chapter 20: the heart Flashcards
Right side of the heart carries blood
to pulmonary circuit
Left side of the heart carries blood to
systematic circuit
Pulmonary circuit
carries blood to and from gas exchange surfaces of the lungs
systematic circuit
transports blood to and from the rest of the body
location of the heart
- cavity
- near
- posterior to
- extends from
- ___ of heart is to the left of the midline
- throacic
- anterior chest wall
- sternum
- T5 to T9
- 2/3
Base of heart location
~3rd costal cartilage
Apex of heart
- definition
- location
- inferior pointed tip
- ~5th intercostal space
Mediasteum
- definition
- what does it contain (5)
region between two pleural cavities
-contains heart, great vessels, thymus, esophagus and trachea
Tissues of the heart
pericardium
pericardium
- definition
- 2 layers
- lining of the pericardial cavity
- fibrous pericardium
- serous pericardium
- fibrous pericardium
fibrous pericardium
- location
- definition
- function
- outer most portion
- dense network of collagen fibers
- stabilizes position of heart and associated vessels
serous pericardium
- definition
- 2 components
- inner “double” serous membrane; fluid secreting layer
- provides lubrication
- visceral pericardium
- parietal pericardium
- visceral pericardium
visceral pericardium
- location
- what does it do
- known as
- inner most layer
- covers and adheres close to outer surface of heart
- epicardium
Parietal pericardium
- definition
- location
- lines inner surface of pericardium
- adjacent to fibrous pericardium
The heart wall
-3 components
- epicardium
- myocardium
- endocardium
epicardium
- known as
- 2 components
- visceral pericardium
- mesothelium
- areolar tissue (connective tissue)
- mesothelium
mesothelium
fluid secreting cells
myocardium
- -definition
- what are the cardiac muscle cells called
- cardiac muscle tissue; muscular wall of heart
- cardiomyocytes
endocardium
- 2 components
- what type of epithelium
- function
- areolar tissue
- endothelium
- areolar tissue
- simple squamous epithelium
- covers all inner surfaces of heart
Cardiac muscle cells
- 3 general characteristics
- 1 special feature
- striated
- small
- branched with a single nucleus
- striated
- intercalated discs
Intercalated discs
- definition
- contains
- function
- specialized membranes b/n adjacent cells
- gap junctions
- allows all cells of the heart to become excited at the same time = heart contracts as a unit
Auricle of right atrium
expands to fill with blood
left pulmonary artery
carries deoxygenated blood to lungs
Pathway of blood through heart
-right side (9 steps)
- superior vena cava
- fossa ovalis (l atrium)
- coronary sinus (l atrium)
- right atrioventricular valve (r AV valve, tricuspid valve) (r ventricle)
- inferior vena cava (r ventricle)
- papillary muscle
- pulmonary semilunar valve
- left and right pulmonary arteries
- to lungs
pathway of blood through heart
-left side (7 steps)
- Left and right pulmonary arteries
- left atrium
- left atrioventicular valve (left AV valve, bicuspid valve)
- left ventricle
- aortic semilunar valve
- aorta
- to body
Superior vena cava
delivers blood from upper extremities
coronary sinus
opening of coronary circulation
right atrioventricular valve
- 2 other names
- function
- right AV valve
- tricuspid valve
- right AV valve
- prevents backflow
inferior vena cava
delivers blood from lower body
papillary muscle
- 1 component
- definition of that component
- chordae tendinae
- cords attached to valves and anchored to papillary muscle
Left pulmonary arteries
-carries what type of blood
oxygen poor blood to lungs
left pulmonary veins
-carries what type of blood
oxygen rich blood to heart
left atrioventricular valve
-3 other names
- left AV valve
- bicuspid valve
- mitral valve
coronary circulation
- definition
- function
- what happens if it becomes partially or completely blocked?
- supplies blood to heart muscle
- penetrates myocardium -delivers O2 and nutrients
- myocardial infarction - heart attack!
5 major arteries of the coronary circulation
- right coronary artery
- left coronary artery
- anterior interventricular artery
- posterior interventricular artery
- circumflex artery
3 veins of the coronary circualtion
- coronary sinus
- great cardiac vein
- middle cardiac vein
origin of the heart beat
- 3 things
- 2 types of cells
- the heart beats (contracts) 60-80 times per min. (~75 bpm average)
- the heart is “self excitatory”- stimulates itself; “automaticity”
- the conducting system of the heart initiates and distributes the stimulus
- the heart beats (contracts) 60-80 times per min. (~75 bpm average)
- contractile cells
- conducting cells
- contractile cells
contractile cells
produce contraction that propel blood
conducting cells
- function
- smaller or bigger than contractile cells
- lacks 2 things
- do they contract
- initiate and spread electrical impulses
- smaller
- lacks actin and myosin
- no
Action potentials
- 3 steps
- 2 periods
- resting
- depolarization
- repolarization
- resting
- absolute refractory period
- relative refractory period
- absolute refractory period
threshold mV
-60 mV
resting phase
- cause
- mV
- lots of protein inside and leakage of K+ out of cell
- -70mV
depolarization
-cause
-movement of Na+ in through open channels
repolarization
-cause
Na+ channels close, K+ channels are fully open and K+ exits
absolute refractory period
- occurs when
- definition
- between depolarization and repolarization
- cannot have another action potential during this time
relative refractory period
- occurs when
- definition
- occurs after an action potential
- can get another action potential but it takes more energy
when does contraction of a skeletal muscle occur
after action potential
action potential in a cardiac myocyte
- conducting cells
- contractile cells
- 3 phases
- initiate and conduct action potentials
- conduct action potentials and contract
- depolarization
- plateau
- repolarization
- depolarization
depolarization in a cardiac myocyte
-cause
-Na+ entry through open channels
plateau phase in a cardiac myocyte
- cause
- what moves
- what does this maintain
- opening of slow Ca++ channels, closing of Na+ channels
- ca2+ ions move from outside to inside and from inside SR into sarcoplasm
- maintains a slightly positive membrane potential
repolarization of cardiac myocyte
-cause
closing of Ca++ channels; opening of K+ channels
absolute refractory period in cardiac myocyte
- long or short
- continues until
- when can it initiate another action potential
- long
- relaxation is underway
- when the heart has already relaxed
the conducting system of the heart
-6 steps
- Sinoatrial (SA) node
- intermodal pathways
- atrioventricular (AV) node
- AV bundle
- Bundle branches (R and L)
- Purkinjie fibers
Sinoatrial node
-function
initiates the action potential- “pacemaker”
Purkinjie fibers
small branches that penetrate the myocardium and deliver action potential
when does the pacemaker (SA node) spontaneously depolarizes
about every 0.8 secs
which node is faster? SA node or AV node?
SA node
what mV is the threshold at for the SA node
-40 mV
Electrocardiogram
- known as
- definition
- 3 steps
- 6 components
- “EKG” or “ECG”
- Action potentials passing through the conducting system are strong enough to be detected by electrodes on the body surface
- atrial excitation begins
- impulse delayed at AV node - Atria contract
- impulse travels toward purkjinie fibers
- ventricular contraction begins
- atrial excitation begins
- P wave, Q, R, S, QRS complex, T wave
P wave
depolarization of atria
QRS complex
depolarization of ventricles
T wave
repolarization of ventricles
What is not seen in the electrocardiogram?
atrial repolarization (masked behind QRS complex)
The cardiac cycle
- definition
- 2 stages
Period between start of one heart beat and beginning of the next
- 1.systole
2. diastole
Systole
- definition
- 2 types
- pressure
- contraction
- atrial systole
- ventricular systole
- atrial systole
- increase pressure
Diastole
- definition
- 2 types
- pressure
- relaxation
- atrial diastole
- ventricular diastole
- atrial diastole
- decrease pressure
overview of the cycle
- 3 steps
- how many sec for each heart beat
- Atria contract (atrial systole); ventricles relax (ventricular diastole) - 0.1 sec
- Atria relax (atrial diastole); ventricles contract (ventricular systole) - 0.3 sec
- Atria relax (atrial diastole); ventricles relax (ventricular diastole) (when heart rate increases this phase gets alot shorter)- 0.4 sec
- 0.8 sec
4 phases of the cardiac cycle
- Late Diastole
- Atrial Systole
- Ventricular systole
- ventricular diastole
Late diastole
- definition
- AV valves
- Semilunar valves
- Blood flow right side
- blood flow left side
- period of passive filling
- atria and ventricles are relaxed
- open
- closed
- Blood will enter the RA and flow into the RV through the open AV valve
- Blood will enter the LA and flow into the LV through the open AV valve
- ~70% of the ventricular volume enters this way
Atrial systole
- definition
- conducting system (3)
- ECG
- ventricles are in systole and diastole
- Blood pumped right side
- blood pumped left side
- atria contract
- Action potentials initiated as SA node
- Travels through internodal branches to AV node
- Atria are depolarized
- Action potentials initiated as SA node
- diastole
- RA pumps blood through open AV valve to RV
- LA pumps blood through open AV valve to LV
Ventricular systole
- atria are in systole and diastole
- 2 steps
- diastole
- isovolumetric contraction
- ventricular ejection
- isovolumetric contraction
isovolumetric contraction
- definition
- conducting system (2)
- ECG
- how do ventricles contract
- ventricular pressure increases or decreases
- when ventricular pressure is > atrial pressure
- heart sound
- blood flow
- same volume
- AV node to AV bundle to R and L bundle branches to Purkinjie fibers
- ventricles are depolarizing
- AV node to AV bundle to R and L bundle branches to Purkinjie fibers
- isometrically
- increasing
- AV valves close on left and right
- Lubb - 1st heart sound
- No blood enters or exits - maintain same volume
Isometric contraction
tension of muscle without movement
Ventricular ejection
- ventricular pressure
- semilunar valves
- Blood pumped right side
- blood pumped left side
- volume ejected
- increasing
- open when ventricular pressure > aortic and pulmonary artery pressure
- Blood pumped through open semilunar valves into pulmonary trunk
- Blood pumped through open semilunar valves into aorta
- stroke volume: volume of blood ejected in one beat
ventricular diastole
-2 components
- isovolumetric relaxation
2. ventricular filling
isovolumetric relaxation
- definition
- conducting system
- ECG
- ventricular pressure
- when ventricualr pressure
- same volume
- repolarization
- T wave
- decreasing
- semilunar valves close
- dubb - 2nd heart sound
- AV valves open
Ventricular filling
- AV valves
- semilunar valves
- blood flow
- open
- closed
- ventricles are passively filling
Cardiodynamics
- definition
- 3 important terms
- examines the factors the effect cardio output
- End-diastolic volume
- End-systolic volume
- Stroke volume
- End-diastolic volume
cardio output (CO)
- definition
- indication of
- amount of blood pumped by left ventricle in one minute
- blood flow through tissues
End-diastolic volume
amount of blood in each ventricle at the end of ventricular diastole
End-systolic volume
amount of blood in each ventricle at the end of ventricular systole
Stoke volume
- definition
- formula
- amount of blood pumped out of the heart in a single heart beat
- SV= EDV-ESV
How do we determine cardio output?
Cardio output (CO) = heart rate (HR) x stroke volume (SV)
What is a normal cardiac output?
CO = 75 bpm x 80 ml/beat = 6000 ml/min
Factors affecting stroke volume
-5
- Venous return (VR)
- Filling time (FT)
- Increased by sympathetic stimulation
- Decreased by parasympathetic stimulation
- Increased by E, NE, glucagon, thyroid hormone
3 factors that determine stroke volume
- Preload
- Contractility
- after load
preload
- definition
- frank-starling law of the heart
-degree to which cardiac muscle cells are stretched just before contracting
-more in = more out; increased VR = increased CO
increased FT = increased CO
What determines the degree to which the heart is stretched?
the EDV; greater the EDV = larger the preload
Contractility
- definition
- example
- 2 types of action
- amount of force produced during a contraction
- increased contractility = decreased ESV = increased SV
- positive inotropic action
- negative inotropic action
- positive inotropic action
positive inotropic action
increase contractility
negative inotropic action
decrease contractility
afterload
- definition
- increased afterload =
- pressure in the pulmonary trunk and aorta the heart must overcome to eject blood
- increased afterload = longer period of isovolumetric contraction = increased ESV = decreased SV
3 factors affecting heart rate
- Autonomic nervous system
- hormones and chemicals
- other (age, sex, and temp)
autonomic nervous system
- definition
- 2 branches
- innervated through cardiac plexus
- sympathetic
- parasympathetic
- sympathetic
sympathetic NS
- definition
- effect on heart rate
- effect on force
- cardioacceleratory center in medulla oblongata; sympathetic nerves supply SA node
- increase
- increase
parasympathetic NS
- definition
- effect on heart rate
- effect on force
- cardioinhibitory center in medulla oblogata; parasympathetic nerves supply SA node
- decrease
- decrease
Hormones and chemicals
-5
- norepinephrine
- epinephrine
- thyroid hormones
- calcium channel blockers
- beta blockers
how does norepinephrine, epinephrine and thyroid hormones effect heart rate and contractility?
- increase heart rate
- increase contractility
how does calcium channel blockers and beta blockers effect heart rate and contractility?
- decrease heart rate
- decrease contractility
age effecting HR
- young
- old
- higher
- lower
sex effecting HR
- females
- male
- higher
- lower
temp effecting HR
- hot
- cold
- higher
- lower