Cardiovascular Physiology Flashcards
the heart
- size of fist
- between ribs 2-5
- 2/3 length at midline
- weighs 10 oz.
- beats 3 billion times in lifetime (80 years)
anatomical axis of heart
45 degrees
what are the four chambers of the heart?
- right atrium
- left atrium
- right ventricle
- left ventricle
what are the four valves of the heart?
- 2 AV valves
- 2 semilunar valves
papillary muscles
attach to tendinous cords
tendinous cords
attack to cusps of AV valves to keep them from prolapsing into atria
- don’t pull valves open
- act only to limit movement
cardiac muscle
myocardium
what are the semilunar valves?
- aortic valve
- pulmonary valve
what are the AV valves?
- bicuspid valve
- tricuspid valve
semilunar valves
3 cusps with “pockets”
- when blood flows back, closes valve
stenosis
narrowed opening due to scar tissue
- when blood is flowing through
- makes whistle sound
stenosis causes
- increased BP causing increased wear / tear
- rheumatic fever = antibodies attack valves
valvular insufficiency
valves don’t close properly blood leaks backward (regurgitation)
- makes a gurgling sound
what is the mot commonly replaced valve?
mitral value
bicuspid valve
pulmonary
- right side
- low pressure
- about 10 mm Hg
systemic
- left side
- high pressure
- about 110 mm Hg
blood flow through the heart
- superior and inferior vena cava
- right atrium
- tricuspid value
- right ventricle
- pulmonary valve
- pulmonary trunk
- R/L pulmonary artery
- lungs
- pulmonary veins
- left atrium
- bicuspid valve
- left ventricle
- aortic valve
- aorta
- systemic capillaries
cardiac muscle tissue
- short, branched cells connected by intercalated discs
- involuntary
- aerobic respiration only
- –> lots of mitochondria (no fatigue)
syncytium
intercalated discs contain gap junctions so that cells contract in unison
all three muscle types are similar by:
- sliding filaments
- ATP power
- elevated Ca+2 triggers
cardiac muscle is like skeletal by:
- sarcomeres
- striations
- troponin
- t-tubules
- SR Ca+2
cardiac muscle is like smooth by:
- small, single nucleus
- pacemaker cells
- gap junctions (syncytium)
- autonomic/hormones modulate
- Ca+2 entry from outside
EC coupling in cardiac muscle
- Ca+2 flow thru the DHPR (L-type Ca+2 channel) opens the RyR releasing Ca+2 from the SR. The Ca+2 induces additions Ryr channels to open
CIRI
Ca+2 induced Ca+2 release
- positive feedback
autorhythmic cells (pacemaker cells)
- <1% of cells
- determine HR
- myogenic
myogenic
- can contract without nervous system input
- beat on its own
- ex: SA node (75 bpm) , AV node (45 bpm)
conducting cells
spread electrical stimulus
- ex: bundle of his (AV bundle) , bundle branches, purkinje fibers
- all of these also have pacemaker activity
contractile cells
- 99%
- myocardium
- all have gap junctions –> AP spreads from one cell to another
- every heart cell contracts with every beat
electrical conduction system
- SA node fires
- excitation spreads through myocardium
- atrial contraction (systole) - AV node fires
- excitation spreads down AV bundle
- purkinje fivers distribute excitation through ventricular myocardium
- ventricular contraction
- 3-5 are fast
electrical conduction through myocardium
- atria contract in unison
- delay at AV node (ventricles fill)
- ventricles contract in unison
sinus rhythm
normal heartbeat triggered by the SA node
- about 75 bpm
ectopic focus
any region of spontaneous firing other than SA node
nodal rhythm
- AV node produces this
- backup pacemaker
- about 45 bmp
bundle of his/bundle branches/purkinje fibers
- < 35 bpm
- not fast enough to sustain life
pacemaker potentials of nodal cells
- Na+ enters = Na+ leak channels always open = no stable RMP
- Ca+2 enters (depolarization) = VG Ca+2 channels
- myogenic (beats on its own)
action potential in contractile cells
- only depolarize when stimulated (no potential activity) VG Na+ channel
- Na+2 inflow depolarizes membrane and triggers opening of more Na+ channels (positive feedback) and rapid increase in voltage change
- Na+ channels close and voltage peaks at +30 mV
- Ca+2 and K+ channels open and inflow of Ca+2 prolongs repolarization (K+ out)
- Ca+2 channels close and K+ outflow returns membrane to RMP
- 99% of myocardium
cardiac muscle AP
- have long refractory period to prevent tetanus
- no temporal summation
electrocardiogram (EKG)
- composite recording of all electrical activity in heart
- not directly APs
- used to determine heath of heart
- HR, regularity, size, position of chambers, damage
Einthoven’s Triangle
combination of 12 leads uses a different combination of reference and recording electrodes to provide different angles for “viewing” the heart
standard limb leads
- lead I
- lead II
- lead III
augmented limb leads
- aVR
- aVL
- aVF
pericardial (chest) leads
use limb leads combined into a reference point at the center of the heart
- V1 - V6
P wave
atrial depolarization
PQ segment
- atrial contraction
- delay at AV node
QRS complex
- ventricular depolarization
- atrial repolarization
ST segment
ventricular contraction
T wave
ventricular repolarization
TP interval
diastole
average MEA
59˚
normal range MEA
-30˚ - +110˚
MEA
tells us the net direction depolarization is heading
QRS complex is highly positive
electrical axis is parallel to that lead
- normal
QRS complex is highly negative
electrical axis is in opposite direction to that lead (inverted QRS)
QRS complex is isoelectric
perpendicular to that lead
left axis deviation (LAD)
MEA < -30˚
causes of left axis deviation
- left ventricular hypertrophy
- right ventricular destruction
- altered body structure
left ventricular hypertrophy:
- from increased BP
- mitral / aortic valve stenosis
right ventricular destruction:
from heart attack (myocardial infarction –> MI)
altered body structure from LAD
short, obese
pathologic hypertrophy
either ventricle, the axis will shift in direction of hypertrophied ventricle
right axis deviation (RAD)
MEA > 110˚
causes of right axis deviation
- right ventricular hypertrophy
- left ventricular destruction
- altered body stature
right ventricular hypertrophy
- caused by pulmonary hypertension
- tricuspid / pulmonary stenosis
left ventricular destruction
heart attack (MI)
altered body structure from RAD
extremely tall, thin
bradycardia
HR < 60 bpm
- increased TP interval
tachycardia
HR > 100 bpm
- decreased TP interval
artificial pacemaker
surgically implanted to provide electrical stimulus (artificial depolarization) to take over for either SA node or AV node