Chapter 18: Heart Flashcards
What are chordae tendinae?
the strings attached to the heart valves that keep the valve from reversing (heart strings)
What is the foramen ovale botalli?
An inter-atrial opening to bypass the lungs in a fetus (because the lungs are filled with liquid)
When does the foramen ovali botalli close?
when the baby is born
What is the bypass between the pulmonary artery and aorta called?
ductus arteriosus
What does the ductus venosus do?
it is an umbilical vein that brings blood to the vena cava (in a fetus)
The heart pumps blood to the rest of the body, but the heart also needs its own blood supply which is provided by _______ via the ________
Coronary arteries via the right atrium
What are the three layers of the heart wall?
epicardium, myocardium, and endocardium
Define epicardium:
the outermost layer, the visceral layer (space without friction)
Define myocardium:
muscle of the heart, cardiac muscle
Define endocardium:
white sheet of endothelium resting on CT layer, it lines the inside of the heart wall
Plasma membrane of cardiac cells interlock via __________.
intercalated discs
Intercalated discs contain anchoring __________ and ______.
desmosomes and gap junctions
The atria and ventricle cells are _______ by gap junctions because ___________________________.
not connected, if they were, the whole heart would contract at the same time and blood wouldn’t flow through properly (atria cells are connected to other atria cells via gap junctions, but atria cells are not connected to ventricle cells by gap junctions)
_______ are what hold the intercalated discs together during contraction.
desmosomes
Syncytial:
one cell depolarizes, the signal gets transmitted to others
Where is the calcium (used in a cardiac action potential) stored?
the sarcoplasmic reticulum
What happens in stage 0 of the cardiac action potential?
cell is at -90mV, depolarizes, Na opens and goes inside (to make more positive)
What happens in stage 1 of the cardiac action potential?
~35+, Na closes, K opens, K goes out (more positive)
What happens in stage 2 of cardiac action potential?
Ca is released (plateau)
What happens in stage 3 of cardiac action potential?
Ca closes
What happens in stage 4 of cardiac action potential?
K closes
You could simplify the stages of a cardiac action potential to three stages: ________, __________, and _________
- Depolarization (due to Na influx) 2. Plateau phase (due to Ca influx, few K channels open) 3. Repolarization (Ca channels close, K opens until -90mV is reached)
How long does a cardiac action potential take?
~200 milliseconds
The plateau phase makes the cardiac action potential _________ than a skeletal action potential because ______________________________________.
longer, because this extends the absolute refractory period so the heart has time to rest so tetanus won’t occur (no matter how fast or slow the heart is beating)
What is tetanus?
when your muscle (skeletal) action potential occurs to fast and too often, which results in your muscle to stop working (overuse causes the muscle to stop working for a short period of time)
What do pacemaker cells do?
get the cardiac muscles to contract
Autorhythmic cells are ____________ that start their own __________ and do not need __________
special cardiac cells, action potential, a stimulus
What is the resting membrane potential and the threshold of an autorhythmic cell?
rmp= -60 threshold= -40
Describe the stages of the action potential of autorhythmic cells (Figure 18.13 in book)
1) Autorhythmic cells has a lot of leaky Na channels which raise the mV to its -40 threshold 2) Voltage gated Ca channel opens and depolarizes cell 3) Ca closes, K opens (more -) to rmp-60 (then back up due to leaky Na channels)
What does the sinoatrial node (SA) do?
sets the pace for the heart because no other region of the conduction system or myocardium has a faster depolarization rate (the heart’s pacemaker)
What is the bundle of His?
(aka atrioventicular bundle) fibers that conduct impulses from the AV node to the right and left ventricles -septum between right and left ventricles
What are Purkinje fibers?
depolarize the contractile cells of both ventricles (located on the outer walls of the ventricles)
What 3 reasons does the cardiac conduction system works the way it does?
- atria and ventricular cells are not connected by gap junctions (so the heart doesn’t contract at the same time) 2. Action potential is delayed in the AV node (so that the atria contracts first) 3. Ventricle contracts form the bottom up
The ____________ nervous system decreases heart rate and inhibits the SA node by releasing _____________ via the _____ nerve.
parasympathetic NS, Ach, vagus
The ______________ nervous system increases heart rate by releasing ___________.
sympathetic NS, Epinephrine and Noepinephrine (direct innervation)
What is arteriole pressure?
blood pressure not in the heart (elsewhere in the body)
When ventricles contract it is referred to as ___________
systolic (blood to arteries), in blood pressure this is the top number (120)
When the atria contracts it is referred to as _____________
diastolic (blood to ventricles), in blood pressure this is the bottom number (80)
Cardiac Output=
volume of blood leaving the heart per minute
What is the equation for cardiac output?
stroke volume times rate
Stroke volume and cardiac output are ________________
directly proportional
What is the Frank Starling Law?
more blood into the heart, the more blood pumps out of the heart
If finger blood vessels dilate, blood pressure would _________ and resistance would _________
decrease, decrease (Ach dilates vessels)
Epinephrine and noepinephrine _________ vessels increases blood pressure and ________ resistance
constricts, increases
When you have heat stroke, your resistance is low and your blood pressure is low. How could you fix this?
By drinking water or eating salty good, this would increase blood volume, which would increase blood pressure and resistance
Diastole is blood flowing from the _____________ to _____________
atria to ventricle
Systolic is blood flowing from the _____________ to _____________
ventricles to the body
Which is longer between sounds (“lub dub”), diastole or systole?
diastole
How are cardiac action potentials different from other action potentials in the body?
cardiac aps have a plateau phase
Pacemaker cells are _____________cells, NOT _____________ cells
cardiac cells, not neural
What is the purpose of gap junctions in heart cells?
so that the action potential can travel through the heart
What is the function of Purkinje fibers in the cardiac conduction system?
they bring the action potential down into the ventricles
Blood pressure is a measure of _____________ pressure
arteriole (not in the heart)
Systolic is the _____________ contracting
ventricles
Diastolic is the when the _____________ contracts
atria
What is this graph?
A normal ECG reading
The P wave (P to Q) corresponds to _____________
atrial depolarization and contrats
The QRS indicates _____________
ventricular depolarization and ventricular contraction
The S to T segment indicates _____________
ventricular repolarization
