Lecture 14 Flashcards by Sydney Perry

SA node (Sinoatrial)
AV node (Atrial Ventricular)
Bundle of HIS
Right and left bundle branches
Purkinje system

How well did you know this?

Not at all

Perfectly

a bundle of cardiac muscles is called _______ and connect to each other by __________

myocytes
intercalated discs

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

normally the heart rate systole is ___ percent and diastole is ____%

40%
60%

How well did you know this?

Not at all

Perfectly

when heart rate is increased, the cardiac cycle is ______ and systole become ____%

decreased
65%

How well did you know this?

Not at all

Perfectly

two bad things that can happen from increased heart rate

reduced ventricular filling time
reduced cardiac perfusion

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

Primary electrical event of the heart
Myocardial cell loses internal negativity
Transmit electrical impulse resulting in myocardial contraction

depolarization

How well did you know this?

Not at all

Perfectly

“Membrane pumps” reverse flow of ions restoring polarity
Relaxation, recovery phase
The muscle returns to steady state

Repolarization

How well did you know this?

Not at all

Perfectly

Excess internal negativity more negative than baseline.

Hyper-polarization

How well did you know this?

Not at all

Perfectly

The ability of cardiac pacemaker cells to generate their own electrical impulses

automaticity

How well did you know this?

Not at all

Perfectly

Irritability, the ability of the cardiac cell to respond to an electrical stimulus

excitability

How well did you know this?

Not at all

Perfectly

ability of conducting system fibers to produce an automatic rhythmical discharge and contraction

Self-excitation

How well did you know this?

Not at all

Perfectly

The ability of cardiac cells to receive an electrical stimulus and then transmit it to other cardiac cells

Conductivity

How well did you know this?

Not at all

Perfectly

The ability of cardiac muscle to contract in response to an electrical stimulus

Contractility

How well did you know this?

Not at all

Perfectly

The period during the action potential when a normal cardiac impulse cannot re-excite an already excited area

Refractory Period

How well did you know this?

Not at all

Perfectly

Normal refractory period of ventricle:________

0.25 to 0.3s

How well did you know this?

Not at all

Perfectly

normal baseline is around____

-70 mV

How well did you know this?

Not at all

Perfectly

At resting state myocardial cell is __________
Electronegative inside (_____mV)

polarized
-85 mV

How well did you know this?

Not at all

Perfectly

Three most important ions/channels in cardiac membrane potential

Sodium (Na+)
Calcium (Ca++)
Potassium (K+)

How well did you know this?

Not at all

Perfectly

At rest, Sodium (Na+) Channels are…

greater outside cell
fast and slow sodium channels

How well did you know this?

Not at all

Perfectly

At rest, Calcium (Ca++) Channels are…

greater outside cell
slow calcium channels

How well did you know this?

Not at all

Perfectly

At rest, Potassium (K+) Channels are…

greater inside cell
potassium channels

How well did you know this?

Not at all

Perfectly

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

1. P 2. Q 3. R 4. S 5. T 6. PR segment 7. ST segment 8. PR interval 9. QT interval 10. 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