16 Questions
What is the effect of Protein Kinase A phosphorylation on L-type Ca2+ channels?
Activate L-type Ca2+ channels
What is the consequence of severe PNS stimulation on the heart?
Heart block
Which receptor is stimulated by norepinephrine in the heart?
β1 adrenergic receptor
What is the effect of Acetylcholine on L-type Ca++ channels in the atria?
Inactivate L-type Ca++ channels
What is the effect of SNS on the effective refractory period?
Shortens the effective refractory period
Which of the following is an exception to sympathetic innervation of blood vessels?
Cerebral blood vessels
What is the effect of PNS on the conduction velocity of the AV node?
Decreases the conduction velocity
What is the result of PKA phosphorylation on the AV nodal cells?
Shortens the effective refractory period
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
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
What is the effect of sympathetic stimulation on the SA node phase 4?
Increase in slope
Which of the following receptors are stimulated by acetylcholine in the parasympathetic innervation of the heart?
Muscarinic (M2) receptors
Which of the following is an effect of parasympathetic stimulation on the heart rate?
Decrease in heart rate
What is the origin of the fibers from the sympathetic nervous system (SNS) that innervate the heart?
T1-T5
Which of the following is a positive dromotropic effect of sympathetic stimulation on the heart?
Increase in conduction velocity via AV node
Which of the following types of nerve fibers are involved in both sympathetic and parasympathetic nervous systems?
Both preganglionic and postganglionic neurons
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
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.
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