Cardiac Physiology Flashcards
One of the three types of muscle tissue
Cardiac Muscle
They branch out and they have an Intercalated Disc
that have tunnels that allows rapid conduction of
action potential where ions can pass through
Cardiac Muscle
three major type of cardiac muscle tissue,
Atrial Muscle Fibers
Ventricular Muscle Fibers
Excitatory and Conductive Muscle Fibers
Muscle fibers that :
Contract feebly, meaning it’s contraction is not that strong due to few contractile fibrils
It exhibits automatic and rhythmical electrical discharge in the form of action potentials or conduction through the heart
Excitatory and Conductive Muscle Fibers
T or F
Your cardiac muscle fibers is arranged in a linear line wherein the fibers are dividing, recombining, and spreading again, showing a straight appearance
FALSE
Your cardiac muscle fibers is arranged in a latticework wherein the fibers are dividing, recombining, and spreading again, showing a branched appearance
Striated due to cardiac ___ which also contains the __and myosin filaments similar to the skeletal muscle fibers
Striated due to cardiac myofibrils which also contains
the actin and myosin filaments similar to the skeletal
muscle fibers
cell membranes that separates individual muscle cells in your cardiac muscle
Intercalated discs
The CArdiac Action Potential has a resting membrane potential of about ____
Has a resting membrane potential of about 80-
85mV
The cardiac Action Potential:
The overshoot is at +____
Characteristically has a plateau, the ___ second duration of pure depolarization
The overshoot is at +20mV
❖ Characteristically has a plateau, the 0.2 second duration of pure depolarization
o Depolarization is caused by the opening of the fast voltage gated sodium channels
o It closes abruptly, and then repolarization occurs
Skeletal Muscle
What phase?
○ The cardiac cell is stimulated causing depolarization of the cardiac cell
○ Your fast voltage gated Na channels opens causing a Na influx
Phase 0
Depolarization Phase
What phase?
○ The slow VG Ca channels are fully open causing the Ca ions influx
○ Ca channels also allows entry of Na ions
○ Na ion influx also takes place
○ Some fast K channels closes here causing a decrease in K efflux
Phase 2
Plateau Phase
What phase?
○The fast voltage gated Na channels closed, thereby, Na influx stops
○ Take note that, the slow K channels are fully open causing the K efflux resulting to repolarization
Phase 1
Initial Repolarization Phase
The normal cardiac refractory period is about _____seconds, which corresponds to the plateau phase of the cardiac action potential
0.25 to 0.30 seconds
T or F
Phase 4 - Heart rate Levels
○Averages to about -80 to -90mV
FASLE
Phase 4 - Resting Levels
○Averages to about -80 to -90mV
What phase?
○ The rapid repolarization
○ The slow VG Ca channels fully closes
○ In here, the Ca and Na influx stops and the slow K channels are still open
○ The point where permeability of the membrane to K increases which allows K efflux to occur
Phase 3
Repolarization Phase
● What gives the rhythmicity to the atrial node?
In comparison to the ventricular muscle,
because atrial muscles should have a
different rate of contraction than the
ventricles
Node delays transmission of AP to the ventricles
➢ This allows the atria to contract and empty their blood into the ventricles before ventricular contraction begins
AV Node
the interval time during which normal cardiac impulse cannot re excite an already excited area of the cardiac muscle
Refractory Period
o The pacemaker of the heart
o It sets the rhythmicity of the heart
SA Node
How does the leakiness not cause constant depolarization?
The opening of many K channels, causes a
K influx, the charge goes back to the
negative charge
The nerve that causes decrease in heart rate, the ??? Nerve, by the parasympathetic nervous system. While the sympathetic nervous system increases heart rate
VAgus Nerve
Where is the AV node located?
Located behind the tricuspid valve
Between the atrium and the ventricles, the only connection is via the _____, so the AP won’t flow from the internodal pathway towards the ventricles
AV bundle of his
The most distal aspect
o They penetrate about 1⁄3 of the way into the muscle mass and becomes continuous with the cardiac muscle
Purkinje Fibers
The stimulus is also the atrial stretch, in here
when your atrial walls are stretched, it activates
stretch receptors
Bainbridge Reflex
The distal portion enters the ventricular septum and divides into two - left and right, a connection
Left and Right Purkinje Fibers
What phase in the cardiac cycle blood from the atria is going to the Ventricle
Phase 1 - Atrial Systole
the cardiac muscles are relaxed, your heart is beginning to pump, the passive flow of the blood
Diastole
What phase in the cardiac cycle AV valves closes and SL valves open, The right ventricular pressure rises above the
pressure of the pulmonary artery and vice versa to the aorta
Phase 3 - Ejection
■ The final 2⁄3 of the phase
■ The remaining 30% is pumped
■ The pressure inside the ventricles decreases, and the pressure build up at the pulmonary trunk and the aorta
Slow ejection
■ Occurs about the first 1⁄3 wherein 70% of blood is rapidly ejected
■ Blood goes to the pulmonary trunk
○ Rapid ejection
What phase in the cardiac cycle - Has two parts
○ Rapid ejection and ○ Slow ejection
Phase 3 - Ejection
What phase in the cardiac cycle ○ Ventricles contract without emptying
Phase 2 - Ventricular Systole or Isovolumetric Contraction
Describes how your heart pumps blood, from atria to ventricles
Cardiac Cycle
Define:
Preload
Afterload
❖ Preload is the ventricular pressure
❖ Afterload is when it exerts the force which the ventricle must contract
What phase in the cardiac cycle
Ventricles relaxes
○ Has four subphases :
➢ Protodiastole,
➢ Isovolumetric Relaxation,
➢ Passive Ventricular Filling,
➢ Aortic Pressure Curve
Phase 4 - Ventricular Diastole
Cardiac Muscle Hypertrophy
increases the stress, decreasing the blood volume.
Wolff’s Law
Parasympathetic Stimulation
o ___ cardiac rhythm and conduction
o ___the rate of rhythm of the SA Node
Parasympathetic Stimulation
o Slows cardiac rhythm and conduction
o Decreases the rate of rhythm of the SA Node
Cardiovascular Center at the ?
Cardiovascular Center at the Medulla Oblongata
Ventricular Escape
o ___ your heart significantly
o When your ventricles stop beating for 5 to 20 seconds, Purkinje Fibers will start its own rhythm that causes ventricular contraction to about 15 to 40 beats per minute
Ventricular Escape
o Slows down your heart significantly
o When your ventricles stop beating for 5 to 20 seconds, Purkinje Fibers will start its own rhythm that causes ventricular contraction to about 15 to 40 beats per minute
Due to the sympathetic fibers it increases the rate of contraction of both atrial and ventricular muscle innervates almost all areas of the heart unlike your vagus nerve that innervates SA and AV Node
Sympathetic Stimulation
The strength of contractility depends upon the amount of venous blood return, the amount of blood coming back from the veins to the right atrium – SVC and IVC and some from the coronary sinus
Frank-Starling Mechanism or Law
Reason for the increase in strength of contractility?
your cardiac muscle in response to a sudden stretch is to contract
➢ The ability to contract is a characteristic of all striated muscles
➢ The amount of strength of contraction of the heart is proportional to the amount of stretch
Baroreceptors and chemoreceptors also takes part
o Baroreceptors in __
o Chemoreceptors in ___
Baroreceptors and chemoreceptors also takes part
o Baroreceptors in circulatory
o Chemoreceptors in pulmonary
Effect of thyroid hormones
Increases contractility and heart rate
o General effect is to increase basal metabolic rate
Hormones that - increases HR and contractility, hormones of the sympathetic nervous system, the fight or flight response
Norepinephrine and epinephrine
excess sodium in the ECF
➢ Decreases force of contraction because excess sodium blocks the inflow of calcium during an action potential
Hypernatremia -
T or F
Newborn baby has lower heart rate since the baby is small, it needs to be conducted slower
FASLE
Newborn baby
o has higher heart rate since the baby is small,
it needs to conduct faster
T or F
Hypokalemia results to cardiac arrest
TRUE
________for athletes is a beneficial effect of endurance type of training, the training focuses on cardiovascular endurance
bradycardia for athletes is a beneficial effect of
endurance type of training, the training focuses
on cardiovascular endurance
T or F
High temperature, increases HR about double the normal and enhances contractile strength - during exercise
TRUE
T or F
Females have slightly higher resting HR than adult males, but with regular exercise thr HR equalizes for both sexes
TRUE
Hypercalcemia means?
Hypercalcemia - an excess calcium
Decreased calcium causes cardiac
weakness similar to hyperkalemia
Hypocalcemia
