Cardiac Muscle Flashcards
What are the two types of myocardium cells?
- Automaticity Cells
2. Contractile Cells
Automaticity cells, which set the pace of the heart, include what?
- Pacemaker (SA Node)
- AV Node
- AV bundle of His
- Purkinje fibers
Contractile cells, which generate force in the heart, include what?
- Actin and Myosin
- Other contractile proteins
- Sarcoplasmic reticulum
Which 4 myocardial cells lack actin and myosin?
Hint: automaticity cells do not have actin/myosin
- SA node
- AV node
- Bundle of His
- Purkinje fibers
(Hint: automaticity cells do not have actin/myosin)
The 3 major types of cardiac muscle are ____ (contractile), _____ (contractile) and _____ (non-contractile or nodal)
- atrial
- ventricular
- excitatory and conductive muscle fibers
What are the 2 similarities of contractile tissue to skeletal muscle?
- Striated
2. Myofibrils which contain actin and myosin
What are the 3 main differences of contractile tissue to skeletal muscle?
- Lattice network
- Intercalated discs to form “communicating” gap junctions
- Syncytium
What is the syncytium?
interconnected heart cells; when one becomes excited, the AP spreads to all cells throughout the latticework interconnections
What are the 2 types of syncytium?
- Atrial
2. Ventricular
The 2 syncytiums are separated by ___ tissue that surround the ___ valvular openings
fibrous; AV
Cardiac action potentials last ____x longer in cardiac muscle vs. skeletal muscle because it is _____ms long (much slower than skeletal 2-5ms)
15x; 200-300ms
What are the phases of action potentials? (in order)
4 = resting membrane potential (-90mv)\
0 = opening of fast V-gated Na+ channels (-70mV)
= opening of slow V-gated Ca2+ channels (-40mV)
1 = closing of V-gated Na+ channels
= opening of V-gated fast K+ channels
2 = slow Ca2+ channels are OPEN (-40mV)
= decreased K+ permeability
3 = Ca2+ channels close
= K+ channels remain open
At what phase of the AP do the V-gated Na+ channels close and the V-gated fast K+ channels open?
1
At what phase of AP do the Ca2+ channels close and the K+ channels remain open?
3
At what phase of AP is the membrane at resting potential?
4
At what phase of AP are the slow Ca2+ channels open and there is decreased K+ permeability?
2
What happens at phase 1 of the AP?
1 = closing of V-gated Na+ channels
= opening of V-gated fast K+ channels
What happens at phase 2 of the AP?
2 = slow Ca2+ channels are OPEN (-40mV)
= decreased K+ permeability
What happens at phase 3 of the AP?
3 = Ca2+ channels close
= K+ channels remain open
What happens at phase 4 of the AP?
4 = resting membrane potential (-90mv)
At what phase(s) is the membrane potential at -40mV?
0 (opening of slow V-gated Ca2+ channels) and 3
At what phase is the membrane potential at -90mV?
4
At what phase is the membrane potential at -70mV?
0 (specifically the opening of fast V-gated Na+ channels)
At what phase is the membrane potential at +20mV?
1
At what phase is the membrane potential at +10mV?
2
Excitation-Contraction Coupling is a mechanism by which the action potential causes the _____ of the muscle to ____
myofibrils; contract
The AP spreads to the interior of the cardiac muscle fiber along the membranes of what?
t-tubules
T-tubules AP act on membranes of the longitudinal ______ tubules to cause release of ___ ions into the sarcoplasm from the SR
sarcoplasmic; ca2+
Ions diffuse into the myofibril to catalyze reactions for binding of ___ and ___ to produce muscle ___
actin; myosin; contraction
What is less developed in the cardiac muscle in comparison to skeletal muscle and does not store enough calcium to provide a full contraction?
sarcoplasmic reticulum
Strength of the cardiac muscle contraction is dependent on the extracellular ____ concentration
calcium
AP of pacemaker cells include phases ___, ___ and ___
4 = membrane potential (-60mV) 0 = calcium channels open at AP threshold 3 = calcium channels close, potassium channels open
At what phase of the pacemaker AP do the calcium channels open?
0
At what phase of the pacemaker AP do the calcium channels close?
3
At what phase of the pacemaker AP do the potassium channels open?
3
At what phase of the pacemaker AP is the resting membrane potential -60mV?
4
In order for passive filling to occur in the heart, blood collects until ____ drops and ____ open
pressure; valves
The atria is considered the ____ pump for the ____
primer; ventricles
80% of blood flows directly through the ____ and into the ___ even before the atria contract (passive process)
atria; ventricles
Passive filling increasing the ventricular pumping effectiveness by ___%
20%
Right atrial pressure is ___ than left atrial pressure
less
right = 4-6mmHg left = 7-8mmHg
Left ventricular pressure rises above __ mmHg and right ventricular pressure rises above ___ mmHg
80; 8
When the R/L ventricular pressures rise, the semilunar valves ___ and blood pours into where?
open; the aorta and pulmonary arteries
The first heart sound is the closure of what?
AV valves
The second heart sound is the rapid closure of what?
semilunar valves
In the volume-pressure diagram, phase I is the period of ____, phase II is the ____ contraction, phase III is the period of ____ and phase IV is the period of ____ relaxation
filling
isovolumetric contraction
ejection
isovolumetric relaxation
The systolic pressure curve shows that _______ filaments of cardiac muscle fibers are pulled far apart and strength of the cardiac fiber contraction becomes what?
actin-myosin; less than optimal
The diastolic pressure curve shows that ___ tissue in the heart will stretch no more and the ____ becomes filled nearly to its limit
fibrous; pericardium
Preload is the ____ pressure the the ____ has become filled
end-diastolic; ventricle
Afterload is the pressure in the ____ leading from the ____
aorta; ventricle
Increase in ____ will increase stroke volume, while increase in ____ will decrease stroke volume
preload; afterload
At rest, cardiac output (CO) is ___L/min. During exercise however, CO is ____x this amount
4-6L/min; 4-7x
There is an intrinsic cardiac regulation of pumping in response to changes in ______ of the blood flowing into the heart from the _____
volume; veins
Stretch of the ____ wall directly increases the ____ by 10-20%
atrial; heart rate
As atrial pressure for each side of the heart INCREASES, the ____ work output for that side also increases until it reaches the limit of the ____ pumping ability
stroke; ventricle’s
The ____ fill in response to higher atrial pressures
ventricles
Each ventricular volume and strength of the cardiac muscle contraction _____, causing the heart to pump ____ quantities of blood into the arteries
increase; increased
Sympathetic activation stimulation increases the ____ and increases the force of ____
heart rate; contraction
Sympathetic activation inhibition ___ heart rate and ___ force of contraction
decreases; decreases
Parasympathetic activation causes the heart rate to ____ and the force of contraction to ____
decrease; decrease
Hyperkalemia is an ___ of K+ (potassium) in the blood, muscle ____, _____, ______, arrhythmias, nausea, and can even lead to cardiac ____ and death.
increase fatigue weakness paralysis arrest
Hypokalemia is a ___ of K+ (potassium) in the blood, muscle _____, weakness, ____, paralysis, abnormal _____, low ____, and even ____ failure
decrease twitches cramps heart rhythms blood pressure respiratory
High amounts of K+ ion concentration cause the heart rate to _____
slow
High amounts of K+ ion concentration in large enough quantities can block the conduction of _____ from the atria to the ventricles through the ____ bundle
cardiac impulse
AV
Hypercalcemia is the increased amount of ____ in the blood which can cause ____ contractions
calcium; spastic
Hypocalcemia is the decreased amount of _____ in the blood and can cause ____ weakness
calcium; cardiac
When the body drops to 60-70F, what happens?
hypothermia
The alterations of which two ions will effect the cardiac pump?
potassium and calcium
