Ex 3: Regulation of the Heart Flashcards
Where is the cardiac control center?
Tractus solitarius in the Medulla Oblongata
The heart is composed by which two opposing divisions of the autonomic nervous system?
sympathetic and parasympathetic nervous systems
In the sympathetic pathway, the sensory fibers from baroreceptors travel via ____ to _____?
CN IX (glossopharyngeal) to Tractus Solitarius
In the sympathetic pathway, name the flow from Tractus solitarius to the heart?
Tractus solitarius -> paramedian reticular nucleus-> cervical and thoracic segments of spinal cord -> pregranglionic fibers from the lower to upper thoracic segment-> sympathetic chain ganglia->postganglionic fibers from cervical ganglia-> cardiac plexus (mediastinum) -> cardiac nerve -> heart
During the sympathetic pathway, where does the sensory fiber terminate on the heart?
SA node, AV node, myocardium, aorta, pulmonary trunk, coronary arteries
Describe the flow of the parasympathetic pathway from the sensory fibers of baroreceptors on CN IX to the heart?
baroreceptors via CN IX -> Tractus Solitarius-> vagal nucleus -> vagus nerve fibers -> cardiac plexus -> cardiac nerve (mix with sympathetic fibers) -> synapse on epicardium. Post ganglionic fibers from right vagus nerve -> SA node. Post ganglionic fibers from the left vagus nerve -> AV node
Where do the postganglionic fibers of right vagus nerve within the parasympathetic pathway travel to?
SA node
Where do the Postganglionic fibers of the Left vagus nerve within the parasympathetic pathway travel to?
AV node
During stressful situations, which nervous system dominates?
sympathetic
What results from the activation of the sympathetic nervous system?
tachycardia, increased CO, increased oxygen demand of the heart
Which nervous system is activated during relaxed states?
parasympathetic nervous system
What happens to the heart during parasympathetic nervous system?
(during sleep) resting heart rate, baseline cardiac output, decreased oxygen demand of the heart
For sympathetic effects, increased contractility would be what kind of effect?
primary
For sympathetic effects, increased heart rate would be what kind of effect?
associated
Describe the sympathetic effect to increase contractility?
Catecholamine binding to B1 receptor which increases cAMP. Results in increased Ca++ which increases contractility
Describe the sympathetic effect of increased heart rate?
increased inward Ca++, faster phase 4 “slow” phase and faster depolarization.
What usually affects contractility?
A. intracellular Calcium levels
B. preload
C. Moving to a higher point on the starling curve
D. all of the above
D. all of the above
How does the parasympathetic effect decrease heart rate?
SA node. Ach activate K+ channels, the increased K+ conductance (out)= fast repolarization or slows depolarization of pacemaker cells
What is Sinus Arrhythmia?
fluctuation in vagal tone, associated with phases of respiration
What drugs could be used to increase HR?
A. Beta 1 agonists
B. Parasympathetic blocking agents
C. A and B
D. None of the above
C. A and B
What drugs could be used to increase HR?
A. YES- epinephrine
B. YES- Atropine blocks vagal activity
C. A and B
D. none of the above
C. A and B
What are chronotropic agents?
agents that influence or change heart rate such as hormones, electrolytes, drugs
What are positive chronotropic agents?
increase heart rate via sympathetic stimulation (EPI/NE, thryoid hormone, hypercalcemia, herpcapnia, acidoses)
What are negative chronotropic agents?
decrease heart rate via parasympathetic stimulation. Ach, hypocalcemia, hypoxia
