Toth- excitatory and conductive system of heart

True or false: atria and ventricles contract contract at the same time

False they contract at different times

True or false: the atrium contracts and relaxes before the ventricles contract

True

Describe 5cardiac muscle characteristics

Branching cells, one or two nuclei per cell, striated, involuntary, medium speed contraction

Cardiac muscle is under the control of what?

ANS-involuntary and endocrine system-hormones

True or false: some cells of the cardiac muscle are auto rhythmic

True

What is meant by the fact that cardiac muscle expresses syncytium?

The fact that they are mechanically and electrically connected to one another if one cell is activated, the signal runs through all of the heart

What percentage of cardiac cells are contractile cells?

99% they do the mechanical work of pumping, and normally do not initiate their own action potential

The other 1% of cardiac muscle are what type of cells?

Autorhythmic cells; they do not contract; specialized for initiating, and conducting an action potential that will lead to the contraction of the other working sales

Why is the SA node able to establish the heart rate contraction?

The impulse sent from the SA node is faster than the AV node

If the SA node is damaged, what will occur?

The AV node can generate an action potential; also, the bundle of His can take over.

What if the AV node and the bundle of His are damaged?

The heart will die

Describe the conduction system pathway of the heart?

SA node, Internodal tracks, AV node, bundle of His, left and right, bundle, branches, Purkinje fibers

What part of the conduction system of the heart has the slowest conduction?

AV node at 0.05 m/s.

Why is it important that the AV node has the slowest conduction?

Because it coordinates between the atrium and ventricles and can slow down the conduction if needed

If the AV node is not working, probably what can occur?

Arrhythmias

What is another way in arrhythmia can occur?

If there's an extra muscle fiber, leading from atria to ventricle

Where is the fastest transmission of the conduction of the heart?

Purkinje fibers at 1.5 to 4 m/s.

What is the contractions start in the heart?

At the apex of the heart, this is to ensure the blood is pushed on the Apex into the large vessels of the heart to the body

Describe the difference in the SA node action, potential in the ventricular action potential

SA node has no stable, resting potential, leaky Ca ion channels, slow, depolarization, and pre-potential a.k.a. pacemaker potential, no fast Na channels

Detail the action potential of the SA node

Funny channels begin depolarization around -60 than the T-Ca channels open then at around -40 the L-type calcium channels open and you begin a sharper depolarization, then the potassium channels open and repolarize the myocyte cells

Detail the ventricular action potential

There's a stable, resting membrane potential at around -70; Na channels open, sharp depolarization, then the K and Ca channels open; the Ca L-type channels, allow for a plateau to prolong the action potential and prevent the next stimuli a.k.a. refractory period; K channels remain open, and re-polarized the cell and in activate Ca channels until stable, resting membrane potential is reached.; Then the sodium potassium ATPase pump resets the ions in the proper place.

How does the autonomic nervous system affect the heartbeat?

Nerve impulses can modify the timing and strength, but do not establish a fundamental rhythm

What is the chronotrophic affect?

A increase or decrease in the timing of the heart rate

What is the iontropic effect?

The increase in contraction

Describe sympathetic stimulation on the SA node

Noradrenaline (NE) to the B1 receptors on the SA node; increase conductivity of calcium and cause AP propagation

Describe parasympathetic stimulation on the SA node

Acetylcholine binds to the M2 receptors on the nodal membrane; contractilty of calcium, increase, potassium

What does Chrono tropic agents do?

Regulate the SA node, and the rate of the action potential

What are some positive chronotropic agent that increase the heart rate

Sympathetic neurotransmitters, noradrenaline and acetylcholine, catecholamines (NE and Epi) nicotine (minds to nicotine receptors), caffeine (activate B1)and hyperkalemia

What are negative chronotropic agents that will decrease heart rate?

Parasympathetic neurotransmitters from cardiac nerves (such as vagus or muscarinic agonist) and hypokalemia

What happens if your heart is removed from your chest and why?

The heart will be faster because there's no nerve innervation to keep it at a basal tone