Exam 4 Lecture 2 Flashcards
Deep to Superficial in Heart: Layers of heart involved in AP
Endocardium - Myocardium - Epicardium - Pericardial Space - Parietal Pericardium - Fibrous Pericardium
Superficial to Deep in Hear: Layers of heart involved in AP
Fibrous Pericardium - Parietal Pericardium - Pericardial Space - Epicardium - Myocardium - Endocardium
Normal Depolarization in the Ventricles: Which direction?
Deep to Superficial
Normal Repolarization in the Ventricles: Which direction?
* + or - deflection?
Superficial to Deep
* + deflection
Normal Vrm in a PM cell in the SA node?
-55 mV
Normal Threshold in PM cell in SA node
-40 mV
Where does the R Vagus nerve terminate?
SA Node
Where does the L vagus nerve terminate?
AV node
Where in the heart does the PNS mostly innervate?
*Which NTM
The nodal area [ACh]
Where in the heart does the SNS innervate most?
* What NTM and where else can it innervate
Atrial/Ventricular Muscle Tissues [NE]
*Can also innervate the nodal areas, but is out strengthened by ACh
Why is the Ventricular Myocyte considered a Fast AP?
*What is the normal Vrm
Phase 0 is straight up and down/rapid onset
*-80 mV
What lead is the normal EKG we see?
Lead 2
Why is the SA node the PM of the heart?
The tissue at the SA node tends to depolarize and spread the AP faster than other cells in the heart
Per lecture, what is a normal HR?
72 b/min
What is the charge of the tissue if the inside is all + and outside is all -?
*Vice Versa
0 mV
*0 mV
L - R, + to - Depolarization: + or - charge
+ charge always
L-R, - to + Repolarization: + or - charge
- charge always
R - L, - to + Repolarization: + or - charge?
+ charge always
Which combination of + and - charges within a tissue produces the most amount of current?
Half + and Half - charges
What happens if you flip the anode and cathode in the electrical tissue experiment?
The graph will look the same, just flipped across the X axis
Where is Lead 1 placed?
*What does this cause in terms of AP
+ electrode in L arm or L chest
*depolarization wave towards electrode in L arm/chest
R to L repolarization causes what in the EKG?
+ deflection in the T wave
What is the 1st structure in the heart to fully depolarize?
Interventricular Septum
How do Beta Agonists/Antagonists regulate HR?: In General
Change the slope of Phase 4
How does mACh-R regulate HR?: In general
Change Vrm
How does Ca++ regulate HR?: In general
Change threshold potential
How does a Beta Agonist [NE] increase HR?
*AC, cAMP, HCN
*Time in P4, Slope of P4
*Na, Ca, K, AP rate
Increase AC, Increase cAMP, increase HCN channels = decreases time in Phase 4 = increases/Steepens P4 slope = increases Na and Ca, increasing AP rate and HR; decreases K+ permeability
PM cell:
*Vrm
*Threshold
*-55 mV
*-40mV
How does mACh-R lower HR?
*P4 slope compared to Beta Agonist, Vrm
*AC, cAMP, HCN
*K+
Same slope, but decreased Vrm = longer time to reach AP
*decreased AC, cAMP, HCN
*Increased K permeability
How does a Beta Antagonist decrease HR?
*AC, cAMP, HCN
*Time in P4, Slope of P4
*Na, Ca, K, AP rate
Decrease AC, Decrease cAMP, Decrease HCN
Decrease P4 Slope [less steep], Increase time in P4
Decreased Na/Ca, increased K permeability
Decrease AP rate = less b/min
What happens if you give atropine?
*Vrm, AP
*K
increased Vrm = shorter time to reach AP
*Decreased K permeability
What is HCN: How does it respond to ions
*What does it stand for
*When is it opened
*What ions come in, in order
Hyperpolarization Cyclic Nucleotide: non-cation specific
*Opens when the cell is reset via repolarization or hyperpolarization, or increases in cAMP
*Na+ first, Ca++ second, K third
How does decreased plasma Ca++ effect HR [hypocalcemia]
*Tell me about the CG
Increased HR, b/c threshold potential is more (-), so able to reach AP faster
* Decreased CG
How does increased plasma Ca++ effect HR [hypercalcemia]
*Tell me about the CG
Decreased HR, b/c threshold potential is more (+), so takes longer to reach AP
*Increased CG
Give me a Threshold potential that would be synonymous with Hypocalcemia
Between -55 mV and -40 mV
Give me a Threshold potential that would be synonymous with Hypercalcemia
> -40 mV, to an extent
In what Phase do HCN channels open in SA node PM cells?
Phase 4
Compare the P4 slope in SA Node compared to Purkinje FIber?
Greater/steeper
Name 3 Ways how the HR is regulated?
Change slope of P4, Change Vrm, Ca++
How does Ca++ change the HR?
*Where is this mechanism only located
Unknown why it does this and only in heart muscle
In what 2 states do we have constant depolarization in an area of the heart?
*Where does injury of current occur
Ischemic/Infart
*In areas where we shouldn’t have or when we shouldn’t have current
What is a ventricular myocyte?
A ventricular muscle cell
What is the P-Wave in terms of Heart function
*How long is a normal PR interval, per lecture picture
Atrial Depolarization
* 0.16 sec
How many mV is a normal QRS complex?
*How many large boxes?
1.5 mV
*3 large boxes
A pt comes in with End-Stage COPD, what would you expect to see in their EKG?
*Why
QRS <1.5 mV
*Air is not conductive to electricity
What is the T-Wave in terms of Heart function
*What is the amplitude of the T-Wave, per lecture picture
Ventricular Repolarization - Superficial to Deep
*0.3 mV (positive deflection)
Why is the T-Wave a positive deflection?
The epicardium repolarizes before the endocardium
Per lecture, what are the names of the K+ channels located between Phase 0-Phase 3 of a cardiac AP?
*What causes these to close
Inward rectifying K+ channels
*Increased Na and Ca permeability cause these to close
Per lecture, what is important for the force of heart contractions?
Extension of the AP
Where do we lose most of our voltage during an AP?
Body tissue
Increased Tissue Resistance = ? voltage in heart?
*More scar tissue from what cells?
Decreased voltage in heart = possible HB’s
*Fibroblasts and stem cells
What is the different between Vrm and Threshold Potential in a normal ventricular myocyte
100 mV
A trauma Pt comes in with a pneumothorax; how would you describe their QRS complex in terms of mV
probably <1.5 mV
You noticed you had Lead 1 on the R arm of the Pt, how would you see their EKG?
It would be flipped to the other side [think a/b what he said flipping the cathode and anode. It would be opposite]
A pt comes in with severe facial twitching and arm spasms. How would their cardiac action potential be different compared to a typical, healthy adult?
Their threshold potential would be decreased, leading to an increase in AP, hence the chvostek and trousseau signs
What phases do HCN open?
Phase 4 and 3, most likely
