19 - Cardiac Muscle Contraction II

The AP is dependent on the movement of __________ across the cell membrane.

ions

The duration of the AP determines the ____________.

refractory

reviewed

Review

The ______________ brings things back to normal/homeostatic level.

Na+/K+ ATP pump

There is not enough muscle mass to see the repolariztion of the __________. However if we do see it is the T (a) Wave.

P wave

What is the heart rate in a horse with a 1.5 sec. RR interval?

1.5 sec = 1500 msec

1000 msec = 1 sec

1 minute = 60 sec = 60,000 msec

60,000 msec / 1500 msec = 40 BPM

What is the heart rate in a cat with an RR interval of 250 msec. interval?

60,000 msec / 250 msec = 240 BPM

___________ = 1/3 PP + DBP

MAP

__________ = SAP - DAP

PP

What is the mean arterial pressure (MAP) if the systolic arterial blood pressure (SAP) is 160 mmHg and the diastolic arterial blood pressure (DAP) is 100 mmHg?

MAP = 1/3 PP + DBP

PP = SAP - DAP

PP = 60 mmHg = 1/3 x 60 mmHg = 20 mmHg.

MAP = 20 mmHg + 100 mmHg = 120 mmHg

What is the ejection fraction (EF) if the stroke volume (SV) is 40 ml and the end diastolic (EDV) volume is 100 ml?

EF = SV/ EDV

EF = 40 ml /100 ml = 0.40 or 40%

__________ = EDV - ESV

Stroke volume (SV)

_____________ = SV/EDV

Ejection Fraction (EF)

What is the ejection fraction (EF) if the end systolic volume (ESV) is 25 ml and the end diastolic volume (EDV) is 50 ml?

Stroke volume (SV) = EDV - ESV

SV = 50 ml - 25 ml = 25 ml

EF = SV/EDV

EF = 25 ml/50 ml = 0.50 or 50%

Ejection fraction should be around _________ or better.

50%

Ejection fraction ________ during exercise, and _________ when sleeping or at rest.

increases; decreases

___________ = SV ml x HR BPM (min.)

Cardiac Output (CO)

What is the cardiac output in the previous animal if the heart rate is 80 BPM?

(SV = 25ml)

CO = SV ml x HR BPM

25 ml x 80 PBM = 2000 ml/min or 2 L/min

T/F: SV x HR is the CO or the total systemic flow

true

The ______________________ is the flow that is going to your body which is equal to the flow going to your lungs.

total systemic flow

The cardiac output of the right heart has to ___________ the cardiac output of the left heart.

equal

The parasympathetic nervous system is innervated by the ___________ and ____________.

vagus nerve and glossopharyngeal nerve

The vagus nerve function in the heart?

- innervates the heart

- when stimulated slows the heart

- decreases contractility

- dilates vessels

When the vagus nerve is stimulated it will ______________ contractility and heart rate.

decrease

____________ is used to treat bradycardia.

atropine

Sympathetic innervation causes the release of ____________ and _____________.

epinephrine and norepinephrine

The drug called ___________, is an alpha 1 and alpha 2 agonist.

xylazine

xylazine is classified with alpha 2 agonist because it's ___________ effect is on the alpha 2 receptor.

predominate

T/F: Important thing about alpha 2 agonist there about 4 or 5 types

true

During cardiac contraction, there is ____________ _____________ that opens the Ca++ channels.

electrical activity

First in a cardiac contraction, _________ depolarizes the membrane until it gets to a certain threshold where it will fire and create phase 1.

Na+

Once the membrane is depolarized, Ca++ can enter and produces the ________ _________.

plateau phase

The plateau phase is important because that is when _______ can enter the cell.

Ca++

Ca++ then enters an intracellular network of tubes called the ____________ ______________.

sarcoplasmic reticulum

Ca+ leaves the sarcoplasmic reticulum by activating the ____________ __________ and goes into the cytoplasm.

ryanodine receptors

Ca++ in the SR is induced by action potentials through the ______________________; and Ca++ is released through the ryanodine receptors.

L-type Ca++ channel

Ca++ is important because it allows the _____________________________ to interact.

actin and myosin filaments

Even though Ca+, actin, and myosin are around all the time, they are not always activated because they are inhibited from interacting because of a substance called ________________.

troponin C

____________ interferes with the binding sites of actin and myosin.

Troponin

_____________ is the biomarker for the severity of heart disease.

Troponin

If an animal goes into heart failure troponin will _____________.

increase

T/F: In cats, troponin is early onset marker of heart failure.

true

If intracellular Ca++ increases, the ___________________ will also increase.

sarcoplasmic endothelial reticulum system

The sarcoplasmic endothelial reticulum system is an ATP pump sometimes referred to as ___________________ ____________.

phospholamban receptor

The phospholamban receptor will pump the Ca++ back into the SR which reduces the Ca++ and cases the heart to go into the _________________ phase.

relaxation

reviewed steps

Review Steps

What are the two main pumps to remember?

Na+/K+ ATPase pump and NCX pump

The _______________ is the Na+/Ca+ exchange mechanism.

NCX pump

? Talk about the SGLT mechanism:

- SGLT2 transports glucose and sodium

- SGLT1 transports glucose and sodium

The drug of choice for 200 years for treating heart failure was _______________.

foxglove/digitalis

Foxglove has a very ___________ therapeutic window.

narrow

Foxglove targets and poisons/blocks the _________________.

Na+/K+ pump

When the atria contract first the _____________ and _____________ open.

tricuspid valve and mitral valve

When the ventricles contract the _______________ and ___________ close.

tricuspid valve and mitral valve

When the ventricles contract the _______________ and ___________ open.

aortic valve and pulmonic valve

Following the blood list the sequence:

Tricuspid valve opens into → the right ventricle → out the pulmonic valve → into the lungs → back to the mitral valve and goes out the → aortic valve

All of the activity between actin and myosin take place in the _____________ of the sarcomere.

A band

When the actin and myosin filaments overlap, it created more of an opportunity for the S1 myosin head to interact with actin and they pull the ______________ toward each other.

Z band

The contractions take place in the ___________________, which are shortening.

sarcomere units

Optimal overlap occurs when the sarcomere is about ______________.

2.2 microns

About ________ of actin and myosin heads are being activated during each contraction.

25%

When the heart is activated more frequently then it causes the __________ inside the cytoplasm to be higher.

Ca++

To increase the force of contraction, you can increase the _________________.

heart rate

The ________________ is when increasing the heart rate will increase the force of contraction.

staircase phenomenon

The Na+/K+ pump is __________ with the NCX mechanism.

linked

If you block the Na+/K+ pump, Na+ cannot leave. So the Na+ concentration increases, which will cause the Na+ to exchange for __________.

Ca++

By blocking the Na+/K+ pump, intracellular Ca++ increases which is referred to as a _________________________.

positive inotropic effect