Cardiac - Pt 3 Flashcards
Cardiac Output =
Heart Rate x Stroke Volume
Ejection Fraction =
(EDV - ESV)/EDV
The [] is the percentage of blood in the ventricle that is ejected each beat. Its roughly ~65-70%.
Ejection Fraction
Stroke Volume =
EDV - ESV
[] [] [] is the amount of blood remaining in the ventricle after contraction…
End Systolic Volume
What are the 3 main factors that regulate Stroke Volume
Preload
Contractility
Afterload
What is “Preload” in terms of stroke volume regulation?
What is the main indicator for the preload?
- It is the degree of stretching in the cardiac muscles before contraction.
- You could call it EDV.
- Frank-Starling
At rest, cardiac muscles are [] than optimal length…
shorter
T/F
Ventricle stretching directly relates to a stronger cardiac muscle contraction.
FALSE
The contractility of cardiac muscles is directly dependent upon the availability of Ca2+ in the sarcoplasm.
T/F
An increase in EDV will lead to an increase in systolic force, to a degree?
True
Frank Starling
Contractile strength at a given muscle length is independent of [] and [] ?
Muscle stretch and EDV
What are positive effectors of muscle contactility?
- Norepinephrine/Epinephrine
- Glucagon
- Thyroxine
- Digitalis
What are negative effectors of muscle contractility?
Acidosis
Increased Extracellular K+
Calcium Channel Blockers
Describe the effect of the following muscle contractility effectors?
- Norepinephrine
- Glucagon
- Extracellular K+ increase
- Digitalis
- Norepinephrine
- increased contractility by stimulating the B1 Adrenergic receptors
- Glucagon
- increased contractility by stimulating the cadiac Ca2+ current by activation of adenylyl cyclase and inhibition of phosphodiesterase
- Extracellular K+ Increase
- Decreased contractility by throwing off the seperation of charge seen in normal cells. This will throw off signal conduction/action potentials and can lead to death.
- Digitalis
- increased contractility dont know why yet.
Describe the effect of the following muscle contractility effectors?
- Thyroxine
- Acidosis
- Calcium Channel Blockers
- Thyroxine
- Increased Contractility -increases transcription of contractile proteins
- Acidosis
- Decreased Contractility by the competitive inhibition of the slow calcium current by hydrogen ions.
- Calcium Channel Blockers
- Decreased Contractility because duh.
What is “Afterload?”
- The pressure that must be overcome for the ventricles to eject blood into the major arteries
As afterload increases, stroke volume []
decreases
In which of the following scenarios would Stroke Volume Increase?
- Increase Afterload
- Increase Preload
- Decreased Contractility
- Increase preload would lead to a higher stroke volume
In which of the following scenarios would stroke volume decrease?
- Increased Preload
- Increased Contractility
- Increased Aortic Pressure
- 3, if you increased aortic pressure, the stroke volume would decrease.
- Because the ventricle would not have as much time to eject blood, therefore ejecting a smaller amount.
Extrinsic Control of the heart is mediated by the [] [] []
Autonomic Nervous System
The effects of the autonomic dnervous system on heart rate are called [] …
Chronotropic Effects
What does Sympathetic innervation do to HR and contractility?
What does Parasympathetic innervation do to HR and contractility?
- Increases
- Decreases
What section of the central nervous system is in charge of heart beat/contractility regulation?
The MEDULLA OBLONGATA
During resting condition, what autonomic branch is effecting heart beat?
The parasympathetic System
- What part of the Medulla Oblongata controls sympathetic inputs to the heart?
- What part of the Medulla Oblongata controls parasympathetic inputs to the heart?
- Cardioacceleratory Center
- Cardioinhibitory Center
Sympathetic Innervation of the Heart:
- Neurotransmitter used:
- Sympathetic cardiac nerve attaches to the [] and [] node as well as [] muscle.
- NTs bind to the [] [] receptors and illicit a [] chronotropic effect
- Norepinephrine
- SA and AV node; myocardium muscle
- B1 Adrenergic Receptors; positive chronotropic effect.
Parasympathetic Innervation of the Heart:
- Neurotransmitter:
- Nerves project to the [] and [] node via the [] nerve
- [] chronotropic effects are decreases in heart rate
- Acetylcholine
- SA and AV node; Vagus Nerve
- Negative
In the parasympathetic nervous system, Acetylcholine is released and binds to [] receptors on the heart.
- What effect does this have on the heart?
- What are the 2 mechanisms that these receptors use to illicit a response from the heart?
- muscarinic
- Decreases heart rate and contractility.
- Mechanisms
- Inhibits adenylyl cyclase
- Directly increases the conductance of K+ in K+-ACh channels which hyperpolarizes the membrane…making it even harder to illicit action potentials.
T/F
On the heart, acetylcholine binds to nicotinic cholinergic receptors?
FALSE
It uses muscarinic cholinergic receptors in its parasympathetic response.
[] recording of the electrical activity of the heart
Electrocardiogram
Generation of ECG waves caused by the [] electrical activity of the heart
CUMULATIVE
Describe both of the axis of EKG paper….
- X-axis: Time (s)
- 1 small box is .04s
- 1 big box is .2s
- Y-axis: Voltage (mV)
- 1 small box 0.1 mV
- 1 big box 0.5 mV
- If a depolarization wave is heading towards a (+) electrode, the deflection will be [] on EKG Paper?
- If a depolarization wave is heading away from a (+) electrode, the deflection will be [] on EKG Paper?
- Positive
- Negative
A flat line on the EKG corresponds to an [] activity in the heart…
isoelectric
How do you get a bi-phasic deflection on EKG paper work?
The (+) electrode has to be in the “middle” of the depolarization’s wave line.
- A repolarization wave heading toward a (+) electrode will have a [] deflection on EKG paper?
- A repolarization wave heading away from a (+) electrdoe will ahve a [] deflection on EKG paper?
- Negative
- Positive
What are the 6 limb leads?
- Lead 1
- Lead 2
- Lead 3
- aVR
- aVL
- aVF
The precordial leads record forces moving [] and [].
How many precordial leads are there?
- Anteriorly to posteriorly
- 6 precordial Leads
T/F
Each EKG electrode records only the average current flow at any given moment.
True!
What causes the slight negative dip of the Q wave on an EKG?
The fact that the left ventricle will depolarize slightly sooner thatn the right ventricle.
The P-Q interval represents [] []
Atrial Depolarization to the start of ventricular depolarization
The QRS complex represents [] [] ?
Ventricular Depolarization
The T Wave represents [] []?
Why is this wave positive??
- Ventricular Repolarization
- Because the heart is Repolarizing “away” from the Normal lead II - which would be a positive deflection.
What does the ST segment represent on an EKG?
The time from the end of ventricular depolarization to the start of ventricular repolarization.
- The P Wave Represents []
- The electrical activity of these elements… immediately follow the P wave, but do not show up on an EKG?
- Atrial Depolarization
- SA Node, AV Node, Bundle of HIS, Bundle Branches, Purkinje Fiber
- The QRS Duration represents…
- The QT interval represents…
- Ventricular Depolarization
- Ventricular Depolarization all the way to Ventrciular Repolarization
What does the R-R interval represents on an EKG?
The time between ventricular contractions/or depolarizations
T/F
If the MEA changes, then the heart has normally changed shape?
True
What 3 things can happen to an EKG wave when a chamber hypertrophies or enlarges?
- EKG wave could increase in duration
- EKG wave could increase in amplitude
- The MEA may shift.
What are the 3 steps of Ischemia to Infarction?
- In the first few minutes, Peaked T-waves, transitioning into inverted T-Waves
- Early sign of ischemia
- Still reversible
- In the following minutes to hours, ST-Segment elevation
- Approaching permanent damage
- After Infarction, Inverted Q-wave/new q-wave
- Permanent damage is done.
Arrhythmias:
- Any alteration to normal [], [], [], or [] of the heart beat
- Not all are [], some are fatal
- Symptoms are usually [] and/or sudden [] - []
- rhytm, regularity, origin, or conduction
- dangerous
- Palpitations, light-headedness
What are 2 forms of SA node Arrhythmias? Which one is more worrying?
- Sinus Bradycardia - rate under 60 bpm, everything else is the same
- Sinus Tachycardia - rate over 100 bpm, everything else is the same
What are 2 forms of Atrial Arrhythmias?
- Atrial Flutter
- rapid, regular, atrial depolatizations
- Has a saw tooth pattern
- Atrial Fibrillation
- No coordination of atrial depolarization
- Not necessarily lift threatening becuase 90% of ventricular filling is passive.
- Can be fixed with a cardioversion.
What is a conduction Block?
What are the 3 tpyes of conduction blocks?
- Depolarizations are not conducted properly from atria to ventricle
- 3 degrees
- 1st Degree - prolonged PR intervals (>.2s)
- due to increased AV node delay
- 2nd Degree - Not all p-waves are conducted via AV node = dropped beats
- 3rd Degree - No conduction via AV node between atria and ventricle
- P and QRS are regular but NOT IN SYNC
- 1st Degree - prolonged PR intervals (>.2s)
The 1st degree of conduction blockage involves a prolonged [] interval.
What type of “delay” is this arrhythmia associated with?
- PR Interval
- Av Node Delay
What are the 2 types of 2nd degree Conduction Blockage?
- Mobitz Type I - Wenckebach
- PR interval gets pregressively longer until a beat is dropped
- Mobitz Type II
- PR interbal is set, but a beat (QRS) is still randomly dropped.
[] arrhythmias can be very deadly, quickly…
Ventricular
What 2 types of ventricular arrhythmia did we cover?
-
Ventricular Tachycardia
- Fast depolarization
- Ischemic event
- Can lead to fibrillation
-
Ventricular Fibrillation
- uncoordinated depolarization
- Rapid Death
Digitalis
- [] contractility, but [] HR
- Inhibits []/[] ATPase
- leads to [] intracellular Na+
- This leads to [] gradient for Na+/Ca2+ exchanged
- Which leads to [] Ca2+ inside the cell
- increase contractility, but decrease HR
- Inhibits Na/K ATPase
- leads to decreased intracellular Na+
- This leads to decreased gradient for Na+/Ca2+ exchanged
- Which leads to increased Ca2+ inside the cell
