cardiovascular system: electrophysiology and ECC Flashcards
what structure most protects the heart
pericardium
pericardium is separated in 2 layers: ___ and ___
fibrous and serous
serous pericardium consists of
parietal and visceral
is supplied by the pericardial cavity, reduces friction within pericardium by lubricating the surface
pericardial fluid
visceral layer of the serous pericardium that is the outmost layer
epicardium
layers of the heart wall
epicardium, myocardium, and endocardium
majority of cells in the myocardium
contractile cells
action potential in contractile cells lead to ____ and _____
contraction and generation of force or pressure
3 different cell types can function as pacemakers
SA node, AV node, purkinje fibers
cardiomyocytes
cardiac muscle cells that have one nucleus and are branched cells
what is smaller sarcoplasmic reticulum in skeletal muscle or cardiac muscle
cardiac muscle
mitochondria occupies ____ of cell volume
1/3, reflects high energy demand
cardiac muscles branching join end to end with neighboring cardiac cells in a _____
complex network
helps to electrically connect cardiac muscle cells to one another, causing a wave of conduction former uniform contraction
gap junctions
myocardia sarcoplasm is smaller and relies on what
extracellular fluid Ca levels for contraction initiation
cell junctions have what 2 components
desmosomes and gap junctions
desmosomes ensure what
force transfer fromm one cell to next
when an action potential arrives it activates what
L-type Ca channels in the T Tubule membrane
provides electrical connection
gap junctions
what type of junction is a desmosome
Anchoring
the skeleton of the heart is made up of
fibrous tissue that forms central support, 4 fibrous rings, 2 fibrous trigons, membranous part of interventricular and interatrial septa
Fibrous skeleton
acts as electrical insulator, prevents free flow of electrical impulses between atria and ventricle
an excitable tissue with the ability to generate APs
cardiac muscle
In cardiac muscle Ca is involved in both
autorythmic and contractile AP
action potentials produced by ventricular and atrial contractile cells are called
“fast response” action potentials.
Action potentials observed in the sinoatrial (SA) node and atrioventricular (AV) node are called
“slow response” action potentials.
phases of cardiac contractile cells
0- upstroke or depolarization
1- early rapid depolarization or partial repolarization
2- plateau
3- repolarization
4- resting membrane potential
phase 0 is due to what
opening of voltage gated Na channels similar to that occurring in nerve and skeletal muscle
phase 1 event
inactivation of Na channel and transient increase in K permeability
Phase 1 cell movement
K out
phase 2 event
activation of slow calcium channels
phase 2 cell movement
Ca entry
phase 3 event
inactivation of calcium and increased permeability to K
phase 3 cell movement
K out
phase 4 event
normal permeability restored
phase 4 cell movement
Na-K- ATPase pumps K in and Na out
longer myocardial action potential helps to prevent what
sustained contraction (tetanus)
What phase is associated with the resting potential
4
the ability of autorhythmic cells to generate spontaneous APs results from their
unstable membrane potential, which starts at about -60 mV and goes up toward threshold
This unstable membrane potential is called
a
pacemaker potential
what happens when the membrane potential is at -60mV
hyper polarization activated cyclic nucleotide gated channels (HCN channels) open.
If channels are permeable to both
K and Na
What If channels open at negative membrane potentials,
Na+ influx exceeds K+ efflux. The net influx of positive charge slowly depolarizes the autorhythmic cell.
are auto rhythmic cells membrane potentials stable or unstable
unstable
what is not an autorythmic cell
contractile cell
Autorhythmic cells _____ fire action potentials
spontaneously
depolarizations of the auto rhythmic cells spread rapidly to adjacent contractile cells through
gap junctions
why can APs not go directly from atrial to ventricular myocardium
they encounter fibrous skeleton of the heart at the junction of the atria and ventricles.
what does the fibrous skeleton of the heart at the junction of the atria and ventricles do
It acts as electrical insulator and prevents the transfer of electrical signals from the atria to the ventricles.
functions of AV node
delays the transmission of APs and is the only pathway APs generated by SA node can reach contractile fibers
purkinje fibers has hoe many BPM
20
which auto rhythmic cell type has the slowest pacemaker activity
purkinje cell
ECG represents
the summed electrical activity of all cells recorded from the surface of the body
The voltage change is much greater when recorded
intercellularly
which indicated the start of a new AP cycle of the heart
P
