Lecture 5.1 - The autonomic nervous system

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Questions and Answers

What is the effect of Protein Kinase A phosphorylation on L-type Ca2+ channels?

Decrease the conduction velocity of L-type Ca2+ channels

Inactivate L-type Ca2+ channels

Increase the refractory period of L-type Ca2+ channels

Activate L-type Ca2+ channels (correct)

What is the consequence of severe PNS stimulation on the heart?

Heart block (correct)

Increase in heart rate

Increase in contractility

Increase in conduction velocity

Which receptor is stimulated by norepinephrine in the heart?

Muscarinic (M2) receptor

β2 adrenergic receptor

β1 adrenergic receptor (correct)

α1 adrenergic receptor

What is the effect of Acetylcholine on L-type Ca++ channels in the atria?

Inactivate L-type Ca++ channels Signup and view all the answers

What is the effect of SNS on the effective refractory period?

Shortens the effective refractory period Signup and view all the answers

Which of the following is an exception to sympathetic innervation of blood vessels?

Cerebral blood vessels Signup and view all the answers

What is the effect of PNS on the conduction velocity of the AV node?

Decreases the conduction velocity Signup and view all the answers

What is the result of PKA phosphorylation on the AV nodal cells?

Shortens the effective refractory period Signup and view all the answers

Which of the following nerve fibers are responsible for the parasympathetic innervation of the ventricles?

None of the above, as parasympathetic innervation has little to no effect on ventricles Signup and view all the answers

Which of the following is NOT a function of the autonomic nervous system (ANS) in relation to the cardiovascular system?

Initiation of electrical activity in the heart Signup and view all the answers

What is the effect of sympathetic stimulation on the SA node phase 4?

Increase in slope Signup and view all the answers

Which of the following receptors are stimulated by acetylcholine in the parasympathetic innervation of the heart?

Muscarinic (M2) receptors Signup and view all the answers

Which of the following is an effect of parasympathetic stimulation on the heart rate?

Decrease in heart rate Signup and view all the answers

What is the origin of the fibers from the sympathetic nervous system (SNS) that innervate the heart?

T1-T5 Signup and view all the answers

Which of the following is a positive dromotropic effect of sympathetic stimulation on the heart?

Increase in conduction velocity via AV node Signup and view all the answers

Which of the following types of nerve fibers are involved in both sympathetic and parasympathetic nervous systems?

Both preganglionic and postganglionic neurons Signup and view all the answers

Study Notes

Location of Autonomic Nervous System (ANS)

Sympathetic nervous system (SNS) originates from thoracolumbar outflow (T1-L2)
Parasympathetic nervous system (PNS) originates from craniosacral outflow (CN III, VII, IX, X, S2-S4)

ANS and Cardiovascular System (CVS)

ANS controls heart rate, force of contraction, and peripheral resistance
ANS does not initiate electrical activity in the heart

Innervation of the Heart

PNS innervation:
- Originates from vagal motor nuclei
- Travels through right and left vagal nerves to the thoracic cavity
- Synapses with postganglionic parasympathetic neurons within the myocardium
- Innervates SA node, AV node, and little to none of the ventricles
SNS innervation:
- Originates from T1-T5
- Synapses at paravertebral sympathetic ganglia
- Postganglionic fibers run with great vessels to reach the heart
- Innervates ventricles, atria, SA node, and AV node

Chronotropic Effects

SNS:
- Positive chronotropic effect: increases heart rate by increasing the slope of SA node phase 4
- Norepinephrine stimulates β1 adrenergic receptors, activating funny Na+ channels
PNS:
- Negative chronotropic effect: decreases heart rate by decreasing the slope of SA node phase 4
- Acetylcholine stimulates muscarinic (M2) receptors, inactivating funny Na+ channels and activating outward flow of K+ currents

Dromotropic Effects

SNS:
- Positive dromotropic effect: increases conduction velocity through AV node
- Activates L-type Ca++ channels, increasing calcium uptake and phosphorylating L-type Ca2+ channels
- Shortens effective refractory period
PNS:
- Negative dromotropic effect: decreases conduction velocity through AV node
- Inactivates L-type Ca++ channels, prolonging effective refractory period
- Can lead to heart block if severe

Inotropic Effects

SNS:
- Positive inotropic effect: increases contractility of the heart
- Norepinephrine stimulates β1 adrenergic receptors, activating L-type Ca++ channels
PNS:
- Negative inotropic effect: decreases contractility of the heart
- Acetylcholine stimulates muscarinic (M2) receptors, inactivating L-type Ca++ channels

Autonomic Effects on Vasculature

Most blood vessels receive sympathetic innervation
Exceptions include some blood vessels that do not receive SNS innervation

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Description

This quiz covers the location and functions of the autonomic nervous system, its impact on the cardiovascular system, and the innervation of the heart. Topics include the sympathetic and parasympathetic nervous systems, heart rate, and contraction force.