Physiology Flashcards
What is prepotential?
Slow polarization of cell that leads to action potential
What is the path of conduction? Please include depolarization
SA node –> AV node and Atrial myocytes -> Bundle of His –> Bundle branches –> Purkinje system –> Ventricular myocytes
Why is there a delay between atria and ventricle depolarization? How does the delay happen?
So atria can completely depolarize and top off ventricles befor ethey depolarize and contract.
The Cardiac Skeleton helps keep the depolarization away from ventricles until the signal can go down the AV node (which is way slow)
Describe the channels in conductance of ventricular muscle action potential?
Phase 0: Depolarize: Fast Na+ channel opens
Phase 1: Dip: Fast K + channels open, Na gates close
Phase 2: Plateau. Ca++ open and K + close. They equilibriate.
Phase 3: Repolarize: Ca++ close, K + open
Phase 4: Resting: K+ closes
Describe the channels in conductance of the SA nodes?
Phase 4: Na (f) channels open slowly as to not start a depolarization.
Phase 0: Ca++ open. Since there’s already Na in there, it’s easier for the SA to start a depolarization here.
Phase 3: Close of Ca++, Open special K +
What are importnat difference between SA node and Muscle action potentials?
SA Node is:
- Automatic
- Uses Ca ++ instead of Na for depolarization
- Unstable resting potential
- No phase 1 or 2
What increases conduction velocity?
Higher inward of Na
Slower inward of Ca
Larger fiber is faster (AV has smaller fibers)
What does chronotropic mean?
Dromotropic?
Inotropy?
Chronotropy: Changes rate of depolarization of SA node
Dromotropic: Speed of conduction
Iontropy: Contractility
Know your Excitation steps: 1) How does Ca++ get into the cell?
2) What happens upon entering?
…..
1) AP moves along sarcolemma innto T tubules and opens voltage gated calcium channel
Dihydrophyridine receptors (DHP) which are L type Ca channels
2) Calcium binds to Ryanodine (RYR) receptors, which releases a calcium stored in the cell.
3) Ca binds troponin C
4) Tropomysin moves
5) Myosin actin crossbridges
6) tension is prodcued
What effects the amount amount of tension?
How can it be increased?
Depends on Calcium stores ICM.
CaATPase sucks Ca back up and reuses it. So the Ca ATPase and the NXC (Na Xchange Ca) increase Ca stores.
What does cardiac muscle have that is different from skeletal muscle?
- Intercalated discs
- Gap junctions
- T tubules are larger. Contain more calcium.
What is the gap junctions role in syncing contraction?
How does it do this?
Gap junctions allow RAPID conduction, allowing simultaneous and coordinated contraction.
Decreases the internal resistance of the cell so that the action potential can go super fast.
What is the role of extracellular calcium in muscle contraction?
Higher calcium influx = higher calcium released into the cleft = higher calcium uptake from ATPase and NXC = more stored Ca2+ = more released on the next action potential = more tension = increased strength in muscle contraction
How does the heart keep the output of the left and right ventricles equal? Explain Starling’s Law.
In general, as pre-load increases, so does stroke volume
To increase pre load, increase venous return. Venous return = Stroke volume.
How does preload affect contractility and ventricle force?
As the blood spills into ventricle, it stretches the ventricle’s muscle fibers to the optimal length for contraction. That’s when we get maximum ventricle force. This allows the heart to use less energy by using elastic energy of the optimally stretched fibers
In a single cardiac cell, what is the length tension relationship?
In general As the length increases, so does the tension. (there is a limit)
In diseased states, there is a limit to this increasing length in which the tension gets weird after a certain length.
What is preload? and End-Diastolic volume?
Preload: The ventricles filling up.
EDV: Maximum blood volume in the ventricle just before ejection
How can we estimate Preload? Which is most reliable?
Ventricular End Diastolic Pressure – Higher the pressure higher the preload
Atrial Pressure – if atrial pressure is high before diastole, higher preload (??)
Venous Pressure – Vasodilation decreases pressure = decrease in preload
VEDP is most reliable because it’s a direct correlation.
What is afterload? How does arterial pressure affect this?
Aortic Pressure.
If arterial pressure increases =
How do the following affect cardiac performance (stroke volume/Cardiac output)
Preload?
Afterload?
Contractility?
High Preload: Increases.
High Afterload: decreases
High Contractility: Increases
What are the phases of the cardiac cycle?
- Isovolumetric contraction
- Systolic ejection
- Isovolumetirc relaxation
- rapid filling
- Reduced filling
What happens in Isovolumetric Contraction?
Phase 1 –> 2
Blood has filled the ventricle. Volume is high, so pressure is low.
Mitral valve closes.
Then ventricle contracts, so volume decreases, pressure is way high - higher than systemic circulation.
Lots of O2 consumed here.
What happens in Systolic Ejection?
Phase 2 –> 3
When the ventricle contracted, volume decreased, pressure became way high - higher than systemic circulation..
blood wants to flow high to low, so Aortic Valve opens.
What happens in Isovolumetric Relaxation?
Phase 3–> 4
Ventricle relaxes. Volume increases, pressure decreases. All valves are closed.
What happens in Rapid Ventricle filling?
Pressure falls to below left atrial pressure. Causes mitral valve to open. Blood flows high to low pressure into the left ventricle.
What happens in Reduced ventricle filling?
Pressure is increased in the L ventricle due to all the blood, so less wants to go in there.
What changes in pressure-volume when preload is increased?
End Diastolic volume increases = increased stroke volume
What changes in pressure-volume when afterload is increased?
Increased aortic pressure, decreased stroke volume, increased ESV.
see card 49 for explanation
What changes in pressure-volume when contractility is increased?
Increased Stroke volume
Increased Ejection Fraction
Decreased End Systolic Volume
What is the equation for stroke work?
Stroke work = Stroke volume x Aortic pressure
What is stroke volume? Where is this on a pressure -volume graph?
The amount of blood ejected from one ventricular contraction.
Subtract the max volume from min volume. Check the LOs for a pic
Where is stroke work on a PV loop graph?
Area of the loop
What is the Fick Principle?
Conservation of O2 in the body
How do you calculate stroke volume, give End Diastolic volume and End Systolic volume?
SV = EDV - ESV
How do you calculate ejection fraction, given End Diastolic volume and End Systolic volume?
EF = SV/ EDV
SV = EDV - ESV
so
EF = (EDV - ESV)/ EDV
What does a low EF indicate?
Heart Failure.
How to calculate O2 consumption with the Fick principle?
O2 consumption = (Maximum O2) - (O2 used up in the body)
How to find these numbers?
Maximum O2 found in pulmonary veins.
O2 used up found in Pulmonary arteries.
O2 consumption = (Cardiac Output x [O2]pulm veins) -
(Cardiac output x [O2]pulmarteries)
How do you calculate cardiac output?
Cardiac output = O2 consumption/(O2 pulm veins - O2 pulm arteries)
How is cardiac output (oxygen levels) maintained in exercise?
Increase Heart rate and stroke volume.
How does a reflex arc work?
stimulus → afferent sensory neuron → enters spinal cord via dorsal root → synapse with interneuron → synapse with motor neuron → efferent motor neuron stimulates muscle
Efferent nerves have how many motor neurons?
Afferent nerves have how many sensory neurons?
Efferent: Primary and secondary
Afferent: Tertiary, Secondary, Primary
What is the hypothalamus responsible for?
Pons?
Medulla?
Hypo: Water balance temperature hunger Pons: Respiration and Cardiac Vasculature Medulla: Respiration
Describe 5 general metabolic stances when the parasympathetic is active?
Plenty of oxygen, heart beats slowly BP is low Blood flow to GI Absorb fuel from GI
Describe 4 general metabolic stances when the sympathetic is active?
More oxygen intake and delivery
HR increase
Conserve energy from GI
increase metabolism for fuel.
Generally describe what these receptors do and where they're located. a1 a2 b1 b2 b3
a1: Contract/Decrease (Vasculature, Lungs, eye, GI)
a2: Inhibits (GI)
b1: Contracts (heart) Lipolysis (GI)
b2: Dilation (Vasculature, lungs, eye lens, GI: glycogenolysis)
b3: Metabolism: Lipolysis.
Describe Sympathetic system.
Short pre-ganglion Long Post- ganglion with branching Adrenergic - uses epi and NE Alpha and beta receptors Found in thoracosacral
Parasympathetic
- Pre-gang, short or long?
- Post- gang, shortor long?
- Types of receptors at pre? post?
- Ligand at pre? Post?
- Where found?
Long Pre Short post pre: Nicotinic recptors for ACh post: Muscarinic receptors for ACh Found in craniosacral
What sympathetic receptors act on the heart?
Parasympathetic?
b1 and b2 to increase heart rate and contractility
M2: decrease HR and contractiility
What sympathetic receptors act on the Vasculature?
Parasympathetic?
A1 Vasoconstrict
B2 Vasodilate
Does zero things
What sympathetic receptors act on the lungs?
Parasympathetic?
A1 decrease secretion
B2 Bronchodilate. decrease secretion
M3 Bronchoconstrict. Increase secretions
What sympathetic receptors act on the eye?
Parasympathetic?
A1 Dilate Pupil (on radial muscle)
B2 Relax ciliary muscle (Allows for far sightedness)
M3 Pupillary sphincter muscle contraction (constrict pupil)
What sympathetic receptors act on the GI?
Parasympathetic?
A1 Contract sphincters
A2 Decrease secretions
B2 Relax smooth muscle
M3 Increase secretion and motility
What sympathetic receptors act on the Metabolism?
Parasympathetic?
B1 All increase lipolysis
B2 Also increases glycogenolysis
B3
M3 Promotes insulin and storage
What sympathetic receptors act on the bladder?
Parasympathetic?
A1 Sphincter contraction
M3 Contracts detrusor muscle and relaxes sphincter
What is lusitropy?
Relaxation
What happens during atrial systole?
Pressures, where is blood.. etc
Atrial pressure goes up due to contraction
Blood flows from atria to ventricle.
Ventricles have less pressure than atria
(Just after P wave)
What happens during Isovolumetric contraction?
Pressures, where is blood.. etc
Ventricle depolarization and contraction All valves are shut Ventricle pressure rises Atria pressures goes up a little bc of bulging valve (QRS)
What happens during Ventricular ejection?
Pressures, where is blood.. etc
Ventricle pressure becomes higher than afterload pressure - semilunar valve opens
(ST segment)
What happens during Reduced Ejection?
Pressures, where is blood.. etc
Ventricular repolarization
VEntricle pressure decreases until aortic valve closes
(T wave)
What happens during Isovolumetric relaxation?
Pressures, where is blood.. etc
All valves close
ventricle relaxes until pressure falls below atrial pressure and mitral opens
Slight increase in aortic pressure due to blood hitting closed valve
What happens during Rapid ventricular filling?
Pressures, where is blood.. etc
Ventricular pressure is lower than atrial, so blood is flowing through it.
What happens during Reduced ventricular filling?
Pressures, where is blood.. etc
Pressure is growing in ventricle as blood flows in, so less and less blood wants to go in.
What is venous pulse?
The veins trying to get back into the right atria
What are 3 pressure differences in venous pulse?
- When the R atria contracts and blood spills back into them (no valve)
- Ventricular contraction - causes atria to bulge and put more pressure on veins
- Pressure increase as the veins come back to the heart but can’t enter ventricle bc its full
How does laminar flow work?
Blood next to the walls not moving, blood in the center moving very fast.
What can cause turbulent flow?
- Branch points in large arteries
- Diseased arteries
- Stenotic arteries
- Stenotic heart valves
What is the consequence of turbulent flow?
Requires more pressure/harder heart work to push through
What effects velocity of blood?
Vessel size: large vessel, low velocity.
What is the Volumetric Flow Rate Equation?
What will you more than likely be asked to find using this equation?
Q = V*A Q = Flow V = Velocity A = Area = π*r^2
Velocity.
V= Q/A
An increase in pressure has what effect on flow?
An increase in resistance has what effect on flow and pressure?
↑Pressure =
↑ Flow Rate
↑ Resistance =
↑ Pressure
↓ Flow Rate
What is the Resistance equation?
What factor has the largest influence on resistance?
R = (V*L)/r^4
Resistance = viscosity * length/ radius
Radius has largest effect on resistance.
What effect does viscosity have on resistance?
What can increase viscosity?
↑ Viscosity = ↑ Resistance
Viscosity is dependent on hematocrit.
Anemia ↓ Hematocrit (↓ Viscosity ↓resistance)
Hyperproteinemia ↑ Hematocrit
What is the relationship between radius, resistance, and flow?
↑ Radius = ↑ Flow = ↓ Resistance
What is the relationship between area, velocity, and flow?
↑ Area =↓ Velocity =
Q = v*A
or
v=Q/A
How does the cross sectional area differ between arteries, capillaries, and veins?
- Aorta has smallest area, increasing until Capillaries, which have the most.
- Veins have the 2nd most area.
- Vena Cava has a bit more area than the aorta
How does the blood volume differ between arteries, capillaries, and veins?
Aorta has little blood volume
Arteries have 2nd highest blood volume to veins.
Capillaries have 3rd highest blood volume.
Veins have highest blood volume.
What is resistance?
What is conductance?
Resistance - Resistance to flow
Conductance - Permeability
Equation for resistance of vessels in a series?
What are vessels in a series?
If you add resistance, what happens to the total resistance?
R1+R2+R3=Rt
artery –> arteriole –> capillary
Rt increases
Equation for resistance of vessels in parallel?
When are vessels in parallel? If you add resistance, what happens to the total resistance?
1/R1+1/R2+1/R3=1/Rt
in organs.
Decreases resistance
If there is a complete occlusion, what happens to the Resistance?
Resistance becomes infinite.
In parallel, this would increase the resistance.
What is the relationship between resistance and flow?
Increase resistance, decrease flow.
What is shear?
Where is shear highest?
This occurs when blood next to each other is traveling at different velocities.
Blood Vessel wall
What is Reynold’s number? What is the equation?
What number is the limit?
an indicator of whether blood is going to be turbulent or not. Nr = pdv/n Nr = Reynolds p = density d= diameter v= velocity n = viscosity
N = 2000+ will be turbulent
What is a bruit? What are bruits caused by?
abnormal sound generated by turbulent flow in an artery
Partial obstruction
Localized high rate of flow
Increase in blood velocity by fever, anemia, hyperthyroidism
How does resistance differ between arteries, capillaries, and veins?
Arterioles - greatest resistance.
Capillaries - high resistance
Veins - low resistance
What is compliance? What does it mean for a vessel to have high compliance
How stretchy/willing to hold a large volume of blood.
High compliance means a larger amount of blood can be held. So veins have high compliance and can hold a lot of blood.
How can stroke volume affect arterial systolic pressure?
diastolic pressure?
Mean pressure?
Pulse Pressure?
↑ in stroke volume: ASP: ↑ DP: ↓ MP: ↑ PP: ↑
What is the equation of total peripheral resistance?
TPR = (Aortic pressure - vena cava pressure) / CO
What the method of action of arteriosclerosis?
stiffening of vessels - decreases compliance.
Increased systolic pressure, pulse pressure, increase mean arterial pressure
What effect does aortic stenosis have on pressures? Stroke volume?
Decrease SV
Decreases systolic pressure,
pulse pressure and mean arterial pressure
What is pulmonary vasculature like?
25/8
Low pressure, low resistance
High compliance
What is the pulse pressure?
Where is pulse pressure located?
How do you calculate?
Difference between systolic pressure and diastolic pressure. same as stroke volume
Arteries only.
Pulse pressure = systolic - diastolic
What is systemic vasculature like?
120/80
High pressure, high resistance,
low compliance
How does age affect vessels?
Increase stiffness of arteries, which decreases compliance
Arterial pressures increased due to this compliance.
What are the equations for cardiac output in regards to..
- heart rate and stroke volume?
- Pressure?
- Venous Return?
- Flow?
CO=SV*HR
CO=(input pressure-output pressure)/TPR
Same as Q=ΔP/R
CO=VR
CO=Q (flow)
How can veins move blood to arteries in order to raise arterial pressure?
Smooth muscle contraction
What’s the equation for Starling’s pressures?
Jv=Kf[(Pc-Pi)-(πc-πi)]
Jv = Fluid movement Kf= fluid movement Pc = capillary hydrostatic pressure Pi = intersitial hydrostatic pressure πc = capillary oncotic pressure πi = interstitial oncotic pressure
How do you calculate Mean Arterial Pressure if given blood pressure?
MAP=⅔ diastolic + ⅓ systolic
How does aortic stenosis change pulse pressure? Is this good for the heart?
pulse pressure is decreased
No, because the heart still has to work way harder.
What consequence happens during reactive hyperemia?
It forms reactive oxygen species.
An ischemic tissue gets a ton of oxygen and makes that stuff.
What is associated with Cushing Reflex?
Short version:
↑ Intracranial pressure results in ↑ BP, irregular breathing, and reduced HR
Long version:
↑ intracranial pressure (due to trauma) → constricts arterioles → cerebral ischemia → ↑PaCO2 (decrease pH) → central reflex sympathetic tone → vasoconstriction (↑ BP) → ↑ stretch on baroreceptors (vagus stimulation) → peripheral baroreceptor induced bradycardia
What is the average pressure of aorta? large arteries? arterioles? capillaries? Vena Cava? Right atrium?
Aorta: 100 large arteries: 100 arterioles: 50 capillaries: 20 Vena Cava: 4 Right atrium: 0-2