Heart

Question 1

Automatism and Rythmicity

Answer 1

Capacity to generate rhythmic electric signals by itself. FREQUENCY OF CONTRACTION

Question 2

Excitability

Answer 2

Ability to respond to effective stimuli, generating action potentials.

Question 3

Conductivity

Answer 3

Ability to conduct the cardiac stimulus in a controlled and organized way to the neighbouring
cells.

Question 4

Chronotropism

Answer 4

Modification of the heartbeat through external influence

Question 5

Inotropism

Answer 5

Contractility: Each cell’s ability to contract with more or less intensity. Depends on the amount of Ca2+ entering the cells and the length of the fibre before
contraction, Contraction strength

Question 6

Myogenic

Answer 6

the stimulation signal

Question 7

Modified specialised fibres (4)

Answer 7

• Auto rhythmic cells
• Sinoartrial node
• AV node
• AV bundel of His

Question 8

Autorythmic cells

Answer 8

Fire action potentials spontaneously, act as pacemaker and form the conduction system of the heart.

Question 9

Sinoartrial (SA) node

Answer 9

• Cluster of cells in the wall of right atrium (anterior to opening of vena cava).
• Begins heart activity that spreads to both atria.
• Excitation spreads to atrioventricular (AV) node as well.

Question 10

AV node

Answer 10

Within interatrial septum, transmits signal to the bundle of His.

Question 11

AV bundle of His

Answer 11

• The connection between atria and ventricles.
• Divides into bundle branches (right and left) and then into Purkinje fibers, large diameter fibers that quickly conduct signals.

Question 12

Pacemaker cells

Answer 12

Within SA node and AV node

Very small cells capable of generating electrical signals and lack contractile fibres.

Question 13

Steps of heartbeat

Answer 13

1. SA node connects with the atrial muscle
2. then spread towards the AV node through the internal pathway
3. towards atrial myocardium via gap junction
4. Transmission slows down from atria to ventricle through the bundle of His
5. this allows for the time- frame between atrial contraction- emptying and ventricular contraction
6. Signal reaches the Purkinje fibres through subendocardium
7. this fibres transmit to all cells in ventricular walls

Question 14

Prepotential (pacemaker potential)

Answer 14

• slow depolarisation
• opening of Na+ channels
• Transient ca2+ channels are open: entry of ca2+

Question 15

DEPOLARIZATION

Answer 15

• Fast depolarization
• Long-lasting(L-type) Ca2+channels are open:
  fast entry of Ca2+

Question 16

REPOLARIZATION

Answer 16

Opening of slow K+ channels

Question 17

Which one is the fastest and the real pacemaker of the heart?

Answer 17

SA node= Hearts pacemaker

Question 18

Sympathetic

Answer 18

1. Binding to β1 receptors in pacemaker cells. If channels open for longer time
2. Na release
3. increase Na+
4. increase Ca2+

= faster depolarisation speed, cardiac rate increases

Question 19

Parasympathetic

Answer 19

1. Binding to ACh receptors (M2) in pacemaker cells
2. Ach release
3. increased K+ (Kathi)
4. decreased Ca2+ (Clari)

= slower depolarisation speed, cardiac rate decreases

Question 20

TRANSMISSION of AP

Answer 20

Contractile cells need a stimulus to generate an action potential.
The stimulus is transmitted from the pacemaker cells through GAP junctions.

Question 21

Skeletal muscle: potential

Answer 21

stable at -70mV (in Form von Arm)

Question 22

Contractile myocardium: potential

Answer 22

stable at -90mV (9 in Form von Herz)

Question 23

Autorythmic myocardium: potential

Answer 23

unstable pacemaker potential, usually starts at -60mV

Question 24

Skeletal muscle. threshold potential

Answer 24

net Na+ entry through Ach channels

Question 25

Contractile myocardium: threshold potential

Answer 25

Depolarization enters via gap junction (contract/ weitergeleitet über gap junction)

Question 26

Autorythmic myocardium: threshold potential

Answer 26

net Na+ entry through I-funny channels, reinforced by ca2+ entry

Question 27

skeletal muscle: action potential

Answer 27

Na+ entry (Natalia)

Question 28

Contractile myocardium. action potential

Answer 28

Na+ entry (Natalia)

Question 29

Autorythmic myocardium: action potential

Answer 29

ca2+ entry (auto- Clarissa)

Question 30

skeletal muscle: repolarization phase

Answer 30

rapid, caused by k+ (Kathi)

Question 31

contractile myocardium: reploraization phase

Answer 31

extended plateau cause by ca2+ entry, rapid phase caused by k+

Question 32

autorythmic myocardium: depolarisation phase

Answer 32

rapid caused by K+

Question 33

skeletal muscle: hyperpolarization

Answer 33

due to excessive K+ Hugh k+ permeability when k+ channels close, leak of k+ and Na+ restores potential to resting state

Question 34

Contractile myocardium: Hyperpolarization

Answer 34

none: resting potential is -90mV the equilibrium potential for k+

Question 35

Autorythmic myocardium: hyperpolarization

Answer 35

none, when depolarisation hits -60mV the funny channels open again

Question 36

skeletal muscle: duration of action potential

Answer 36

short 1-2 sec

Question 37

Contractile myocardium: duration of action potential

Answer 37

extended 200+ msec

Question 38

autorythmic myocardium: duration of action potential

Answer 38

variable, generally 150+ msec

Question 39

Skeletal muscle: refractory period

Answer 39

generally brief

Question 40

Contractile myocardium: refractory period

Answer 40

Long cause preexisting of Na+ channels gates delayed until end of action potential

Question 41

Autorythmic myocardium: refractory period

Answer 41

none

Question 42

Internodal pathway

Answer 42

Propagation of the AP from the SA node to the atrioventricular (AV) node (100 ms delay) and from there to the bundle of His to the Purkinje fibres: excitation of the myocardium in the ventricle

Question 43

Action potential:

Answer 43

The influx of Ca2+ lengthens the total duration of a myocardial AP. Due to the plateau phase, repolarization in cardiac muscle lasts longer than in neurons or skeletal muscle fibres.

Question 44

Contraction:

Answer 44

Refractory period: time interval during which a second contraction cannot be triggered. In cardiac muscle, the refractory period is longer than contraction. Tetanus (maintained contraction) cannot occur in cardiac muscle.

Question 45

Energy production

Answer 45

The ATP production is mainly aerobic from oxidation of fatty acids and glucose (during rest) and also lactic acid (during exercise).

Question 46

What does prevent cardiac muscle fibres from suffering tetanus?

Answer 46

a longer refractory period

Question 47

On what does the strength of contraction depend on?

Answer 47

on the intracellular calcium

Question 48

p- wave

Answer 48

atrial depolarization

Question 49

PQ or PR segment

Answer 49

conduction through AV node and A-V bundle

Question 50

PQ or PR segment

Answer 50

Conduction continues through the atrioventricular (AV) node and the bundle of His

Question 51

QRS complex

Answer 51

Represents the rapid ventricular depolarisation It starts in the atrioventricular (AV) node - interventricular septum – apex - ventricular layers (from endocardium- pericardium)

Question 52

ST segment

Answer 52

ventricles contract

Question 53

T wave

Answer 53

ventricular repolarization

Question 54

Large P wave

Answer 54

enlargement of an atrium.

Question 55

Large Q wave

Answer 55

could indicate myocardial infarction

Question 56

Large R wave

Answer 56

enlarged ventricle

Question 57

Flat T wave

Answer 57

insufficient oxygen reaching the heart

Question 58

Longer P-Q segment:

Answer 58

presence of scar tissue probably due to coronary artery disease.

Question 59

Elevated S-T segment

Answer 59

acute myocardial infarction

Question 60

Longer Q-T segment

Answer 60

myocardial damage, ischemia (low blood flow).