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Cardiac Output
Overview
38
Anatomy
Undergraduate 1
03/01/2013

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Term
As heart rate goes up, does stroke volume rise or fall?
Definition
Falls
Term
As stroke volume goes up, does heart rate increase or decrease?
Definition
Decrease
Term
Tachycardia
Definition
Persistent resting heart rate in adults over 100bpm
Term
Bradycardia
Definition
Persistent resting heart rate in adults below 60bpm
Term
Positive chronotropic agents
Definition
Factors that raise heart rate
Term
Negative chronotropic agents
Definition
Factors that lower heart rate
Term
Where in the brain are the cardiac centers located?
Definition
Reticular formation of the medulla oblongata
Term
Reticular formation
Definition
A region in the brainstem that is involved in multiple tasks such as regulating the sleep-wake cycle and filtering incoming stimuli to discriminate irrelevant background stimuli
Term
What does it mean if neurons in the reticular formation of the medulla oblongata have a cardiostimulatory effect?
Definition
They transmit signals to the heart via sympathetic pathway
Term
What type of pathway transmits signals from the medulla to the heart - sympathetic or parasympathetic?
Definition
Sympathetic
Term
Are the sympathetic postganglionic fibers adrenergic or dopaminergic?
Definition
Adrenergic
Term
Adrenergic
Definition
Having to do with adrenaline (epinephrine) and/or noradrenaline (norepinephrine)
Term
What do the postganglionic sympathetic fibres release?
Definition
Norepinephrine (noradrenaline)
Term
Postganglionic fibres
Definition
In the autonomic nervous system, fibers from the ganglion to the effector organ
Term
What does noradrenaline bind to in the heart?
Definition
ß-adrenergic fibers in the heart
Term
What does the binding of ß-adrenergic fibers in the heart to noradrenaline activate?
Definition
Cyclic adenosine monophosphate (cAMP) second messenger system in the cardiocytes and nodal cells
Term
What is cAMP?
Definition
Cyclic adenosine monophosphate (cAMP) - a second messenger system in the cardiocytes and nodal cells
Term
What does cAMP activate?
Definition
An enzyme that phosphorylates and opens a calcium channel in the plasma membrane
And also ccelerates uptake of Ca2+ by sarcoplasmic reticulum
Term
What is the effect of the inflow of calcium ions in the plasma membrane of cardiocytes?
Definition
Accelerates depolarisation of the SA node and contraction of the cardiocytes - speeds up the heart
Term
What is the effect of cAMP accelerating the uptake of Ca2+ by sarcoplasmic reticulum?
Definition
Enables cardiocytes to relax more quickly
Term
What is the effect of noradrenaline and cAMP accelerating both contraction and relaxation of the heart?
Definition
They increase heart rate
Term
Why does cardiac output peak at 160-180bpm?
Definition
Any higher and the ventricles have too little time to fill between heart beats
Term
What type of effects do parasympathetic vagus nerves have on the SA and AV nodes?
Definition
Cholinergic, inhibitory effects
Term
Cholinergic
Definition
Typically refers to acetylcholine in the neurological sense
Term
What does acetylcholine (ACh) bind to in the SA and AV nodes?
Definition
Muscarinic receptors
Term
What is the effect of acetylcholine (ACh) binding to muscarinic receptos in nodal cells?
Definition
Opens K+ gates and they become hyperpolarised, fire less frequently, the heart slows down
Term
Do sympathetic or parasympathetic nerves act faster on the heart?
Definition
Parasympathetic
Term
What is the vagal tone?
Definition
Steady background firing of the vagus nerves
Term
What is the benefit of placing heart rate under influence of cardiac centers in medulla?
Definition
Centers receive input from many other sources and integrate into reaction
Term
Which chemical has the greatest chronotropic effect?
Definition
K+
Term
What three variables govern stroke volume?
Definition
Preload, contractility, and afterload
Term
Do increased preload or contractility cause an increased or decreased stroke volume?
Definition
Increased
Term
Does an increase in afterload cause an increase or decrease in stroke volume?
Definition
Decrease
Term
Preload
Definition
The amount of tension in the ventricular myocardium immediately before it begins to contract
Term
Contractility
Definition
How hard the myocardium contracts for a given preload
Term
Positive ionotropic agents
Definition
Factors that increase contractility
Term
Negative ionotropic agents
Definition
Factors that reduce contractility
Term
Afterload
Definition
The blood pressure in the aorta and pulmonary trunk immediately distal to the semilunar valves - it opposes these valves and thus limits stroke volume
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