Lecture 14 Flashcards
- SA node (Sinoatrial)
- AV node (Atrial Ventricular)
- Bundle of HIS
- Right and left bundle branches
- Purkinje system
a bundle of cardiac muscles is called _______ and connect to each other by __________
myocytes
intercalated discs
each disc has _____ connecting the cells
this allows ________ facilitating spread of the action potential from one cell to the next allowing rapid ________ depolarization
gap junctions
diffusion of ions
synchronous
in the conduction system cardiac muscle responds to the electrical impulses generated by the pacemaker cells (_______).
Cardiac action potentials can:
Be ____- generating
Be conducted ___________
Have ____ duration
SA node
self generating
directly from cell to cell
long
normally the heart rate systole is ___ percent and diastole is ____%
40%
60%
when heart rate is increased, the cardiac cycle is ______ and systole become ____%
decreased
65%
two bad things that can happen from increased heart rate
reduced ventricular filling time
reduced cardiac perfusion
Ischemia of a major coronary vessel can cause damage to the conducting system of the heart, called a _______.
Impulses from SA node are partially or completely obstructed at the _______ of his level
heart block
AV note/ bundle
Primary electrical event of the heart
Myocardial cell loses internal negativity
Transmit electrical impulse resulting in myocardial contraction
depolarization
“Membrane pumps” reverse flow of ions restoring polarity
Relaxation, recovery phase
The muscle returns to steady state
Repolarization
Excess internal negativity more negative than baseline.
Hyper-polarization
The ability of cardiac pacemaker cells to generate their own electrical impulses
automaticity
Irritability, the ability of the cardiac cell to respond to an electrical stimulus
excitability
ability of conducting system fibers to produce an automatic rhythmical discharge and contraction
Self-excitation
The ability of cardiac cells to receive an electrical stimulus and then transmit it to other cardiac cells
Conductivity
The ability of cardiac muscle to contract in response to an electrical stimulus
Contractility
The period during the action potential when a normal cardiac impulse cannot re-excite an already excited area
Refractory Period
Normal refractory period of ventricle:________
0.25 to 0.3s
normal baseline is around____
-70 mV
At resting state myocardial cell is __________
Electronegative inside (_____mV)
polarized
-85 mV
Three most important ions/channels in cardiac membrane potential
Sodium (Na+)
Calcium (Ca++)
Potassium (K+)
At rest, Sodium (Na+) Channels are…
greater outside cell
fast and slow sodium channels
At rest, Calcium (Ca++) Channels are…
greater outside cell
slow calcium channels
At rest, Potassium (K+) Channels are…
greater inside cell
potassium channels
all channels at rest are _____
closed
what opens first
then what happens
sodium and calcium
they close and potassium opens
“Muscle contraction” facilitating _____ function
At rest, regulatory proteins ______________ interfere with cross bridging of _____________
As cell depolarizes, _____ enters the cell and couples with ________
Promotes cross bridging resulting in cell contraction
pump
troponin/tropomyosin
actin and myosin
Ca++
troponin C
What has highest frequency of spontaneous firing?
how much per minute?
SA node
72/min
AV node fires at _______
Ventricles at _____
40/min
30/min
the conducting system consists of _____ and _______
nodal tissue
conducting fibers
initiates the heart beat and coordinates contractions of the four chambers
nodal tissue
conduct impulses rapidly to different areas of the heart
conducting fibers
what has very slow conduction velocities?
what has fastest?
SA and AV node
purkinje system
Sinoatrial (SA) Node is a strip of conductive tissue at __________
SA node initiates and regulates the impulse for contractions of the heart
The impulse spreads through the ______________ via the ________________
Rate __________
right atrium
musculature of both atria
interatrial bundle toward the AV node
60-100 bpm
Atrioventricular (AV) Node is located along the ___________
______ transmission by _____ from ____ to _______ due to the reduction of gap junctions and passes them to the ____________
Intrinsic rate _______
posterior inferior wall of Right Atrium
delays
0.13 seconds
atria
ventricles
AV bundle of HIS
40-60 bpm
Why is it important for the AV node to slow the Action Potential?
so that both ventricles can fill up before the blood is forced out
What causes the slowing of signal?
less gap junctions
Increases resistance to conduction of one fiber to the next
What is the bundle of HIS
Group of modified muscle fibers that conduct impulses
bundle of HIS arises in ________ and continues in the ________ as a single bundle
Splits into __________ that branch into ______
AV node
interventricular septum
right and left branches
terminal conducting fibers (Purkinje fibers)
Purkinje fibers spread out into the ________
- _______ depolarizes first, then ______, _______, ______.
ventricle walls
septum
apex
left ventricle
right ventricle
perking system is terminal ventricular conducting fibers on the __________ surface of the _______
endocardial surface
ventricles
perking system has intrinsic rate of _______ and is _______ and ______.
15-40bpm
“idioventricular”
Non-perfusing
How do these purkinje fibers have a faster conduction?
larger fibers
believed to have a higher permeability of the gap junctions
Why does the SA node control the heart?
Fires the fastest
Override AV node and Purkinje fiber by depolarizing them before self depolarization
AV node and Purkinje fibers act as back up generators when SA node fails
Pattern of Ventricular Conduction
Starts with initial septal depolarization
Impulse travels to apex
Impulse is distributed to both ventricles - left then right
Total time it takes 0.03 sec (very short)
Almost simultaneous contraction!!
action potentials are a result of transient changes in ionic permeability of cell membrane, triggered by initial ___________
Typical nerve: ____
Skeletal muscle cell: _____
Cardiac cell: ______
depolarization
1 ms
2-5 ms
200 to 400 ms
what are the 2 types of action potentials
fast response
slow response
what has fast response
ventricular
atrial muscles
purkinje fibers
(more of a spike)
what has a slo response
SA
AV
nodal type
atrial type
ventricular type
Ventricular Action Potential
- Phase 0 is _________
what occurs?
ventricular depolarization
Mediated by sodium (Na+) entry into the cells due to an increase in the number of open fast sodium channels in the cell membrane
Inside of the cell becomes less negative and the difference of the charge decreases
ventricular action potential
- Phase 1 is ______
what occurs?
partial ventricular repolarization (spike in graph)
Potassium (K+) exits from the cells as the sodium channels are closed and the potassium channels open
Phase 2 of ventricular action potential is the _____
what occurs?
plateau
slow entry of calcium into cells
counteract effects of potassium
- levels out charge
phase 3 of ventricular action potential is ________
what occurs?
rapid ventricular repolarization (downhill)
potassium permeability is highest
potassium exits from the cells as the sodium channels are closed and the potassium channels open
phase 4 of ventricular action potential is _____
what occurs?
recovery
sodium leaves and potassium re-enters the cell
atrial action potential
- average velocity of conduction through the atrial muscle is ______
- Similar to ventricular
- Phase 2 (Plateau) is ____________
- Phase 3 (Repolarization) is more ______
0.3m/sec
narrower due to smaller Ca++ influx
gradual
what is the source of the pacemaker?
hyperpolarization (SA node)
In hyper-polarization, between heartbeats, ____ ions slowly leak into the cell causing a slow ____ in resting membrane potential toward the _______ direction. When it reaches _______ the _____ channels become activated and cause AP
The channels then become rapidly inactivated while simultaneous___ diffuses out-both of these _______ intracellular potential back to _____.
Resting membrane potential reaches __________
sodium
rise
positive (slow Na+ channel stays open)
-40mvs
calcium
K
reduce
negative
-55 to -60mvs
the reason there is a flat line is because ?
calcium movement
75 percent of parasympathetic comes from ______
vagus nerve
the sympathetic system with the heart has signal and it moves through the _____, particularly the _____. This is sent to the ______ and ___________ rate of rate.
ganglia
T1 and T5
SA, AV, atrial and ventricular myocardium
increase
parasympathetic innervation signal is sent to ____ and ____
SA and AV nodes
and atrial myocardium
Sympathetic Nervous system
- signals come from spinal cord between _____ levels
- stimulates _____________________________
- supplies_______ sensory fibers which are sensitive to _____
Epi: stimulates alpha-, beta1-, and beta2-adrenergic receptors resulting in:
Cardiac stimulation
Increases heart rate (+chronotropic effect)
Increases force of contraction (+Inotropic effect)
Stimulation can increase CO 100%
T1-T5
SA and AV nodal tissue, atrial and ventricular myocardium
visceral
ischemia (makes it more sensitive to pain)
epinephrine stimulates ____, _____, and ____ adrenergic receptors resulting in cardiac ______, _____ in heart rate, _____ in force of contraction, and can _____ CO 100%.
alpha
beta1
beta2
cardiac stimulation
increase heart rate
increase force
increase CO
Parasympathetic NS
75 % of pre-ganglionic vagal fibers originating in the __________
____ binds to _________ receptors of SA node, AV node, and specialized conducting tissues atrial myocardium
Myocardial depressant
- ________ rate
- ________ force of contraction
medulla oblongata
Ach
muscarinic
decreases
reduces
order of a heart pound on an EKG
PQRST
P=___________
T=____________
QRS=__________
atrial contraction
ventricular repolarization
ventricular contraction
- P
- Q
- R
- S
- T
- PR segment
- ST segment
- PR interval
- QT interval
- QRS complex
EKG records ______________
atrial and ventricular depolarization and repolarization
EKG baseline is called _______
isoelectric baseline
interval area on EKG that includes a waveform and connecting straight line (_________) is the _________________.
isoelectric line
PR interval
QT interval
line between to waves is _______ and includes ______________
segment
ST segment
PR segment
Atrial depolarization is the ______ on the EKG and measures what two pathways?
P wave
Internodal
- anterior, middle posterior pathway
interatrial pathways
- Bachman’s bundle
what is not seen on EKG
atrial depolarization
During Ventricular Depolarization a conduction system consists of large fibers transmitting impulses at __________
current goes to ______, which divides into two bundles. then ______ deliver current into myocardium
1.5-4 m/sec
bundle of HIS
purkinje fibers
