11/15/24 - Cardiac Physiology (Part 3) Lecture Questions

What are the two branches of the ANS?

Sympathetic and Parasympathetic Nervous Systems

What do Sympathetic Nerves innervate?

What does this allow it to regulate?

Innervates the SA Node, AV Node, and the Ventricular Myocardium

Allows it to regulate the HR (increase) and force of contraction (increase)

What do Parasympathetic Nerves (Vagus Nerve) innervate?

What does this allow it to regulate?

Innervates the SA Node and the AV Node

Allows it to regulate HR (decrease)

Where in the heart are the Muscarinic Cholinergic Receptors located?

What happens when Acetylcholine binds to these receptors?

On the SA and AV Nodes

Decreases heart rate

What mechanism does the Parasympathetic Nervous System use to lower heart rate?

Direct Coupling with G-protein

What does Parasympathetic Stimulation do to the phases of the Pacemaker Potential?

Delays the opening of T-type Calcium channels —> makes Slow Depol. longer

Delays closing of V.G. Potassium channels —> makes Repol. longer

Indirectly delays the opening of Funny Sodium channels

Where in the heart are the Beta-One Adrenergic Receptors located?

What happens when Norepinephrine / Epinephrine binds to these receptors?

Located in the SA Nodes, AV Nodes, and the Ventricular Myocardium

Increase heart rate

What mechanism does the Sympathetic Nervous System use to raise heart rate?

cAMP Second Messenger System

What does Sympathetic Stimulation do to the phases of the Pacemaker Potential?

Protein Kinase A phosphorylates Funny Sodium Channels and T-type Calcium channels —> opens them earlier; Slow Depol. is faster

Indirectly closes V.G. Potassium channels earlier —> shorter Repolarization

How does the Sympathetic Nervous System increase the force of Ventricular Contraction in Cardiac Contractile Cells?

1. Phosphorylates L-Type Calcium channels

   • Opens faster = more calcium = greater force

2. Phosphorylates Ryanodine channels on SR

   • Opens faster

3. Phosphorylates Myosin head

   • Increases Myosin-ATPase activity

4. Phosphorylates Calcium-ATPase

   • Allows for faster Calcium reuptake; muscles relax faster and can contract sooner

What is meant by Systole?

Diastole?

Systole — Ventricular Contraction

Diastole — Ventricular Relaxation

What is the Cardiac Cycle?

All of the events associated with blood flow through the heart in one complete heartbeat

How are Heart Sounds created?

Created as blood moves through a closing valve

What are the two kinds of Heart Sounds?

1. LUB / LUBB / S1

   • First Heart Sound

   • Turbulent blood flow through the closing AV Valve

2. DUB / DUBB / S2

   • Second Heart Sound

   • Turbulent blood flow through the closing SL Valve

What is Cardiac Output?

What is the formula for calculating it?

What do the abbreviation in this formula stand for?

Volume of blood pumped by each ventricle per minute (liters / minute)

CO = HR x SV

CO — Cardiac Output

HR — Heart Rate

SV — Stroke Volume

What is Stroke Volume?

How can Stroke Volume be calculated?

Volume of blood pumped per beat or stroke (~70 ml / beat normally)

SV = EDV - ESV

EDV — End Diastolic Volume

ESV — End Systolic Volume

What is End Diastolic Volume (EDV)?

End Systolic Volume (ESV)?

EDV — max amount of blood in the Ventricle before contraction

ESV — max amount of blood in the Ventricle after contraction

Why is the volume of blood pumped by each ventricle the same?

Because of Isovolumetric Contractions

What factors can affect Heart Rate when looking at Cardiac Output?

1. Neural Control (via Autonomic Innervation)

2. Hormones (Epinephrine and Thyroid Hormone)

3. Fitness Level

4. Age

What factors can affect Stroke Volume when looking at Cardiac Output?

1. Ventricular Contractility (how hard the ventricles contract)

2. End Diastolic Volume (EDV; influenced by Starling’s Law)

3. Fitness Level

4. Gender / Heart Size

What is Starling’s Law?

Rate at which blood flows back into the heart

Increase blood flow to heart = increased EDV = increased SV

What two methods of control are used to regulate Stroke Volume?

1. Intrinsic Control — based on what is happening to the organ itself and venous return; autoregulation

2. Extrinsic Control — based on Neural or Hormonal Control; sympathetic (N / E) or hormonal (E)

How do we increase the strength of contraction using Intrinsic Control?

Somehow stretch the cardiac muscles to optimal length using EDV

What is Intrinsic Control of SV dependent on?

Dependent on the Length-Tension relationship of the cardiac muscle (which is dependent on EDV)

What is Extrinsic Control of SV dependent on?

Dependent on Sympathetic Nerves and Epinephrine

Sympathetic innervation —> increase in force and contractility

Sympathetic Innervation + Starling’s Law —> increase in force and venous return; closest to optimal length + Epinephrine