Chapter 13 Flashcards
The heart contains
blood vessels and blood
What substances does the heart transport
- Oxygen and nutrients to cells
- Wastes from cells to liver and kidneys
- Hormones, immune cells, and clotting proteins to specific target cells
Label heart diagram
heart-> _____-> ____-> ____-> ____-> veins
arteries; arterioles; capillaries; venules
Arteries
large, branching vessels taking blood away from the heart
Arterioles
small branching vessels with high resistance
Capillaries
site of exchange between blood and tissue
Venules
small converging vessels
Veins
relatively large converging vessels that conduct blood to the heart
Pulmonary circuit
- Supplied by right heart
- Blood vessels from heart to lungs, and from lungs to heart
Systemic circuit
- Supplied by left heart
- Blood vessels from heart to systemic tissues, and from tissues to heart
how does oxygenation of blood occur?
- Exchange between blood and tissue occurs in capillaries
- Pulmonary capillaries
Blood entering lungs =
deoxygenated blood
Blood leaving lungs =
oxygenated blood
Blood entering tissues =
oxygenated blood
O2 diffuses from
blood to tissues
Blood leaving tissues =
deoxygenated blood
Cardiovascular system is a ____ system
closed
Path of blood flow
Left ventricle->aorta-> systemic circuit- >vena cavae- >right atrium- >right ventricle- >pulmonary artery-> pulmonary circuit- >pulmonary veins ->left atrium - >left ventricle
Coronary circulation
- Parallel with other organs in the systemic circuit
- Blood in chambers does not supply nutrients to cardiac cells
Heart has its own set of
capillaries
Heart capillaries are supplied by
coronary arteries (left and right) that arise from the aorta
The heart is located in what cavity
thoracic
What separates the abdominal cavity from the thoracic
diaphragm
Pericardium
- Membranous sac surrounding the heart
- Lubricates the heart and decreases friction
Pericarditis
inflammation of pericardium
label heart and lungs diagram
Three layers of the heart wall
- Epicardium (outer)
*External membrane - Myocardium (middle)
*Cardiac muscle - Endothelium (inner)
*Layer of endothelial cells
Pressure within chambers of the heart varies with
heartbeat cycle
Normal direction of flow
Atria to ventricles
Ventricles to arteries
What do valves prevent
backward flow of blood
All valves open ______based on pressure gradient
passively
Right AV valve =
tricuspid valve
Left AV valve =____ =____
bicuspid valve = mitral valve
function of Papillary muscles and chordae tendinae
Keep AV valves from everting
Semilunar valves
Aortic valve
Pulmonary valve
Autorhythmicity
the ability to generate own rhythm
Autorhythmic cells provide what
pathway for spreading excitation through the heart
Pacemaker cells
- Spontaneously depolarizing membrane potentials generate action potentials
- Coordinate and provide rhythm to heartbeat
Conduction fibers
Rapidly conduct action potentials initiated by pacemaker cells to myocardium
Pacemaker cells of the myocardium
- Sinoatrial node (Pacemaker of the heart)
- Atrioventricular node
Conduction fibers of the myocardium
- Internodal pathways
- Bundle of His
- Purkinje fibers
Know the firing rates of Autorhythmic cells
Cardiac cells are linked by
gap junctions
Fastest cells = _____ = ______
pacemaker; set rate for rest of heart
Atria contract, then ____ contract
ventricles
Intercalated disks
- Junctions between adjacent myocardial cells
- Desmosomes to resist mechanical stress
- Gap junctions for electrical coupling
Initiation and conduction of an impulse
- AP initiated in SA node; signals spread through atrial muscle via interatrial pathways
- Signal travels to AV node via internodal pathway; AV nodal delay
- Atrioventricular bundle (bundle of His)
- Splits into left and right bundle branches
- Purkinje fibers
label heart conduction diagrams
Ionic Basis of Electrical Activity in the Heart
Spontaneous depolarizations caused by closing K+channels and opening two types of channels
Depolarizing to threshold consists of
- Open fast Ca 2+ channels—action potential
- cell with a less negative charge than the outside (+)
Repolarization of the heart
Open K+ channels
- return to a negative value
Five phases of electrical activity in cardiac contractile cells
Phase 0: increased permeability to Na+
Phase 1: decreased permeability to Na+
Phase 2: increased permeability to Ca2+, decreased permeability to K+
Phase 3: increased permeability to K+ , decreased permeability to Ca2+
Phase 4: resting membrane potential
look at table 13.2
properties of excitation-contraction coupling in cardiac contractile cells: skeletal
- similar to skeletal muscle
- T tubules
- Sarcoplasmic reticulum Ca2+
- Troponin-tropomyosin regulation
properties of excitation-contraction coupling in cardiac contractile cells: smooth muscle
Gap junctions
Extracellular Ca2+
First three steps of excitation-contraction coupling:
- Depolarization of cardiac contractile cell to threshold via gap junction
- Opening of calcium channels in plasma membrane
- AP travels down T tubules
Steps 4-7 of excitation-contraction coupling
- Calcium is released from sarcoplasmic reticulum
- Calcium binds to troponin, causing a shift in tropomyosin
- Binding sites for myosin on actin are exposed
- Crossbridge cycle occurs
Relaxation of cardiac muscle
- Removes calcium from cytosol
- Ca2+ ATPase in sarcoplasmic reticulum
- Ca 2+ATPase in plasma membrane
- Na+ -Ca2+ exchanger in plasma membrane
- Troponin and tropomyosin return to their positions covering myosin-binding sites on actin
Electrocardiogram
- Can be recorded from electrodes on the skin
- Noninvasive technique
- Used to test for clinical abnormalities related to conduction of electrical signals in the heart
Distance and amplitude of spread depend on two factors:
Size of potentials
Synchronicity of potentials from other cells
P wave:
atrial depolarization
QRS complex
ventricular depolarization and atrial repolarization
T wave
ventricular repolarization
PQ segment
AV nodal delay
QT segmant
ventricular systole
QT interval
ventricular diastole
First-degree heart block
- Slowed/diminished conduction through AV node occurs in varying degrees
- Increases PQ segment duration
- Increases delay between atrial and ventricular contraction
Second-degree heart block
- Slowed, sometimes stopped conduction through AV node
- Lose 1-to-1 relationship between P wave and QRS complex
- Lose 1-to-1 relationship between atrial and ventricular contraction
Third-degree heart block
- Loss of conduction through the AV node
- P wave becomes independent of QRS
- Atrial and ventricular contractions are independent
Extra contraction
- Results in an extra systole
- Premature atrial contraction (PAC), followed by an extra ventricular contraction
Ventricular fibrillation
- Loss of coordination of electrical activity of heart
- Death can ensue within minutes unless corrected
Cardiac Cycle
- Events associated with the flow of blood through the heart during a single complete heartbeat
- Two main periods of cardiac cycle
systole
ventricle contraction
- Aortic valve opens
- Pressure rises rapidly with ejection
- Highest point = systolic pressure
- Aortic valve closes
- Backflow of blood causes slight increase—dicrotic notch
diastole
ventricle relaxation
- Aortic valve closes
- Blood is still leaving aorta, so pressure falls
- Lowest point = diastolic pressure
Phases of Cardiac Cycle
- ventricular filling
- Isovolumetric ventricular contraction
- Ventricular ejection
- Isovolumetric ventricular relaxation
What occurs during ventricular filling
- Middle of ventricular diastole
- Venous return
- AV valve opens
- Blood moves from atria to ventricle
- Pulmonary and aortic valves are closed
- Passive until atrium contracts
What occurs during Isovolumetric ventricular contraction
- Start of systole
- Ventricle contracts—increases pressure
- AV and semilunar valves closed
- No blood entering or exiting ventricle
What occurs during Ventricular ejection
- Remainder of systole
- Pressure in ventricles > pressure in arteries
- Semilunar valves open
- Ventricular pressure < aortic pressure
- Semilunar valves close
What occurs during Isovolumetric ventricular relaxation
- Onset of diastole
- Ventricle relaxes—decreases pressure
- AV and semilunar valves closed
- No blood entering or exiting ventricle
Atrial and Ventricular Pressure : Phase 1
- Atrial pressure rises slowly with filling of blood
- Ventricular pressure is low
- Small rise in VP at end due to atrial contraction
Atrial and Ventricular Pressure: Phase 2
- Rapid rise in ventricular pressure
- Atrial pressure falls
- Phase 3
- Ventricular pressure falls
- Atrial pressure falls further until late systole
Aorta (and large arteries)
- Pressure reservoir
- Stores energy during systole as walls expand
- Releases energy during diastole as walls recoil inward
- Aortic pressure maintains blood flow through the entire cardiac cycle
EDV
- end-diastolic volume
- Volume of blood in ventricle at the end of diastole
ESV
- end-systolic volume
- Volume of blood in ventricle at the end of systole
SV
stroke volume
Volume of blood ejected from ventricle each cycle
SV = EDV – ESV
Ejection fraction (EF)
- fraction of end-diastolic volume ejected during a heartbeat
- EF = stroke volume/end diastolic volume
- EF = 70 mL/130 mL = 0.54
First heart sound
- Soft “lubb”
- AV valves close simultaneously
Second heart sound
- Louder “dupp”
- Semilunar valves close simultaneously
Cardiac output (CO)
SVxHR
Extrinsic
neural and hormonal
Intrinsic
autoregulation
Heart rate
- determined by SA node firing frequency
- SA node intrinsic firing rate = 100/min
during rest what system dominates
parasympathetic system dominates; HR = 75
During excitement what system dominates
sympathetic system takes over; HR increases
Epinephrine
- Same effect as sympathetic nervous system
- Increases action potential frequency at SA node
- Increases velocity of action potential conduction in muscle fibers
Activity of sympathetic neurons projecting to SA node does what?
raises HR
Activity of parasympathetic neurons projecting to SA node does what?
lowers HR
Levels of circulating epinephrine
raises HR
Epinephrine binds to
B1 adrenergic receptors
Thyroid hormones, insulin, and glucagon increase
force of contraction
Starling’s law
- Increased EDV stretches muscle fibers
- Fibers closer to optimal length
- Optimal length → greater strength of contraction
- Result → increased SV
Factors affecting end-diastolic volume
- End-diastolic pressure =preload
*Filling time
*Atrial pressure
*Central venous pressure - Afterload = pressure in aorta during ejection
