Review Questions Flashcards
What are the 2 main divisions?
pulmonary (low pressure) and systemic (high pressure)
What are the 4 components of each division?
Describe each
Pump: generates energy (atria and ventricles)
Distribution: arteries and arterioles
Exchange: capillaries, via diffusion and ultrafiltration
Collection reservoir: venules and veins (80%)
Define: Blood Flow
volume of blood that moves past a particular point per unit time
F = (P1-P2)/R
What are the two components that determine flow?
blood pressure and resistance
What are the three factors that contribute to changes in pressure?
frictional forces, vessel diameter, vessel length
What is the point of having direct electrical coupling between myocardial cells?
to allow for rapid impulse conduction and depolarization across the myocardium
How is the cardiac action potential different from a skeletal action potential?
it is much broader
Describe the autonomic and hormonal control of the cardiac system.
Preganglionics: nicotinic, acetylcholine
Postganglionic: muscarinic (para), acetylcholine, alpha or beta adrenoreceptors, norepinephrine
Hormones: RAAS, vasopressin, epinephrine (adrenal medulla)
The resting membrane potential (RMP) of cardiac myocytes is primarily a function of __________. This ion is drawn into the cell by the presence of ________.
its high permeability to K+ and low permeability to other ions (Na+ and Ca2+)
large negatively charged proteins (A-)
What happens to the resting membrane potential (RMP) when you: increase extracellular K+
increases (depolarization)
What happens to the resting membrane potential (RMP) when you: increase extracellular Na+
no change (because channels are closed; will lead to a higher peak potential when channels do open)
What happens to the resting membrane potential (RMP) when you: increase extracellular Ca 2+
no change
Why is the myocardial action potential so much longer than skeletal muscle?
there is an influx of Ca 2+ during depolarization in addition to the Na+ and, Ca 2+ channels open and close slowly compared to Na+
What are two types of AP’s and where are each of them found?
Fast type: atrial and ventricular myocytes and Purkinje fibers; rate of rise is fast due to fast type Na+ channels
Slow type: pacemaker cells of SA and AV nodes; conduction velocity slow due to “funny” type Na+ channels
Describe the 5 phases of fast type action potentials
Phase 0: Rapid depolarization- rapid influx of Na+ (fast type channels numerous on myocardial cells, open/close quickly)
Phase 1: Transient repolarization- Na+ channels rapidly close and K+ currently activated
Phase 2: Plateau phase- slow type Ca 2+ channels begin to open and large influx into cell, gradually close
Phase 3: Rapid repolarization- K+ flows out as channels open, hyperpolarization
Phase 4: Resting membrane potential- previous changes fixed by Na+/K+ ATPase, Ca 2+ changes fixed by both Na+/Ca 2+ exchanger and reuptake of Ca 2+ into sarcoplasmic reticulum
What is the point of an extended refractory period?
allows for adequate filling time and enough time for sufficient Ca 2+ reuptake
When is the absolute refractory period? The relative?
Abs: phases 1-2
Rel: phase 3
Phase 2 of the cardiac action potential is:
a) absent in the fast type action potentials
b) dependent upon an increase in Ca 2+ conductance
c) dependent upon an increase in K+ conductance
d) prolonged in slow type action potentials
e) dependent upon an increase in both Ca 2+ and K+ conductances
B) dependent upon an increase in Ca 2+ conductance
Fast response cardiac action potentials are normally found in:
a) SA nodes
b) Purkinje fibers
c) AV node
d) Ventricular myocardium
e) B & D
E) B & D
With your knowledge of the ventricular cardiac myocytes and Nernst equation (Ek= -61.5 log ([K+]i/[K]o)), an increase in extracellular Ca 2+ should result in:
a) a more positive equilibrium potential for Ca 2+
b) a more negative equilibrium for K+
c) hyperpolarization of the resting membrane potential
d) depolarization of the resting membrane potential
e) B & D
A) a more positive equilibrium potential for Ca 2+
What is the effective refractory period? When does it occur?
period cell is effectively refractory but a local action potential can be stimulated with no propagation
happens during beginning of phase 3
Cardiac action potentials are described as slow versus fast. This difference is primarily based on the rate of rise of the membrane potential in phase 0. Phase 0 in the slow type action potential is primarily dependent upon:
a) the opening of a “funny” Na+ channel
b) the closing of a fast Na+ channel
c) the opening of a slow voltage dependent Ca++ channel
d) the opening of Ca++ activated K+ channels
e) the presence of inward rectifying K+ channel
c) the opening of a slow voltage dependent Ca++ channel
Relative to Phase 4, Na+ conductance during Phase 0 in the slow type cardiac action potential is:
a) increased
b) decreased
c) unchanged
d) i don’t know
e) only Dick Cheney knows for sure :)
b) decreased
Increased levels of circulating catecholamines will have the following effects on cardiac function:
a) a decreased heart rate & contracility
b) a decrease in “funny” Na+ current conductance
c) an increase in “funny” Na+ current conductance
d) more negative maximum diastolic potential
e) what’s a catecholamine?
c) an increase in “funny” Na+ current conductance
examples of catecholamines include epinephrine and norepinephrine, which increase contractility
Calculate the heart rate if the P-P interval on the ECG is 225 ms.
a) 57 bpm
b) 85 bpm
c) 125 bpm
d) 227 bpm
e) 267 bpm
e) 267 bpm
1000 ms/225 ms =4.4444 beats per second
4.4444 beats per second x 60 seconds per minute
Acetylecholine directly influences cardiac output by:
a) binding to beta-1 receptors in the AV node
b) moving the maximum diastolic potential of the SA node to a less negative potential
c) binding to muscarinic receptors in the SA node
d) decrease K+ conductance
e) increasing “funny” Na+ conductance
c) binding to muscarinic receptors in the SA node
With your knowledge of the ventricular cardiac myocytes and the Nernst equation (ECa++ =-log([Ca++]i/[Ca++]o), an increase in extracellular Ca++ should result in:
a) a more positive equilibrium for Ca++
b) a more negative equilibrium potential for K+
c) hyperpolarization of the resting membrane potential
d) depolarization of the resting membrane potential
a) a more positive equilibrium for Ca++
The best treatment for second degree AV nodal blockade is:
a) cholinergic agonist
b) alpha-2 receptor antagonist
c) muscarinic agonist
d) muscarinic antagonist
e) increased carrot intake
d) muscarinic antagonist
Muscarinic antagonist ex.- atropine, increases sympathetic drive to the heart, increases HR
An ectopic pacemaker in the left ventricle could potentially result in:
a) increased duration of the P wave
b) increased number and increased duration of QRS waves
c) increased interval between R waves
d) decreased number of QRS waves in the ECG
b) increased number and increased duration of QRS waves
A normal sinus arrythmia may be characterized by:
a) an increase in heart rate during inspiration
b) an increase in parasympathetic drive during inspiration
c) an increase in heart rate during expiration
d) sinus arrythmias are not normal
a) an increase in heart rate during inspiration
If cardiac output is 4.5 L per minute and stroke volume is 30 mL, what is the heart rate?
a) 15 beats/min
b) 6.6 beats/min
c) 66 beats/min
d) 150 beats/ min
d) 150 beats/min CO=SVxHR 4500 mL/min = 30 mL x HR 4500 mL/min / 30mL = HR 150 beats/min
Which wave is caused by atrial contraction?
a) P wave
b) QRS wave
c) Q wave
d) a wave
e) v wave
d) a wave
Which wave is associated with the depolarization of the ventricle?
a) P wave
b) QRS wave
c) Q wave
d) a wave
e) v wave
b) QRS wave
The amplitude of this wave increases during the phase of ventricular contraction in an animal with an insufficient mitral valve:
a) P wave
b) QRS wave
c) Q wave
d) a wave
e) v wave
e) v wave
Which of the following will have a positive inotropic effect?
a) an increase in Na+/K+ pump activity
b) an increase in intracellular Na+
c) a decrease in extracellular Ca++
d) a decrease in circulating norepinephrine
b) an increase in intracellular Na+
more intracellular Na+ means less of a drive to bring Na+ inside, decreasing the Ca/Na pump pushing Ca out of the cell, more Ca in the cell leads to higher contractile force
Inotropic relates to contractility and is directly related
(positive goes up, negative goes down)
Cardia muscle relaxation is aided by:
a) an increase in Ca++ binding to myosin kinase
b) an efflux of 80% of the Ca++ into the extracellular fluid
c) Ca++ ATPase dependent pump on the sarcoplasmic reticulum
d) decreased K+ conductance
e) calcium-triggered calcium release
c) Ca++-ATPase dependent pump on the sarcoplasmic reticulum
(pg. 44) Relaxation of the myocardium occurs as Ca++ is removed from the cytoplasm through mechanisms which returned Ca++ to both the sarcoplasmic reticulum (SR; internal stores) and the extracellular space
Which represents a sudden increase in sympathetic drive to the myocardium?
B
Which represents a sudden increase in sympathetic drive to myocardium and increased aortic pressure?
D
The splitting of the second heart sound:
a) is best heard during inspiration
b) is associated with decreased venous return
c) is heard best through AV node blockage
d) is heard best in January and February
a) is best heard during inspiration
(pg. 53) An audible splitting of the the 2nd heart sound during inspiration can occasionally be heard in healthy larger breed dogs and is commonly heard in horses. This is due to increased venous return and prolongation of RV
ejection.
Aortic stenosis is characterized by:
a) diastolic murmur
b) systolic murmur
c) decreased end-diastolic pressure
d) increased aortic pressures
b) systolic murmur
Aortic valve insufficieny is characterized by:
a) diastolic murmur
b) systolic murmur
c) decreased end-diastolic pressure
d) increased aortic pressure
a) diastolic murmur
A decrease in mean arterial pressure will trigger which of the following baroreflex mediated changes:
a) an increase in sympathetic drive to SA node
b) an increase in parasympathetic drive to the SA node
c) an increase in both sympathetic and parasympathetic drive to the SA node
d) a decrease in sympathetic drive to the SA node
e) a decrease in both sympathetic and parasympathetic drive to the SA node
a) an increase in sympathetic drive to the SA node
