Physiology Exam II
Terms
undefined, object
copy deck
- SA node is located in
- superior right atrium
- What created heart beat
- SA nodal pacemaker potential
-
AP's from SA node are propagated to right atrium AV node by
left atrium by -
INTERNODAL TRACTS
BACHMANS BUNDLE - AV node is located
- inferior right atrium
- What is the function of AV node
-
Delays signal to allow atria to beat first and help fill ventricles
Also a back up pacemaker - Overdrive suppression
- signal from SA node suppresses AV nodal pacemaker
-
Ventricular conduction system
starts with - bundle of His and branches into righ and left bundle branches which give rise to smaller branches
- What controls heart rate
- ANS
- Sympathetic innervation... heart rate via...
-
increases
beta 1 receptors - Parasympathetic innervation decreases heart rate via
- muscarinic receptors
- Main 2nd messenger in heart
-
cAMP
cAMP dependent protein kinase phosphorylates "funny" Na channel increasing its rate of opening
beta 1 receptors stimulate cAMP via Gs
M2 receptors inhibit cAMP via Gi - Sinus rhythm
-
Normal
set by SA node, adult at rest is 70-80 bpm - Abnormal rhythms
-
AV nodal - starts if SA node fails since overdrive suppression stops - 40-50 beats per min
Ventricular - from ventricular conduction system if both nodes fail 20-40 bpm
Ectopic- in hypoxia, when heart cells become depolarized - Purkinje cells are specialized for
- high velocity conduction, not contraction
- Phase 0
- Stimulus opens voltage gated Na channels (Na rushes in), membrane rapidly depolarizes
- Phase 1
- Na gates close quickly, K gates open
- Plateau phase
- 200-250 msec, sustains contraction
- Phase 2
- slow Ca channels open, Ca binds to Ca channels on SR, releases Ca into cytosol which leads to contraction
- Phase3
- Repolarization - Ca channels close, K channels remain open
- Phase 4
- Resting membrane potential
- Standard leads=
- Einthovens leads
- Augmented leads =
- Goldbergers leads
- What causes P wave
- phase 0 in atrium
- What causes Q, R, S wave
- phase 0 in ventricle
- What causes T wave
- phase 3 in ventricle
- What do intervals represent
- Delay in propagation
- P-R interval is
- AV node delay
- QRS (Q-S) interval
- ventricular conduction delay
- Q-T interval
- Duration of ventricular action potential
- Segments vs Intervals
-
Segments are straight or continuously curved lines between events
Intervals are periods of time that include events - Stroke VOlume SV is
- amount of blood the heart forces in aorta with every heart beat
- End diastolic volume
- amount of blood in heart just before contraction
- End systolic volume
- amount of blood remaining in heart just after contraction
- Formula for SV
- SV = EDV - ESV
- How can you increase SV
- Increase EDV or decrease ESV
- Cardiac output formula
- CO= SV * HR= (EDV-ESV) * HR
- What is the most important measure of cardiac performance
- Cardiac output
- Normal cardiac output
- 4-6 L/min
- How do you increase CO
-
Increase HR
Increase EDV
Decrease ESV - Ejection fraction
- Fraction of EDV that was ejected
- Formula for EF
- SV/EDV
- Normal EF
- 0.5-0.75
- What sets preload
- Ventricular filling pressure
- What regulates filling pressure
- CENTRAL VENOUS PRESSURE
- Best clinical measure of preload
- EDV
- Inotropic state is
- hearts contractility - both rate of contraction and total force
-
Increasing inotropic state..
ESV - decreases
- What determines inotropic state
- Ca
- Lusitropic state
- Rapidity at which heart relaxes
- Net effect of catecholamines
- Increase both inotropic and lusitropic states of heart and shorten systole while increasing contractility
- Afterload
- pressure against which ventricle ejects stroke volume
- Contraction velocity is ... to afterload
- inversely related
- P wave causes
- atrial contraction
- QRS wave causes
- ventricular contraction
- S1 first heart sound occurs when
- ventricular pressure > atrial pressure so AV valves close
- S2 second heart sound occurs when
- arterial pressure closes arterial valves
- SP systolic pressure
- maximum arterial pressure
- DP diastolic pressure
- minimum arterial pressure
- Pulse pressure
- SP-DP
- A wave is caused by
- atrial contraction
- c wave is when
- ventricular contraction pushes AV valves closed
- v wave is when
- blood returning from veins builds up behind AV valves