Cardiovascular homeostasis II Flashcards
What is the definition of Cardiac Output?
The amount of blood pumped by the ventricles in a minute
What is the stroke volume?
Volume of blood ejected per minute
What is afterload?
The force of contraction that the ventricles have to work against to push blood out of the ventricles into the aorta (related to aortic pressure)
What is preload?
The load/tension exerted on the muscle walls just after diastole so prior to contraction
What are the three major controls of cardiac output?
Nervous control, Intrinsic control and Atrial reflex
What is EDV?
The volume of blood present at the very end of the diastolic phase just prior to contraction
What is ESV?
The volume of blood present inside the ventricle immediately after contraction is completed
What is the purpose of increasing the force of contraction
(under sympathetic control)
Increases stroke volume which Increases the venous return
contraction of vascular
smooth muscle cells in the
veins
What does parasympathetic control do to the atria and ventricles?
Has no effect on ventricles but decreased atrial contractility
less blood pumped into ventricles - drop in stroke volume
What is the Frank-Starling Mechanism?
Increase of blood filling up the ventricles causes the muscle fibres to stretch more, leading to a greater force of contraction and increased stroke volume
only occurs within normal physiological range
How does the Frank-Starling mechanism work?
In terms of actin and myosin fibres
Increase stretching causes actin and myosin fibres to stretch to their optimal levels
What kind of receptors do atria have in them?
Atria have low pressure receptors and they detect changes in blood volume
What happens when a higher blood volume is detected?
The stretch receptors in the atria detect this and the cardiovascular inhibitory centre is activated
cardiovascular inhibitory centre is in the medulla
What kind of receptors are found in the aortic arch?
Baroreceptors sense wall stretch/ increase in blood volume
these are also found in the carotid arch
What are the two things that a reduction in sympathetic input to the kidney does?
Dilates the afferent arterioles
inhinits the renin-angiotensin aldosterone system
What is the effect of dilating the afferent arterioles in the kidney?
It increases the flow of blood to the glomerulus which increases the GFR, more blood is filtered therefore the overal volume is decreased
What is the effect of inhibiting the renin system when blood volume is too high?
Less Na+ is absorbed into the blood therefore less water is absorbed and blood pressure decreases
What is the effect of inhibiting vasopressin release from the pituitary gland?
Vasopressin acts on the tubules in the nephron to increase H20 uptake via aquaporins
Vasopressin increases blood volume/ pressure
What is the function of ANP?
ANP increases loss of Na+ and H20 therefore reducing blood volume
What is the effect of CO and O2 demand on tissues whilst you are sleeping?
There is a decreased demand for O2 causing CO levels to drop and blood is only supplied to vital organs
What is the O2 and CO2 concentrations during exercise/ work?
Increased O2 consumption so more blood is required by the muscles
Increased heart rate and vasodilation
