Electrical Activity of the Heart

Question 1

Calcium is released from the

Answer 1

Sarcoplasmic reticulum

Question 2

All cells of the heart are connected

Answer 2

Physically and electrically

Question 3

What allows for physical connection of cells

Answer 3

Desmosomes

Question 4

What allows for electrical connection of cells

Answer 4

Gap junction

Question 5

Desmosomes and gap junctions together form

Answer 5

Intercalated discs

Question 6

Cardiac muscle froms a

Answer 6

Functional syncytium

Question 7

Action potential of cardiac muscle

Answer 7

250ms

Question 8

Why can cardiac muscle not exhibit tetanic contraction

Answer 8

Due to long refractory period

Question 9

Tetanus

Answer 9

Sustained contraction

Question 10

What regulates the contraction of cardiac muscle

Answer 10

Calcium ions entry from outside the cell

Question 11

Cardiac muscle can only contract in the presence of

Answer 11

Calcium ions

Question 12

More calcium ions results in

Answer 12

Greater strength of contraction

Question 13

Cells with unstable resting membrane potentials act as

Answer 13

Pacemakers

Question 14

2 types of cardiac muscle

Answer 14

Non-pacemakers and pacemakers

Question 15

Resting membrane potential of non-pacemaker cardiac muscle is maintained by

Answer 15

Potassium ions leaving the cell

Question 16

Initial depolarisation in non-pacemaker cardiac muscle occurs by

Answer 16

Entry of sodium ions into cell

Question 17

Plateau in non-pacemaker cardiac muscle is reached by

Answer 17

Entry of calcium ions via L-type voltage gated channels and potassium ions leaving the cell

Question 18

Repolarisation in non-pacemaker cardiac muscle occurs by

Answer 18

Calcium ions leave the cell and potassium ions enter the cell

Question 19

Action potential on pacemaker cardiac muscle occurs by

Answer 19

Entry of calcium ions inside the cell via L-type channels

Question 20

Pacemaker potential/pre-potential occurs by

Answer 20

Gradual decrease (leave) of potassium ions inside cell, early increase (entry) of sodium ions and late increase (entry) of calcium ions via T-type channels

Question 21

Autorhythmic

Answer 21

Heart has its own rhythm

Question 22

How is the heart autorhythmic

Answer 22

By pacemakers always reaching threshold and contraction

Question 23

Modulators of electrical activity

Answer 23

Sympathetic and parasympathetic systems
Drugs
Temperature
Potassium ions
Calcium ions

Question 24

Effect of calcium ion channel blockers

Answer 24

Decrease force of contraction

Question 25

Effect of cardiac glycosides

Answer 25

Increase force of contraction

Question 26

Effect of increase of temperature

Answer 26

Increases electrical activity

Question 27

Effect of hyperkalemia

Answer 27

Fibrillation and heart block

Question 28

Heart block

Answer 28

Smaller electrical currents causing everything to work much slower than it should

Question 29

Effect of hypokalemia

Answer 29

Fibrillation and heart block

Question 30

Effect of hypercalcemia

Answer 30

Increased heart rate and force of contraction

Question 31

Effect of hypocalcemia

Answer 31

Decreased heart rate and force of contraction

Question 32

Sinoatrial node

Answer 32

Node containing the most pacemakers

Question 33

Function of sinoatrial node

Answer 33

Causes atrial excitation and sets the pace for the rest of the heart (0.5m/s)

Question 34

Location of sinoatrial node

Answer 34

Right atrium

Question 35

Annulus fibrous

Answer 35

Fibrous tissue that separates atrium and ventricle

Question 36

Atrioventricular node is also known as

Answer 36

Delay box

Question 37

Function of atrioventricular node

Answer 37

Slows down excitation until the atrium is finished contracting (0.05m/s)

Question 38

Bundle of His function

Answer 38

Conducts the electrical impulses from the atrioventricular node to the purkinje fibres

Question 39

Function of purkinje fibres

Answer 39

Cause ventricle excitation (5m/s)

Question 40

Bundle of His divides into

Answer 40

Purkinje fibres

Question 41

How are large extracellular electrical waves formed

Answer 41

Summation of many small extracellular electrical potentials

Question 42

Electrical activity can be recorded at the periphery as an

Answer 42

ECG (electrocardiodiagram)

Question 43

P wave of ECG corresponds to

Answer 43

Atrial depolarisation

Question 44

QRS complex corresponds to

Answer 44

Ventricular depolarisation

Question 45

T wave corresponds to

Answer 45

Ventricular repolarisation

Question 46

2 things that ECG can indicate

Answer 46

Disorders of conduction | Disorders of rhythm