Blood pressure Flashcards
Define blood pressure
pressure exerted by the blood on the wall of a blood vessel -mmHg
Define systolic blood pressure
highest pressure, measured when the LV is contracting and expelling blood into the aorta
Define diastolic blood pressure
lowest pressure, measured when the LV is relaxing and blood is flowing into peripheral blood vessels
What is blood pressure measured with/
Sphygmomanometer
Define pulse pressure
difference between systolic and diastolic blood pressure and can be felt at the arteries
What is the pulse pressure equation?
pp= SBP- DBP
What is textbook normal BP?
120/80mmHg
Define mean arterial pressure
pressure that propels blood through tissues.
-equivelant to DBP +1/3 of PP
Define peripheral resistance
vessel diameter and length
eg, vasoconstriction increases BP
vasodilation decreases BP
What determines BP?
-Cardiac ouput
-peripheral resistsnce
-blood volume
-blood viscosity
How does blood volume effect BP?
increased blood volume increases BP
decreased blood volume, decreases BP
How does blood viscosity effect BP?
thicker blood is harder to pump, increases BP
How does cardiac output determine BP?
more blood the heart pumps out, the higher the BP
Whats the relationship between vasodilation and BP?
-widening blood vessel lumen via relaxation of the muscle wall
decrease BP
Whats the relationship between vasoconstricion and BP?
-narrowing blood vessel lumen via constriction of muscle wall, increases BP
Define vascular tone
at rest it is the state of constriction of the vessel relative to its maximally dilated state
Name some intrinsic factors of BP
-myogenic mechanisms
-endothelilal factors eg Nitric oxide
-local hormones
-metabolic by products
-hypoxia
Name some extrinsic factors of BP
-sympathetic nerves
-circulating hormones
Describe the neutral control of BP
-cerebral cortex
-limbic system and thalamus
-hypothalamus
-pons
-medulla oblongata
-spinal cord T1-L2
-Spinal cord s2-s4
What is Marey’s law?
there is an inverse relationship between BP and HR
Bp increases, HR decreases
BP decreases, HR increases
Describe what happens to BP during excersise
-increased muscle contraction
-increases skeletal muscle pump
-increased blood flow back to heart
-increased rate and depth of respiration increases blood flow into the thoracic cavity (inspiration) and blood entering the heart. (expiration)
Describe the bainbridge reflex
-blood returning to the heart enters the RA
-RA contains stretch receptors that detect increased atrial filling
-stretched atrial walls initiate a bainbridge reflex
-results in an increase in HR to clear extra blood
Define frank starling’s law of the heart
the force of ventricular contraction is determined by the length of the cardiac muscle fibres
Describe the events that occur in relation to frank starling’s law
-more blood enters ventricles from atria
-ventricles fill more and ventricular muscles are streched more
-greater the stretch = greater the force of ventricle contraction
-greater force of contraction= greater stroke volume
Define stroke volume
amount of blood ejected from the ventricle during one contraction
Define end diastolic volume
amount of blood in the ventricle at the end of diastole
Define end systolic volume
amount of blood in the ventricle at the end of systole
what is the Stroke volume equation?
SV = EDV- ESV
What is preload?
the degree to which the ventricular musle is stretched just before contracting
What is afterload?
The pressure that the ventricles must overcome to push the blood through the SLV as the ventricles are contracting
How is the renin-angiotensin aldosterone system in initiated?
decreased blood flow to the kidnet, results in an increase in blood volume and stimulates vasoconstriction
Describe what happens to BP during excersise regarding hr,sv,q
-increase in HR and SV increases Q
-increase in Q, increases BP
-designed to meet increased demands of muscles- increased O2 supply, glucose and removal of waste products
-increased muscle activity is a stimulus detected by proprioreceptors
-stimulated proprioreceptors cause an increase in HR, SV, Q and BP
What happens when chemoreceptors detect acidosis?
-increased cardiac output
-increase respiratory rate to help the body achieve a steady state
What factors effect mean arterial pressure?
-increased activity of muscular pump and respiratory pump
-decreased released of ANP
-fluid loss from hermorage or sweating
-crisis stressores
-bloodborn chemicals
-dehydration/high haematocrit
-increased body size
What factors are involved in cardiac ouput regulation?
-excersise
-decreased HR
-bloodborn epinephrine, thyroxine , ca2+
-excersise
What factors enhance cardiac output?
-excersise
-decreased BP activates cardiac centres in medulla
How does a rise in BP result in a decreased HR?
-baroreceptos detect a rise in BP
-impulses sent to medulla
-more impulses sent to the SAN via PSNS
-Decrease in frequency of impulses from SAN
-decreased HR
