Blood pressure Flashcards
What is another name for blood pressure? What is blood pressure?
hydrostatic pressure - the force blood exerts against vessel walls
BP = Cardiac Output x Peripheral vascular resistance
What relationship does blood velocity and cross sectional area have?
inverse
Describe systolic and diastolic blood pressure. What is mean arterial pressure, and how do you calculate it?
systolic - highest pressure in arteries, closest to aorta
diastolic - heart is at rest
MAP = diastolic + pulse pressure/3
pulse pressure= systolic - diastolic
MAP is closer to diastolic
What is cardiac output? What affects it?
volume of blood pumped out of one ventricle over one minute
- greater the cardiac output = greater the force pushing on vessel walls
affected by:
- heart rate
- stroke volume: volume of blood per stoke
How is heart rate affected by the following:
parasympathetic
sympathetic
How is heart rate affected by the following:
parasympathetic
sympathetic
thyroid hormone
estrogen
cortisol
hyperalkemia
parasympathetic - ACH from vegas decreases cAMP - lowers HR
sympathetic - NE/EPI increases cAMP - increases HR
thyroid hormone - increase HR
estrogen - decreases heart rate - inhibitory effect on vg Ca
cortisol - increases
hyperalkemia - decreases
How does blood viscosity, vessel length and radius affect peripheral resistance?
blood viscosity - thicker the blood, the higher the BP
length of the vessel - higher the BP
- greater the force of the heart is needed to pump
- adipose tissue has more vessels = obese people have higher peripheral resistance
larger the radius - lower the peripheral resistance
- factor of 4
what are the three vasoconstrictors?
norepinephrine
angiotensin II
vasopressin
What is hematocrit?
% cell volume/plasma volume
higher RBC # = higher viscosity
What affects the viscosity of blood?
Increases viscosity
- diuretics - loss of fluid
- atrial natruietic hormone - loss of urine
- dehydration
- blood doping - increases RBC
- erythropoietin - Increase RBC
- high altitude
decreases viscosity
- ADH/aldosterone - increase fluid
- anemias - decrease cell count
plasma proteins, chemical composition (CO2, O2, H+), temp, drugs
What is the main coordinating center for blood pressure in the brain? Where are the reflex controls of blood pressure?
medulla oblongata
baroreceptors in the aortic arch
chemoreceptors in the carotid sinus
atrial receptors in wall of R atrium
Describe how the barometer reflexes work
minute to minute basis
increased in MAP is sensed by baroreceptors
- increase in PS activity: decreases HR
- decrease in Sympathetic activity: decrease HR, decreases stroke volume, decreases peripheral resistance
all decrease MAP
How do hormones regulate blood volume?
ADH from posterior pituitary - increases H2O reabsorption in kidneys
- vasoconstriction
- increases volume, venous return, end-diastolic volume, stroke volume, cardiac output, blood pressure
Aldosterone - from adrenal glands
- increase Na absorption in kidneys - along with H2O
- increases everything - BP
Atrial naturietic peptide - decreases Na reabsorption from kidneys
- opposite of aldosterone
- released when there is too much blood in R atrium - too much stretching
- responds by releasing ANP
- diuretic - increased peeing
What are the vasoconstrictors?
NE - binds to a1 receptors - activate IP3 - Ca release - smooth muscle contraction
angiotensin II
ADH
dopamine
endothelin
What are the vasodilators?
Epi - binds B2 receptors - activated cAMP system - dephosphylation of myosin - smooth muscle relaxation
nitrous oxide
CO2
Describe the baroreceptor reflex
operate minute to minute
located in aortic arch and carotid sinus
increased BP stretches walls - baroreceptors release NTs to neurons in vessel walls
- APs conducted by vagus and glossopharyngeal nerves to medulla
- medulla tells PS to decrease HR, inhibits sympathetic from increasing HR/contractility
- vasomotor center decreases sympathetic innervation - vasodilation
Describe the chemoreceptor reflexes for blood pressure
responds to decrease in O2 tension/increased CO2/H+ concentrations
chemoreceptors in aortic arch and carotid sinuses
changes in chemicals may increase/decrease release of NTs which determines rate of AP formation of glossophayngeal and vagus nerves
medulla responds to decreased O2, increased CO2/H
- causes decreased PS response, increase sympathetic
- increased HR, stroke volume, increased vasoconstriction
How does the adrenal medullary mechanism affect blood pressure?
activated by large decreases in blood pressure: sudden, substantial increase in physical activity/stress
adrenal medulla releases epi resulting in increased HR, stroke volume, vasoconstriction of blood vessels in skin and viscera
- short, rapid acting
How does the renin-angiotensin-aldosterone mechanism regulate blood pressure?
in response to low pressure - kidneys release renin
renin activates angiotensinogin in blood - produces angiotensin I
angiotensin I goes into the ling and activated by enzyme to angiotensin II (active): causes vasoconstriction of arterioles and slightly in veins
- increases peripheral resistance and venous return
angiotensin II also:
stimulates release of aldosterone by adrenal cortex - increase Na and water reabsorption
stimulates ADH secretion which stimulates H2O reabsorption and vasoconstriction
How does atrial natriuretic hormone regulate blood pressure?
released by atrial cells due to increased venous return - stretches atrial muscle site
- ANH binds to receptors in the kidneys to increase Na loss in urine
- dilates arteries and veins - decreasing in blood volume, venous return and blood pressure
Describe hypovolemic shock.
shock due to low blood volume that results in decreased cardiac output
caused by hemorrhage, dehydration, trauma
Describe vasogenic shock
release of toxic substances resulting in vasodilation
- neurogenic - nerves decrease sympathetic NT release
- anaphylactic - release of histamine from basophils and mast cells
- septicemia - material toxins
Describe cardiogenic shock
decreased pumping ability of the heart
- myocardial infarct
- cardiac arrhythmias
- congestive heart failure
describe obstructive shock
external pressure on the heart decreases cardiac filling/outpuf
- pericardial cardiac tamponade
- pulmonary embolism
What are the stages of circulatory shock?
- Non-progressing (compensatory)
- rapid compensation - baroreceptor, chemoreceptor reflexes
- intermediate compensation - renin-angtiotensin and fluid shift mechanism
- long term - restoration of fluid/RBC numbers - Progressive - compensatory mechanisms are unable to stop progression
- Irreversible shock and death
