40 Questions
Which cells in the heart generate force and are connected by intercalated discs?
Work cells
What initiates the heartbeat in the heart?
Sinoatrial node
What is the role of the nerve supply in the heart?
To regulate the heartbeat
What drives the beating of the heart?
Electrical signals generated by the heart itself
What happens to the heart if it is not provided with oxygen and kept moist?
The heart gradually slows down and eventually stops.
Which node in the heart initiates the electrical impulse?
Sino atrial node (SAN)
What happens if the SA node is damaged?
AV node takes over as pacemaker
What is the main cause of the AV delay in the heart?
Very few gap junctions
Which fibers carry the electrical signal to the ventricle muscle cells?
Purkinje fibers
Which type of action potential is exhibited by the SA node and AV node?
Slow response action potential
Which channels are stimulated during hyperpolarization in slow response cardiac fibers?
Funny channels
What is the membrane potential during repolarization in slow response cardiac fibers?
-70 mV
What is the main characteristic of the pacemaker potential in slow response cardiac fibers?
Slow depolarization
Which node in the heart acts as the fastest pacemaker and can be influenced by the autonomic nervous system?
SA node
During phase 0 of the action potential in working cells (ventricular cells), what causes depolarization?
Opening of Na channels
What initiates repolarization during phase 1 of the action potential in working cells?
Closing of Na channels
What causes the plateau phase during phase 2 of the action potential in working cells?
Ca influx > K efflux
What initiates rapid repolarization during phase 3 of the action potential in working cells?
Opening of delayed K channels
Which type of muscle contraction requires intracellular support to induce contraction?
Cardiac muscle contraction
What is the mechanism by which ryanodine receptors in cardiac muscles are operated?
Ca binding
What is the term for the process where the opening of ryanodine receptors allows more Ca in cardiac muscles?
Calcium induced Calcium release
What provides 90% of the intracellular Ca in cardiac muscles?
Intracellular source
Which type of channel blocker is commonly used to control force of contraction in cardiac muscles?
L-type Ca+ channel blocker
Which part of the heart is primarily innervated by the right vagus nerve?
SA node
Which part of the heart is primarily innervated by the left vagus nerve?
AV node
Which part of the heart is lightly innervated by vagal efferent nerves?
Ventricular myocardium
Which receptors are activated by the parasympathetic nervous system in the heart?
Muscarinic ACh receptors
Which receptors are activated by the sympathetic nervous system in the heart?
B1-adrenergic receptors
What effect does the sympathetic nervous system have on the cardiac excitability of the fast response action potential in cardiac muscle?
Positive bathmotropic effect
What effect does the sympathetic nervous system have on the rate and rhythm of the fast response action potential in cardiac muscle?
Positive chronotropic effect
What effect does the sympathetic nervous system have on the conduction speed of the fast response action potential in cardiac muscle?
Positive dromotropic effect
Which ion is primarily responsible for speeding up the rate of pacemaker depolarization in the presence of sympathetic nervous system activation?
Na+
What effect does the parasympathetic nervous system have on the rate of firing of the slow response action potential in cardiac muscle?
Decreases the rate of firing
Which channels are inhibited by the parasympathetic nervous system in order to slow down the rate of pacemaker depolarization?
Ca++ channels
Why does smoking increase the likelihood of a heart attack?
It helps atheroma to develop
Which type of muscle does not tetanize?
Cardiac muscle
During which phase of the action potential in working cells does depolarization occur?
Phase 0
What is the duration of the absolute refractory period?
2/3rd part of the cardiac AP
What happens if a new stimulus occurs during the absolute refractory period?
It is unable to elicit a new response
What is the effect of the relative refractory period on the generation of an action potential?
A stronger stimulus is needed to generate an action potential
Test your knowledge on Myocardial Electrophysiology and learn about the action potentials of sinoatrial node and ventricular muscle cells. Explore what drives the heart to beat and discover interesting facts about the heart's autonomic regulation and nerve supply.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
