Cardiovascular system Flashcards
Value of interstitial fluid pressure of a) subcutaneous tissue. b) liver and kidneys c) brain
a) -2 mmHg below atmospheric pressure
b) less than 6 mmHg but greater than 0mm Hg
c) as high as mmHg
Osmotic pressure gradient formula
Osmotic pressure gradient = Oncotic pressure of plasma (in capillaries) minus oncotic pressure of insterstitial fluid
Net flow of fluid a) at arterial end b) venous end of capillaries
a) at arterial end moves out of capillaries
b) at venous end moves into capillaries
Cardiac cells that determine heart rate.
SA node since it discharges more rapidly than other other cardiac cell; it is the CARDIAC PACEMAKER
Anatomic location of SA node
At junction of right atrium and superior vena cava
Anatomic location of AV node
right posterior portion of interatrial septum
What are the INTERNODAL ATRIAL PATHWAYS?
3 bundles of fibers from atria containing Purkinje-like fibers and connecting the SA and AV nodes
Structures through which conduction passes from SA to AV nodes
- atrial myocytes
2. internodal pathway fibers (anterior, middle, posterior tracts)
what is tract of a) Wenckebach b) Thorel and c) Bachmann bundle?
Mnemonic from anterior to posterior tracts: Batman Whacked Thor!
Batman - Bachmann bundle–> anterior tract
Whacked - Wenckebach tract –> middle tract
Thor - Thorel –> posterior tract
Structures making up conduction system
SA node –> Internodal atrial pathways –> AV node –> bundle of His –> Purkinje fibers
bundle of His located at _______ and continues as the
a) left bundle branch
b) right bundle branch
bundle of His located at the top of the interventricular septum
continues as the right bundle branch but gives off the left bundle branch
Which bundle branch (right or left) divides into anterior and posterior fascicles?
Left bundle branch
differentiate cells of conduction system from the normal cardiac myocytes
cells of conduction system are modified to have less striations and indistinct boundaries
Name the fibers that 1. connect the left and right atria
2. connect the atria and ventricles
- Bachmann bundle connects the two atria
2. Bundle of His connects atria and ventricles
Based on embryologic development, explain why left vagus mainly distributed to AV node and right vagus majorly given to SA node.
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
Ganglion from which most sympathetic fibers to SA and AV nodes arise?
Stellate ganglion
True or false: Vagal fibers are epicardial.
False: Vagal nerves are endocardial while noradrenergic nerves are epicardial
Coronary vessels are located in which layer of the cardiac wall?
Epicardial layer
Describe Phase 0 to 4 of nonpacemaker cells.
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
Define the prepotential/pacemaker potential.
the slowly rising positive increase in voltage that happens between the end of one action potential and triggers the next action potential
Events leading to prepotential/paceaker potential stages 1 and 2
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
Difference between depolarization phase of pacemaker cells and nonpacemaker cells?
Pacemaker cells’ depolarization phase owed to Calcium influx (calcium current) through long-lasting (“L”) calcium channels while Nonpacemaker cells is due to sodium influx
function of “f” or “h” channel
permeable to both potassium and sodium. activated by hyperpolarization of pacemaker cell so initiates stage 1 of prepotential
Mechanism of cholineric vagal stimulation in slowing down heart rate.
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
- Effect 2: lowers levels of cAMP to slow opening of calcium channels and prevent prepotential from developing
Mechanism of noadrenaline in speeding up the heart rate
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
Mechanism of digitalis
- Blocks sodium potassium ATpase causing an increase in Calcium levels in the cell leading to increase in FORCE of contraction
- decreases conduction velocity of AV node to slow down transmission of signals to ventricles
Uses of digitalis
- treating atrial flutters
- treating atrial fibrillation
- systolic failure
- improve cardiac output
- decreases ventricular filling pressure
Delay that occurs between signal being sent from atria to ventricles.
0.1second delay because AV node is slow at conducting
Which component of conduction system as the highest conduction rate?
Purkinje fibers
What does a)a positive deflection b)a negative deflection say about the depolarization?
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
