Lesson 8 - The Circulatory System: Heart Flashcards
cardiac cycle
one complete contraction and relaxation of all four chambers of the heart
two main variables govern fluid movement: _____ causes flow, and _____ opposes it
pressure, resistance
flow requires a _____ ______
pressure gradient
there is an _____ relationship between volume and pressure
inverse
blood pressure is measured with?
a sphygmomanometer
when the ventricles relax and expand, what happens to its internal pressure?
it falls
if the mitral valve is open, blood flows…
into the left ventricle
when the ventricles contract, what happens to its internal pressure?
it rises
what happens to the aortic semilunar valve when the AV valve closes?
it is pushed open and blood flows into the aorta form the left ventricle
the AV valves are _____ when the ventricles are relaxed
limp
when the ventricle is relaxed, what is happening to the semilunar valves?
and why?
they’re under pressure from blood in the vessels
valvular insufficiency (incompetence)
any failure of a valve to prevent reflux (regurgitation)
regurgitation
backward flow of blood
valvular stenosis
cusps are stiffened and opening is constricted by scar tissue; often caused by rheumatic fever
regurgitation can be heard as a _____ _____
heart murmur
mitral valve prolapse (MVP)
insufficiency in which one of both mitral valve cusps bulge into the atria during ventricular contraction; often hereditary
auscultation
listening to the sounds made by the body
first heart sound (S1)
louder and longer “lubb”, occurs with closure of AV valves, turbulence in the bloodstream, and movements of the heart wall
second heart sound (S2)
softer and sharper “dubb”, occurs with closure of the semilunar valves, turbulence in the bloodstream, and movements of the heart wall
third heart sound (S3)
results from the transition from the expansion of the empty ventricles to their sudden filling with blood
what heart sound is rarely heard in people over 30? what could its presence indicate?
S3; enlarged or failing heart
phases of the cardiac cycle (4)
- ventricular filling
- isovolumetric contraction
- ventricular ejection
- isovolumetric relaxation
phases of the cardiac cycle: ventricular filling
ventricles expand as they relax and their pressure drops below that of the atria causing AV valves to open and blood to flow in
ventricular filling occurs in three phases
- rapid ventricular filling: first third
- diastasis: second third, slower filling
- atrial systole: last third, atria contract
the P wave occurs at the end of _____ of ventricular filling
diastasis
end-diastolic volume (EDV)
amount of blood in the ventricles BEFORE ventricular systole
phases of the cardiac cycle: isovolumetric contraction (2)
- atria repolarize, relax, and remain that way for the rest of the cycle
- ventricles begin to contract closing AV valves
heart sound S1 is heard at the beginning of this phase of the cardiac cycle
isovolumetric contraction
why is it called isovolumetric contraction?
because although the ventricles contract, they do not eject blood
phases of the cardiac cycle: ventricular ejection
begins when…
begins when the ventricles pressure exceeds atrial pressure in the aorta/pulmonary trunk and the semilunar valves open
ventricular ejection - two parts
rapid ejection: blood spurts out of ventricles quickly
reduced ejection: slower flow under less pressure
stroke volume (SV)
the amount of blood ejected
ejection fraction
SV(stroke volume)/EDV(end-diastolic volume)
end-systolic volume
blood remaining in the ventricles after ventricular ejection
phases of the cardiac cycle: isovolumetric relaxation
blood from aorta/pulmonary trunk briefly flows backward filling cusps and closing semilunar valves
the _____ wave ends and ventricles being to relax and expand during isovolumetric relaxation
T
what heart sound occurs during isovolumetric relaxation?
S2
why is isovolumetric relaxation called ‘isovolumetric’?
semilunar valves are closed and AV valves have not yet opened, so no change in blood volume
most of the ventricular filling occurs during what?
atrial diastole
atrial systole lasts about…
0.1 seconds
ventricular systole lasts about…
0.3 seconds
quiescent period
when all four chambers are in diastole, lasts about 0.4 second
congestive heart failure (CHF)
results from the failure of either ventricle to eject blood effectively
what is congestive heart failure usually due to? (4)
mi.ch.vi.cd.
a heart weakened by a myocardial infarction, chronic hypertension, valvular insufficiency, or congenital defects in heart structure
left ventricular failure (2)
what happens and what does it cause?
blood backs up into the lungs causing pulmonary edema, shortness of breath and a sense of suffocation
right ventricular failure (5)
blood backs up into the vena cava causing systemic generalized edema, enlargement of the liver, ascites, distension of jugular veins, swelling of the fingers/ankles/and feet
ascites
pooling of fluid in abdominal cavity
heart rhythm and contraction are controlled by two cardiac centers
- cardioacceleratory center
- cardioinhibitory center
where are the two cardiac centers located?
the medulla oblongata
cardioacceleratory center
how does it communicate with the heart?
communicated with heart via the right and left cardiac nerves carrying sympathetic postganglionic nerve fibers
cardioinhibitory center
communicated with heart via right and left vagus nerves carrying parasympathetic preganglionic nerve fibers
sympathetic stimulation _____ heart rate and contraction rate
increases
sympathetic pathway - heart innervation: stimulatory signals from the _____ center descend to the upper thoracic segments of the spinal cord where they synapse with sympathetic _____ neurons in the _____ horn, whose axons enter sympathetic _____ _____
cardioacceleratory, preganglionic, chain ganglia
sympathetic pathway - heart innervation: some fibers synapse with _____ neurons at the level of entry, other ascend to _____ ganglia
postganglionic, cervical
sympathetic pathway - heart innervation: _____ fibers pass through the _____ _____ in mediastinum and continue as _____ nerves to the heart
postganglionic, cardiac plexus, cardiac
sympathetic pathway - heart innervation: fibers terminate in _____ and _____, in the atrial and ventricular myocardium (and also in the aorta, pulmonary trunk, and coronary arteries)
SA and AV nodes
parasympathetic stimulation _____ heart rate
decreases
parasympathetic pathway - heart innervation: beings with nuclei of the _____ nerves in the _____ _____; exiting this structure and traveling through the _____
vagus, medulla oblongata, mediastinum
parasympathetic pathway - heart innervation: _____ fibers of the _____ travel through the _____ _____, synapse with _____ neurons in the plexus or the epicardium of _____ near the SA and VA nodes
preganglionic fibers, vagus, cardiac plexus, postganglionic, atria
parasympathetic pathway - heart innervation: short _____ fibers of the _____ _____ nerve lead mainly to the SA node; fibers of the _____ _____ nerve lead mainly to AV node
postganglionic, right vagus, left vagus
there is little or no _____ innervation of the myocardium or ventricles
parasympathetic
cardiac output (CO)
amount ejected by each ventricle in one minute
cardiac output (CO) equation
heart rate (HR) x stroke volume (SV)
cardiac reserve
difference between a person’s maximum and resting cardiac output
how is cardiac reserve different in those with heart disease?
they have litter reserve and little tolerance for exertion
what artery is used to check pulse in the wrist?
radial artery
what artery is used to check pulse in the neck?
common carotid
tachycardia
persistent, resting HR above 100bpm
causes of tachycardia (6)
s.a.s.h.f.b.
stress, anxiety, stimulants, heart disease, fever, or blood loss
bradycardia
persistanting, resting adult HR below 60bpm
causes of bradycardia (2)
common in endurance-trained athletes, also caused by hypothermia
positive chronotropic agents
factors that raise HR
negative chronotropic agents
factors that lower HR
the autonomic nervous system does/doesn’t initiate heartbeat
does NOT; it modulates rhythm and force
sympathetic postganglionic fibers are _____
adrenergic
sympathetic postganglionic fibers release what hormone?
norepinephrine (NE)
the adrenal medulla secretes.. (2)
norepinephrine (NE) and epinephrine (Epi)
what happens when NE and Epi bind the B-adrenergic receptors in the heart?
it activates cAMP second-messenger systems in cardiomyocytes and nodal cells, leading to the opening of Ca2+ channels in the plasma membrane
what does sympathetic stimuli do to calcium flow in the heart?
increases inflow accelerating the depolarization of the SA node
what does sympathetic stimulation do to calcium reuptake?
increased cAMP accelerated uptake of Ca2+ by the SR, allowing cardiomyocytes to relax more quickly
sympathetic division: by accelerating both contraction and relaxation, _____ (through cAMP) increases heart rate as high as 230 bpm
norepinephrine
at excessively high heart rates, diastole becomes…
too brief for adequate filling, causing both stroke volume and cardiac output to be reduced
parasympathetic vagus nerves have _____, _____ effects on the SA and AV nodes
c.i.
cholinergic, inhibitory
parasympathetic division: _____ binds to muscarinic receptors opening _____ chemically gated channels in nodal cells
acetylcholine, K+
parasympathetic division: as _____ leaves the nodal cells, they become _____ and fire less frequently, causing what?
K+, hyperpolarized, causing heart rate to slow down
parasympathetic division: steady background firing of the _____ nerves continually keeps HR _____ to the usual
vagus, down
vagal tone
constant firing of the vagus nerves that keep heart rate down
inputs to the cardiac centers in the _____ _____ are diverse
medulla oblongata
_____ in muscles and joints inform cardiac centers about changes in _____, causing HR to increase before metabolic demands on muscles arrive
proprioceptors, activity
_____ in the aorta and internal carotid arteries send signals to the medulla regarding _____ _____, so HR can be adjusted accordingly
baroreceptors, heart rate
baroreflex
if BP decrease, HR increases and vice versa
_____ detect chemical stimuli in the aortic arch, carotid, and medulla oblongata
chemoreceptors
chemoreflex (2)
- CO2 accumulation lowers pH, both conditions stimulate receptors to increase HR and increase tissue perfusion
- also respond to low O2, resulting in decrease in HR
hypercapnia
carbon dioxide accumulation
hypoxemia
low oxygen levels
autonomic neurotransmitters (2)
n.a.
norepinephrine and acetylcholine
blood-borne adrenal catecholamines (2)
norepinephrine and epinephrine - potent cardiac stimulants
_____ stimulates catecholamine secretion
nicotine
_____ hormone increases the number of adrenergic receptors on the heart so it is more responsive to adrenergic stimulation
thyroid
_____ inhibits cAMP breakdown, prolonging adrenergic effect
caffeine
hyperkalemia of the heart (3)
(1) excess K+ diffuses into cardiomyocytes (2) making them less excitable and resulting in a (3) slow, irregular heartbeat
hypokalemia of the heart (3)
(1) deficiency of K+ inside the cell causes the cell to (2) hyperpolarize and therefore requires (3) increased stimulation
hypercalcemia of the heart
does what?
excessive Ca2+ decreases heart rate
hypocalcemia of the heart
deficiency of Ca2+ increases heart rate
three variables go into stroke volume
p.c.a.
- preload
- contractility
- afterload
preload
amount of tension (stretch) in the ventricular myocardium immediately before it begins to contract
Frank-Starling law of the heart
stroke volume is proportional to end-diastolic volume aka ventricles eject as much blood as they receive
contractility
refers to how hard the myocardium contracts for a given preload
positive inotropic agents
increase contractility
negative inotropic agents
decrease contractility
examples of positive inotropic agents (4)
c.n.g.d.
calcium, norepinephrine, glucagon, digitalis
examples of negative inotropic agents (2)
- hyperkalemia
- vagal stimulation on artia (ventricles not innervated)
afterload
sum of forces a ventricle must overcome before it can eject blood
what are the greatest contributors to afterload? (2)
a.p.
blood pressure in the aorta and pulmonary trunk
factors that increase afterload (2)
h.a.
hypertension, atherosclerotic plaques
cor pulmonale
r
right ventricular failure due to obstructed pulmonary circulation (high afterload)
high afterload causes these common complications of lung disease (2)
e.c.
emphysema, chronic bronchitis
exercise has what impact on cardiac output?
increases it
At the beginning of exercise, how does the body signal the heart to increase cardiac output?
signals from joints and muscles reach the cardiac center of the brain where it sends out sympathetic signals to increase cardiac output
increased cardiac output due to exercise increases… (2)
v.p.
venus return and preload
exercise produces _____ _____
ventricular hypertrophy
ventricular hypertrophy causes…
increased stroke volume, allowing the heart to beat more slowly at rest
coronary artery disease (CAD)
degenerative disease in the coronary arteries usually resulting from atherosclerosis
what can increase risks for getting coronary heart disease? (3)
what do they do?
h.d.s.
hypertension, diabetes, and smoking
- damage inner lining of arteries
how does coronary heart disease progress? (2)
- monocytes adhere and penetrate walls of vessels and become macrophages
- macrophages and smooth muscle cells absorb cholesterol and fat, becoming frothy foam cells and form yellow fatty streaks
outcomes of coronary heart disease progression (2)
- fatty streaks have the potential to progress into life-threatening atheromas
- alternatively, damaged vessels can scar and accumulate calcium
atheromas
plaques of fatty tissue
atherosclerosis
l
an accumulation of lipid deposits and necrotic tissue that obstructs the lumen and may cause a heart attack
arteriosclerosis
hardening of the arteries
major risk factors of coronary artery disease (2)
- excess low-density lipoproteins (LDL) in the blood
- defective LDL receptors in arterial walls
other risk factors of coronary artery disease (8)
h.a.o.s.l.h.d.
heredity, aging, obesity, smoking, lack of exercise, stress, hypertension, diet
eating what can lower blood cholesterol?
soluble fibers
how is coronary artery disease often treated?
with a coronary artery bypass graft
coronary artery bypass graft
sections of a vessel are used to construct a detour around the obstruction in the coronary artery
balloon angioplasty
another treatment for CAD; catheter is threaded into the coronary artery and inflated to press and flatten atheromas against the aterial wall
laser angioplasty
atheroma is vaporized with a lazer
restenosis
regrowth of atheromas
