Physiology: Electrical Activity of the heart

Question 1

What are sum of the structures found in the myocardium?

Answer 1

Actin and Myosin Z line T-tubule Sarcoplasmic Reticulum Sarcolemma

Question 2

What forms functional syncytium?

Answer 2

Intercalated Discs

Question 3

What structures are involved in intercalated discs

Answer 3

Gap Junction Desmosomes

Question 4

What are the functions of gap junctions?

Answer 4

Electrically connects intercalated discs

Question 5

What are the functions of Desmosomes?

Answer 5

Physically connects intercalated discs

Question 6

Describe the action potential of cardiac muscle?

Answer 6

Long action potential (250msec) with long refractory period

Question 7

What does the the long refractory period of cardiac muscle?

Answer 7

No tetanic contraction can be observed

Question 8

What is the effect of Ca2+ outside the cells on cardiac muscle?

Answer 8

Can be used to regulate the contraction of the muscle Ca2+ cannot saturate troponin Regulation of the release of Ca2+ can vary strength of contraction

Question 9

Can you describe the resting membrane potential potential of pacemaker cells?

Answer 9

They are unstable

Question 10

What does the action potential of Non-pacemaker cardiac muscle look like?

Answer 10

Question 11

What does the action potential of Pacemaker cardiac muscle look like?

Answer 11

Question 12

What ions are involved in the resting and action potential in non-pacemaker myocardium cells?

Answer 12

K+

Na+

Ca2+ (L-Type)

Question 13

What ions have the highest concentration of resting potential in non-pacemaker cells?

Answer 13

K+

Question 14

What happens within non-pacemaker for an action potential to occur?

Answer 14

Initial increase in PNa+ followed by and increase in PCa2+ and decrease in PK+

Question 15

What occurs in non-pacemaker cells during repolarization?

Answer 15

There is a decrease in PCa2+ and an increase in PK+

Question 16

What ions are involved in a pacemaker cell?

Answer 16

Ca2+ (L-Type)

K+
Na+

Ca2+

Question 17

What happens to the pacemaker cell before an action potential?

Answer 17

There is a gradual decrease in K+ with an early increase in Na+ and late increase in Ca2+(T-type)

Question 18

What happens to a pacemaker cell when an action potential occurs?

Answer 18

An increase in Ca2+ (L-type)

Question 19

Name factors that modulate electrical activity of the heart

Answer 19

Sympathetic and Parasympathetic

Drugs

Temperature

Hyperkalaemia

Hypokalaemia

Hypercalcaemia

Hypocalcaemia

Question 20

What are some drugs that effect electrical acitvity of the heart and what is there effect?

Answer 20

Ca2+ - Channel Blockers decrease the force of contraction

Cardiac Glycosides increase the force of contraction

Question 21

What does hypekalaemia do to the electrical activity to the heart?

Answer 21

Can cause fibrillation and heart block

Question 22

What does hypokalaemia do to the electrical activity to the heart?

Answer 22

Can cause fibrillation and heart block

Question 23

What does hypercalcemia do to the electrical activity to the heart?

Answer 23

Increase HR and force of contraction

Question 24

What does hypocalcemia do to the electrical activity to the heart?

Answer 24

Decreases the HR and force of contraction

Question 25

What is the conducting system of the heart?

Answer 25

Sinoatrial Node

Annulus Fibrosis

Atrioventricular Node

Bundle of His

Purkinje Fibres

Question 26

What is the function of the sinoatrial node?

Answer 26

Pacemaker

Question 27

What is the function of the Annulus Fibrosis?

Answer 27

It is non-conducting

Question 28

What is the function of the Atrioventricular Node?

Answer 28

Acts as a delay box

Question 29

What are the functions of the purkinje fibres?

Answer 29

Acts as a rapid conduction system

Question 30

Describe the electrical activity of the heart during contraction?

Answer 30