cardiac action potential

What are the two types of heart fibers

contractile and autorhythmic fibers

Contractile fibers

contract in response to electrical stimulation and generate force

Pacemaker cells or autorhythmic cells

generate electrical signals spotaneously

• sets pattern for heart beat and create rhythm

Pacemaker potential channels

1. If channels or funny channels

2. sodium channels

3. T-type calcium channels

4. I-type calcium channels

5. Potassium channels

pacemaker potential steps

1. If funny channels open when the membrane is negative

2. Na+ moves into the cell depolarizing it

3. as it gets closer to threshold the T-Type Ca+ channels open and allow calcium to enter the cell

4. at threshold -40 I-type calcium channels open and allow more calcium to move in

5. K+ channels open when the i-type channels close

6. potential goes back to -60

What are the channels associated with a cardiac action potential

1. Na+ channels

2. fast k+ channels

3. Ca+ channel

4. slow k+ channels

What are the steps of the cardiac action potential?

1. has a resting potential of -90 that is triggered by the pacemaker potential which opens Na+ channels at -70

2. Na+ moves into the cell depolarizing it

3. Na+ channels close at peak and K+ fast channels open

4. Ca+ channels open at the same time counteracting their repolarization

5. slow k+ channels open as soon as Ca+ channels close and repolarizes the cell

When does calcium induced calcium release occur?

It happens during the excitation-contraction coupling

excitation contraction coupling

1. AP arrives at the contractile cardiac muscle and a contraction occurs

2. The main help of this process is L-type ca+ channels

Excitation-contraction Coupling steps

1. an AP arrives on the cell membrane, which is spread from adjacent cells

2. depolarization causes L-type Ca2+ channels to open, which are located in T-tubules

3. Ca+ eneters the cell and binds to RyR

4. RyR releases more Ca2+ when opened from the SR to cell

5. this release of calcium makes a calcium spark

6. overload of Ca+ causes a contraction

Can the strength of a cardiac muscle twitch vary?

Yes, the strength of a cardiac muscle twitch can alter because the autonomic nervous system can alter how much Ca2+ enters the cell

What is something that allows the heart to filled up with blood properly

a longer refractory period

What are two things that a longer refractory period causes?

No tetanus

no summation

what are the parts of the heart associated with the conduction of the heart

1. autorhythmic cells

2. Sinoatrial Node or SA node

3. atrioventricular node or AV node

4. AV Bundle

5. His purkinje system

6. Purkinje fibers

7. internodal pathways

what are the steps of the conduction of the heart?

1. A signal depolarizes the right atria SA node which then depolarizes the left atria and they contract

2. The signal then passes from SA node to AV node where this a short delay allowing the blood to fill the ventricles

3. after the pause the signal moves down to the bundle of HIS

4. goes to the left and right bundle branches

5. finally hits the purkinje fibers which then contracts and pumps blood out to the lungs and body

What are the bpms of the three main conduction components

1. SA node: 100 bpm

2. AV node: 50 bpm

3. His Purkinje system: 30 bpm

P Wave

start of a new heart wave

P-R interval

atria has fully depolarized and are contracting

QRS complex

ventricular depolarization

Q

AP traveling down AV bundle

R

AP traveling up the purkinje fibers, contraction of atria relaxes

S

AP spreads to the ventricle

S-T interval

the ventricles of the heart maintain contraction and pump blood out to the body.

T

ventricle contraction relaxes