A&p2 The heart and blood vessels
2 main variables that govern fluid movement
(1)PRESSURE: causes a fluid to flow (2)RESISTANCE: opposes fluid flow > great vessels have positive blood pressure so ventricular pressure must rise above this resistance for blood to flow into great vessels
During ventricular systole, what happens?
*ventricles eject blood *Ventricles contract, closing AV valves (ventricular pressure rises above atrial pressure). Hear S1 *Ventricles generate so much pressure that they overcome the pressures in the great arteries
sinusoidal capillaries
- most permeable capillaries - wide open intercellular clefts (gaps of unjoined membrane through which small molecules can enter and exit). Found in organs where large proteins & cells need to migrate in & out - incomplete basement membrane - have a large diameter and a twisted course - occur in red bone marrow, liver, and spleen-macrophage migrate into sinusoids & hepatic tissue, clotting factors made in liver
3 factors affecting flow (and therefore resistance)
1)Size of lumen of vessel 2)Blood viscosity 3)Blood vessel length "S-V-L" like SML size of lumen is most important of the 3 factors BC nervous system can control this
short term blood pressure regulation (happens quickly)
1. Baroreceptor reflex 2. Chemoreceptor reflex 3. Hormones: Nor/Epinephrine ANP ADH
Baroreceptor reflex: What happens when arterial blood pressure rises above normal?
1. Baroreceptors in carotid sinuses & aortic arch stimulated 2. More Impulses from baroreceptors stimulate CIC (and inhibit CAC & vasomotor center) 3. Fewer sympathetic impulses to heart cause lower heart rate, lower contractility & lower cardiac output 4. Decrease in vasomotor impulses allows vasodilation causing less resistance in arteries 5. Low CO & Low R return blood to homeostatic range
Summary of the paraSympathetic Activity of autonomic control of cardiovascular system
1. Decrease heart rate 2. Decrease force of contraction of ventricles, thus decreasing SV (and contractility) 3. Vasodilation of blood vessels Outcome: Decreased cardiac output and decreased BP
4 inputs to cardiovascular center (nerve impulses)
1. From higher brain centers: cerebral cortex, limbic system & hypothalamus 2. From proprioceptors: monitor joint movements 3. From baroreceptors: monitor blood pressure 4. From chemoreceptors: monitor blood acidity & CSF H+, CO2 & O2
Summary of the Sympathetic Activity of autonomic control of cardiovascular system
1. Increase heart rate 2. increase force of contraction of ventricles, thus increasing SV 3. Vasoconstriction of blood vessels Outcome: increased cardiac output & increased BP
3 output to effectors of cardiovascular center
1. Parasympathetic-CIC-Heart:decreased rate 2. Sympathetic-CAC-Heart: increased rate & contractility (strength of force of contraction) 3. Sympathetic-blood vessels-vasoconstriction
Aortic stenosis would most affect which of the 3 factors of stroke volume? Does Cardiac output increase or decrease?
Afterload. Car
What will happen to the level of exercise tolerance in a person whose heart is being paced by the AV node? a. level of exercise tolerance will stay the same b. level of exercise tolerance will decrease c. level of exercise tolerance will increase
B
Reduction in the concentration of albumin in blood plasma would alter capillary exchange by ________ .A) increasing hydrostatic pressure and blood volume, blood pressure increases B) decreasing colloid osmotic pressure and edema will occur C) increasing hydrostatic pressure and edema will occur D) decreasing colloid osmotic pressure and blood volume, blood pressure increases
B) decreasing colloid osmotic pressure and edema will occur
Stroke volume plays an important role in cardiac output. Select all the factors below that influence stroke volume: A. Heart rate B. Preload C. Contractility D. Afterload E. Blood pressure
B, C, D
Which pressure results from the force of water moving toward the plasma proteins of the blood?
Blood colloid osmotic pressure water in the interstitial space is attracted to the hydrophilic plasma proteins in the blood. BCOP is a very strong force and the driving force for reabsorption
Which side of the heart pumps the most blood?
Both ventricles pump the same amount but the left ventricle must generate greater pressure to overcome greater resistance in the systemic circuit
Which of the following is not a result of sympathetic nerve stimulation? A. Release of epinephrine B. Increased heart rate C. Negative chronotropic effect D. Increased Action Potential firing
C
which of the cardiac centers sends efferent signals to the heart through adrenergic fibers that secrete NE?
CAC cardioacceleratory center
Which of the cardiac centers sends afferent signal to the heart through cholinergic fibers that secrete ACh?
CIC cardioinhibitory center
what channels are responsible for plateau?
Ca++ & K+
Substances causing Vasomotion-vasoconstrictors What does this do to BP?
Constrictor--more pressure in vessels Sympathetic nerves (epinephrine, norepinephrine)-reroute blood in survival mode Angiotensin II-hormone- POWERFUL VASOCONSTRICTOR-raises BP Endothelin-local vasoconstrictor-released by simple squamous endothelium/inner lining of blood vessels SHIFT/REROUTE blood flow SAvE ENE RAISES BP
What are the 2 kinds of cell to cell junctions found in intercalated discs?
Desmosomes- anchor, mechanical stress Gap junctions-allow diffusion of electrical signal, nutrients & O2
When does atrial repolarization occur?
During the QRS complex; it is not seen on the ECG because it is masked by the much greater electrical activity in the ventricle
Preload is equivalent to
EDV
In preload, SV is proportional to
EDV (if EDV is high, SV will be high. If EDV is low, SV will be low)
During capillary exchange, fluid that is __ moves __ the capillary
Filtered/out of reabsorbed/into
Flow formula
Flow = change in pressure/resistance Delta P/R difference in pressure between 2 points Resistance: anything/forces that opposes blood flow
Blood always flows from ___________ pressure to ___________ pressure.
High to low
increased contractility
How would an increase in the sympathetic nervous system increase stroke volume?
What are the 2 septa of the heart?
Interatrial septum (Fossa ovalis) and Interventricular septum
what occurs during repolarization?
K+ exits until channels close
Ions affecting heart rate
K+, Hyperkalemia/hypokalemia=expect arrhythmias
The greater the length of a vessel, there will be more or less resistance to flow?
MORE. Friction along the vessel gives more and more resistance
Which chamber of the heart is thickest?
Myocardium of left ventricle is significantly thicker than the right
AV valves are open or closed during ventricular diastole? wHY?
Open bc pressure in atria is higher than pressure in the ventricles
CIC (cardioinhibitory center)
Parasympathetic fibers reach vagus nerve and release acetylcholine which decreases HR and force of contractions.
Factors affecting heart rate--decrease
Parasympathetic stimulation=CIC-ACh Negative chronotropic drugs-Beta blockers (keeps heart restful)
Substances causing Vasomotion-Vasodilators What does this do to blood flow?
Prostaglandins-important role in inflammation Nitric Oxide (NO)-secreted by endothelial cells-antagonistic to Endothelin. Used when we need to get more blood to come into the tissue ARTERIES WIDEN, MUSCLE RELAXING "Dilators open up muscles/cervix in childbirth *tunica media is responding--smooth muscle relaxing Blood flow increases. BP goes down VPN
long term blood pressure regulation (takes longer to kick in)I
Renin Angiotensin Aldosterone (RAA) system 3 hormones that work together to regulate BP
What events happen at end of ventricular diastole?
SA node fires an AP, depolarizes atrial cells & atria contract-->atrial systole-completes ventricular filling
As contractility increases...
SV increases. As contractility decreases, SV decreases. Directly proportional
increased contractility will increase ___? How?
SV. By sympathetic stimulation or positive inotropic drugs (which increase tension of the heart wall) [such as Angiotensin 2}
decreased contractility
SV. Examples: heart failure (thin wall of heart), negative inotropic drugs-Beta blockers
stroke volume formula
SV=End-diastolic volume -End-systolic volume EDV-ESV Ex. 120 ml-50 ml=70ml
Capillaries are
Smallest blood vessels in body, only tunica interna
what is an electrocardiogram?
Summary/composite of all action potentials of SA & AV nodal & myocardial cells 1)detected, 2)amplified & 3)recorded by electrodes on arms, legs & chest
A patient has a blood pressure of 220/140. The physician prescribes a vasodilator. This medication will?* A. Decrease the patient's blood pressure and increase cardiac afterload B. Decrease the patient's blood pressure and decrease cardiac afterload C. Decrease the patient's blood pressure and increase cardiac preload D. Increase the patient's blood pressure but decrease cardiac output.
The answer is B. The patient has a high systemic vascular resistance...as evidenced by the patient's blood....there is vasoconstriction and this is resulting in the high blood pressure. Therefore, right now, the cardiac afterload is high because the ventricle must overcome this high pressure in order to pump blood out of the heart. If a vasodilator is given, it will decrease the blood pressure (hence the systemic vascular resistance) and this will decrease the cardiac afterload. The amount of the pressure the ventricle must pump against will decrease (cardiac afterload decrease) because the blood pressure will go down (hence the systemic vascular resistance).
True or False: Pulmonary and systemic vascular resistance both play a role with influencing cardiac afterload.
The answer is True. If pulmonary vascular resistance or systemic vascular resistance is high, it will create an increased cardiac afterload. If pulmonary vascular resistance or systemic vascular resistance is low, it will create a decreased cardiac afterload.
What conditions below can result in an increased cardiac afterload? Select all that apply: A. Vasoconstriction B. Aortic stenosis C. Vasodilation D. Dehydration E. Pulmonary Hypertension
The answers are A, B, and E. Vasoconstriction increases systemic vascular resistance which will increase cardiac afterload. It will increase the pressure the ventricle must pump against to open the semilunar valves to get blood out of the heart. Aortic stenosis creates an outflow of blood obstruction for the ventricle (specifically the left ventricle) and this will increase the pressure the ventricle must pump against to get blood out through the aortic valve. Pulmonary hypertension increases pulmonary vascular resistance which will increase the pressure the right ventricle must overcome to open the pulmonic valve to get blood out of the heart....all of this increase cardiac afterload.
Frank-Starling Law
The greater the stretch, the stronger is the heart's contraction and preload. This increased contractility results in an increased volume of blood ejected (Increased SV)
Frank-Starling Law
The greater the stretch, the stronger is the heart's contraction. This increased contractility results in an increased volume of blood ejected (Increased SV) or the greater the stretch, the more preload--like a spring--greater SV/ejection
What are the alternate names for the A-V valves?
Tricuspid (R A-V valve) and Mitral or Bicuspid valve (Left A-V valve)
what happens in ventricular diastole?
Ventricles relax semilunar valves close-hear S2 "dub" blood flows into atria AV valves open ventricles fill to 70% of final volume ventricular diastole=repolarization=t wave
End Diastolic Volume (EDV)
Volume of blood in the ventricles at the end of diastole (ventricular relaxation--before they contract) ("preload")
vasomotor center
adjusts blood vessel diameter for blood pressure regulation. Autonomic control
quiescent period
all four chambers relaxed at same time
the plateau lasts...
almost 200 ms
stroke volume
amount of blood ejected from one of the ventricles per heartbeat
Viscosity of blood
amount of cohesion (stickiness) between particles in a mixture--honey, oil, molasses
P wave represents what?
atrial depolarization & is followed by atrial contraction (systole). Depolarization is trigger for systole
A-V valve is short for
atrioventricular valve
ejection
blood flows up semilunar valves
peripheral chemoreceptors are located
carotid and aortic bodies-same place as baroreceptors
Baroreceptors are located in
carotid sinus and aortic arch
Chemoreceptors
chemical sensors in the brain and blood vessels that identify changing levels of oxygen and carbon dioxide and blood or CSF pH
3 types of capillaries
continuous, fenestrated, sinusoidal
during the plateau phase, cardiomyocytes...
contract
increased afterload
decreases stroke volume. Inversely proportional
The pulmonary arteries carry O+ or O- blood?
deoxygenated
QRS complex represents
depolarization of the ventricles and is followed by ventricular contraction
fluid flows ---- from - pressure to - pressure
down its pressure gradient from high to low pressure
Blood flowing up from semilunar valves
ejection
Hormones that regulate BP are ___ & ___. They are secreted by___?
epinephrine & nor-epinephrine. Adrenal medulla
capillaries are
exchange vessels, bring to cells, carry away from cells
Purpose of capillaries thin walls
facilitate exchange of fluid with surrounding tissue
venous return does what when exercising? when dehydrated? affects what?
goes up when exercising. Goes down when dehydrated. Affects EDV
fenestrated capillaries
have protein pores "punched" into vessel wall; Large pores ALLOW LARGE AMOUNTS OF SMALL SOLUTES TO EASILY & QUICKLY PASS THRU RAPIDLY (glucose, ions, AAs) found in kidneys, intestines, and endocrine glands-
Function of chordae tendineae and papillary muscles
hold cusps closed while ventricles contract. Prevent backflow from ventricle to atria
Preload is increased by ______ and ________
hypervolemia, cardiac valve regurgitation, heart failure
Central chemoreceptors are located
in the medulla oblongata--mainly monitor ph of CSF which is affected by CO2
Preload is increased in
increased blood volume and venous return. this increases EDV, stretch on ventricular muscle according to Frank Starling law and increases SV. Ex: overhydration
increased viscosity of blood=
increased resistance
vasoconstriction ___ resistance to flow
increases. A narrower vessel creates more resistance. Strangulation/4 lane highway becomes 2 lane hwy--more resistance to forward movement
Vasodilation increases or decreases flow downstream?
increases. Lets more fluid into the vessel & to pass downstream quickly
CAC (cardioacceleratory center)
innervates the heart via sympathetic cardiac nerves that increase cardiac activity
Continuous capillaries
least permeable, most common type of capillary, simple squamous endothelium w basement membrane. Only gaps are INTERCELLULAR CLEFTS=easy way for things to get in & out. All skeletal muscles have these
Describe the A-V valves
made up of 3 or 2 cusps which attach to papillary muscles through chordae tendineae inside the ventricles. Thin
Cardiac Output (CO)
measurement of the amount of blood ejected per minute from either ventricle of the heart
What part of the brainstem controls heart rate?
medulla oblongata
Aortic Stenosis (AS)
narrowing of the aortic valve, which may be acquired or congenital. Gives high resistance to ejection
What is the cardiac cycle?
one complete cycle of contraction and relaxation of all 4 chambers of the heart--all the events in 1 heart beat
Hypercalcemia
positive inotropic agent--excess contractility, longer, more sustained contractions, more Ca++ binds to more troponin, etc. Triggers sarcomeres to contract/shorten
3 major factors that affect stroke volume (all related)
preload, contractility, afterload
What is afterload?
pressure against which the ventricles eject their blood *RESISTANCE TO EJECTION*
driving force for blood flow
pressure gradient--difference in pressure from arteries to veins. Higher in arteries, lower in veins
All chambers are __ at beginning of diastole?
relaxed
What are the four chambers of the heart?
right atrium, right ventricle, left atrium, left ventricle
capillaries are made up of
simple squamous endothelium w basement membrane
what is an intercalated disc?
specialized junctional connections between adjacent cardiomyocytes. Connects 2 adjacent cardiomyocytes
Amount of blood ejected from one ventricle
stroke volume
Cardiac output formula
stroke volume x heart rate. measured in ml/min
Factors affecting heart rate--increase
sympathetic nervous system=CAC Positive chronotropic drugs-Epinephrine Hormones-Epinephrine & thyroxine
plateau phase corresponds with ventricular systole or diastole?
systole bc cardiomyocytes contract. "strong & long contractions for full ejection of blood"
Automaticity
the ability of the heart to initiate its own rhythm
Preload is determined by
the amount of blood returning to the heart from the venous system (right heart) and pulmonary system (left heart) or by the volume of blood in the ventricles at the end of diastole (EDV)
What is contractility?
the amount of tension generated by a contraction for a given preload--doesnt change how much it fills. Its either stronger or weaker contractions
Preload
the amount of tension in the ventricular myocardium just before contraction--how stretched myocardium is before systole
Baroreceptors send signals to the cardiovascular center in
the medulla oblongata
atrial diastole occurs when?
the ventricles are in systole.
blood in capillaries is most important bc
they exchange fluid & nutrients
BP increases with ?
vasoconstriction
Stimulation of the vasomotor center in the medulla causes ___________________ and inhibition of the vasomotor center causes _______________
vasoconstriction and raises BP Vasodilation & lowers BP
__ creates a cinch point that limits blood flow
vasoconstriction. Limits blood flow Then blood is diverted into other blood vessels
Vasoconstriction or dilation causes BP to go down?
vasodilation
Preload is decreased by
venous return and decreased blood volume (ex. dehydration or bleeding)
atrial systole occurs when?
ventricles are in diastole
What happens in ventricular systole?
ventricles contract av valves close-Hear S1 "lub" semilunar valves open blood is forced out of ventricle pressure in atria lower than in ventricles ventricular systole=depolarization=QRS wave
During __ __ ventricles fill with blood
ventricular diastole
T wave represents
ventricular repolarization and marks beginning of ventricular relaxation
What occurs during depolarization of a cardiocyte?
voltage gated ion channels open at 30 mv.. Influx of Na+ into the cell
Stroke Volume (SV)
volume of blood ejected from each ventricle per beat. Measured in ml/beat Ex. 120 ml-50 ml=70ml
End Systolic Volume (ESV)
volume of blood remaining in each ventricle after systole (after ejection-what's left over)
Venous Return (VR)
volume of blood returning to either right or left side of heart per minute
Hypocalcemia causes
weak, irregular heart beat, abnormal EKG, weak ejection
Decreased blood O2 Increased blood CO2 Decreased blood pH
will increase sympathetic stimulation to the heart and raise HR & raise SV Will also decrease parasympathetic stimulation to heart and increase HR Will also increase sympathetic stimulation to blood vessels & vasoconstriction
What is the plateau phase?
• Opening of "slow" L-type Ca2+ channels at beginning & close at the end Keeps the cell positive inside. Ca++ goes in bc 1) cell needs Ca++ & 2)there's a higher conc of Ca++ outside (low inside). Theres so much Ca++ outside that it diffuses in. Used in scarcomeres to bind to troponin (thin filaments) & shorten K+ also leaving so the plateau line is flat
