Lecture 9 - Cardiovascular System 2 Flashcards
Blood flow
What are hemodynamics
A collection of mechanisms that influence the dynamic circulation of blood
- diff rates/min in diff areas
- greater activity requires greater blood flow
What are the 2 control mechanisms of hemodynamics
- Maintenance of circulation
2. Vary volume and distribution of blood
What causes fluids to flow in circulation
Pressure gradients from high to low
How does heart circulate blood
By changing pressure
What is a local pressure gradient known as
Perfusion pressure
Characteristics of arterial BP
- needs high pressure to keep blood flowing
- arterial BP is directly proportional to arterial blood volume
What are 2 important factors in arterial BP
- Cardiac output
2. Peripheral resistance
What does cardiac output influence
Amount of blood entering arteries
What does peripheral resistance influence
Amount of blood leaving arteries
Cardiac output formula
CO = SV x HR
CO= amount of blood that flows out of a ventrical/min Sv = volume/ beat Hr = beat/min
What is impacted by changes in SV or HR
CO, BP and arterial blood volume in the same direction
What is cardiac reserve
Amount that CO can increase above normal expressed as %
What is the typical resting cardiac output
5000 ml/min or 5L/min
What is inotropic factors
Factors caused by changes in myocardial contraction
Mechanical, chemical or neural (like length of myocardiac fibers at start of contraction)
What is Starlings law
Longer fibers make strong contractions up to a point (350 mL)
What is End Distal Volume (EDV)
More blood returned, more stretched fibers, stronger contractions
-too much blood will result in lowered elasticity
What does Norepinephrine do
Increases contractility of the heart
Where does Norepinephrine come from
Sympathetic nerve fibers or adrenal glands
What is ejection fraction
Ratio of SV to EDV
(SV/EDV x 100%),-55%
What is afterload
Work necessary to pump blood into arteries
What is mean pressure
Usually about (2 x diastolic + systolic) ÷3
What is result in increase of CO or PR
Increase in blood volume and thus increase in arterial BP
What typically controls chronotropic factors
Sinoatrial node
What affects stroke volume
Inotropic factors
Ejection fraction
Afterload
What affects CO through what heart rate factors
Chronotropic factors ( timing) Other reflexes
What typically controls chronotropic factors
Sinoatrial node (SA node)
What innervates SA node to correct beat
Sympathetic (Nor) nerves
Vagus (ACh) nerves
How do nerves send impulses to SA node to change timing
Cardiac Pressoreflexes
How does cardio pressoreflexes work
Send info to cardiac control centers in medulla
- starts a negative feedback loop that responds to increased pressure from barorecptors in:
Carotid sinus reflex
Or Aortic reflex
- receptors in SA node get message to increase CO or decrease
What are other reflexes that affect heart rate
Emotions Exercise Hormones Blood temp Pain Acceleration typically from epinephrine Nerves : sympathetic causes increase, parasympathetic causes decrease
Where are baroreceptors located
Common carotid
Aorta
What would be variable, sensor, integrator, effector of CO feedback loop
Variable = BP Sensor = baroreceptors Integrator= cardioregulatory centers in medulla oblongata Effector= SA node
What is peripheral resistance
Resistance to flow from friction between blood and walls of vessels
- how hard the blood is pushing against walls of vessel
Where does peripheral resistance develop from
The viscosity (thickness) of blood and small diameter of arterioles and capillaries. - creates a "back up in blood traffic" which helps maintain pressure
What can too much peripheral resistance “back up in blood traffic” cause
In extreme
Chronic hypertension or high BP, and plaque build up.
What causes blood viscocity to increase
Mainly proportion RBC (hematocrit level)
Also
-proteins and other dissolved molecules
What is vasomotor mechanism
A way to decrease blood viscosity -> decrease peripheral resistance
How does vasomotor mechanism work
Contraction or dilation of arterioles to change resistance to flow
- vasoconstriction/ vasodilation
This will change arterial runoff and total peripheral resistance
Why do small changes to vessel size have large impact on blood flow
Because blood is quartic
Where is vasomotor motor control mechanisms controlled from
Medulla (vasomotor / vasoconstrictor center)
What happens when vasomotor center is activated
Causes constriction of blood reservoirs
- this venoconstriction increases amount of blood moving
Where are main reservoirs that vasomotor center constricts
Skin and abdominal organs (venous plexuses and sinuses)
How does vasomotor pressoreflexes from BP work
- same system as cardiac pressoreflexes
What happens with vasomotor pressoreflexes when sudden BP increase
- sudden increase in arteriole BP stimulates aortic and carotid baroreceptors which results in arterioles and venules of blood reservoir dilating
What happens with vasomotor pressoreflexes when BP decreases
Decrease in arterial BP results in stimulation of vasoconstrictor centers, causing vascular smooth muscle to constrict
What do chemoreceptors do
Detect changes in chemical composition
What do baroreceptors do
Detect stretch
What do chemoreceptors in aorta and carotid detect that affect vasomotor control mechanisms
Hypercapnia -> excessive CO2
Hypoxia -> diminished O2 (less sensitive)
How does chemoreceptor reflex work
Sends signal to vasomotor center which causes constriction of arterioles
What is medulla ischemic reflex
If flow to medulla low (ischemic)
The chemoreceptors in medulla signal vasomotor center to greatly restrict arterioles and venous centers so more blood flows to medulla
What else can influence medullary signaling
Hypothalamus and cortex if emotions like fear or anger are high
Can local tissue affect vasodilation
Yes in things like active hyperemia (increased movement/excercise)
What are 3 major things that influence amount of blood returned to heart by veins
Reservoirs
Gravity
Total blood volume
What is the stress- relaxation effect
Due to elasticity of venous walls
Low pressure shrink reservoirs and high pressure expands reservoirs
Which helps to maintain blood flow
What is gravity effect of venous blood
Pulls blood to legs when upright as walls are too elastic to resist
- has no effect if lying down
What is Orthostatic effect
When you stand from lying down blood all tries to go down to feet worse in elderly can cause syncope
What overcomes Orthostatic effect
Use of venous pumps, back up valves, and movement that keep pressure gradient
What facilitates venous pumps
Respirations and skeletal muscles
They increase pressure gradient between peripheral and central veins
How does respiration facilitate venous pump
- contraction of diaphragm on inspiration increases thoracic cavity volume, decreases pressure of vena cava , atria
- diaphragm pumps blood up as inspire and expire (deeper respirations intensify effects)
How do skeletal muscles help venous pumps
Muscle contractions serve as booster pumps by squeezing blood up
- one way valves prevent backflow as muscle contraction moves it up with each contraction
Where is retention of water mainly done
Kidneys
What is total blood volume affect on vous pumps
Greater total volume -> more blood returned (pressure gradient)
How is movement of blood accomplished with increased total blood volume
By movement of water through retention
What happens if kidneys retaining too much water
Could cause high BP as too much blood constantly returning to heart
How is total blood volume affected by capillary exchange
Movement of fluid between plasma (blood) and interstitial fluid (fluid between cells in system)
Starling’s law re: capillary exchange affected total blood volume
- osmosis promotes fluid flow into plasma due to large colloids that cannot migrate through capillaries; small in arterioles, reverse in venules
- hydrostatic pressure gradient, fluid leaves high pressure in arterioles to low pressure in tissue, large in arterioles, less in venules
- 90 % water retained 10% returned to lymph
What is hydrostatic pressure
Pressure generated when a force is applied to water (pushing force)
What is osmotic pressure
Pressure due to gradient generated across a semi-permeable membrane (pulling force)
What are 4 ways to control total blood volume
ADH Mechanism
Renin-Angiotensin-Aldosterone (RAAS) system
ANH Mechanism
Balance of Regulation
What is ADH mechanism
Anti diuretic hormone released by pituitary gland to reduce amount of water lost in kidneys
- by increasing absorption of water from urine thus increasing blood volume
What is renin-angiotension-aldosterone (RAAS) system
Renin released when kidney detects BP low
- promotes release of aldosterone from adrenal glands
- aldosterone promotes sodium retention
- promotes water retention by osmosis if ADH active
- angiotensin ll promotes vasoconstriction sending blood back up
What does angiotensin converting enzyme (ACE) do
Limits angiotensin ll and can combat high BP (hypertension)
What is ACE inhibitor
Usually med to control high BP / hypertension
What is ANH Mechanism
Atrial natriuretic hormone secreted by pericytes in atria in response to overstretching
- if atria chronically overstretched by high venous return to heart will release this hormone
- ANH reduces water in plasma by increasing sodium loss in kidneys and water loss by osmosis
What is balance of regulation
ANH opposes ADH and RAAS
- multiple systems increase precision of volume regulation
How does sphygmomanometer work
Approximates air pressure equal to BP
- cuff wrapped around arm over brachial artery
- air added until exceeds BP
- pressure reduced until it approximates BP
- vessel will open, blood will spurt through making tapping sound that gets louder then muffled then dissapeared
- tapping sound approximates systolic BP
- lowest pressure where sounds are heard is diastolic BP
(Sounds called korotkoff sounds heard between 120 and 80mmHg -> first sounds when you start to open artery until fully open)
Other ways to measure BP
Directly with catheter or connecting a cannula to a nanometer
Ideal BP
120/80
What is systolic BP
Force of L ventricle contraction
What is diastolic BP
Resistance of blood vessel
What is difference between SBP &DBP
Pulse pressure
What is normal ranges of MAP
70 to 110 mmHg at rest
What is enough MAP to supply brain, kidneys, other vitals
6 mmHg
Pressure of veins is practically uniform because
Blood enters them at a steady pressure from arterioles elastic movement
How does blood leave vessels
Spurts from arteries
Drains from veins
Hypotensive range
<90 SBP <60DBP
Desirable range BP
90 -119 SBP
60-79 DBP
Prehypertension range
120 - 139 SBP
80-89 DBP
Stage 1 hypertension
140-159 SBP
90-99 DBP
What is minute volume of blood
Volume of blood circulating through body per minute
What determines minute volume of blood
Magnitude of BP gradient and peripheral resistance
What is poisuilles law minute volume equasion
Minute volume = pressure gradient / resistance
Or
Minute volume = (MAP - central venous pressure) / resistance
Breakdown of poisuilles law
Increase in peripheral resistance mathematically reduces minute volume but biologically reduces arterial runoff -> increases blood in arteries-> increases arterial pressure
When is blood velocity greatest
When pressure is greatest
What reduces conduction velocity
Larger surface area makes effects more diffuse. Less conduction volume because it is split amongst larger surface
What is the pulse
Alternate expansion and recoil of elastic artery
What 2 factors are responsible for a pulse that can be felt
- Intermittent interjections of blood into the aorta from the heart, leading to alternating increase and decrease in pressure in that vessel
- Elasticity of artery walls, allowing the vessel to expand and contract with alterations in BP
What would cause you to not fee pulse
Constant pressure or rigid material
What starts a new pulse wave
Each ventricular systole (as it moves through arteries it dissipates until it disappears in capillaries)
What produces dicrotic notch in pulse wave
Produced by closure of aortic valve and noticeable in carotid but not radial
What is noticeable about pulse the further distance from heart
More delay
How does pulse wave conserve energy
By shifting energy from contractions into elastic arterial walls
What are 9 pulse locations
Radial Temporal Common carotid Facial Brachial Femoral Popliteal Posterior tibeal Dorsalis pedis
Where is radial pulse
Wrist
Where is temporal pulse
In front of ear, above outer edge of eye
Where is common carotid pulse
Along anterior edge of sternocleidomastoid and lower margin of thyroid cartilage
Where is facial pulse felt
Lower margin of lower jawbone, in line with mouth
Where is brachial pulse felt
In the bend of elbow along inner margin of biceps
Where is femoral pulse felt
In groin where it passes over the pelvic bone
Where is popliteal pulse felt
Behing knee
Where is posterior tibeal pulse felt
Behind medical malleosus (inner ankle)
Where is dorsalis pedis felt
Dorsum of foot
What are 6 pressure points for bleeding
- Temporal
- Facial
- Common carotid (same as pulse with pressure on spinal column)
- Subclavian (behind medial 3rd of clavicle, pressing against first rib)
- Brachial (few inches above elbow, pressing against humerus)
- Femoral (same as pulse)
What is key note about apply pressure to pressure points
Pressure must be applied at the pressure point above the lesion between the heart
What is anemia
RBC disorder
Not enough Hgb to carry enough O2 for the production of ATP
What causes anemia
Bleeding
Destructive mechanism for RBC
Incapacity of the red bone marrow
What is polycythemia
Excess RBCs which cause increased viscosity of blood and decreased circulation
What is aplastic anemia
Abnormally low RBCs from destruction of red bone marrow
What is pernicious anemia
Low RBCs from vitamin B12 deficiency due to lack of intrinsic factor
What is folate deficiency anemia
Usually from vitamin B9 deficiency, common in alcoholism
What can cause changes in hemoglobin
Hyperchromic or hypochromic
- inadequate iron in diet leads to iron deficiency anemia
- pregnancy, wound healing, nutritional deficiency
What is hemolytic anemia
Various inherited conditions
Like sickle anemia, thalassemia
What are some WBC disorders
Multiple myeloma
Leukemia
Infectious mononucleosis (mono
What is multiple myeloma
Cancer of b Lymphocytes, creates defective antibodies
What is leukemia
Cancer of WBCs, marked leukocytes
Cell counts in excess of 100000/mm3
Acute vs chronic, lymphocytic vs myeloid
What is infectious mononucleosis
Caused by a virus found in saliva
Atypical WBCs with large body and nucleus
What are clotting disorders
1 Thrombosis
- formation of clot in unbroken blood vessel
- dislodged clot is embolus or embolism
2 Hemophilia
- failure to produce proteins for clot formation
- x-linked inherited disorder
Heart valve disorders
Rheumatic heart disease
Mitral valve prolapse
Aortic regurgitation
What is rheumatic heart disease
Inflammation of cardiac valves and other tissues (rheumatic fever) stemming from delayed inflammatory response to streptococcal infection
What is mitral valve prolapse
Flaps extend back into atrium causing leak
What is aortic regurgitation
Blood returns to left ventricle after ejection, increasing load on LV leading to myocardial ischemia
Myocardium disorders
Coronary artery disease
Myocardial infarction
Angina pectoris
Cardiomyopathy
What is coronary artery disease
Reduced blood flow to coronary arteries from atherosclerosis
What is myocardial infarction
Death of myocytes (muscles cells)
Basically heart attack
What is angina pectoris
Pain caused by decrease for a moment or irrigation of myocardium
- temporary lack of O2 which weakens myocardial cells
(Often precursor to myocardial infarction)
What is cardiomyopathy
Abnormal enlargement of the heart
What is dysrhythmia
Abnormal heart rhythm
What is heart block
Interference stops SA node signals from reaching AV node
Whay is bradycardia
Slow heart rhythm below 60 Bpm
What is tachycardia
Rapid Heart rhythm above 100Bpm
What is sinus dysrhythmia
Variation in heart rate during breathing cycle
What is premature contractions
Contractions that occur before next set of expected contractions, can be atrial or ventricular, can lead to fibrillation
What is atrial fibrillation
Common with mitral stenosis
What is ventricular fibrillation
Immediately life threatening due to blood not reaching vital tissues
What is heart failure
Inability to pump blood to sustain life
- a combination of previous disorders
What is CHF
Left sided heart failure
What is Cor pulmonade
Right sided heart failure
What is arteriosclerosis
Thickening of walls due to calcium deposits
What is aneurysm
Abnormally widened section of artery
- can form thrombus, embolus or burst- hemorrhage
What is ischemia
Decreased blood supply to tissue, leads to necrosis
- necrotic tissue with bacterial action - gangrene
What is varicose veins
Enlarged veins where blood pools
What are Hemorrhoids
Varicose veins in anal canal
What is phlebitis
Vein inflammation
What is thrombophlebitis
Due to clot
What is DVT
Clot in deep vein
What is circulatory shock
Failure to deliver O2 to tissue, ultimately caused by reduced blood flow
What is carcinogenic shock
Any type of heart failure
What is hypovolemia shock
Loss of blood volume ex. Hemorrhage
What is neurogenic shock
Widespread dilation of blood vessels from imbalance in ANS
- sometimes called vasodilatory shock
- damage to medulla, depressive drugs, stress
What is anaphylactic shock
Acute allergic reaction , anaphylaxis
What is septic shock
Complications of septicemia, where infectious agents release toxins into blood
