Phys

Front 1

What is the orgin of cardiac excitation?

Back 1

the pace maker cells in the SA node located in the right atrium

Front 2

_____ are excitatory tissues known as the true pace maker of the heart.

Back 2

pacemaker cells

Front 3

Pacemaker cells have ____ ability t0 generate ______ which cause the _____ of the heart.

Back 3

intrinsic ; action potentials, excitation

Front 4

The activity of the SA node determines ____ and _____ known as ______

Back 4

excitiablity; contractibility; heart rate

Front 5

the activity of the SA node brings about a wave of ______ that spreads throughout the ______, and reaches the ________

Back 5

depolarization; atria muscle;ventricle muscles

Front 6

How does the excitation generated by the SA node reach the atrial and ventricular muscles?

Back 6

1. direct to the atrial muscles
2.through specialzed conducting tissues to the ventricle muscles
internodal tracts---> AV node--->Thru AV Bundle---> thru HIS---> then finailly the Ventricle muscles

Front 7

Other parts of the heart other than the SA node that act as a orgin of excitation?

Back 7

AV node ; HIS-purkinje fibers

Front 8

The _____ and ____ have the capicity to generate electric potential but their rate of _____ is slower than that of the _____node

Back 8

AV ; HIS ; discharge ; SA

Front 9

When the SA node is active the HIS and AV node are not activiated and remain silent, which is why they are reffered to as _______

Back 9

latent pacemakers

Front 10

When the SA node is active, the latent pacemakers serve as _________ carying the ______ generated by the SA node to the ventricles. They only become active if the ____________

Back 10

condicting tissues; action potential; SA nodal discharge is lost

Front 11

Under abnormal conditions other areas of the heart can be inapporopraly activated despite the presences of the ______, this gives rise to _______ and _________

Back 11

SA nodal excitation; loss of rhythm of the heart (arrthymia); uncordinated contractions

Front 12

electrical generator and pacemaker of the heart

Back 12

SA node

Front 13

latent pace makers

Back 13

HIS, AV node

Front 14

conducting tissues

Back 14

AV node, internodal tracts, purkinje fibers,

Front 15

contracting tissues when the SA is inactive

Back 15

HIs, AV

Front 16

Why does the activity of the SA node determine HEart Rate?

Back 16

the inherent rate of discharge of the node

Front 17

SA rate

Back 17

100-120

Front 18

AV

Back 18

80

Front 19

HIS

Back 19

30-50

Front 20

the suression of pacemaker activity of other pacemakers because of the high frequency excitation is known as _____________

Back 20

overdrive supression

Front 21

When the latent pace maker takes over, it drives the heart at its own ____ which is usually_______than the SA node

Back 21

intrinsic rate, slower

Front 22

A Slow conduction of the _______ allows time for the __________ to become completly ________, followed by its __________ before the ventricles are depolarized, thus allowing time for the _____ to empty their blood into the ventricles before ventricular contraction begins. The ___ of conduction of the ____ is crucial to the establishement of the rhythm of the heart.

Back 22

AV node
Atrium, Depolarized,contraction,Atria,. Slow rate of conduction, AV node,

Front 23

Except in ______ the physiologic direction of conduction in the heart between the ____ and the ______ is only in the forward direction thro the _______, conduction is from the atrial region to the ventricular region only and occurs thro the AV bundel. Conduction thro the muscles of the atria and ventricles is prevented by a ________

Back 23

abnormal stats;atria; ventricles ; Av bundle; contious fibrous barrier

Front 24

How long is the delay at the AV node?

Back 24

= .12 sec

Front 25

What causes the delay in the AV node?

Back 25

AV bundle

Front 26

Why do the whole atria and the whole ventricles conttract as single units when they recieve electrical stimulation?

Back 26

When the action potentials reach the muscle cells, they are conducted very rapidly from muscle cells to muscle cells, in such a way that it appears that all the muscle cells have been depolarized at the same time.

Front 27

The heart muscle is described as a ____________

Back 27

functional syncytium

Front 28

how is it possible for the whole atria and the whole ventricles to contract as single units when they recieve electrical stim?

Back 28

There are many cells that make up the atria ventricles. and are joined together by special electrical conducting discs called intercated discs that have extremely low electrical resistance compared to regualr cardiac muscle membrand { 1/400} of a regular cardiac muscle cell

Front 29

Muscle cells are joined together by special electrial conducting discs called ____________ that have extremely low electrical resistance compared to regualar ______

Back 29

intercalated discs; cardiac muscle membrane

Front 30

muscle membranes also have _____ at the intercalated discls between the successive cells. ________ are therefore transmitted easily from from one cell to the next enhancing the ____ of conduction

Back 30

gap junction; ions; velocity

Front 31

______ and _____ Are Attributes that allow the current to rapidly flow thro the heart muscles and contract as if they have all been depolarized at the same time. In this way the heart functions as a _____ and even tho it is not a ______

Back 31

Gap junction; intercalted discs, functional syncitium; anatomical syncitium

Front 32

_____________ as it flows from one heart cell to another, the heart behaves as if it is one unit of muscles instead of consisting of many muscle cells. As a result each ______ is excited as if it was a ____ and contracts as a ______

Back 32

current is not delayed ;heart chamber; single unit; single unit

Front 33

For the ventricles, rapid conduction by the ______ allows for rapid spread of impuleses thru-out ventricular muscles allowing them to contract as a single unit./ conduction in the ventricles is from the _____ to the ______, and repolarization takes place in the _________

Back 33

His purkin, endocardium, epicardium, opposite direction

Front 34

Electrial activity clinically recorded for the heart is the , electrical activity of the _______
those of the atria muscles and the ventrial muscles.

Back 34

cardiac muscle cell mass

Front 35

oscilloscope or recorded on paper, the electrial activity is called and ______

Back 35

Electrocardiogram (EKG, ECG)

Front 36

The ECG represents the electrial activity of the ___ and ___ and is done by recording them thro the ____

Back 36

atrial, ventricular muscle mass, skin

Front 37

Why do you need to record the electrical activity of the heart?

Back 37

To determine of the heart muscles ( atria and Ventrical muscles) are recieving and responding to the electrial activity generated by the SA node. The electrirical activity that gives rise to the ECG is a culmination of the electrial activity of the individual muscle cells.

Front 38

____ occurs during each heartbeat in all of the cardiac cells. These electrical changes summate in a complex way to create several electric fields during each heartbeat.Since the heart is surrounded and connected with the body surface by tissues containing ______, these electric fields conduct to the body surface.

Back 38

transmembrane action potential-electrolytes

Front 39

Electric feilds which conduct to the body surface, _______ to all points of the body surface. _____ develope between regions of the body surface during each ___.

Back 39

do not conduct with equal intensity or simultaneously; Potential differences; beat

Front 40

PD's can be detected and recorded b the use of appropriate methods and a voltage device called and _____. The magnitude of these PDs is small, the largest is no larger than 2 or 3 mV , therefore condiderable amplifcation is necessary.

Back 40

eectrocardiograph

Front 41

What is the use of the ECG information?

Back 41

1.Heart rate- atrial rate and ventrical rate can be detected
2. Site of orgin of pacemaker for any single beat
3.Sequence and time for conduction to occur throughout the heart can be determined
4.Any abnormality in site of orgin or sequence of conduction can be detected and analyzed and specific treatment devised.
5.Effectiveness of therapeutic maneuvers

Front 42

Various abnormal conditions that alter the ECG

Back 42

1. abnormal enlargement one or another heart chamber
2. inadequate blood flow thro conoary arterires
changes in ionic composition of blood plasma
4. Certin drugs alter the ECG in specific ways.

Front 43

The Electrical activity of the indvidual muscle cells is the ________ which are iniated by the electrical activity generated by the _______ and conducted to the muscle cells. The action potentials in the heart muscle or the ______ are brought about movement of charges thero changes in _____ across there plasma membrane. Charges involved in the electrial activity in the exctibale tissues of our bodies is carrried by ions.____,____,____,____. It is the movment of these ions in and out of cells that bring about changes in __________ that results in the depolarization and ______ that we describe.

Back 43

action potentials; pacemaker cells, SA node; ion flow ;Na+,K+,Ca++,Cl- ; membrane potential; action potentials.

Front 44

The effects of ion charge flow in the electrical activtites of the nodal muscle cells can be learned by studying a recording of the _________ of single cells of the pacemaker cells, and as well as those of single cells of the ______ and matching each phase of the action potential with the ____ involved

Back 44

trans membrane potential; heart muscles; ion charges

Front 45

Recording of the action potentials on the nodal and muscle cells are done by recording the electrical activity of ______ and _______ by inserting electrodes into single cells of the SA node as well as the ventricular muscle and recording the potential across the cell membrane at _____ and when the action potential s generated.

Back 45

single SA nodal cells ; single ventricular muscle cells; rest

Front 46

It is the activity of the indivual unit cells, that bring about the oberserved electrical activity that give rise to the ECG.

Back 46

SA node, Atrial muscles, AV node, Bundle branch, Pukin fibers, ventricle muscle.

Front 47

Phases of Cardiac and muscle action potentials

Back 47

Phase 4
phase 0
phase1
phase2
phase3

Front 48

Phase 4

Back 48

resting membrane potential called diastolic potential- resting phase of condration

Front 49

phase 0

Back 49

upstroke of the action potential

Front 50

phase 1

Back 50

transient and inital repolarization, this phase is absent for action potential of the nodal cells

Front 51

phase 2

Back 51

plateau- maintained state of depolarization- little repolarization

Front 52

phase 3

Back 52

repolarization

Front 53

each phase is brought about by movement of specific ions across the membranes of the cells.

Back 53

phases

Front 54

Transmembrane potential of the SA node: RMP starting around ______. RMP is not steady and undergoes _________, bc the membranes of these cells are ____, which means some passive ion channels ______ and allows ions to flow into the cells. The flow of positive charged ions into the cells causes the observed ______ which occurs during the ______of the cardiac contraction and is called phase 4 of the diastolic depolarizatin which initates the spontanous generation action potential that starts the whole exciation of the heart going

Back 54

-55 to -60mv; spontanous depolarization toward threshold; unstable; open without any stimulus.; spontaneious depolarization; diastole or resting phase

Front 55

phase 4- diastolic depolarization-
is( ______ )decline in K+ permeability of nodal tissues(_______) and leads to decreased K+ leaving leads to __________ in cells, leads to _________ in the cell leads to _________

Back 55

(Indirectly);gk2 channels close;increaed K+; Retention;increased positive changes; depolarization

Front 56

Phase 4-
_____ by progressive increase in permeability of ______ to Na+ leads to _________ leads to

Back 56

directly; passive Na channels of the nodal membrane;increased positive charges into the cell, depolarization

Front 57

Phase 4
The result of entry of positive charges into the cell is that the cell is ___ to threshold (-40mv) Threshold potential is the potential at which ____ open up tremend. increasing the perm of the ion across the cell membrane.

Back 57

depolarized;votage gated ion channels;

Front 58

Phase 0=

Back 58

Begins at the threshold potential from diastolic depolairzation

Front 59

Phase 0= 2nd step

Back 59

Upon reaching threshold, more slow calcium channedls up and more calcium comes in causing further depolarization that will eventually lead to complete reversal of the moembrane potential positive. This is the upshoot or upstroke of the action potential

Front 60

phase 0= 3rd step

Back 60

the full upstroke is therefore brought about predominately by continued entry of Ca+ into the cell by slow Ca+ channels. It is aided in a very small way by entry of NA via Ca+ channels

Front 61

Phase 0= after 3rd

Back 61

after a while the entry Ca+ and Na+ slow down but do not stop completely

Front 62

Phase 1=

Back 62

the Spike

Front 63

Phase 1 the spike

Back 63

Only present in muscle cells, not presnt in a nodal cells

Front 64

Phase 2

Back 64

plateu

Front 65

Phase 2 brought about by

Back 65

*Continued slow entry of Ca+ into the nodal cells from phase 0

Front 66

Phase 2 plateu is aided by

Back 66

--transient reduction in membrane permeability to K+ at the end of each phase
---the slow calcium channels are inactivated. The next phase begins

Front 67

Phaes 3

Back 67

repolarization

Front 68

phase 3 repolarization, brought about by

Back 68

--increased permeability to K+ to greater than normal levels after the inactiviation of the CA channels,
--which leads to loss of K+ from the cell leads to loss of postitive charges from the cell l

eads to --->decreased postivity and increased negativity. This brings the membrane back to near normal levels.

Front 69

Phase 3 repolarization is brought about by increased permeability to _____, to greater than normal levels, leads to a _____ if K from the cell, leads to loss positive charges from the cell, leads to _____ and ___. This brings the membrane back to near normal levels

Back 69

K+ ; loss of K+; decreased postivity and increased negativity

Front 70

At the end of repolarization the ion levels within the cell are brought back to normal by the activity of several pumps

Back 70

Na+, Ca+ pump

Front 71

Increased activity of Na+ pump helps return

Back 71

Na+ and K+ back to normal locations

Front 72

Increased activity of Ca pump

Back 72

helps bring Ca back to normal levels.

Front 73

depolarization-->upstroke---> repolarization repeats itself

Back 73

REpeats itself

Front 74

Ventricular muscle membrane
RMP

Back 74

-80V to -95 V
RMP STEADY does not undergo spontan. depolarization toward threshold

Front 75

Ventricular muscle membrane

Back 75

Action potentionals in the cardiac muscle cell is generated physioloally when the muscle is stimulated by electrical current coming from the SA node

Front 76

a change in the Ventruclar muscle membrane permiabilty to ions creates the _______

Back 76

action potental in the cardiac cell

Front 77

Action potential of cardiac cell ________

Back 77

Physiologaclly generated only by the stim, of the SA node

Front 78

Ventruclar muscle membran- trans membrane potential
phase 4=

Back 78

Resting membrane potential ( steady and not depolarizing)

Front 79

transmembrane pot ( ventrcile )

Phase 4= Brought about by

steady hight level increase of permeablility of the _______, leads to K+ leaves the cell , leads to _________

Back 79

muscle membrane K+; inceased negativity of the inside of the cell

Front 80

Phase 4=aided by increase in the membrane permeablilty to________, this acts to increase slightly the positive charges of the inside of the membrane and hleps prevent ______ by the increase in K+ efflex

Back 80

Na+ and Ca+; hyperpolarization

Front 81

resting membrane potential is dominated by______

Back 81

K effluz from the muscle cells as in other muscles and neurons

Front 82

Phase 0=upstroke stimulated by the spread of _____ to the ____ from the _____

Back 82

action potentials ; ventricles ; SAnode

Front 83

arrival of the SA node leads to activiation and opoenin of voltage gated______ channels. which leads to entry of Na+ions into the muscle cell which leads to _____ of the membrane potentail to postitive. About ____ which is equlibirum potential of Na+

Back 83

FAST Na+;reversal; 30 mv

Front 84

The entry of Na is ________, and leads to fast response action potential

Back 84

sudden, rapid, fast, brief

Front 85

Since the upshoot is brought about by entry of Na+ it can be ____ by drugs that select. block fast Na+ channels examples are
______

Back 85

tetratixub TTX poison

Front 86

at the end of the upshoot Na channels are inactivated to end phase 0 and in readyness of rnext phase

Back 86

end if phase 0

Front 87

Phase 1 is brought about by opening of the voltage gate K+ , leaving an outward current out of the cell. This current is ____ and K+ close very quickly and decreased perminablty to K+ by _________ to end phase 1 and in readiness for phase 2

Back 87

short lived; 5X normal

Front 88

phase 2 pleateu- brought about by the opening of ______ which leads to slow inward diffusion of Ca+ which leads to increae in positive charges in the cell thus keeping the membranes ______ for a longer period of time, and leads to ____

Back 88

voltage gated slow calcium channels; depolarized, plateu phase

Front 89

it is the ____ that gives rise to the ________ of the action potental in the cardiac muscle and is the major reason why cardiac contractions cannot be ____. the heart cannot ungergo tetanic contractions.

Back 89

plateu phase, refractory phase, summated

Front 90

external influces that affect rhythem of the heart?

Back 90

Autonomic nerve fibers that inervate the SA and AV nodes- the sympathetic and parasympathic,
blood levels of circlulating hormones such as Epinephrine,
plasma electroleyte concentrations.

Front 91

General Characteristics of autonomic control of the function of SA and AV noes:

The autonomic fibers only serve to ____ the exisitng intrisic automaticity.
They are NOT the ________
They control excitiaton in a way as to affect the ______.
Can also affect the _____ of contraction.

Back 91

regulate;
primary cause of cardiac excitation;
Rate of the heart beat
Force

Front 92

Parasympateic nerves innervate only the ____ and ____

Back 92

SA and AV ndoes

Front 93

Sympatheic nerves innervate both _______ and ________

Back 93

nerves and ventricle muscles

Front 94

at rest there is a ________ of the ________ to the heart. At rest the parasympathetic nerves to the heart are tonically active, the neruonal centers from where they orginate in the brainstem are generating action potentials by temselves and sding them down ________ to the SA node and AV node

Back 94

tonic discharge , motor efferent vagal parasympathic nerves; steadily

Front 95

the effect of the parasympthtic is to ______the intrinsic rate of discharge of the SA node from_______ giving us the average heart rate recorded under _________ conditions

Back 95

decrease; 100-120 to 70; resting

Front 96

Parasympathetic nerves to the heart, by effernt motor vagus nerve ____________

Back 96

constitute the dominant regulatory influence on the SA node at rest

Front 97

the increase activity of the vagus nerve will ____

Back 97

slow the heart down

Front 98

vagus nerve Activity increase will slow the heart by decreased rate of ______,
decreased excitability of ______ which leads to decreased rate of conduction which leads to _______ of cardiac impulse to the ventricles, leads to decreased heart rate (brayicardia_

Back 98

SA nodal discharge; AV junction fibers; slowed conduction

Front 99

the slowing of the vagus nerver or any other means is reffered to as a __________

Back 99

negative chronotopic effect

Front 100

Consequences for loss of SA nodal discharge or complete block of cardiac impulse thro AV juncton ( VENDRICULAR Escape)

Back 100

1. Ventricles stops for 4-10secs during which time
2. perkinje fibers dev. a rhythm and takes over the pace maker function sending AP to the vendricle muslces which will contract in response to excitation despicte the absence of the SA node excitation. In this way the ventricle has escaped the block.

Front 101

increased negativity results in Slowing rate of depolarization because it _____ the time needed to _________the membrane to __________ during phase _____ diastolic depolarization of the the sa node, this causes a _____

Back 101

increases; depolarize;threshold; phase 4; decrease in heart rate

Front 102

The sympatheic innervation to the heart does not have ___. Effect is seen only when physicall y activated by the right types of conditions. Such as the rate of ____ will increase resulting in , increased heart rate which is _______
and the excitiability of the junctional fibers will increase which will increase the rate of conduction thro the ___ to the ventricles.

Back 102

tonic discharge;SA nodal discharge will increase; tachycardia; av junction

Front 103

any condition that increase heart rate is said to have a ____

Back 103

positive chronotropic effect

Front 104

the limit to how high the heart rate can go when under intesnce stimulation? this upper limit for conduction of impulses is determined by the conduction thro the ___

Back 104

250 bpm; Av node