Review Questions

Question 1

What are the 2 main divisions?

Answer 1

pulmonary (low pressure) and systemic (high pressure)

Question 2

What are the 4 components of each division?

Describe each

Answer 2

Pump: generates energy (atria and ventricles)
Distribution: arteries and arterioles
Exchange: capillaries, via diffusion and ultrafiltration
Collection reservoir: venules and veins (80%)

Question 3

Define: Blood Flow

Answer 3

volume of blood that moves past a particular point per unit time
F = (P1-P2)/R

Question 4

What are the two components that determine flow?

Answer 4

blood pressure and resistance

Question 5

What are the three factors that contribute to changes in pressure?

Answer 5

frictional forces, vessel diameter, vessel length

Question 6

What is the point of having direct electrical coupling between myocardial cells?

Answer 6

to allow for rapid impulse conduction and depolarization across the myocardium

Question 7

How is the cardiac action potential different from a skeletal action potential?

Answer 7

it is much broader

Question 8

Describe the autonomic and hormonal control of the cardiac system.

Answer 8

Preganglionics: nicotinic, acetylcholine
Postganglionic: muscarinic (para), acetylcholine, alpha or beta adrenoreceptors, norepinephrine
Hormones: RAAS, vasopressin, epinephrine (adrenal medulla)

Question 9

The resting membrane potential (RMP) of cardiac myocytes is primarily a function of __________. This ion is drawn into the cell by the presence of ________.

Answer 9

its high permeability to K+ and low permeability to other ions (Na+ and Ca2+)
large negatively charged proteins (A-)

Question 10

What happens to the resting membrane potential (RMP) when you: increase extracellular K+

Answer 10

increases (depolarization)

Question 11

What happens to the resting membrane potential (RMP) when you: increase extracellular Na+

Answer 11

no change (because channels are closed; will lead to a higher peak potential when channels do open)

Question 12

What happens to the resting membrane potential (RMP) when you: increase extracellular Ca 2+

Answer 12

no change

Question 13

Why is the myocardial action potential so much longer than skeletal muscle?

Answer 13

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+

Question 14

What are two types of AP’s and where are each of them found?

Answer 14

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

Question 15

Describe the 5 phases of fast type action potentials

Answer 15

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

Question 16

What is the point of an extended refractory period?

Answer 16

allows for adequate filling time and enough time for sufficient Ca 2+ reuptake

Question 17

When is the absolute refractory period? The relative?

Answer 17

Abs: phases 1-2
Rel: phase 3

Question 18

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

Answer 18

B) dependent upon an increase in Ca 2+ conductance

Question 19

Fast response cardiac action potentials are normally found in:

a) SA nodes
b) Purkinje fibers
c) AV node
d) Ventricular myocardium
e) B & D

Answer 19

E) B & D

Question 20

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

Answer 20

A) a more positive equilibrium potential for Ca 2+

Question 21

What is the effective refractory period? When does it occur?

Answer 21

period cell is effectively refractory but a local action potential can be stimulated with no propagation
happens during beginning of phase 3

Question 22

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

Answer 22

c) the opening of a slow voltage dependent Ca++ channel

Question 23

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 :)

Answer 23

b) decreased

Question 24

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?

Answer 24

c) an increase in “funny” Na+ current conductance

examples of catecholamines include epinephrine and norepinephrine, which increase contractility

Question 25

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

Answer 25

e) 267 bpm 1000 ms/225 ms =4.4444 beats per second 4.4444 beats per second x 60 seconds per minute

Question 26

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

Answer 26

c) binding to muscarinic receptors in the SA node

Question 27

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

Answer 27

a) a more positive equilibrium for Ca++

Question 28

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

Answer 28

d) muscarinic antagonist | Muscarinic antagonist ex.- atropine, increases sympathetic drive to the heart, increases HR

Question 29

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

Answer 29

b) increased number and increased duration of QRS waves

Question 30

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

Answer 30

a) an increase in heart rate during inspiration

Question 31

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

Answer 31

``` d) 150 beats/min CO=SVxHR 4500 mL/min = 30 mL x HR 4500 mL/min / 30mL = HR 150 beats/min ```

Question 32

Which wave is caused by atrial contraction? a) P wave b) QRS wave c) Q wave d) a wave e) v wave

Answer 32

d) a wave

Question 33

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

Answer 33

b) QRS wave

Question 34

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

Answer 34

e) v wave

Question 35

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

Answer 35

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)

Question 36

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

Answer 36

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

Question 37

Which represents a sudden increase in sympathetic drive to the myocardium?

Answer 37

B

Question 38

Which represents a sudden increase in sympathetic drive to myocardium and increased aortic pressure?

Answer 38

D

Question 39

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

Answer 39

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.

Question 40

Aortic stenosis is characterized by: a) diastolic murmur b) systolic murmur c) decreased end-diastolic pressure d) increased aortic pressures

Answer 40

b) systolic murmur

Question 41

Aortic valve insufficieny is characterized by: a) diastolic murmur b) systolic murmur c) decreased end-diastolic pressure d) increased aortic pressure

Answer 41

a) diastolic murmur

Question 42

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

Answer 42

a) an increase in sympathetic drive to the SA node