxation period - Diastole
 All 4 chambers relaxed
 75% of blood in atria moves to ventricles
2. Atrial contraction - Atrial systole
 Follows P wave
 Force last 25% of blood into ventricles
 AV valves open, semilunar valves closed
3. Ventricular contraction- Ventricular systole
 QRS complex
 Pressure pushes semilunar valves open
D. Heart sounds
 Comes from turbulence in blood flow caused by closure of valves
 Lubb
◦ Long, booming sound
◦ AV valves closing
◦ After ventricular systole begins
 Dupp
◦ Short, sharp sound
◦ Semilunar valves closing
◦ End of ventricular systole
 Pause
◦ Relaxation period
E. Regulation of Heart Rate
 AV node sets at about 100 beats/min
 Can vary due to many factors
 Autonomic regulation
◦ Cardiovascular center in medulla oblongata
◦ Receives info and adjusts heart rate
 Chemical regulation
◦ Hormones
◦ Ions: K and Na decrease rate; Ca increases rate
 Other factors
1. Age: Adults (75 beats/min) lower than babies (120 beats/min)
2. Gender: Females higher than males
3. Fitness: Exercise lowers resting heart rate
4. Body temp: High temp = high rate
F. Summarize Cardiac cycle
ECG wave
P
What is happening?
What part of the
cardiac cycle?
What is the heart
sound?
What valves are open?
What valves are
closed?
What part of the
heart conduction
system is activated?
16.1 Blood Vessels
A. Arteries
 Function: Carry blood away from heart to the body
 Hold 13% of blood
 Largest: aorta and pulmonary trunk
◦ Arteries
◦ Arterioles
 Structure: 3 layers of tissue
◦ Endothelium: simple, squamous epithelial layer
◦ Middle layer: smooth muscle and elastic tissue
 Large arteries have more elastic
 Medium arteries have more muscle
◦ Outer layer: elastic and collagen
QRS
T
B. Capillaries
 Function: microscopic vessels that connect arterioles to venuoles
◦ Site of exchange of nutrients, gases, wastes
◦ Tissues with high metabolic needs have more capillaries
◦ Ex: Muscle, liver, kidneys
 Hold 7% of blood
 Structure: Single layer of epithelium
C. Veins
 Function: Carry blood back to the heart from the body
 Hold 64% total volume of blood
 Largest: Vena cava (superior and inferior) and pulmonary vein
◦ Veins
◦ Venuoles
 Structure
◦ Inner and middle layers: thinner than arteries
◦ Outer layer: thicker
◦ Contains valves to prevent backflow
◦ Larger lumen (hollow central cavity)
D. Blood Pressure
 Contraction of ventricles generate blood pressure
 Pressure highest in aorta/ arteries
◦ 100 mm Hg during systole
 (contraction)
◦ 70 mm Hg during diastole
 (relaxation)
 Falls as distance from left ventricle increases
◦ 35 mm as enters capillaries, 16 mm as leaves capillaries, 0 mm in vena cava
 Pressure depends on total blood volume
◦ Normal volume is 5L
◦ If it drops more than 10% it will affect BP
 Also depends on vascular resistance
◦ Size of lumen: narrow will increase resistance
◦ Blood viscosity: thicker will increase resistance
◦ Total blood vessel length: longer vessels will increase resistance
 1 lb of fat contains 400 miles of blood vessels
16.2 Circulation
A. Checking Circulation
1. Pulse
◦ Alternate expansion and elastic recoil of an artery
◦ After each contraction and relaxation of left ventricle
◦
◦
◦
Usually same as heart rate
Tachycardia: rapid, over100 beats/min
Bradycardia: slow, below 50 beats/min
2. Measurement of Blood Pressure
 Use sphygmomanometer
 Inflate cuff over known systolic BP
 Artery is compressed, blood flow stops
 Cuff is deflated
 When artery opens, hear the sound of blood passing through: 1st sound = systolic BP
 Sound suddenly becomes faint: Sound stops = diastolic BP
 Average below 120mm Hg/ 80 mm Hg
B. Circulatory routes
 Systemic circulation: AortaBody Vena cava
 Pulmonary circulation: Pulmonary trunk (left and right)LungsPulmonary veins
◦ Only artery with low O2 / Only vein with high O2
 Hepatic Portal Circulation
◦ Delivers blood from GI organs and spleen to the liver
◦ Uses hepatic portal vein
◦ Liver processes the products of digestion before they are delivered to the body
 Fetal circulation
◦ Skips lungs, kidneys, GI organs
◦ Fetus gets nutrients and O2 from maternal blood
◦ Comes in to placenta and through umbilical cord to fetus
◦ Foramen ovale
 Hole in heart btwn right and left atria
 Keeps blood from moving into lungs