Neurohumeral Influences Flashcards
Parasympathetic Stimulation is also known by what term?
Cholinergic
Where is the PNS control center located?
Medulla oblongata; Cardioinhibitory center
What structures does the PNS innervate?
Via vagus n. (CN X), innervates SA/AV node
Sparsely innervates myocardium
What hormone does the PNS (cholinergic) release?
Acetylcholine
What is the function of the PNS system?
Slows rate and force of myocardial contraction and decrease myocardial metabolism
Causes coronary artery vasoconstriction
What is another term for SNS ?
Adrenergic
Where is the SNS control center located?
Medulla oblongata, cardioacceleratory center
The SNS innervates what?
Via cord segments T1-T4, upper thoracic to superior cervical chain ganglia—Innervates SA/AV node, conduction pathways and myocytes; releases epinephrine and norepinephrine
What is the function of the SNS?
Causes increase in the rate and force the myocardial contraction and myocardial metabolism
Causes coronary artery vasodilation
What are drugs called that increase sympathetic functioning?
Sympathomimetics
What are drugs called that decrease sympathetic functioning?
Sympatholytics
Baroreceptors (pressreceptors) are located where?
-closed in walls of arctic arch and carotid sinus; via vasomotor center
What are baroreceptors main function?
Control HR
The baroreceptor circulator reflex..explain.
Respond to changes in blood pressure
Explain the concept of circulatory reflex.
- Increased BP > PNS stimulated > Decreased rate/force of cardiac contraction > Sympathetic inhibiton > decreased Peripheral resistance
- Decreased BP > SNS stimulated > increased HR/BP + vasoconstriction of peripheral blood vessels
- Increased R atrial. Pressures causes reflex acceleration of HR
Where are chemoreceptors located?
Carotid body
Chemoreceptors are sensitive the changes in what?
Blood chemicals: O2, CO2, lactic acid
Concept of chemoreceptors
Increased CO2 or decreased O2, or decreased pH (elevated lactic) results up ab Increase in HR
Increased O2 levels result in a decrease in HR
When body temperature increases what happens to the HR?
Increase in body temp = increase in HR
What is hyperkalemia?
Increased K+ ions, which DECREASE rate and force of contraction
Hyperkalemia results in what kind of ECG changes?
- widened PR interval and QRS
2. tall T waves
What is hypokalemia?
Decrease K+ ions
What kind of changes does hypokalemia produce?
Flattened T waves
prolonged PR and QT intervals
Arrhythmias, may progress to ventricular fibrillation
What is hypercalcemia
Increased Ca+ ions
What does hypercalcemia do to the Heart?
Increase heart actions
What is hypocalcemia?
Decreased Ca+
How does hypocalcemia affect the heart?
Depresses heart actions
What is hypermagnesemia?
Increased magnesium is a calcium blocker which can lead to arrhythmias or cardiac arrest
What is hypomagnesemia?
Decreased magnesium causes ventricular arrhythmias, coronary artery vasospasms, and sudden death
Increased peripheral resistance __________ arterial blood volumes and pressure
Increases
