Cardiology Flashcards
Three main components of the cardiovascular system?
- Heart
- Vasculature
- Blood
Role of the heart?
-Pump that generates pressure that moves blood through the circulationsystem
Two circuits of the heart?
- Pulmonary circuit: pumps blood to the lungs
- Systemic circuit: pumps blood to the body
What is the role of the vasculature?
-These are the tubes of the body they hold and move blood
Three types of vasculature ?
Arteries: move blood from the heart
Capillaries: move blood from the arteries to veins
Veins: move blood back to the heart
Role of the blood?
Carries nutrients, oxygen and waste
Functions of the CV system?
Transports molecules and other substances rapidly over long distances between cells, tissues and organs
ex (fuel to cells, nutrients to body, O2 from lungs, hormones)
How does the CV system help to maintain homeostasis?
-Regulates pH
-Regulates water balance
-Thermoregulation
DO all organisms require a circulation system?
NO, small organisms do not
Diffusion
-Spontaneous movement of particles caused by random thermal motion
- Diffusion is drive by concentration gradients
-Diffusion over large distances is slow
-mainly occurs across capillary walls/cell membranes
Factors that affect diffusion?
- Temperature
- Distance
- Solvent
- Molecular weight of the diffusing molecule
- Barrier permeability to the molecule
- Surface area of the barrier
What is connective/bulk flow?
-“Bulk” movement of material driven by pressure gradients
-Used to move molecules over larger distances than diffusion
Driving force behind diffusion?
The concentration gradient
T/F: In diffusion particles move in all directions?
True, movement of particles is random and occurs in both directions however the net movement of the particles is driven by the difference in concentration of a particle on either side of the barrier
T/F: Diffusion across membranes is faster than in water?
F its 1000 times slower
Diffusion inversely depends on what factors?
- Distance(smaller = more diffusion)
- Relative molecular weight(smaller = more diffusion)
- Charge of the molecule(polar diffuse less fast)
- Concentration gradient (larger = more diffusion)(not inversely)
What is the equation for flux?
J= Flow/area = D X ((Co-Ci)/d)
What is flux?
the number (in moles) of the particle crossing a unit area (1 cm squared) per unit time
What does D represent?
Diffusion coefficient
-the rate the particle moves through the membrane
What d represent?
distance of the membrane (membrane thickness)
What increases flow?
Area
Solubility
Concentration gradient
What decreases flow?
thickness of the membrane
MW of the substance
Do insects have closed or open CV systems?
Open
Do insects have blood?
No, they have hemolymph which transports hormones, immunes cell, waste and nutrients
Do insects CV systems transport CO2 and O2?
No, respiration is carried out by another system called the tracheal system
How many chambers do insects hearts have?
Several chambers separated by valves. The valves close with each contraction allowing fluid to move from the back to the front controlling fluid flow
What does the Open circulatory system mean?
Organ consists of a pump and a valved tube extending the length of the insect, which act to force hemolymph from the hind end to the head
How does the insect circulation system work?
- Hemolymph is pumped from the posterior end of the insect out to the head of the insect
- Hemolymph is pumped out of the insect head
- Due to pressure gradients the hemolymph makes its way back to the posterior and enters through ostia
What are Ostia?
small openings that let lymph in/out and have a valve-like structure, they draw the hemolymph back into the insects circulation
What type of circulation system do fish have?
A single closed-circuit system (one single loop)
-Blood cells are entirely contained within the system
How many heart chambers do they have?
Two heart chambers
- an atria which recieves blood
-A ventricle which pushes the blood to the rest of the body
How does fish circulation work?
- Ventricle contract generating pressure which forces blood into the gills, arteries and then to the capillaries
- Deoxygenated blood passes through the gills and is oxygenated since the water contains higher concentration of oxygen than the blood inside the gills
- Oxygenated blood then perfuses the organs
What type of circulatory system do amphibians and reptiles have?
Closed-circuit system with two loops
How many heart chamber do amphibians and reptiles have?
three chambers
-One ventricle
-Two atria
What are the two circuits in amphibians and reptiles?
- Pulmocutaneous circuit: Ventricles are toward the lungs and skin places where gas exchange take place
- Systemic circuit
Is there mixing of blood in amphibians and reptiles?
Yes, but overtime their hearts have evolved to make it so that most of the blood doesn’t mix
but this does make concentration of O2 in their blood lower than in mammals/birds
What type of circulatory system do Crocodiles and Alligators have?
Double-looped closed circuit system
How many heart chambers do crocodiles and alligators have?
Four chambers
- Two ventricles
-Two atria
What is the foramen of Panizza and what is its role in crocodiles and alligators?
Foramen of Panizza is a valve between the right and left aorta that allows the circulatory system to bypass the pulmonary circuit which allows them to stay underwater for long periods of time by preventing blood from entering the pulmonary system and going right to their cells
What happens when crocodiles and alligators are above the water?
When they have access the fresh air their heart behaves similar to humans and the foramen of Panizza shunt reopens to allow blood flow
What type of circulatory system do mammals and birds have?
Double-looped closed system
How many chambers do mammals and birds have?
Four chamber
- Two atria
-Two ventricles
What separates the ventricles?
A septum
What are the two circulation systems in mammals/birds?
- Right circulation
Pulmonary ciruclation pumps blood to the lungs - LEft circulation
Systemic circulation pumps blood to the body
What is average blood volume?
5L
What is one blood unit?
450 mL(how much blood you donate)
What is stroke volume and what does it represent?
70 mL represents each time your heart beats how much blood is pumped out
How to calculate SV?
SV = end diatolic volume - end systolic volume
What is diastole?
Relaxation phase of the heart
What is systole?
Contraction phase of the heart
What is Cardiac output?
CO = SV X SR
Amount of blood that the heart pumps in one minute
How much blood is in the arterial system(arteries, arterioles and capillaries)?
18% of the blood
How much blood sits in the capillaries?
5% of the blood
How much blood sits in the venous system(veins and venules)?
61% of the blood
How much blood sits in the heart?
9%
How much blood sits in the pulmonary circulation including the lungs?
12%
What determines the distribution of blood in compartments?
The compliance of the compartment.
Ateries are relatively stiff have low compliance due to the SM around them which is why they carry less blood than the venous system
Are the systemic organs in parallel or series?
They are in aprallel which means each systems gets a fraction of the total cardiac output
Are lung in series with the systemic circulation?
Yes, systemic and pulmonary ciruclation are in series which means they both have the same cardiac input and output
What is stroke rate(SR) ?
How many times your heart beats in a minute
What is the normal cardiac output?
5000mL/min
What is venous return?
Flow of blood back to the atrium it must be equal to cardiac output
Equations for flow(2)?
- Flow = volume/Time(mL/min or L/min)
- Flow = area(cross section of a vessel) X mean velocity(velocity of fluid moving through a vessel)
Flow velocity equation?
Flow = area X mean velocity
Area = cm squared
Velocity = cm/sec
Cm2 X cm/sec = cm3/sec = mL/sec
Is flow velocity constant through veins?
No, flow is faster in the centre of the vein compared to the edges. This is why we take the mean velocity which is the average across the entire vein
What are the capacitance vessels?
Veins and venules that have thin muscle walls and are compliant so they can hold more blood
What are the eachange vessels?
Capillaries are thin vessels involved in diffusive exchange with tissues
What are the resistanc vessels?
Arteries and arterioles have thick muscular walls and low compliance
What are the distribution vessels?
Large arteries and the aorta their primary function is transport
The aorta splits up many times
How many aortas, arteries, arterioles, capillaries, venules, veins and vena cavas do we have?
Aorta - 1
Arteries- 160
Arterioles- 50 million
Capillaries - 10 billion
Venules - 100 million
Veins - 200
Vena cava -2
Order the following from larges tdiameter to smallest: aortas, arteries, arterioles, capillaries, venules, veins and vena cavas?
Largest:
Vena cava
Aorta
Veins
Arteries
Arteriole
Venules
Capillaries
Order the following from thickest wall to smallest: aortas, arteries, arterioles, capillaries, venules, veins and vena cavas?
Thckest:
Aorta
Vena Cava
Arteries
Veins
Venules
Capillaries
Why does velocity of blood flow drop as total cross-sectional area increases?
Flow = area X mean velocity, flow doesn’t change since it is a closed-circuit, the velocity must drop as the mean area increases
How come mean area increases as we get to the capillaries which have the smallest diameter?
Mean area increases because we are increasing the number of capillaries dramatically. A capillary is 1/5000th the diameter of an aorta but there are billions of them
Total cross-sectional area of all the capillaries is 5000 square centimeters
What are the advantages of having a branching network of capillaries?
-All of the cells are close to a capillary
-THis branching gives a high total cross-sectional area for capillaries which means: high total surface area for the capillaries(increases rate of diffusion)
Low velocity gives more time for diffusion to occur
What is blood pressure?
the force exerted by blood on the blood vessel walls
What is normal BP and what do the numbers represent?
120/80
120 (systolic pressure)
80 (diastolic pressure)
What is central venous pressure and what does it normally measure?
This is the arterial pressure coming directly out of your heart
5 to 10 mmHg
What is the equation for pressure?
Pressure = Force/Area
Force = amount of push on the blood
Describe pressure in a closed vessel?
Pressure is the same anywhere and there is no flow since there is no pressure differential
Describe pressure in an open system?
There is flow due to a pressure gradient which is uniform. Particle would move at the same velocity due to a uniform gradient
What is a gradient in terms of pressure?
Change in pressure as a function of distance
What do we need in order for bulk flow to occur?
A pressure gradient
T/F: The flow through large arteries to small arteries to arterioles is constant?
True
Equation for flow?
Flow = perfusion pressure/resistance
What vessels undergo the largest pressure drop and why?
Small arteries undergo a pressure drop of 50 mmHg and arterioles undergo a drop of 20 mmHg. These vessels create more resistance to blood flow (smaller diameter+SM). Since flow must remain constant this means that as the resistance increases the perfusion pressure decreases
Why do large arteries not have a large pressure drop?
Large arteries have a large diamter which means lower resistance which means less pressure drop
What is pressure oscillations?
Fluctuations in pressure due to each heart beat. THe oscillations basically disappear once we reach the venules/veins because the arterioles and arteries have lowered the pressure.
What is the average pressure of the systemic and pulmonary systems?
Systemic = 100 mmHg
Pulmonary = 40 mmHg
How is the mean pressure for systemic and pulmonary circulation calculated?
MAP = DP + ⅓ (SP-DP)
or
MAP = DP + ⅓(PP)
PP = pulse pressure which is systolic pressure - diastolic pressure
Is MAP a simple average?
No the graphs are weird so we can’t just take the biggest value and substract the smallest. Heart is in systole for a short amount of time compared to relaxation phase
What is Hydrostatic pressure?
The pressure exerted by a fluid at equilibrium(no flow) at a given point within the fluid, due to the force of gravity.
What is the equation for hydrostatic pressure?
P = p X g X h
g: gravity
p: fluid density
h: height
Does area/diameter of the column affect hydrostatic pressure?
NO
How does hydrostatic pressure change in a column?
-Top of a column has lower pressure
-Bottom of the column has higher pressure since it has a higher h
-There is a continuous gradient of pressure from the top of the column to the bottom
How was the first measurement of blood pressure performed?
Sticking a glass tube into a major artery of a horse, the height of the blood in the column was 280 cm
Why do giffares have high blood pressure?
Since their heads rise about 6m above ground, they have a BP of 220/180 to get a BP of 110/70 at the brain (normal for a large mammal)
Do we measure venous pressure directly or indirectly?
Directly
How do we measure venous pressure?
Insert a cannula into the superior vena cava which allows us to measure the central venous pressure. A manometer filled with sterile saline will connect to the cannula. The column of saline has to be above the patient, and the base has to be level with the tip of the cannula in the vein. The level of saline will then drop until it is countered by the the central venous pressure
What does it mean when we say organs and tissues are perfused with blood?
Blood is flowing into and out of the structure
Why is a pressure gradient required to move blood?
Since the vessels have resistance
Pressure gradient equation?
P =Pin -Pout
What is systemic circulation perfusion pressure?
P = Pa - Pv (100mmHg -5 mmHg)
Because Pv is so small we approximate perfusion pressure of the systemic circulation to be P = Pa
What does the systemic pressure represent?
Pressure of blood flowing into the systemic circulation
How do we find pulmonary perfusion pressure?
This is the blood flow into the lungs
P = Pa - Pv(20 mmHg - 5 mmHg)
Here we cannot assume P = Pa
Pa = blood pressure going into the lungs
Pv = blood pressure coming out of the lungs
Why isn’t blood always accelerating?
We have frictional resistance in our system which acts against flow
Equation for resistance of a vessel?
Resistance = delta P/flow
Resistance normally has no units
What causes blood flow to not be constant throughout a vessel?
Friction causes the blood near the wall of the vessel to travel slower and there is a gradual increase of the velocity to the center of the vessel
Parabolic shape
What is laminar flow?
Smooth flow of liquid through a tube, where all the flow is in the same direction
Also called non-turbulent
What is turbulent flow?
Flow of liquid through a tube, where the flow is in various directions
Liquid can be conceptually divided into laminae?
Laminae are an infinite series of infintely thin tube each laminae slides against each other, with the outermost tube being static and the central tube flowing fastest
Why is heat generated during laminar flow?
Since laminae are sliding agaisnt each other this process generates heat through friction which results in energy losss and is responsible for resistance of flow through vessels
T/F: the loss of pressure down a pressure gradient can be thought of as due to frictional losses of flow through vessels
True
Poiseuille’s Law
R = (8vL)/pi(r^squared)
v: viscosity
L: vessel length
r: radius of the vessel
When is Poiseuille’s Law valid?
During laminar flow
What does resistance depend on the most strongly?
The radius of the vessel. Small decreases in radius size increase resistance largely
Small changes in the radius can have dramatic effects on perfusion
Many metabolites, innervation and hormones act to control vessel radius, changing its resistance and ultimately controllling flow and perfusion
Flow through two vessels/organs in series?
Flow thorugh both of the vessels/organs must be the same
Pressure gradients through vessels/organs in series?
Pressure gradients sum, each vessel genertes its own drop in pressure, so the total pressure gradient must increase
P = P1 + P2
Resistance for vessels/organs in series?
Total resistance is the sum of the individual resistance and the resistance of the serial network is greater than it was for each individual segment
Flow when vessels/organs are in parallel?
Flows sum
Pressure gradient for vessels/organs in parallel?
Pressure gradient for both must be the same because inlet pressure and outlet pressure are the same
Resistance for vessels/organs in parallel?
Resistance must decrease.
1/R = 1/R1 + 1/R2
T/F: vessel compliance depends on their structure?
True
Why are arteries, arterioles and small arteries less compliant?
Surrounded by muscle
Why are veins so compliant?
Veins have much less smooth muscle and can stretch to accomodate blood
Equation for compliance?
C = delta V/delta P
Aterial compliance vs Venous Compliance?
Arterial Compliance:
- Very steep slope = low compliance
- Large changes in pressure result in small changes in volume
Venous compliance:
-Very compliant
-Large changes in pressure result in large volume changes
What is total peripheral resistance?
Systemic vascular resistance, the resistance over the entire systemic system
How to calculate total peripheral resistance?
TPR = systemic pressure / flow
TPR = MAP/CO
Systemic pressure can be approximate by Pa
Equations for MAP ?
MAP = CO X TPR
MAP = HR X SV X TPR
Pulmonary vascular resistance(PVR)?
Resistance over the entire pulmonary system
How to calculate PVR?
PVR = pulmonary pressure(Pa-Pv)/flow
T/F: flow to the lungs is the same as the systemic circulation?
True, since the pulomanry and systemic circulation are in series
Is PVR greater than TVR?
No TVR is greater than PVR
What happens if you double capillary lengh but halve the total number of capillaries?
Parallel connections reduce resistance by removing half the capillaries you are removing half the parallel connections, Now more capillaries will be in series which will increase resistance and reduce flow
Name the four chambers of the heart?
- Left atria
- Right Atria
- Right ventricle
- Left ventricle
Describe the right hearts function?
Right atria recieves deoxygenated blood and pums it into the right ventricle which sends it into the pulomnary circulation
Describe the left heart?
Left atria recieves oxygenated blood which is pumped into the left ventricle and then into the systemic circulation
Name the five great vessels?
- Superior vena cava
- Inferior vena cava
- Left pulmonary artery
- Pulmonary trunk
- Right pulmonary artery
Arteries vs Veins?
Arteries:
- move blood from the heart
-Carry oxygenated blood (except for the pulmonary arteries)
Veins:
- bring blood back to the heart
-Carry deoxygenated blood(except for the pulomnary veins)
Role of the superior and inferior vena cavas?
Superior: brings blood to the heart from the top of the body
Inferior: brings blood to the heart from the bottom of the body
Role of the pulmonary trunk?
The right ventricle fills with deoxygenated blood and then contracts and sends blood to the pulmonary trunk which splits into the right and left pulmonary arteries which go to the lungs
Role of the pulmonary veins?
After blood is oxygenated in the lungs the blood reenters the heart via the left and right pulmonary veins which send the blood into the left atria
T/F: Left ventricle is larger than the right ventricle?
True
Left is higher pressure and needs to be larger
What is the interatrial septum?
This separates the left and right atria preventing them from communicating
What is the coronary circulation?
The hearts own circulation system
How does the coronary circulation work?
- Left and right coronary arteries branch off of the aorta right after the aortic valve and supply oxygenated blood to the heart muscle
- Deoxygenated blood returns via cardiac veins, and collects in the great cardiac vein which leads to the coronary sinue which drains into the right atrium
What is a heart attack?
Blockages of coronary arteries
What are the four cardiac valves?
- Tricuspid valve (between right atria and ventricle)
- Pulmonary valve(between right ventricle and pulmonary circulation)
- Mitral valve(between left artria and ventricle)
- Aortic valve (between left ventricle and the systemic circulation)
What are the Atrioventricular valves(AV)?
The tricuspid and mitral valves
Where do all four valves sit?
Fibrous ring, a structure between the atria and ventricles
What is the fibrous ring?
-Made up of tissue that isn’t excitable, the fibrous ring electrically isolates the atria and ventricles except through a small narrow channel
T/F: The atria beats a fraction of a second before the ventricles do?
True this is because the atria and ventricles are electrically isolated via the fibrous ring
What are the papillary muscles?
-Muscles that are attached to the valves via CT called the chordae tendinae
What is the function of the papillary muscles?
Papillary muscles are electrically connected to the ventricles and contract when the ventricles do, pulling on the chordae tendinae and generating a downward force toward the ventricles, This prevents the valves from prolapsing upward into the atria when the ventricles contract
What is the chordae tendinae?
Cartilagenous fibres that connect the papillary muscle to the valves and help prevent valve prolapsing and thus blood flowing in the wrong direction
What is the pericardial sac?
An inelastic bag that contains the heart and the roots of the great vessels
It is fluid filled
What is the function of the pericardial sac?
-Protects the heart physically
-Counters the act of friction to allow for smooth contraction of the muscle
-Provides pericardial fluid which lubricates the heart allowing it to freely contract
Layers of the pericardial sac/pericardium?
Outer layer: made of inelastic tissue
Inner layer: serous membrane that secretes the pericardial fluid
What is the Myocardium?
This is the heart muscle and this sits between the endocardium and epicardial layers
What is the Epicardium?
Outermost layer of heart tissue that is made up of specialized epithelial cells
What is the endocardium?
Innermost layer of heart tissue that is made up of endothelial cells
Blood flow from the right atrium.
- Right atrium
- Right AV valve
- Right ventricle
- Pulmonary valve
- Pulmonary trunk
- Pulmonary arteries
- Pulmonary arterioles
- Capillaries of the lungs
- Pulmonary venules
- Pulmonary veins
- Left atrium
- Left AV valve
- Left ventricle
- Aortic valve
- Aorta
- Arteries
- Arterioles
- Capillaries
- Venules
- Veins
- Vena cavae
Activation sequence of the heart?
- Sinus Node
- Atriventricular Node
- Bundle of His
- Left & right bundle branches
- Septum
- Purkinje fibers
- Left and right ventricular myocardium
Impulse at the sinus node?
- impulse originates in the sinus node of the right atria and causes the atria to contract
-The depolarization of the SN causes a wave to propagate through the atria causing atrial systole
How often doe the atria depolarize in a healthy individual ?
Roughly once per second
Activation of the AV node?
-AV node is a special cluster of cells that conduct electrical impulses very slowly
- Signal propagates very slow through the AV node
Left & Right bundle branches?
-Fast conducting cells that conduct the signal rapidly
Purkinje fibres activation?
-Form electrical connections with the left +right ventricular wall
Left & right ventricular myocardium?
The ventricles contract from the inside out (endo to epi)
What parts of the activation sequence have pacemaking activity?
-The SA node is the main pacemaker
- The AV node and cells of the His-Purkinje system can spontaneously beat if the SA node fails to fire
What prevents impulses from propagating to rapidly?
The AV node
What is atrial tachycardia?
Electrical impulses impinging on the AV node frequently and it effectively acts like a filter and prevents the ventricles from firing too quickly
What is the AV node?
It is the narrow channel found in the fibrous ring between the atria and the ventricles
What is pacemaking?
The idea that with every heartbeat the sinus node initiates an impulse
Heart’s natural pacemaker?
Sinus node
Why do the ventricles fire after the atria?
The AV node propagates the signal slowly which allows the artia to finish contracting, which helps to optimize filling of the ventricles
What are the left & right bundle branches?
-They run on either side of the septum and they activate the left and right ventricles synchronously
Right bundle branch vs Left bundle branch?
Right Bundle branch: completely surrounded by CT which means that the electrical signal does not activate the septum
Left bundle branch: not completely surrounded by CT
In what direction is the septum activated and by which bundle branch ?
Septum is activated from left to right and top to bottom via the left bundle branch
What are the purkinje fibers?
Highly branched structures that spread from the bundle branches to the rest of the ventricles
-these cells sit on the inside of the ventricles
Do purkinje fibers contract?
-Purkinje cells barely contract but they do propagate signals very rapidly
-Prukinje cells can acts as back up pacemaking cells
Why do the ventricles contract at the same time?
To maximize the amount of pressure generated
What are myocytes?
Muscle cells that can geenrate action potentials and cause their neighbouring cells to fire
What connects myocytes together electrically?
Gap junctions
What are intercalated disks?
Connective proteins structures and gap junctions that connect myocytes to one another
What is a gap junctions?
specialized pores that connect two cells, these allow the flow of Na+, K+ and Cl- and Ca2+ between cells (permeable to all important ions responsible for maintaining resting potential and generating an action potential)
T/F: Gap junctions occur primarily at the ends of cells and longitudinally?
True
What is a local circuit current?
currents that occur due to the passive spread of charge on either side of the membrane
What causes an action potential ?
LArge current flows across the cell membrane through voltage gated channels
What happens prior to an action potential and voltage gated ion channels opening?
- Cell A is depolarized (positive charges on the inside and negative on the outside). While cell B is polarized(positive charge on the outside)
- Positive ions typically potassium since the concentration is high in the cell move through gap junctions between cell A to B
- On the outside of the cells sodium ions move from cell B to cell A but do not yet enter the cell
- The net flow of ions from the inside of cell A to B causes cell B to start to depolarize
After cell B depolarizes?
When cell B depolarizes a cascade of events occur that cause voltage gated channels to open between the outside and inside of cell B that result in an action potential in B
T/F: Sodium concentrations are high outside of the cell?
True
T/F : K+ concentrations outside the cell are high?
False
Electrocardiograph
The device that makes the measurement for.an electrocardiogram
Electrocardiogram
Extracellular recording of the electrical activity of the heart, in the form of one or more time series
Each box on an ECG measure ?
200 ms long
What do leads measure?
Potential differences between different locations on the body
Lead vs Electrodes?
Lead: graphical desription of the electrical activity of the heart created by analyzing several electrodes
Electrodes: Conductive pad attached to the skin that enables the recording of electrical currents there is Na+ in the gel of the pad which allow us to sense changes that are local to the surface of the body
What is an electrode pair?
Two electrodes used together to measure the potential difference between two points. This creates a single lead in the recording system
T/F: The number of physical electrodes is usually less than the number of lead?
True
What is the ground electrode?
An electrode is added to the right angle and isn’t used as part of a lead but is needed to reject electronic noise in other leads
Transverse plane?(Horizontal)
Chest leads detect any positive charge coming out to them
These include the chest leads
Coronal Plane(vertical)
positive charge going out from the heart
These include the RA, LA, LL electrodes
And the Limb Leads I, II and III
Lead I Limb Lead
Goes from RA to LA
Limb Lead II
Goes from Right arm to left leg
Limb Lead III
Goes from Left arm to Left leg
Bipolar Leads
Measure the electrical potential between two electrodes
Ex. The Limb Leads I, II and III
Unipolar leads
Measure the electrical potential at a single electrode and compare it to a combined reference point
ex. Chest leads: V1, V2, V3, V4, V5, V6
Unipolar limb leads: aVR, aVL, aVF
Exploratroy Electrode
An electrode placed on the skin that will detect the electrical potential at a specific location
In bipolar limb leads two exploratroy electrodes aare used
In unipolar limb leads one exploratory limb lead is used and one reference limb lead
Reference electrode
Serves as a baseline/neutral point in which the exploratory electrodes are compared to in unipolar leads
How much is the potential difference seen in an ECG ?
+ 1 mV
What is the baseline of the ECG?
All waves start/end at the baseline. It is determined by the segment between the P-wave and beginning of the GRS complex
What activations are not seen on the ECG?
- Sinus node firing
- AV node activation
- His bundle
- Left bundle branch
- Purkinje fibres
What does the P-wave represent?
Atrial Activation
What does the Q-wave represent ?
Septum activation
What does the R-Wave represent?
Ventricular activation
What does the S-wave represent?
Late activation of the ventricles
What does the T-wave represent ?
Ventricular repolarization
Where is the P-R segment and what does it represent?
-Flat segment from the end of the P-wave to the start of the QRS complex
-Represents the time delay between the end of atrial repolarization and the beginning of ventricular activation
-Baseline
Where is the P-R interval and what does it represent?
-From the start of the P-wave to the start of the QRS complex
- Represents the AV transit time since the AV node is activated during the P-wave
-This interval includes atrial activation
What does a long P-R interval indicate?
A long AV transit time which could indicate an AV block
Where is the S-T segment and what does it represent?
-End of the S wave to the beginning of the T-wave
- It is the time between ventricular depolarization and repolarization
What does an elevated S-T segment mean?
Some tissues have abnormal APs typical of infarction
Where is the Q-T interval and what does it represent?
-Starts at the beginning of the Q-wave and end at the end of the T-wave
-proportional to action potential duration
What does a long Q-T interval indicate?
Problems with ventricular repolarization and can lead to arrhythmias
What is the QRS interval and what does it represent?
-Beginning of the Q-wave to the end of the S-wave
-Represents the entire activation of the ventricles
What does a long QRS interval mean?
-More than 100 ms = slow activation of the ventricles and possible problems in the His purkinje (bundle branch block) or slow conduction in cardiac muscle
Segment vs Interval?
Segments: flat
Interval : includes waves
What causes a deflection in the ECG?
potential differences between two extracellular electrodes
If all cells of the heart are depolarized what is the potential difference?
There is none
No wave on the ECG
T/F: Repolarization and Depolarization both result in deflections?
True
How ar evoltage differences calculated?
substracting the voltage at the negative electrode(cathode) from the positive one(anode)
V = (+) - (-)
If cell A is depolarized and cells B and C to the right of it are polarized will the voltage be positive or negative?
Depolarization wave is going toward the anode
V = +
Repolarization what is going toward the cathode
V = +
If cell A is polarized and cells B and C are depolarized to the right of it what will the voltages be?
Depolarization is going toward the anode
V = -
Repolarization is going toward the cathode
V = -
What is the voltage when depolarization goes toward the anode(+)?
Positive
What is the voltage when depolarization is going toward the cathode(-)?
Negative
What is the voltage when Repolarization is going toward the anode(+)?
Negative
What is the voltage when the repolarization goes toward the cathode(-)?
Positive
Why does the T-wave not being negative not make sense?
T-wave is the repolarization of the ventricles, since the QRS-complex which is the depolarization of the ventricles is positive the T-wave should be in the opposite direction but instead it is also positive
Why is the T-Wave in the same direction as the QRS-complex?
The repolarization wave of the T-wave travels in the opposite direction as the QRS-wave.
There is a gradient of action potential durations, with the cells on the endo having longer APs than those on the epi this means that the ventricles repolarize from the outside in. Depolarization occurs from epi to end
When not firing action potentials what potential are the cardiac cells at?
Negative potential (resting potential)
-Near the nernst potentia l for potassium since the membrane is permeable to potassium (near -80 mV)
Do cells with pacemaking current have resting potentials?
No
Stages of the ventricular action potential?
- Fast upstroke: from -80 mv to +20mV (1-2msec)
- Plateau: long action potential duration of about 250-300 ms where the cell remains relatively depolarized
- Repolarization
What cells with pacemaking current do not a have a resting potential?
-SA node cells
-AV node
-Purkinje cells
How do pacemaking cells fire an action potential?
They slowly depolarize until they reach threshold, they have shorter AP duration
What gives cardiac cells there resting potential?
Prior to APs cardiac cell membranes are relatively permeable to potassium (K+) and impermeable to sodium and calcium. Resting potential sits near the nernst potential for potassium -80mV
How do cells get depolarized?
Local circuit currents start to depolarize the cell, once a certain threshold voltage is reached the voltage gated sodium channels change their shape and open. This alllows sodium to enter the cell which generates the fast inward sodium current and causes the cell to depolarize
What happens after the voltage gated sodium channels open?
Shortly after they open they close. The potassium channels sense voltage and the depolarization caused by the sodium in turn causes the permeability for potassium to drop. The calcium channels then open which creates an influx of Ca++ into the cell which triggers calcium induced calcium release from the SR
How does the repolarization of the cell occur?
Potassium permeability increases and this allows a large amount of K+ to leave the cell, resulting in repolarization
What generates the depolarization of the sinus node?
Influx of Ca++,
What generates the depolarization in the purkinje fiber action potential?
Influx of Na+
Do the purkinje fibers have a rapid upstorke?
Yes
Do the sinus nodeshave a rapid upstroke?
No
What is a fast action potential ?
Cells that have a fast upstroke velocity generated by the fast influx of Na+ through voltage gated sodium channels
What cells undergo fast action potentials ?
- Ventricular muscle
- Atrial muscle
-Bundle of his
-Bundle branches
-Purkinje fibres
What is a slow action potential?
Action potential with a slow upstroke velocity generated by the slow influx of Ca++ through calcium channels
What cells have slow action potentials?
-SA nodal cells
-AV nodal cells
T/F: upstroke velocity affects conduction velocity?
True, if cell A starts an AP it will cause it neighbour cell B to depolarize and reach threshold faster if that cell A has a fast upstroke
What influences conduction velocity?
Gap junction connectivity and the upstroke velocity
Refractory period?
Length of time between two action potentials where the cell cannot fire again
Why do we not see the repolarization of the atria on the ECG?
The atria repolarize just as the ventricles depolarize therefore there electrical difference is hidden
When does the atrial cell fire in the idealized ECG?
In the middle of the P-wave
When does the ventricle cell fire in the idealized ECG?
Right as the atria are repolarizing generating the R-wave
Normal sinus rhythm
ABout 70 bpm
Bradycardia
An abnormally slow rhythm less than 60bpm
Tachycardia
An abnormally fast rhythm more than 100 bpm
When are bradycardia and tachycardia physiological(healthy)?
In athletes
Respiratory sinus arrhythmias?
When the sinus rate increases as you breathe in and slows as you breathe out
Pathological tachycardia vs pathological sinus tachycardia
If at rest your heart rate is over 100bpm
It is called pathological sinus tachycardia if the rhythm was driven by a rapidly beating sinus node
Complete AV block, ECG?
No impulses from the SA node make it to the ventricle
ECG: shows P-waves but will have a missing QRS and T-Waves
May still have QRS and T-waves due to the backup pacemaking sites but they won’t be synchornized to the P-waves
Partial AV block, ECG?
Every second or third impulse makes it to the ventricle
ECG: will show all waves but there will be a long pause between the waves
What is a Premature ventricular contraction (PVC) ?
When regions in the ventricles can, under pathological codnitions, generate activation waves on their own
The exciation: coupling contraction
As the AP comes along the muscle cell it causes L type Ca2+ channels in the T-tubules to open. This causes Ca++ to enter the cytoplasm which then leads to the opening of the Ryanodine receptors in the SR to open. This allows a large influx of Ca++ from the SR to move into the cytoplasm where it causes the cardiac muscle cells to contraction
WHy is there a delay between AP and muscle contraction?
Takes a while to release Ca++ from the SR
Ectopicpacemaker?
When you have a group of heart cells outside of the sinus node that spontaneously depolarize causing an extra beat out of time of the normal heart contraction
How are PVCs seen on the ECG?
They are easy to spot since the ddirection and velocity changes compared to sinus rhythm
Parasystole?
Arrhythmia causes by frequent PVCs often benign
-Reduces the efficiency of the heart if you have a bunch of them
T/F: PVCs can trigger reentry?
True
Reentry?
When the excitation pulse generated by the PVC circles back on itself and repeatedly re-excites the cardiac tissue
Ventricular Reentrant Tachycardia
When the PVC causes reentry and the sinus node no longer drives activity and the rate of ventricular contraction is greater than 100bpm
The heart can now. no longer pump blood in an efficient manner
Ventricular Fibrillation cause
When the ventricular reentrant tachycardia degenerates into a much more deadly condition
Characteristics of Ventricular Fibrillation?
- Small reentrant waves travelling in the heart
- Ventricles no longer contract in a coordinated way
- Drop in perfusion pressure
Deadly if not treated in minutes
How do we treat ventricular fibrillation ?
The use of an AED to cardiovert the patient
Atrial Fibrillation
When the atria fire out of synchrony with themselves
caused by PAC (premature atrial contractions)
Is Atrial fibrillation deadly?
No, since the atria only increase the efficiency of the heart and don’t maintain BP like the ventricles
How does the AV node respond to atrial fibrillation?
Impulses from the atria are triggering the AV node in an irregular way. The AV node helps by filtering out the impulses and preventing the ventricles fron contracting too fast
How to treat atrial fibrillation?
Pulmonary vein isolation
What is a sock array ?
Records electrical activity across the entire surface of the heart by having electrodes all around the heart (tells us where waves are propagating)
What is the morphology of reentrat waves?
Spirals
What is the morphology of ventricular fibrillation waves?
Spiral waves brwak into wavelets
What is the morphology of a normal wave through the heart?
Propagates in one signular direction across the heart
What ions are permeable during the upstroke of fast APS?
K + and Na+
What ions are permeable during the plateau of fast APS?
Ca++
What ions are permeable during the repolarization of fast APS?
K+
What ions are permeable during the upstroke of slow APS?
Ca++
What ions are permeable during the plateau of slow APS?
Ca++
What ions are permeable during the pacemaking of slow APS?
K+ and a tiny bit of Na+
What ions are permeable during the repolarization of slow APS?
K+
Desribe the Cardiac cycle starting prior to sinus node activation?
- AV valves are open and the pulmonary and mitral valves are closed. The atria and ventricles are filling with blood
- Atrial systole: the atria contract
- Atrial kick : Ventricles are filled a bit more due to the atrial contraction
- Ventricles now contract and the AV valves shut preventing back flow
- For a brief moment all valves are closed and pressure in the ventricles rises(isovolumetric ventricular contraction)
- When the ventricular pressure exceeds that in the pulmonary trunk the the pulmonary valve open
- Blood flows into the pulmonary trunk
- Ventricles relax and the pressure drops
- The pulmonary valve closes again and the AV valves open and the ventricles fill agains
When is ventricular volume at its max?
During atrial systole
When is ventricular volume at its min?
Beginning of ventricular diastole
What is the first heart sound caused by?
Generated by the mitral and tricuspid valves closing at the beginning of ventricular systole
What is the seond heart sound caused by?
Generated by the closing of the pulmonary and aortic valves at the beginning of ventricular diastole
T/F: Extra sound can exist in diseased states?
True
Describe ventricular presure throughout the cardiac cycle?
- Pressure starts off lower than atrial pressure(allows blood to flow from atria to ventricle when filling)
- Pressure in the ventricles increases during ventricular systole as all the valves are closed
- Ventricular pressure increase above that in the pulmonary trunk which causes the pulmonary valve to open
- When the pulmonary valve open blood leaves the ventricle decreasing pressure
- Pulmonary valve closes as soon as the ventricle has lower pressure than the pulmonary trunk
Marker of the end of ventricular systole in pressure graft?
Dicrotic notch occurs after closing of the pulmonary/aortic valve
Does pressure in the ventricles reach 0?
Yes, pressure in the ventricles during diastole reaches almost 0
Why does the pressure in the aorta remain elevated thorughout the entire cardiac cycle?
Due to the Windkessel Effect
- Large vessels coming out of the heart are elastic and store energy in them during the massive increase in pressure at the peak. They then release this pressure slowly during the rest of the cardiac cycle (this is responsible for maintaining your BP in your system during diastole)
Windkessels Effect lowers the maximum pressure and raises the minum pressure?
yes
What happens if you have stiff arteries?
This means the aorta will not stretch as much during ventricular systole which means it will be under more pressure(higher systolic pressure) and during diastole since you stored less energy you lose more (lower diastolic pressure)
What happens if you have very compliant arteries?
This means during ventricular systole the aorta will stretch a lot causing lower systolic pressure and during diastole since the aorta will have stored more it will have a higher pressure
What is the isovolumetric ventricular contraction?
-This is at the beginning of ventricular systole
-All of the valves are closed
-The pressure in the ventricle is increasing
What is ventricular ejection?
-This occurs during the second half of ventricular systole when the pressure in the ventricles becomes higher than in the aorta/pulmonary trunk the pulmonary and aortic valves open
- Blood then flows from the ventricles
-Ventricle pressure peaks then falls
Isovolumetric Ventricular Relaxation?
-Ventricular contraction stops and the pressure in the ventricles decrease
-When pressure is below that in the aorta the aortic valve closes
-Aortic pressure remains high
- When the valves close, we enter a phase of ventricular relaxation with no change in ventricular volume
-Atria are filling
Ventricular Filling?
-Pressure in the atria is higher than the ventricles, blood flows into the ventricles
-AV valves are open
-Sinus node then fires lead to atrial activation which pushes more blood into the ventricles(atrial kick)
Aortic pressure?
Highest when the aortic valve opens and blood enters from the left ventricle
Lowest after contraction but still remains elevared due to Windkessel
Filling Phase
-From the beginning of diastole the ventricles start to fill
-Pressure in left ventricle lower than left atria
-Mitral valve open
-Ventricle mostly fills
P-Wave
Atrial contraction + artial kick
QRS wiggers
-Presssure in left ventricle increases
-Pressure in ventricle is higher than the atria about 10 ms after contraction starts(mital valve closes)
-Pressure increases(isovolumetric phase)
T/F: Cardiac events in the left and right heart are identical ?
Both sides of the heart undergo the same events but the left heart which goes to the systemic circulation undergoes higher pressures
3 indirect methods of blood pressure measurement?
- Palpitation
- Ausculation
- Oscillometry
What is needed for indirect measurement of BP?
-Blood pressure cuff that inflates around the arm to the point where blood flow is obstructed
-Need a valve that allows slow release
-Attachment measures the pressure in the cuff
Aneroid Sphygmomanometer
-Used for all indirect blood pressure measurements
- Consists of a cuff with a bladder, an inflating bulb,a needle valve and an aneroid gauge (measures pressure)
How to measure BP using palpitation?
- Cuff is inflated so pulse can no longer be felt, pressure exceeds that of the aortic pressure
- Pressure in the cuff is slowly released via the valve
- As soon as the pulse is felt again, this gives the measure of systolic pressure
- As you decrease the pressure more you get past diastolic pressure but cannot be measured
How to measure BP using Auscultation?
- Cuff is inflated to no pulse, cuff restricts flow.
- Slowly release pressure in the cuff, as soon as flow starts again turbulent flow can be heard with a stethoscope(Systolic pressure)
- Continue release the cuff when turbulent flow is no longer heard you have reached laminar flow which is the diastolic pressure measurement
What are Korotkoff sounds ?
Sounds heard during Auscultation measurement of BP
What is Oscillometry?
-How BP is measured in modern day
-Measure oscillation in the cuff pressure caused by cardiac pressure waves
Frank Starling Mechanism
The heart can adjust its force of contraction to increase stroke volume(increase amount of blood pumped in one beat) in response to increased blood volume in the ventricles
Ex. Exercise
T/F: Amount of force generated during contraction is proportional to the amount of stretch imposed on the cell before contraction?
True, greater the filling = greater the contraction
What happens when ventricular filling increases?
If ventricles are filled more, they stretch more which leads to an increase in stroke volume and contraction
Preload?
The amount of ventricular wall stretch
-Just measure end diastolic volume
How does Preload change during exercise?
During exercise your cardiac output increases(increase in amount of blood pumped per minute) which causes the preload(ventricular wall stretch to increase)
Does. the frank starling mechanism require neural control or hormonal regulation?
No
Autoregulation
Mechanism used to maintain flow wihtout nerural or hormonal regulation
Example of Autoregulation?
If you lower coronary perfusion pressure the rate of coronary flow will drop since flow = delta P/R. However, after a few seconds flow increases. This means that resistance dropped to compensated the decrease in pressure
Autoregulatory Range?
range of blood pressures that can be at least partially compensated for by this mechanism (40 mmHg - 160 mmHg)
Myogenic Autoregulation
Stretch activated channels in vessels walls, when the wall is stretched the channels open and release Ca++ which causes the vessels to restrict. The increased restriction reduces the effects of increased pressure on blood flow.
-Activated by differences in vessel wall stretch
Metabolic Autoregulation
When metabolic demand increases blood vessels dilate more to allow more blood flow to the tissues
-This is activated by an increase in metabolites and or decrease of O2
When PO2 decreases blood vessels dilate to allow more blood flow which allows more O2 to reach tissues
Are Metabolic and Myogenic autoregulation mechanisms negative feedback loops ?
Yes
Desribe Myogenic autoregulation when arterial pressure decreases?
Arterial pressure decreases, leading to less blood flow. Which means vessel-wall stretch will be decreased. Myogenic autoregulation will thus decrease resistance in vessel walls by decreasing Ca++ release and then blood vessels will dilate which will restore normal blood flow
Describe Metabolic regulation when blood pressure increases?
Blood pressure increases which causes an increase in blood flow. This will cause aan increase of O2 to tissues and decrease of metabolites which will lead to blood vessel constriction and restoration of blood flow.
How does exercising a lot increase blood flow?
Exercise increases metabolic activity which increases metabolites and decreases PO2. This causes blood vessels to dilate because of metabolic autoregulation and increases blood flow to the organs
What does the sympathetic system modulate?
HR, SV and TPR
What does the parasympathetic system modulate?
HR
Cell bodies of the parasympathetic system?
Located in the brainstem
Axon projects from the brainstem onto a ganglion in…
The cardiac fat pads
Desribe the firing of action potential in the parasympathetic control?
- Starts in the brainstem then propagates down the preganglionic axon
- Ach neurotransmitter is released onto the nicotinic receptors in the cardiac fat pads which causes then to fire an action potential
- Postganglionic axon propagates the AP and releases ACh onto muscarinic receptors in the sinus node
How does parasympathetic control the HR?
Causes it to decrease
What does Atropine do?
Blocks muscarinic receptors which prevents the parasymapthetic system from lowering the HR
Cell bodies of the sympathetic system?
Located in the spinal cord
Propagation of AP from the sympathetic system ?
- Preganglionic axon projects from the spinal cord to ganglio right next to the spinal cord
- Preganglionic axon releases ACh onto nicotinic receptors in the ganglia causing it to fire an action potential
- AP propagates down the postganglionic axon and releases norepinephrine onto the beta adregenergic receptors of the sinus node
How does the sympathetic system affect the HR?
Causes it to increase
What do Beta agonists do?
Binds the adrenergic receptor and increases HR and increase stroke volume
What do beta antagonists do ?
Binds the adrenergic receptor and blocks it lowering HR and decrease stroke volume
How does the sympathetic system increase HR?
- Increases the upstroke velocity of the AP which increases conduction velocity
- Decrease action potential duration which reduces refractory period
How does the sympathetic system affect stroke volume(blood pumped out) ?
Norepinephrine increases contractility by changing various channel condcutance which increase Ca++ concentrating. This increase force and contraction which increase blood pumped. Reduces duration of the contraction
Frank Starling vs Systemic System
Frank Starling increases the stroke volume due to an increase in end diastolic volume
Sympathetic system increases contractility and SV without increasing the EDV just by increasing force and contraction
Vessel Tone
State of contraction of the smooth muscle cells in the walls of the vessel (degree to which a blood vessel constricts relative to its maximum diameter)
What system can control blood vessel diameter?
Sympathetic system
What receptors are found on Blood vessels?
Alpha-adrenergic receptors
What happens if given alpha-agonist?
Binds to alpha-adrenergic receptors on blood vessels and causes them to constrict
What blood vessels cannot be controlled?
Capillaries since they have no SM
How does the sympathetic system affect blood vessels?
Norepinephrine binds to alpha-adrenergic receptos on blood vessel walls and causes them to contract increasing resistance
How does blood vessel diameter change things?
MAP = HR X SV X TPR
Impacts perfusion pressure
Alpha-agonists?
activate alpha adrenergic receptors resulting in an increase in TPR and thus MAP
Constriction of blood vessels
Alpha-blocker?
bind to alpha adrenergic receptors and block NE from them decreasing TPR and MAP
Adrenal Glands
-Part of the sympathetic nervous system
-Two situated above the kidneys
-Come from cells of the neural crest
-No ganglion
-Innervated by a preganglionic axon from the sympathetic system that releases ACh
What do cells in the adrenal glands make?
Synthesize and release catecholamines(norepinephrine and epinephrine) into the bloodstream
The adrenal glands have a global effect on all the tissues because they get perfused throughout your entire system
T/F : Norepinephrine and Epinephrine are both alpha and beta antagonists?
True, they cause an increase in TPR and HR and thus MAP
Two mechanisms that control BP?
- Baroreceptors(act quickly by changing HR, TPR and SV)(very strong)
- Renal System (acts slowly and controls total fluid volume)(strongest)
Where are baroreceptors located?
In the aortic arch and carotid sinus, receptors here sense pressure(sensory arm) and then signal to the brainstem which activates the motor arm of the reflex
What type of receptors are baroreceptors?
Mechanoreceptors
What do baroreceptors do?
With each heart beat the aorta and carotid sinus stretch which open channels in the baroreceptors located there which then signal the brainstem
How does an increase/decrease in BP affect baroreceptor firing rate?
Increase in BP: Increase in baroreceptor firing rate
Decrease in BP: Decrease in baroreceptor firing rate
Orthostasis?
Ability to maintain MAP when standing
What happens when we stand up?
400mL of blood flows from the trunk into the legs (drop in central blood volume)
This results in a drop in BP
Hydrostatic forces lower BP
Pressure increases and since veins have high compliance blood pools in the legs
-Lower CO, VR drops, Lowers SV
Baroreceptors when we stand up?
Baroreceptors fire less when we stand up which increases sympathetic tone and decreases parasympathetic tone
Lower baroreceptor results in:
- Increase in HR (sympathetic + parasympathetic)
- Increase in SV by increasing contractility(Sympathetic)
- Increase TPR by contricting arterioles(sympathetic)
- Constrict capacitance vessels(sympathetic via alpha receptors)
- Increase venous return, and SV via Starling
- All the increase MAP
Baroreceptors are a negative feedback system?
- Low MAP
- Decreased Baroreceptor firing
- Increase sympathetic tone and decreased parasympathetic tone
- Increased MAP
- Increased Baroreceptory firing
Peripheral Chemoreceptors?
Chemoreceptors close to the baroreceptors in the carotid and aortic body that sense O2, CO2 and pH of the arterial blood.
Role of the peripheral chemoreceptors?
Cause you to breathe more frequently if you are short of breath or need to expel more CO2
Two systems of renal control of BP
- Pressure diuresis
- Renin Angiotensin Aldosterone(RAA)
Role of the kidneys?
Maintain ion levels in the plasma and remove waste
- Nephrons expel (H2O + Waste)
Pressure diuresis during increased arterial pressure?
Increased arterial pressure results in higher filtration rate by the kidneys, which increases urinary loss and decreases plasma volume and blood volume. Stroke volume then decreases because the heart fills less which then decreases MAP.(Negative feedback)
Does increases pressure result in more sodium loss?
Yes more sodium is filtered out which helps to draw even more fluid out.
Pressure sensing in kidneys?
-Changes in filtration rates are sensed as changes in excreted sodium by the kidneys
-When the kidneys sense the decrease in sodium they release renin
Pressure sensing by the brain via osmoreceptors
- Indirectly via osmoreceptors
Osmoreceptors in the hypothalamus check the osmotic value of your blood (how thick it is) and can cause changes to increase the amount of liquid in your system
Pressure sensing by the brain via baroreceptors
- Baroreceptors result in ADH release from neurons in the hypothalamus(more important for large fluid loss(hemorrhage))
-Release vasopressin
RAA System I
- MAP decrease which results in the release of renin
- Renin converts angiotensinogen to angiotensin I
- ACE(enzyme) in the lungs converts angiotensin I to angiotensin II
- Angiotensin II is a vasoconstrictior which increases TPR and thus MAP
Where is angiotensinogen made?
Liver
Where is ACE found?
Lungs produced by the pulmonary endothelium
Vasopressin
ADH (antidiuretic hormone), synthesized in the hypothalalmus and released by the pituitary gland
What triggers the release of vasopressin?
Low output from arterial baroreceptors(drop in blood volume + MAP)
How does ADH increase MAP?
-Increases TPR
- Renal Na+ and H2O excretion decreases
-Plasma blood volume increase
-Blood volume increases
-Venous return increases
-EDV increase
-SV increase
-Co increases
RAA System III
- MAP decreases which results in an increase in renin from the kidneys and leads to production of angiotensin II (RAA I)
- Angiotensin II binds receptors of the adrenal glands and causes the release of aldosterone
- Aldosterone binds the kidneys and causes Na+ & H2O retention which increase CO and MAP
Aldosterone receptor antagonists?
-Binds to aldosterone receptors in the adrenal glands and block them
-Decrease MAP and BP
Angiotensin II receptor blockers?
-Prevents binding of angiotensin II in the brain, arterioles and adrenal glands
-Decreases BP and MAP
ACE inhibitors ?
-Prevent conversion of angiotensin I to angiotensin II
-Acts near the lungs
-Decrease BP
Renin Inhibitors?
-Prevents conversion of agiontensinogen to angiotensin I
-Decreases BP
MAP stays relatively constant while standing up?
Yes due to the baroreceptor reflex which acts within seconds
When standing up how much does CO fall?
From 6 to 4.5
How much does SV fall from standing up?
50%
Since CO = HR X SV what is HR when standing up?
0.75 = HR x 0.5
HR = 1.5
When standing HR increases by 50%
Since CO is 0.75, how is MAP maintained?
MAP = CO X TPR
MAP = 0.75
TPR must increase to maintain MAP
What is a muscle pump?
When you are standing for a long time you need to flex your calf muscles to increase your venous return which in turn increases SV and decreases your need for a high HR. THis prevents you from faiting due to standing for a long time. Moves fluid from your legs and into your trunk
Two reasons why you faint when standing for too long?
- Blood pools in the leg veins which lowers your neous return
- Loss of plasma volume
How do you lose plasma volume when standing?
Water passes to the interstitial space through the capillaries when standing. High pressure in the legs increases plasma volume loss. This results in a drop of VR. When you do the muscle pump blood flows out of the veins and reduces pressure in them reducing loss of plasma to interstitial space
After 15 minutes of standing how much plasma volume can you lose?
750mL
How much plasma do we lose on average per day?
4L per day is lsot and returned back to the blood
How is plasma volume drained?
By the lymphatic system which has vessels that drain around the heart. Thoracic duct and right lymphatic duct connect to the large veins which drain into the heart.
What causes plasma to move from the capillaries into the interstitial space?
Starling Forces create pressure gradients which cause the plasma to move into the interstitial space
Regional blood flow during exercise?
Blow flow to muscles increases the most by 12x
Blood flow to skin increases 5x
Blood flow to heart increases 3.5x
Blood flow everywhere else(ex. gut) decreases
What is the max HR of a person?
max HR = 220 -age
Heart rate during exercise can increase from 70 bpm to over 200 bpm what is the cause?
Increased sympathetic tone and decreased parasympathetic tone
T/F: SV increases as exercise intensifies?
False, SV increases modestly and then dips as the intensity of exercise increases even as HR increases.
Why does SV not increase as exercise intensifies and HR increases?
The diastolic period is greatly reduced(less relaxation phase of the heart), so there is not enough time to fully fill the ventricles whic results in the heart beating prior to reaching its optimal volume. The end diastolic falls and via the frank starling mechanism the SV is reduced
T/F: The stroke volume is still higher than SV at rest even during intense exercise?
True, the sympathetic system causes contractility of thr heart to increase which increases the SV but at high HR the SV does decrease due to lower EDV
T/F: CO increases linearly with exercise intensity?
True
How does TPR change during exercise?
MAP increases by 20% and CO increases 3x
MAP = CO X TPR
1.2 = 3 X 0.4
TPR must drop to 0.. The blood flow to muscle increases to meet energy and O2 needs, so perfusion to muscle increases enabled by a drop in resistance
Does TPR decrease in all organs/tissues during exercise?
NO, in organs not needed for exercise such as the gut and kidneys resistance increases but resistance in the skin, muscles and heart does decrease
How much does O2 consumption change in exercise?
Increase by about 9X
250mL/min to 2000mL/min
At rest how much O2 do the muscles consume?
100 mL of arterial blood contains 20mL of O2 and 100mL of venous blood contains 15mL of O2 therefore the muscles extract 5mL of O2 at rest
During exercise how much O2 do the muscles extract?
100 mL of arterial blood contains 20 mL of O2 and 100mL of venous blood contains 5mL of O2. Therefore the muscles extracted 15mL of O2 which is 3X as much than at rest
Why does O2 consumption increase by 9X?
- CO increases by 3X
- O2 consumption increases by 3X
T//F: Metabolic autoregulation overrides the parasymapthetic and sympathetic systems during exercise?
True
Name all CV parameters that increase during exercise?
- CO
- HR
- SV
- MAP
- PP
- EDV
Name all CV parameters that decrease during exercise?
- TPR (only in organs needed for exercise)
Does training affect max heart rate?
NO
What does training affect?
Increases CO
T/F: At the same work level an untrained person has a higher heart rate than a trained person?
True
What causes CO to increase overtime due to training?
CO = HR X SV
An increase in SV results in increase in HR
Does contractility increase with training?
Yes,
-hypertrophy occurs where the heart cells get bigger
-resting HR falls and SV increases
Heart gets bigger when you exercise?
Yes, this increases the total efficients of your heart by increasing the muscle mass in your heart. Your heart will now pump fewer times to pump the same amount of volume
People that exercise are at risk of arryhtmias?
Since they have reduced cardiac action potential times
