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52 Cards in this Set

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The heart is innervated by the sympathetic and parasympathetic systems, they increase the heart rate and decrease the heart rate according to what neurotransmitter is released, if those two systems are cut off will the heart still beat? Why or why not?

Yes because of the pace makers cells. They set the pace of the heart beats

Explain what the conduction pathway is.

The path that conducts electricity through the heart
Muscle cells are modified to conduct electrical information (myogenic pacemaker)

How do autorhythimcal cells communicate to one another?

Gap Junctions

Explain an autorythmical Cell.

They initiate or propagate the APs that initiate muscle contraction, however they do not actually contract.

Do autorhythmical cells contract?

No, they carry the Action Potentials

What are the five autorhythmical cells?

SA Node
AV Node
Bundle of His
Bundle Branches
Purkinje Fibers

What can the SA Node and AV Node do that the other cells can't do? What are the two names for that?

They can initiate the Action Potential, they can generate the actual current
Pace makers cells OR Myogenic cells (muscle-beginning)

What's the actual name for the SA node?

Sinoatrial Node

After the signal is generated in the SA node, where does the signal go next?

The interatrial pathway and the AV node

Does the SA node depolarize the interatrial pathway first or the AV node?

Does the SA node depolarize the interatrial pathway first or the AV node?

What is the Interatrial pathway?

Conduction Pathway between the two atriums

What is the actual name for the AV node?

Atrial Ventricular Nerve

Where will the AV node send the signal next?

The AV Bundle (Bundle of HIS)

After the Bundle of His depolarizes, what happens next?

The Bundle of His splits into two branches (the left and the right) which both get depolarized

After the Bundle branches get depolarize, where does the electrical signal travel to?

The Purkinje Fibers

Where does the signal ultimately stop?

The Purkinje Fibers

In the big picture of the heart, what contracts first and what second?

The atria contracts first then the ventricles

The SA node starts the Action Potential and goes to the interatrial pathway along with the hitting the AV node, but what does the interatrial pathway contract and what is first and second?

Will contract both atria
Both atria will contract at the exact same time

Since the heart has a steady rhythm that it follows by itself, can the heart fluctuate out of that rhythm? Why or Why not?

Yes it will definitely fluctuate because of the neurotransmitters in the sympathetic and para-sympathetic nervous systems

What nerve allows the sympathetic nervous system to act on the heart? Where does the nerve start? Where is it attached to?

The sympathetic cardiac nerve
Starts near para vertebral ganglia
Attached to the SA node and the AV node

Does the SA node or the AV node depolarize faster?

The SA node

What pace maker cells are the backup to the SA node? If something would happen to the SA node what would be the result? Why?

The backup is the AV node
If something happened to the SA node, the AV node would take over and generate action potentials but at a much slower rate because it does not depolarize as fast

What would happen if norepinephrine was released? Where would it bind to and what would be the cause?

It would be released from the sympathetic cardiac nerve and would bind to beta receptors
It would up regulate the SA node to depolarize faster

When you increase norepinephrine, what ion/ions will INFLUX?

Sodium and Calcium
Will cross into the SA node faster

What nerve allows the parasympathetic nervous system to act on the heart? Where does the nerve start?

Vagus Nerve
Starts from cranial nerves

Once acetylcholine is released from the vagus nerve, what will happen to the heart, why?

The heart will down regulate because parasympathetic only releases acetylcholine and since parasympathetic will down regulate the heart, the heart beat will decrease

What ion/ions will EFFLUX out of the heart when you want to down regulate?

Potassium (K+)

What do you have to do to repolarize a cell?

Make the inside more negative (less positive)

If the cell is more negative then the resting membrane potential, what is that called?

Hyper-polarization

What does the long refractory period in the ventricular muscle ensure?

A regular heart beat


Since the muscle is so big, it needs time for the signal to get to the whole muscle, therefore it needs to stay depolarized longer, ultimately having a longer refractory period.
With a longer refractory period, the ventricles can't beat again unless the first one is fully complete (which is longer than the atrias) therefore ensuring a regular heart beat.

What is a refractory period?

The time it takes for another action potential to cause a reaction

Why would the purkinje fibers want to stay depolarized longer?

They stay depolarized longer because then they have a longer refraction period

Is the conductive pathway the same or different between the atrias and the ventricles?

Very different


The purkinje fibers stay depolarized MUCH longer

We know that the pathway is longer to ventricular muscle compared to the atria but which physically CONTRACTS slower?

The ventricles



There is more muscle so it will take longer to contract


It is slow to start (longer pathway) and slow to stop (physically contracts slower)

Why does the ventricular muscle take so long to contract?

There is a longer pathway, going from the SA node to the AV node and then to the ventricular muscle

What happens to the permeabilities of the ions when we want to repolarize?

Ca+ decrease


Na+ decrease


(we are making the cell less positive so we don't want to bring any of these ions in)


K+ Increase


(we don't want any more positive so we wil let some K+ out until we get down to -60 mV

What do we have to do inside the cell to repolarize?

Make more negative or less positive

What is the value that we will get to after done depolarizing and the signal to start repolarizing?

+5 mV

Once we hit the -40 mV, what will happen?

An action potential that will now go to all the cells

If we are depolarizing the cell, what do we do to the permeability of Na+? Why?

We are going to INCREASE the permeability of Na+.


Na+ is high outside so we want all the positive inside the cell so we will increase the permeability so the ions can come in

If we are depolarizing the cell, what do we do to the permeability of Ca+? Why?

We are going to INCREASE the permeability of Ca+.


Ca+ is high outside so we want all the positive inside the cell so we will increase the permeability so the ions can come in

If we are depolarizing the cell, what do we do to the permeablity of K+? Why?

We DECREASE the permeablity of K+



If we are depolarizing the cell then we need to make the inside more positive so we need to keep all the positive we have and gain more. K+ has a high concentration inside the cell so we are going to lower the permeability to keep all positive inside the cell.

If we are going to depolarize a pace maker cell, what is the threshold potential to get the action potential?

-40 mV

If we want to depolarize the cell, what do we need to do?

Make the inside of the cell less negative or more positive

What is the charge normally inside the pace maker cells?

-60 mV

Explain permeability. If you have a high permeability, can ions get in easy or hard, what about low?

Permeability: how easy ions can cross the membrane



High permeability: the ions can cross the membrane easy



Low permeability : it is hard for the ions to cross the membrane



Each ion has an individual permeability to a membrane due to certain proteins on the membranes that either allow that ion to come in or not

What ion/ions have a low concentratino inside the cell and a high concentration outside of the cell? If diffusion took place, what would happen?

Ca+ calcium


Na+ sodium



Ions would INFLUX into the cell

What ion/ions naturally have high concentratino inside the cell and a low concentration outside of the cell? If diffusion took place, what would happen?

K+ potassium



Ions would efflux (go out of the cell)

What are the 3 ions that are involved in the contractino of the heart?

Ca+, Na+, and K+

So what are the only two signals that the heart recieves in terms of cells?

Depolarization and Repolarization

Do you have a resting membrane potential in the heart? why?

No because the heart is always beating you would not want the heart to have a resting membrane potential because it should either be depolarizing or repolarizing

How do cells send one signal from one to another?

Lateral connection between cells Gap Junctinos