Lecture 7 - Blood Pressure I Flashcards
What is Mean Arterial pressure?
Driving force for blood flow
Average pressure driving blood toward into tissue throughout cardiac cycle
What is the equation of MAP?
MAP = CO x TPR
What are main determinants of MAP?
Cardiac output
Heart rate
Stroke volume
Total pressure resistance
What is Heart rate controlled by?
ANS
What is stroke volume influenced by?
Venous return which is influenced by skeletal muscle pump, respiratory activity
Blood volume
Inotropy and ventricular preload
What does TPR depend on?
Blood viscosity
Arteriolar radius
Length of vessel
Normal blood pressure
120/80mmhg
Hypertension
140/90mmHg
Hypotension
100/60mmHg
What is the equation for cardiac output?
CO = HR x SV
What is pulse pressure?
Force that the heart generates every time it contracts
Difference between systolic and diastolic pressure
What is equation of pulse pressure?
SBP-DBP
What is MAP
DBP + 1/3(PP)
An increase in cardiac output
Increase in the volume of blood contained in the aorta
Increase in mean arterial pressure when total peripheral resistance remain the same
Constant cardiac output
Increase in volume of blood contained in aorta
Increase in mean arterial pressure when total peripheral resistance increases
Short term regulation
Secs —> Mins Regulate CO and TPR Involves heart and blood vessels Neural control (ANS) Response augmented by chemoreceptors
Long term regulation
Mins —> days
Regulate total blood volume (TBV)
Involves kidneys
Hormonal control
Too high (MAP)
Extra work for heart
Increases risk of vascuature damage
Rupture of small blood vessels
Too low (MAP)
Insufficient driving pressure
Brain and other tissues will not receive adequate blood flow
Where are chemoreceptors located?
Aortic and carotid arteries
What does chemoreceptors respond to?
Very low oxygen
High acid levels
What does stroke volume increase in response to?
Sympathetic activity
How do you maintain blood pressure?
Negative feedback loop
What is the detector of short term regulation?
Baroreceptors
Where is the location of the baroreceptors?
Carotid sinus
Aortic arch
What is the integration centre for short term regulation located?
Medulla Oblongata
What are the inputs of the integration centre of short term regulation?
Baroreceptors
Chemoreceptors
Proprioceptors
Higher brain centres
What are the contents of the short term regulation?
Autonomic nervous system
Sympathetic and parasympathetic divisions
What are the effectors of short term regulation?
Heart and blood vessels (arterioles and veins)
Increase or decrease MAP
What is the function of baroreceptors?
Increased pressure > increased AP frequency
Decreased pressure > decreased AP frequency
What are Baroreceptors/mechanoreceptors?
Stretch receptors
Located: carotid sinus and aortic arch
What are the high pressure receptors?
Baroreceptors
What are the low pressure receptor (volume receptors)?
Venous and cardiac baroreceptors
What does baroreceptors provide?
Critical information about arterial blood pressure in the vessels leading to the brain
What does baroreceptors continuously generate?
AP in response to ongoing pressure within arteries
What is the heart innervated by and what does it depend on?
ANS
Depend on: HR and strength of contraction
What supplies the atrium (SAN and AVN)?
Parasympathetic, vagus nerve
ACH and cholinergic receptors
What supplies the atria (SAN and AVN) and ventricles?
Sympathetic neves
Norepinephrine and B1 adrenergic receptors
What is SA node intrinsic firing rate?
100/min
What does ACH inhibit the release of?
Norepinephrine
During activity
Sympathetic dominates and heart rate increases
What is the resting HR?
75bpm
What is the effect of SAN on heart (synpathetic)?
Increase depolarisation of SAN Increase HR
Increase Na+ and Ca2+ into cell
Increase frequency of APs
What is the effect of SAN on heart (parasympathetic)?
Decrease depolarisation of heart decrease heart rate
Increase permeability to K+
Hyperpolarise membrane
Decrease frequency of APs
What is the effect of Atrial contractile cells on sympathetic?
Increase contractile strength
Increase ca2+ permeability
Increase inward current of ca2+
More ca2+ > more cross bridge formation > increase strength of contraction
What is effect of Atrial contractile cells on parasympathetic?
Decrease contractile strength
Decreased inward current of ca2+
Shorten plateau phase of AP
Decrease strength of contraction
What is effect of ventricle contractile strength of sympathetic ?
Increase contractile strength
Heart beats more forcefully
Increase stroke volume
Increase in sympathetic activity
SAN (increase heart rate)
Ventricular myocardium (Increase contractility Increase SV)
Arterioles (vasoconstriction, increase resistance, increase TPR)
Veins (increase venomotor tone, increase VR, increase EDV, Increase SV)
What is consequence of hemorrhage?
Decrease in blood volume
Decrease in MAP
What is the long-term regulation?
Renal Regulation
Blood volume
What are the hormonal long term regulation?
Vasopressin/ADH
Angiotensin II
Epinephrine
Vasopressin/ADH & Angiotensin II
Vasoconstrictors
Conserve blood volume
Increase water and sodium reabsorption in kidneys
Epinephrine
Neural hormone Increase in response to sympathetic activity act on heart Act on smooth muscle of arterioles Act on smooth muscle of veins
What is the thermoregulatory response?
Thermoregulation = hypothalamus
Increase body temperature
Decrease sympathetic activity to skin Vasodilation to skin
Increase heat loss to environment
What is the primary fu croon of chemoreceptor reflex?
Regulate blood carbon dioxide levels
What does ventilation increase an decrease?
Increase carbon dioxide, increase TPR
Decrease HR
How is the pressure in brachial artery measured and via what ?
Indirectly
Sphygmomanometry and auscultation
Laminar flow
No sound
Turbulent flow
Sound
What happens when cuff pressure > 120mmHg?
No blood flows through vessel
No sound
No blood is flowing
What happens when cuff pressure is between 120 and 80mmHg ?
Blood flow through the vessel is turbulent
Because
Blood pressure > cuff pressure
First sound: peak systolic pressure
What ha pens when cuff pressure is less than 8mmHg ?
Blood flows through vessel in smooth, laminar fashion
Last sound heard: minimum diastolic pressure
What is Hypertension?
MAP > normal (140/90 mmHg)
What is the cause of hypertension?
Genetic predisposition Contributing factors: Stress Obesity Smoking Diet
What is the current research for Hypertension?
Salt Diets low in fruit, veg, diary plasma membrane abnormalities Excessive vasopressin Abnormalities in vasoactive chemicals
What are the complications of hypertension?
Stress on heart and blood vessels Congestive heart failure Stroke Myocardial infarction Renal failure
What are the treatment for hypertension?
Diuretics Antihypertensive meds Exercise Weight control Diet
What is the effect of hypotension?
Inadequate BF to tissues?
What are the causes of Hypotension?
Disproportion between vascular capacity and blood volume
Heart too weak to impart sufficient driving pressure to blood