WEEK 3: Regulation of Cardiovascular Function Flashcards
What is cardiac output
Stroke volume x Heart Rate
Define cardiac output
Volume of blood ejected from the left ventricle each minute
What units is cardiac output expressed in?
L/min
At resting position, what is one’s normal cardiac output?
4-5 L/min
While running, what is one’s normal cardiac output?
20-25 L/min
Why is cardiac output higher while running?
More blood is circulated around the body
Why is atrial pressure on the X axis?
It measures the venous return
T or F: Cardiac output (ventricular output) increases with increased atrial pressure
T
how does exercise influence venous return
muscle pump promotes increase in venous return
How does hypovolemia influence venous return
It decreases it with severe dehydration/blood loss
How do postural changes influence venous return
Causes fluctuations depending on a rapid shift in body position
How does the frank-starling mechanism work?
Increased venous return > increased atrial pressure > increased ventricular filling
What kind of relationship is the frank sterling mechanism
a length-tension relationship (cardiac muscle active tension increases with muscle length for example) can think of this as further along x axis = higher up the y axis
which nervous system regulates the heart
autonomic nervous system
What does the ANS consist of ?
sympathetic and parasympathetic innervation
What kind of effect does sympathetic stimulation have on the heart?
a chronotropic and inotropic effect
What does chronotropic mean?
Increased heart rate
What does inotropic mean
Increased contractibility
What effect does the parasympathetic nervous system have on the heart?
Suppresses heart rate, slows AV conduction and relatively reduces contractility
What effect does sympathetic stimulation have on cardiac output?
Increases it
What effect does parasympathetic stimulation have on cardiac output?
Reduces it compared to sympathetic stimulation, but there is still a slight increase
T or F: sympathetic and parasympathetic nervous system can operate on the heart at the same time
T
What is intrinsic heart rate?
The natural heart rate without any effect from the ANS
What keeps heart rate at lower rates?
Vagal parasympathetic NS
To increase the heart rate, what does the heart do in relation to the ANS
Decrease parasympathetic activity (breaking) and increase sympathetic activity (accelerating)
At what pace does vagal activity work
Very quickly, constantly modulating
At what rate does sympathetic activity work*
Slowly,
How does the endocrine system influence the cardiac function?
Through the central nervous system (CNS) through release of adrenaline and noradrenaline through receptors (Beta-1)- increase heart rate contractability as well as alpha adrenergic receptors
How much adrenaline and noradrenaline is released from stimulation of SNS
80% adrenaline
20% noradrenaline
What mediates control of blood pressure?
Baroreflex
T or F: Blood pressure is constant
F: constantly fluctuating
What is baroreflex?
negative feedback loop that regulates blood pressure by regulating things like cardiac output
How does the baroreflex work?
- baroreceptors detect BP changes
- generates a response via the ANS
- output activated by medulla by either adjusting the parasymapthetic/sympathetic nervous system
what are two different types of baroreceptors?
- arterial
-cardiopulmonary
Where is the central command for the cardiac system?
The brain
What do metaboreceptors do?
Detect the degree of metabolic activity in the muscles
In what direction is the afferent pathway?
receptors -> central command
