Physiological regulation of blood pressure Flashcards
What is blood pressure
the hydrostatic pressure exerted by blood on the walls of the blood vessels
How will the blood pressure differ in the arteriole and venous system
Arteriole= high
Venous= low
Blood flows from arteriole to venous system
What is systolic pressure
the maximum pressure achieved during ventricular contraction
What is diastolic pressure
The lowest level of arterial pressure
What is the mean arterial pressure (MAP)
Pressure that propels blood to tissue
How is MAP calculated
(2x diastolic)+ systolic / 3
What is the usual MAP range for dogs
70-110mmHg
What MAP is necessary to perfuse coronary arteries, brain, kidneys
60mmHg
What is MAP dependent on
- Cardiac output
- Total peripheral resistance
- volume of blood
What affects cardiac output
heart rate and stroke volume
How do the flexible walls of the arterial system affect the flow of blood
Flexible walls absorb pressure energy, reducing the amplitude. The wall returns the energy after the wave, maintaining the pressure
What is the starling effect with regards to blood pressure
Leads to increased stretching of heart muscle, leading to increased contraction
How does the sympathetic nervous system affect blood pressure
increases HR and force of contraction (increasing BP)
How does the parasympathetic nervous system affect blood pressure
Decreases HR and contraction force (decreasing BP)
What is total peripheral resistance
The overall resistance of the entire systemic circulatory system
What factors can affect the total peripheral resistance
- Blood volume and viscosity
2. Vascular elasticity
What impact would exercise have on MAP
Exercise would increase heart rate, stroke volume and MAP. More proportion of the cycle will become systole
What techniques can be used to measure MAP
- Sphygmomanometer
- Invaise methods (direct) using fluid filled catheter
What factors could affect the BP measure
- Stress
- Position
- Temperature
- Position of the cuff
- Full bladder
What is pulse pressure
is the difference between systolic and diastolic pressure
pulse pressure= systolic- diastolic
What is autoregulation of blood flow
how blood flow to an organ remains constant over a wide range of perfusion pressures
What are baroreceptors
Baroreceptors sense changes in BP from vasoconstriction and vasodilation
What are chemoreceptors
A receptor that responds to a change in the chemical composition (PaCO2 and pH) of the fluid around it
How can haemorrhage affect cardiac function?
- Decreased preload, due to loss of venous return
- Decrease stroke volume
- Decrease in MAP
- Decrease in tissue oxygen delivery
What will recognise the reduce blood pressure after haemorrhage?
Baroreceptors due to loss of stretch
What are the autonomic affects from the heart
- Noradrenaline released from nerve endings to act of B1 adrenoreceptos
- Parasympathetic vagal tone decreased
- HR increases
- Increased force of contraction
What is the result of these changes from the autonomic affects of the heart
- Increased stroke volume and Cardiac output
- This increases MAP back toward normal
What happens to blood vessels during haemorrhage?
Vasoconstriction, increased systemic vascular resistance
What is the role of angiotensin II during haemorrhage?
Increases blood vessel tone (vasoconstriction)
What is the effect of increased perfusion pressure on the kidney
- Reduced Na+ and thus water resorption in proximal tube
- Increased Na+ and water excretion
- ECF volume decreases and thus BP increase diminished
What is hypovolemia
decreased blood volume, loss from the vasculature itself
leads to inadequate oxygen delivery to tissues
How is dehydration different to hypovolemia
Dehydration= loss of fluids from ECF and ICF Hypovolemia= a decreased volume of circulating blood in the body- is loss from vasculature
What are some signs of hypotension
- prolonged CRT
- tachypnoea
- pale mucous membranes
- poor pulse pressure
- tachycardia
- weakness
- thirst
What are the signs that distinguish dehydration from hypotension
- Skin/ fur tenting
- altered packed cell volume
