Cardiovascular system

Question 1

Value of interstitial fluid pressure of a) subcutaneous tissue. b) liver and kidneys c) brain

Answer 1

a) -2 mmHg below atmospheric pressure
b) less than 6 mmHg but greater than 0mm Hg
c) as high as mmHg

Question 2

Osmotic pressure gradient formula

Answer 2

Osmotic pressure gradient = Oncotic pressure of plasma (in capillaries) minus oncotic pressure of insterstitial fluid

Question 3

Net flow of fluid a) at arterial end b) venous end of capillaries

Answer 3

a) at arterial end moves out of capillaries

b) at venous end moves into capillaries

Question 4

Cardiac cells that determine heart rate.

Answer 4

SA node since it discharges more rapidly than other other cardiac cell; it is the CARDIAC PACEMAKER

Question 5

Anatomic location of SA node

Answer 5

At junction of right atrium and superior vena cava

Question 6

Anatomic location of AV node

Answer 6

right posterior portion of interatrial septum

Question 7

What are the INTERNODAL ATRIAL PATHWAYS?

Answer 7

3 bundles of fibers from atria containing Purkinje-like fibers and connecting the SA and AV nodes

Question 8

Structures through which conduction passes from SA to AV nodes

Answer 8

1. atrial myocytes

2. internodal pathway fibers (anterior, middle, posterior tracts)

Question 9

what is tract of a) Wenckebach b) Thorel and c) Bachmann bundle?

Answer 9

Mnemonic from anterior to posterior tracts: Batman Whacked Thor!
Batman - Bachmann bundle–> anterior tract
Whacked - Wenckebach tract –> middle tract
Thor - Thorel –> posterior tract

Question 10

Structures making up conduction system

Answer 10

SA node –> Internodal atrial pathways –> AV node –> bundle of His –> Purkinje fibers

Question 11

bundle of His located at _______ and continues as the

a) left bundle branch
b) right bundle branch

Answer 11

bundle of His located at the top of the interventricular septum
continues as the right bundle branch but gives off the left bundle branch

Question 12

Which bundle branch (right or left) divides into anterior and posterior fascicles?

Answer 12

Left bundle branch

Question 13

differentiate cells of conduction system from the normal cardiac myocytes

Answer 13

cells of conduction system are modified to have less striations and indistinct boundaries

Question 14

Name the fibers that 1. connect the left and right atria

2. connect the atria and ventricles

Answer 14

1. Bachmann bundle connects the two atria

2. Bundle of His connects atria and ventricles

Question 15

Based on embryologic development, explain why left vagus mainly distributed to AV node and right vagus majorly given to SA node.

Answer 15

AV node develops from left side of heart so gets the left vagus nerve mostly. SA node develops from right side of heart so gets right vagus nerve mostly

Question 16

Ganglion from which most sympathetic fibers to SA and AV nodes arise?

Answer 16

Stellate ganglion

Question 17

True or false: Vagal fibers are epicardial.

Answer 17

False: Vagal nerves are endocardial while noradrenergic nerves are epicardial

Question 18

Coronary vessels are located in which layer of the cardiac wall?

Answer 18

Epicardial layer

Question 19

Describe Phase 0 to 4 of nonpacemaker cells.

Answer 19

Phase 0 - rapid depolarization via opening of sodium channels
Phase 1 - rapid repolarization due to closing of sodium channels
Phase 2 - plateau phase; Potassium channels open (potassium efflux) while Calcium channels open (calcium influx)
Phase 3 - slow repolarization; calcium channels close and potassium continues to efflux
Phase 4 - resting membrane potential is reached

Question 20

Define the prepotential/pacemaker potential.

Answer 20

the slowly rising positive increase in voltage that happens between the end of one action potential and triggers the next action potential

Question 21

Events leading to prepotential/paceaker potential stages 1 and 2

Answer 21

Stage 1; “Funny” channel which is activated by hyperpolarization at the end of the action potential is permeable to both potassium and sodium = depolarization

Stage 2; at certain voltage level “T” (transient) Calcium channels open on plasma membrane and there is also local release of calcium from sarcoplasmic reticulum, completing the prepotential

Question 22

Difference between depolarization phase of pacemaker cells and nonpacemaker cells?

Answer 22

Pacemaker cells’ depolarization phase owed to Calcium influx (calcium current) through long-lasting (“L”) calcium channels while Nonpacemaker cells is due to sodium influx

Question 23

function of “f” or “h” channel

Answer 23

permeable to both potassium and sodium. activated by hyperpolarization of pacemaker cell so initiates stage 1 of prepotential

Question 24

Mechanism of cholineric vagal stimulation in slowing down heart rate.

Answer 24

acetylcholine binds to and activates M2 receptors which are inhibitory
1. Effect 1: lowers slope of prepotential by increasing potassium conductance via opening special set of potassium channels through beta gamma subunit of G protein, to counter effect of depolarization

2. Effect 2: lowers levels of cAMP to slow opening of calcium channels and prevent prepotential from developing

Question 25

Mechanism of noadrenaline in speeding up the heart rate

Answer 25

binds to Beta 1 receptors = increase in cAMP levels = increase in calcium current by opening of “L” calcium channels –> which speeds up the depolarizing effect of “funny” channel

Question 26

Mechanism of digitalis

Answer 26

1. Blocks sodium potassium ATpase causing an increase in Calcium levels in the cell leading to increase in FORCE of contraction
2. decreases conduction velocity of AV node to slow down transmission of signals to ventricles

Question 27

Uses of digitalis

Answer 27

1. treating atrial flutters
2. treating atrial fibrillation
3. systolic failure
4. improve cardiac output
5. decreases ventricular filling pressure

Question 28

Delay that occurs between signal being sent from atria to ventricles.

Answer 28

0.1second delay because AV node is slow at conducting

Question 29

Which component of conduction system as the highest conduction rate?

Answer 29

Purkinje fibers

Question 30

What does a)a positive deflection b)a negative deflection say about the depolarization?

Answer 30

a) positive deflection means the depolarization is moving towards the electrode; so the active electrode becomes positive relative to the inactive one
b) negative deflection means depolarization is moving away from the electrode; so the active electrode become negative relative to the inactive electrode