Lecture 2 – Circ Sys II – ECG and blood vessels Flashcards
the cardiac cycle:
systole and diastole –> which is contraction/relaxation?
systole –> contraction
diastole –> relaxation
LO: flow of blood in cardiac cycle:
what happens when ventricles relax?
- pressure (drops/rises?) inside the ventricles
- ___ close as blood attempts to back up into the ventricles from the vessels
- AV valves (open/close)…why?
- blood flows from ___ to ventricles
pressure drops inside the ventricles
semilunar valves close
AV valves open –> (when ventricles relax, pressure inside ventricles is less than inside atria. AV valves open so that atria can pump blood into ventricles to even out the pressure differences)
blood flows from atria to ventricles
LO: flow of blood in cardiac cycle:
what happens when ventricles contract?
- AV valves (open/close?) as blood attempts to back up into atria
- pressure (drops/rises) inside of the ventricles
- semilunar valves (open/close?) and blood flows into great vessels
AV valves close
pressure rises inside of the ventricles
semilunar valves open and blood flows into great vessels
LO: coronary circulation –> describe the arteries that nourish the myocardium and the veins that draw it
why is coronary circulation necessary? what are the vessels that make up coronary circulation?
heart is a muscle and needs oxygen to sustain its workload. 5% of blood pumped by heart goes to the heart itself thru coronary circulation
right coronary artery
left coronary artery
coronary sinus
LO: describe the arteries that nourish the myocardium
what is angina pectoris?
chest pain from partial obstruction of coronary blood flow
LO: describe the arteries that nourish the myocardium
what is myocardial infarction (MI)?
sudden death of a patch of myocardium resulting from long-term obstruction of coronary circulation
LO: describe the unique structural and metabolic characteristics of cardiac muscle
cardiomyocytes (describe):
- striations?
- length?
- thickness?
- branching in cells?
- cell structure?
striated
short
thick
branched cells
one nucleus surrounded by light-staining mass of glycogen
LO: structure of cardiac muscle –> explain the nature and functional significance of the intercellular junctions b/n cardiac muscle cells
intercalated discs (describe)
join cardiomyocytes end to end w/ 3 features
(1) interdigitating folds – interlock and increase area of contact
(2) mechanical junctions – fascia adherent and desmosomes
(3) electrical junctions (gap junctions) – ions flow b/n cells; allow entire myocardium of either 2 atria or 2 ventricles to act like single, unified cell
LO: metabolism of cardiac muscle
cardiac muscle depends almost exclusively on ___ to make ATP
as such, cardiac muscle is rich in ___ and ___
cardiac muscle have (tiny/huge?) mitochondria that fill ~___% of cell
aerobic respiration
rich in myoglobin and glycogen
huge mitochondria –> fill 25% of cell
LO: metabolism of cardiac muscle
cardiac muscle metabolism is adaptable to different ___ ___, such as….
organic fuels
fatty acids (60%), glucose (35%), ketones, lactate, and amino acids (5%)
LO: metabolism of cardiac muscle
cardiac muscle is more vulnerable to ___ ___ than a lack fo a specific fuel
vulnerable to oxygen deficiency
LO: metabolism of cardiac muscle
is cardiac muscle easily fatigued?
no; does not fatigue for a lifetime
it mostly uses aerobic respiration and not anaerobic fermentation or oxygen debt mechanisms
LO: describe the heart’s pacemaker and electrical conduction system
what does the pacemaker and electrical conduction system do?
how much of the myocardium is made of this electrical conduction system?
coordinates heartbeat
~1% of the myocardium
LO: describe the heart’s pacemaker and electrical conduction system
what is the system composed of?
internal pacemaker (SA node) and nerve-like conduction pathways (made of modified cardiomyocytes) thru the myocardium
structures:
- Sino-atrial (SA) node
- atrioventricular (AV) node
- atrioventricular bundle
- interventricular septum
- right and left bundle branches
- Purkinje fibers
LO: describe the heart’s pacemaker and electrical conduction system
describe the steps:
(1) SA node fires
(2) excitation spread thru atrial myocardium
(3) AV node fires
(4) excitation spreads down AV bundle
(5) subendocardial conducting network distributes excitation thru ventricular myocardium
LO: explain why the SA node fires spontaneously and rhythmically:
cardiac rhythm:
what is the sinus rhythm?
what is ectopic focus?
normal heartbeat triggered by the SA node
a region of spontaneous firing other than the SA node
LO: explain why the SA node fires spontaneously and rhythmically:
describe pacemaker physiology
describe pacemaker potential:
SA node does not have a stable resting membrane potential
starts at -60 mV and drifts upward due to slow Na+ inflow
gradual depolarization is called pacemaker potential
LO: explain why the SA node fires spontaneously and rhythmically:
describe pacemaker physiology
describe pacemaker threshold and depolarization:
when SA node reaches threshold of -40 mV, voltage-gated fast Ca2+ and Na+ channels open
faster depolarization occurs, peaking at 0 mV
this generates an action potential –> allows SA node to fire –> sets of heartbeat (muscle contraction)
LO: explain why the SA node fires spontaneously and rhythmically:
describe pacemaker physiology
describe pacemaker repolarization:
depolarization peaks at 0 mV
K+ channels then open and K+ leaves cell –> causes repolarization
once K+ channels close, pacemaker potential starts over
LO: explain how the SA node excites the myocardium
SA node stimulates 2 atria to contract almost simultaneously
signal slows down thru AV node
signals travel very quickly thru AV bundle and subendocardial conducting network (Purkinje fibers)
ventricular systole (contraction) progresses up from apex
basically, signal goes down interventricular septum and then to outer walls of ventricles
LO: describe the unusual action potentials of cardiac muscle and relate them to the contractile behavior of the heart
electrical behavior of the myocardium:
depolarization:
(1) voltage-gated Na+ channels open
(2) Na+ inflow depolarizes the membrane and triggers the opening of still more Na+ channels, creating a positive feedback cycle and a rapidly rising membrane voltage
(3) Na+ channels close when the cell depolarizes, and the voltage peaks at nearly +30 mV
plateau:
(4) Ca2+ entering thru slow Ca2+ channels prolongs depolarization of membrane, creating a plateau. Plateau falls slightly because of some K+ leakage, but most K+ channels remain closed until end of plateau
repolarization:
(5) Ca2+ channels close and Ca2+ is transported out of cell. K+ channels open, and rapid K+ outflow returns membrane to its resting potential
the heartbeat is coordinated by the cardiac ___ system
conduction
in a healthy person at rest, the SA node normally fires about how many times per minute?
70-80
a spontaneously developing local potential that generates action potentials in the SA node is called what?
pacemaker potential
where does ventricular contraction begin?
apex
Consider the phases of the action potential in a cardiocyte. After depolarization, contraction of the cardiocyte continues during the ___ phase of its action potential
plateau
during which stage of an ECG does atrial systole occur?
PQ segment
the QRS wave of an ECG represents what event in the heart?
depolarization of the ventricles
what is a type of arrhythmia?
ventricular fibrillation
depolarization of a cardiocyte is due to opening of which channels?
sodium
the contraction of a cardiocyte occurs during which phase of its action potential?
plateau
on an ECG, atrial systole begins during the ___
PQ segment
the QRS wave of an ECG represents ___ of the ventricular myocardium
depolarization
why is it important for conducting arteries to maintain elasticity?
their recoil helps maintain blood pressure b/n heartbeats
their expansion reduces systolic stress on smaller arteries
their expansion and recoil helps keep the blood flowing during diastole
A weak, bulging sac in the wall of an artery that pulsates with each beat of the heart and which may eventually rupture is called a(n) ___
aneurysm
which term refers to short vessels that link arterioles to capillaries?
metarterioles
what are the small blood vessels that nourish the walls of larger vessels?
vasa vasorum
sensory signals travel from aortic bodies to the brainstem via which cranial nerve?
vagus nerve
where are carotid bodies located?
near the branch of the common carotid arteries
which are chemoreceptors that are located in the aortic arch?
aortic bodies
what are metarterioles and what do they do?
short vessels
in some places, metarterioles link arterioles to capillaries or provide shortcuts that bypass the capillaries
sensory signals travel from heart to brainstem via which cranial nerve?
carotid bodies
aortic bodies
carotid bodies: arteries –> brainstem via glossopharyngeal nerves
aortic bodies: aortic arch –> brainstem via vagus nerves
which are regarded as the capacitance vessels because they expand easily to accommodate an increased volume of blood?
veins
arrange capillaries from most permeable to least:
sinusoids (most)
fenestrated
continuous (least)
which refers to a circulatory route in which blood flows thru 2 consecutive capillary networks before returning to the heart?
portal system
what best defines a capillary bed?
a network of capillaries supplied by a single arteriole or met arteriole
which term can refer to a collateral route of blood supplied to a tissue?
anastomosis
blood flow into capillary beds is regulated by smooth muscle structures called ___ sphincters which surround the openings to the capillaries
precapillary
the type of blood vessel regarded as capacitance vessels are ___
veins
rank types of veins from smallest to largest:
postcapillary veins
muscular venules
medium veins
venous sinuses
large veins
where do portal systems occur?
b/n hypothalamus and anterior pituitary gland
kidneys
b/n intestines and liver
an anatomical convergence where 2 blood vessels merge and combine their bloodstreams is known as a(n) ___
anastomesis
components of ECG:
P wave:
atrial depolarization
components of ECG:
P wave:
atrial depolarization
components of ECG:
QRS complex:
ventricular depolarization
(also when atrial repolarization occurs)
components of ECG:
T wave:
ventricular repolarization
cardiac arrhythmias:
tachycardia vs. bradycardia
tachycardia – resting HR greater than 100 bpm
bradycardia – resting HR lower than 60 bpm
what is stenosis?
when a valve is narrowed and doesn’t open properly
what makes the lub sound?
which heart sound is it?
1st heart sound
AV (tricuspid and mitral) valves snap shut
(also semilunar pulmonary and aortic valves open)
what makes the dub sound?
which heart sound is it?
2nd heart sound
semilunar (pulmonary and aortic valves) snap shut
(also AV valves open)
in terms of lub/dub (or S1/S2), when does systole and diastole occur?
systole (ventricles contracting) occurs in b/n S1 and S2
diastole (ventricles relaxing) occurs in b/n S2 and the next S1
