Blood pressure and cardiac output Flashcards
(22 cards)
What is blood pressure?
Blood Pressure is the force blood exerts on the artery wall
What are the functions of blood pressure?
- Blood pressure pushes blood though blood vessel
- Filtration of blood in the kidneys
- Drives capillary exchange between blood and cells
Vessel diameter is the most importance influencer of what?
BP
What factors influence blood pressure?
- Peripheral resistance
- Blood vessel diameter
- Blood viscosity
- Blood vessel length
- Cardiac output
What is blood viscosity?
The thickness of blood
What does increased blood viscosity increase?
Increased BP
What other factors can cause increased BP?
Dehydration or increased haematocrit
What is cardiac output?
Cardiac output (CO) is the amount of blood pumped out by a ventricle in one minute.
What is the equation to work out CO?
CO=SV x HR
What factors affect stroke volume?
- Preload
- Afterload
- Contractility
What is preload?
The amount of blood in the ventricle before it contracts, also knows as end diastolic volume
What is afterload?
- The resistance that ventricles must
overcome to circulate blood
What is contractility?
- How strongly the ventricle can contract
Describe the cardiac centre?
The cardiac centre in the medulla oblongata controls the rate and force of the heart contraction
Describe the vasomotor centre?
The vasomotor centre in the medulla oblongata controls the diameter of blood vessels
What are baroreceptors?
Baroreceptors are pressure receptors that respond rapidly to maintain homeostasis during short-term or acute changes in the blood pressure.
Where are the baroreceptors found?
- Carotid arteries
- Aortic arch
What is the role of adrenaline and noradrenaline?
These are hormones which enhance the response of the sympathetic nervous system.
How does adrenaline and noradrenaline raise BP?
- increasing heart rate and force of contraction
- constricting many arterioles
- increasing venous pressure
How do the kidneys control BP?
The kidneys control blood
volume by increasing urine
output when blood volume is high
Describe some age related changes to Blood pressure and cardiac output
- Decreased compliance of the aorta
- Loss of cardiac muscles size and strength
- Increased systolic BP
- Increased in total blood cholesterol
What are three factors that can affect blood pressure?
vessel length, viscosity and vessel diameter
