Cardiovascular System Flashcards
Cardiology
scientific study of the heart and the treatment of its disorders
cardiovascular system
heart and blood vessels
Circulatory system
heart, blood vessels, and the blood
Two major circuits of the circulatory system
systemic circuit
pulmonary circuit
Systemic circuit
left side of the heart
takes blood from heart to the body
fully oxygenated blood arrives from lungs via pulmonary veins
blood is sent to all organs of the body via aorta
pulmonary circuit
right side of the heart
takes blood from the heart to the lungs for gas exchange and back to heart
lesser oxygenated blood arrives from inferior and superior vena cava
blood is sent to lungs via pulmonary trunk
vena cava
largest vein in the body
pulmonary trunk
main pulmonary artery
diverged to left and right pulmonary arteries
Position of the heart
mediastinum, between lungs
base of the heart
wide, superior portion, where the blood vessels attached
apex of the heart
inferior end, tilts to the left, tapers to point
size of the heart
3.5 in wide at base
5 in from base to apex
2.5 in anterior to posterior
weight of heart
10 oz
Pericardium
double-walled sac that encloses the heart
allows heart to beat w/o friction, provides room to expand but not excessive
anchored to diaphragm inferiority and sternum anteriorly
Pericardial cavity
space inside the pericardial sac filled with 5-30 mL of pericardial fluid
pericarditis
inflammation of the membranes
painful friction rub with each heart beat
What makes up the heart wall?
Epicardium, endocardium, and myocardium
Epicardium
serous membrane covering heart
adipose in thick layer in some places
coronary blood vessels travel through this layer
Endocardium
smooth inner lining of heart and blood vessels
coverts the valve surfaces and continuous with endothelium of blood vessels
myocardium
layer of cardiac muscle proportional to work load
fibrous skeleton of the heart
In the myocardium there is a layer of cardiac muscle that spirals around the heart and produces what kind of motion?
A wringing motion
In the myocardium there is a fibrous skeleton, what does it do?
framework of collagenous and elastic fibers
provides structural support and attachment for cardiac muscle and anchor for valve tissue
electrical insulation between atria and ventricles important in timing and coordination of contractile activity
What are the 4 chambers of the heart?
Right atrium
left atrium
right ventricle
left ventricle
Which are the two superior chambers that receive blood returning to heart?
Right and left atrium
What do the left and right atriums have that slightly increase its volume
auricle
What are the 2 inferior chambers that pump blood into arteries?
right and left ventricle
Interatrial septum
wall that separates the atria
Interventricular septum
muscular wall that separates ventricles
Atrioventricular (AV) valves
controls blood flow between atria and ventricles
right and left
Semilunar valves
control flow into great arteries
open and closed because of blood flow and pressure
Right AV valve
3 cusps (tricuspid valve)
Left AV valve
2 cusps (mitral/bicuspid valve)
has chordate tendinae
prevent av valves from flipping inside out/bulging into the atria when the ventricles contract
Chordae tendinae
cords in the left AV valve that connects the AV valves to papillary muscles on floor of ventricles
pulmonary semilunar valve
in opening between right ventricle and pulmonary trunk
aortic semilunar valve
opening between left ventricle and aorta
When ventricles relax what happens?
pressure drops inside the ventricles
semilunar valves close as blood attempts to back up into the ventricles from the vessels
AV valves open
blood flows from atria to ventricles
When ventricles contract what happens?
AV valves close as blood attempts to back up into the atria
pressure rises inside the ventricles
semilunar valves open and blood flows into great vessels
Blood flow through the heart
- blood enters right atrium from superior and inferior venae cavae
- blood in right atrium flows through right AV valve into right ventricle
- contraction of right ventricle forces pulmonary valve open
- blood flows through pulmonary valve into pulmonary trunk
- blood is distributed by right and left pulmonary arteries to the lungs, where it unloads CO2 and loads O2
- blood returns from lungs via pulmonary veins to left atrium
- blood in left atrium flows through left AV valve into left ventricle
- contraction of left ventricle forces aortic valve open
- blood flows through aortic valve into ascending aorta
- blood in aorta is distributed to every organ in the body where it unloads O2 and loads CO2
Systemic Circulation
blood circulation from heart to the body and back again
Pulmonary Circulation
blood circulation from the heart to the lungs and back again
What percentage of blood pumped by the heart is pumped to itself?
5%
How much blood is pumped by the heart to itself per minute?
250 mL
Why is blood flow to the heart slowed during ventricular contraction?
- contraction of the myocardium compresses the coronary arteries and obstructs blood flow
- opening of aortic valve flap during ventricular systole covers the openings to the coronary arteries blocking blood flow into them
- during ventricular diastole, blood in the aorta surges back to the heart and into the openings of the coronary arteries
Blood flow to the myocardium during ventricular relaxation x?
increases
Aortae
largest artery
Venules
smallest veins
Venae Cavae
the largest veins
myocardial infarction
heart attack; complete blockage of blood supply
interruption of blood supply to the heart from a blood clot/fatty deposit can cause death of cardiac cells within minutes
results in long-term obstruction of coronary circulations
responsible for about half of all deaths in the united states
How is some protection from myocardial infarction given?
arterial anastomoses which provide an alternative route of blood flow known as collateral circulation
Atheroma
blood clot/fatty deposit that obstructs coronary arteries
In myocardial infarction cardiac muscle down stream of the blockage
dies
What is a symptom of myocardial infarction?
heavy pressure/squeezing pain radiating to the left arm
Some painless heart attacks may disrupt x, lead to fibrillation and cardiac arrest
electrical conduction pathways
Which population experiences silent heart attacks?
Diabetics
Elderly
Angina Pectoris
chest pain from partial obstruction of coronary blood flow
pain caused by ischemia of cardiac muscle
obstruction partially blocks blood flow
myocardium shifts to anaerobic fermentation producing lactic acid stimulating pain
Anastomosis
connection that is created between tubular structures, such as blood vessels or loops of intestine
cardiocyte structure
striated, short, thick, branched cells, one central nucleus surrounded by light staining mass of glycogen
intercalated discs
join cardiocytes end to end
interdigitating folds
folds interlock with each other, and increase surface area of contact
mechanical junctions
tightly join cardiocytes
fascia adherens
broad band in which the actin of the thin myofilaments is anchored to the plasma membrane
each cell is linked to the next via transmembrane proteins
desmosomes
weldlike mechanical junctions between cells
prevents cardiocytes from being pulled apart
electrical junction- gap junctions
allows ions to flow between cells- can stimulate neighbors
entire myocardium of either 2 atria or 2 ventricles acts like single unified cell
How is damaged cardiac muscle repaired?
fibrosis
What does cardiac muscle depend on to make ATP?
aerobic respiration
The cardiac muscle is rich in x and y and has huge z.
myoglobin and glycogen
mitochondria that fill 25% of the cell
What organic fuels does the heart use?
60% fatty acids
35% glucose
5% ketones, lactic acid, and amino acids
Cardiac muscle is fatigue resistant because it makes little use of ?
anaerobic fermentation or oxygen debt mechanisms
ischemia
deficient supply of blood to a body part that is due to obstruction of the inflow of arterial blood
The cardiac conduction system coordinates the heartbeat. How does it do this?
internal pacemaker and nerve-like conduction pathways through myocardium
generates and conducts rhythmic electrical signals
sinoartrial node
modified cardiocytes
initiates each heartbeat and determines heart rate
signals spread throughout atria
pacemaker in right atrium near base of superior vena cava
atrioventricular node
located near the right AV valve at lower end of interatrial septum
electrical gateway to the ventricles
fibrous skeleton acts as an insulator to prevent currents from getting to the ventricles from any other route
atrioventricular bundle
bundle forks into right and left bundle branches
branches pass through inter ventricular septum toward apex
purkinje fibers
nerve like processes spread throughout ventricular myocardium
How do signals pass from cell to cell in the cardiac conduction system?
gap junctions
Cardiac Conduction system general process
- SA node fires
- excitation spreads through atrial myocardium
- AV node fires
- Excitation spreads down AV bundle
- subendocardial conducting network distributes excitation through ventricular myocardium
Sympathetic nerves in the heart
raise heart rate and contraction strength
dilates coronary arteries to increase myocardial blood flow
is in the lower cervical to upper thoracic segments of the spine
continues to adjacent sympathetic chain ganglia
some pass through cardiac plexus in mediastinum
continue as cardiac nerves to the heart
fibers terminate in SA and AV nodes, in atrial and ventricular myocardium, as well as the aorta, pulmonary trunk, and coronary arteries
Parasympathetic nerves in the heart
slow heart rate
pathway starts with nuclei of vagus nerves in medulla oblongata
extend to cardiac plexus and continue to the heart by way of cardiac nerves
fibers of right vagus -> SA node
fibers of left vagus -> AV node
little/no vagal stimulation of myocardium
systole
atrial/ventricular contraction
pushes blood out of the heart into the large vessels of the circulatory system, blood pressure increases
diastole
atrial/ventricular relaxation
chambers of the blood fill with blood, blood pressure decreases
sinus rhythm
normal heartbeat triggered by the SA node
set by the SA node at 60-100 bpm
adults at rest is 70-80 bpm (vagal tone)
ectopic focus
another part of heart fires before SA node
spontaneous
caused by hypoxia, electrolyte imbalance, caffeine, nicotine, or other drugs
nodal rhythm
if SA node is damaged, heart rate is set by AV node, 40-50bpm
intrinsic ventricular rhythm
if both SA and AV nodes are not function, rate set at 20-40 bpm
requires a pacemaker to sustain life
arrhythmia
any abnormal cardiac rhythm
failure of conduction system to transmit signals (heart block)
bundle branch block
total heart block (damage to AV node)
atrial flutter
ectopic foci in atria
atrial fibrillation
atria beat 200-400 times per minute -> type of tachycardia
premature ventricular contractions
extra heartbeats that start in ventricles
caused by stimulants, stress, or lack of sleep
ventricular fibrillation
serious arrhythmia caused by electrical signals reaching different regions at widely different times; heart can’t pump blood and no coronary perfusion
kills quickly if not stoped
defibrillation
strong electrical shock whose intent is to depolarize the entire myocardium, stop the fibrillation, and reset SA nodes to sinus rhythm
ectopic foci
region of spontaneous firing from some part of the heart that is not the SA node
Does the SA node have a stable resting membrane potential?
no
What is the starting potential of the SA node?
-60 mV, drifts upward with an inflow of sodium
Gradual depolarization of the SA node is called
pacemaker potential
pacemaker potential
slow inflow of sodium ions without a compensating outflow of potassium
In SA node potentials, when -40mV is reached what opens?
voltage gated calcium and sodium channels open
Faster depolarization occurs at which voltage?
0 mV
Repolarization of the SA node opens what kind of channels?
Potassium
When does pacemaker potential start over?
When potassium channels close
Each depolarization of the SA node sets off how many heart beats?
1
How often does the SA node fire at rest?
every 0.8 seconds/75bpm
The SA node is the cardiovascular system’s?
pacemaker
Signal from the SA node stimulates 2 what to contract almost simulataneously?
atria
After contraction of the atria by the SA node, how long does it take the signal to reach the AV node?
50 milliseconds
Once the signal from the SA node reaches the AV node it slows down. Why?
thin cardiocytes have fewer gap junction
delays signal 100 milliseconds which allows the ventricles to fill with blood prior to the contraction
The signal from the SA node reaches the AV bundle and Purkinje fibers which causes the entire ventricular myocardium to ?
depolarize and contract in near unison
What is the stable resting potential of cardiocytes?
-90 mV
Electrical behavior of myocardium process
- Voltage gated sodium channels open
- sodium inflow depolarizes membrane, positive feedback cycle opens more sodium channels and incr membrane voltage
- sodium channels close when cell depolarizes, voltage peaks at 30mV
- calcium from calcium channels prolongs depolarization and creates a plateau that falls slightly because of potassium leakage
- calcium channels close, potassium channels open, return to resting membrane potential
Depolarization phase
stimulus opens voltage regulated sodium gates, membrane depolarizes rapidly
action potential peaks at 30 mV
sodium gates close quickly
Plateau phase
lasts 200-250 milliseconds
sustains contraction for expulsion of blood from heart
Calcium channels are slow to close and sarcoplasmic reticulum is slow to remove calcium from the cytosol
repolarization phase
calcium channels close
potassium channels open
rapid diffusion of potassium out of the cell
return to resting potential
What is the refractory period of the myocardium?
250 milliseconds
What is the refractory period in skeletal muscle?
1-2 milliseconds
Why is there a refractory period in the myocardium?
to prevent wave summation and tetanus which would stop the pumping action of the heart
Ventricular systole progresses up from the apex of the heart. It is made of spiral arrangements of cardiocytes that
slightly twists ventricles
Tetanus effects on myocardium behavior
stimulus frequency is high
relaxation phase disappears
contractions become continuous
Action potential of a cardiocyte
- Sodium gates open
- rapid depolarization
- sodium gates close
- slow calcium channels open
- calcium channels close, potassium channels open
Electrocardiogram
composite of all action potentials of nodal and myocardial cells detected, amplified and recorded by electrodes on arms, legs, and chest
P wave
SA node fires, atria depolarize and contract
atrial systol begins 100 milliseconds after SA signal
QRS complex
ventricular depolarization
complex shape of spike due to different thickness and shape of the two ventricles
ST segment
ventricular systole
plateau in myocardial action potential
T wave
ventricular repolarization and relaxation
Electrical Activity of Myocardium
- atrial depolarization begins
- atrial depolarization complete- atria contracted
- ventricles begin to depolarize at apex; atria repolarize- atria relaxed
- ventricular depolarization complete- ventricles contracted
- ventricles begin to repolarize at apex
- ventricular repolarization complete- ventricles relaxed
PQ segment
signal conduction from SA node to AV node; atrial systole begins
Diagnostic Values of ECG
abnormalities in conduction pathways
myocardial infarction
nodal damage
heart enlargement
electrolyte and hormone imbalances
Atrial fibrillation EKG
no P wave
has QRS complex
irregular depolarization
Heart Block EKG
fails to generate QRS complexes
Premature Ventricular Contraction EKG
no P wave
inverted QRS complex
Ventricular Fibrillation EKG
no P wave
no QRS complex
irregular depolarization, MI
Oxygen poor blood circulates from
body tissues to vena cava to right atrium to right ventricle to pulmonary arteries to lungs
Oxygen rich blood circulates from
lungs to pulmonary veins to left atrium to left ventricle to aorta to body tissues
coronary circulation
blood circulation to supply the blood to the heart
What variables govern fluid movement?
pressure and resistance
Pressure
causes fluid to flow
gradient can represent a difference between 2 points
measured in mmHg with a manometer/sphygmomanometer
Resistance
opposes fluid flow
great vessels have positive blood pressures
ventricular pressure must rise above this for blood to flow into great vessels
Fluid flows only if there’s a?
pressure gradient
high->low
when a ventricle relaxes/expands its internal pressure?
falls
if bicuspid valve is open blood flows into?
the left ventricle
When a ventricle contracts, internal pressure?
rises
When AV valves close and the aortic valve is pushed open, blood flows into aorta from?
the left ventricle
Opening and closing of valves are governed by ?
AV valves going limp when ventricles are relaxed
semilulnar valves under pressure from blood vessels when ventricles are relaxed
valvular insufficiency
any failure of a valve to prevent reflux, the backward flow of blood
valvular stenosis
cusps are stiffened and opening is constricted by scar tissue
result of rheumatic fever autoimmune attack on the mitral and aortic valves, heart overworks and may become enlarged
heart murmur
abnormal heart sound produced by regurgitation of blood through incompetent valves
mitral valve prolapse
insufficiency in which one or both mitral valve cusps bulge into atria during ventricular contraction
hereditary: 1/40 people
may cause chest pain and shortness of breath
auscultation
listening to sounds made by body
first heart sound (S1)
lounger 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 dump occurs with closure of semi lunar valves, turbulence in the bloodstream, and movements of the heart wall
S3
rarely heard in people over 30
exact cause of each sound is not known with certainty
Phases of Cardiac Cycle
ventricular filling
isovolumetric contraction
ventricular ejection
isovolumetric relaxation
Ventricular filling
during diastole ventricles expand
pressure drops below that of the atria
AV valves open and blood flows into the ventricles
Phases of ventricular filling
- rapid ventricular filling; blood enters very quickly
- diastasis; marked by slower filling, P wave occurs at the end of diastasis
- atrial systole; atria contract
End-diastolic volume
amount of blood contained in each ventricle at the end of ventricular filling
130 mL of blood
Isovolumetric Contraction
atria repolarize and relax; remain in diastole for the rest of the cardiac cycle
ventricles depolarize, make the QRS complex, and begin to contract
AV valves close as ventricular blood surges back against the cusps
heart sound S1
no blood ejected because pressure in aorta and pulmonary trunk is greater than the ventricles
Ventricular Ejection
ventricular pressure exceeds arterial pressure and forces semilunar valve opens
pressure peaks in left ventricle at 120 mmHG and 25mmHg in the right
first rapid ejection, then reduced injection
lasts about 200-250 milliseconds
T wave occurs late in this phase
Stroke volume ejected
70mL
ejection fraction about 54%
In vigorous exercise what percentage of blood is ejected from the ventricle?
90%
end systolic volume
60 mL of blood left behind
Isovolumetric Relaxation
early ventricular diastole
ventricles expand after T wave ends
elastic recoil and expansion would cause pressure to drop rapidly and suck blood into ventricles
blood flows backwards form aorta and pulmonary into the semilunar valves and closes the cusps
S2 heart sound
AV valves have not opened
both ventricles must eject the same amount of blood
QT interval
duration potential of ventricular action
Unbalanced Ventricular Output
- Right ventricular output exceeds left ventricular output
- Pressure backs up
- Fluid accumulates in the lung and systemic tissue
Congestive Heart Failure
results from the failures of either ventricle to eject blood effectively
usually due to a heart weekend by myocardial infarction, chronic hypertension, valvular insufficiency, or congenital defects in heart structure
eventually leads to total heart failure
Left ventricular failure
blood backs up into the lungs causing pulmonary edema
shortness of breath or sense of suffocation
Right ventricular failure
blood backs up in the vena cava causing systemic or generalized edema
enlargement of the liver, as cites, distension of jugular veins, swelling of the fingers, ankles and feet
Stroke volume
volume of blood pumped out of the left ventricle of the heart during each systolic contraction
cardiac output
amount of blood ejected by a ventricle in 1 minute
heart rate x stroke volume
4-6 L/min at rest
A RBC leaving the left ventricle will arrive back at the left ventricle in about?
1 minute
vigorous exercise increases cardiac output to ?
21 L/min for a fit person
35 L/min for world class athlete
cardiac reserve
difference between a person’s maximum and resting cardiac output
increase in cardiac function from rest to peak exercise
increases with fitness, decreases with disease
15 L/min
To keep cardiac output constant as we increase in age, the heart rate increases as
the stroke volume decreases
pulse
surge of pressure produced by each heart beat that can be felt by palpating a superficial artery with the fingertips
heart rate of infants
120 bpm/ +
young adult female heart rate
72-80 bpm
young adult male heart rate
64-72 bpm
Heart rate rises in which age group?
elderly
tachycardia
resting adult heart rate above 100 bpm
stress, anxiety, drugs, heart disease, or fever
loss of blood/damage to myocardium
bradycardia
resting adult heart rate less than 60 bpm
in sleep, low body temp, endurance trained athletes
Positive chronotropic agents
factors that raise the heart rate
potassium deficiency, excess calcium, endogenous catecholamines, nicotine, thyroid hormone, caffeine
Negative chronotropic agents
factors that lower the heart rate
excess potassium, deficiency of calcium, ACh
What does the ANS do to the heartbeat?
modulates rate and force
Cardiac centers in the reticular formation of the medulla oblongata initiate what?
autonomic output to the heart
deciding whether to speed or slow the heart
cardiostimulatory effect
some neurons of the cardiac center transmit signals to the heart by way of sympathetic pathways
cardioinhibitory effect
others transmit parasympathetic signals by way of the vagus nerve
Chronotropic effects of the ANS- sympathetic
post ganglionic fibers are adrenergic, bind to beta 1 fibers
release norepinephrine
activates cAMP -> opening of Ca^2+ in plasma membrane
depolarization of SA node
Ca^2+ taken up by sarcoplasmic reticulum -> cardiocytes relax
heart rate could increase up to 230 bpm
inadequate filling of diastole
stroke volume and cardiac output are reduced
Blood pressure= ?
Systematic vascular resistance x cardiac output
Cardiac output =
stoke volume x heart rate
What are some determining factors of cardiac outputs?
heart rate
contractibility
preload
afterload
heart rate
number of beats per minute
What is the cardio output at rest?
4-6 L/min
What is the cardio output after vigorous exercise?
21 L/min
What pathological conditions decrease cardiac output?
hypertension
myocardial infarction
arrhythmias
cardiac diastole
all chambers relax, blood flows into the heart
artial systole, ventricular diastole
atria contract, pushing blood into the ventricles
Atrial diastole, ventricular systole
after atria relax, ventricles contract and push blood out of the heart
What variables govern stroke volume?
preload
contractility
afterload
What impact does increased preload or contractility have on stroke volume?
increases it
What impact does increased afterload have on stroke volume?
It decreases it
Contractility
force of contraction of the heart muscle which contributes to stroke volume and end-systolic volume
If contractability of the heart muscle increases, cardiac output ?
increases
If contractility is impaired, cardiac output will?
decrease
If there is too much contractility of the heart what happens?
heart stops or collapses
increase in mortality
Inotropic agents
medicines that change the force of your heart’s contractions
positive ionotropic agents
increase contractility
catecholamines increase calcium levels
glucagon stimulates cAMP production
digoxin raises intracellular calcium levels and contraction strength
negative ionotropic agents
decreases contractility
hyperkalemia reduces strength of myocardial action potentials and the release of calcium into the sarcoplasm
vagus nerves have effect on atria but too few nerves to ventricles for a significant effect
Preload
degree of myocardial distension prior to contraction
largely dependent on amount of ventricular filling
filling pressure of the heart at the end of diastole
Afterload
amount of pressure (mmHg) that the heart has to exert to eject the blood during ventricular contraction
dependent on arterial blood pressure and vascular tone
blood pressure in aorta and pulmonary trunk immediately distal to the semilunar valves
opposes opening of valves, limits stroke volume
Ejection fraction = ?
(stroke volume/ end diastolic volume) x 100
Factors affecting preload
increased preload causes increased force of contraction
exercise increases venous return and stretches myocardium
cardiocytes generate more tension during contraction
increased cardiac output matches increased venous return
Frank-Starling Law of Heart
stroke volume is proportional to end diastolic volume
ventricles eject as much blood as they receive
the more the heart fills, the stronger the force of contraction
cardiac output of the left ventricle is the same as the right ventricle
What does hypertension increase? What does it oppose?
increases afterload
opposes ventricular ejection
What can increase afterload?
Anything that impedes arterial circulation
lung diseases that restrict pulmonary circulation
cor pulmonale- right ventricular failure
emphysema
chronic bronchitis
black lung disease
Emphysema
damage to walls of alveoli in lungs
fewer alveoli, less oxygen gas in blood stream
Black lung disease
coal worker’s pneumoconiosis
End diastolic volume
amount of blood contained in each ventricle at the end of ventricular filling
end systolic volume
volume of blood in each ventricle at the end of the systole
Stroke volume =
EDV-ESV
As preload increases, the volume of blood in the heart at the end of diastole?
increases
What are some inputs to the cardiac center?
sensory/emotional stimuli
proprioceptors
baroceptors
chemoreceptors
Proprioceptors
in muscle and joints; sensory receptors
inform cardiac center about changes in activity, heart rate increases before metabolic demands of the muscle arise
Baroreceptors
pressure sensors in aorta and internal carotid arteries
blood pressure decreases, signal rate drops, cardiac center increases heart rate
if blood pressure increases, signal rate rises cardiac center decreases heart rate (negative feedback loop)
Hypercapnia
elevation in the arterial carbon dioxide tension
chemoreceptors
in aortic arch, carotid arteries and medulla oblongata
sensitive to blood pH, CO2 and O2 levels
more important in respiratory control than cardiac control
negative feedback
If CO2 accumulates in blood/CSF and reacts with water, what happens to the H^+ levels? Why is this a problem?
they increase
not good because it lowers blood pH and may create acidosis
Ionotropic influences muscular contractility and chronotropic influences?
heart rate
hypokalemia
deficiency in potassium in cardiocytes, increased excitability
hypercalcemia
excess of calcium
Nicotine stimulates?
catecholamine secretion
Thyroid hormone increases the number of adrenergic receptors on the heart making it more responsive to?
sympathetic stimulation
caffeine
adenosine receptor agonist
increases neurotransmission
when the adenosine receptor is active what decreases?
neural activity
hyperkalemia
excess of potassium
myocardium less excitable, heart rate slows
hypocalcemia
deficiency of calcium
decreases heart rate and contraction strength
ACh is a negative chronotropic agent that does what?
binds to muscarinic receptors
opens potassium gates in nodal cells
hyperpolarizes cells as potassium leaves
Coronary Artery Disease
coronary heart disease/ ischemic heart disease
caused by plaque accumulation of arterial walls and accumulation of lipid deposits
Atherosclerosis
accumulation of lipid deposit is that degrade the arterial wall and obstructed in the lumen
Symptoms of Coronary Artery Disease
chest pain
weakness, light-headedness, nausea
pain/discomfort in arms/shoulder
shortness of breath
How can coronary artery disease be treated?
coronary bypass surgery- take arteries/veins from other parts of body
balloon angioplasty followed by a coronary artery stent
laser angioplasty followed by placement of a coronary artery stent
Arteries
carry blood away from the heart, oxygenated
sometimes called resistance vessels
thicker tunica media in proportion to lumen, little tunica externa
high blood pressure
no valves
biggest: aorta ; smallest: arteriole
Veins
carry blood back to the heart, deoxygenated
greater capacity for blood containment than arteries
thinner walls, larger lumen
tunic media has less smooth muscle and tunica externa has thick, collagen and elastic fibers
subjected to relatively low blood pressure (10mmHg)
biggest: vena cava ; smallest: venule
Capillaries
connect arteries and veins, smallest blood vessels
contacts tissues and supplies oxygen, CO2, waste, nutrients, and hormones
gas exchange
only tunica intima, very small lumen thickness
distribution varies with metabolic activity of body tissues
low pressure, no valves
What are the layers of the blood vessel?
Tunica extrema/adventitia: outer layer
Tunica media: middle, thickest layer
Tunica intima/interna: innermost layer
What is the tunica intima made of?
squamous epithelium
surrounded by a connective tissue basement membrane and elastic fibers
What is the tunica media made of? What is it regulated by? What does it regulate?
smooth muscle, elastic fiber
regulated by ANS
regulates blood flow and pressure
What is the tunica extrema do and what is it made of?
protects and structural enforcement
connective tissue, elastic, and collagenous fibers
Conducting arteries
biggest arteries, near heart, pumps blood to body
aorta, common carotid, subclavian, pulmonary trunk, and common iliac arteries
layer of elastic tissue, internal elastic lamina, at border between interna and media and external elastic lamina at the border between media and external
expand during systole, recoil during diastole
lessens fluctuations in blood pressure
Distributing arteries
distributes blood to specific organs, most abundant arteries
brachial, femoral, renal, splenic
smooth muscle layers constitute 3/4ths of wall thickness
arterioles
smallest arteries
connect to capillaries, low blood pressure, thin wall thickness
control amount of blood to various organs
metarterioles
short vessels that link arterioles to capillaries
muscle cells form precapillary sphincter about entrance to capillary
constriction reduces/shuts of blood flow
diverts blood to other tissues
continuous capillaries
tight junctions, lowest permeability
most common, in skin and muscles
allows passage of solutes such as glucose
fenestrated capillaries
pores, relatively high permeability
kidney’s, small intestine
organs that require rapid absorption/filtration
pore receive nutrients and hormones, allow passage of only small molecules
Sinusoids (discontinuous capillaries )
large intracellular gaps and gaps in between basement membrane
extremely high permeability
liver, bone marrow, spleen
allows proteins, clotting factors, and new blood cells to enter circulation
Capillary beds
capillaries organized into networks
supplied by a single metarteriole
Thoroughfare channel-metiarteriole
continues through capillary bed to venule
vascular shunt mechanism- redirection of blood flow
precapillary sphincters
control which beds are well perfused
when sphincters open capillaries well perfused 3/4ths of capillaries in body shut down
when sphincters closed, blood flows through vascular shunt
What fraction of the bodies capillaries are shut down at a given time?
3/4ths
Blood flow in capillaries is also known as ?
micro circulation
Venous valve
prevents backflow of blood, so blood can flow against gravity
postcapillary venules
10-20 um in diameter
smallest veins
receive blood from capillaries
muscular venules
up to 1mm in diameter
receive blood from postcapillary venules
medium veins
up to 10 mm in diameter
most veins have individual names
venous valves are a type of this
venous sinuses
veins with thin walls, large lumens, no smooth muscle, no vasomotion
larger veins
greater than 10mm in diameter
examples include venae cavae, pulmonary veins, internal jugular veins, and renal veins
Blood pressure
force blood exerts against a vessel wall
How do you measure blood pressure?
brachial artery of arm using sphygmomanometer
Systolic blood pressure
top number
pressure in arteries when the heart is beating and sending blood into arteries
maximal aortic pressure following ejection
Diastolic blood pressure
bottom number
minimum arterial blood pressure taken during ventricular relaxation between heart beats
Hypertension
high blood pressure
Normal Blood Pressure
Systolic: less than 120
AND
Diastolic: less than 80
Elevated blood Pressure ranges
systolic: 120-129
AND
diastolic: less than 80
High Blood Pressure Stage 1 Ranges
systolic: 130-139
OR
diastolic: 80-89
High Blood Pressure Stage 2 Ranges
systolic: 140 or higher
OR
diastolic: 90 or higher
Hypertensive crisis ranges
systolic: higher than 180
AND/OR
diastolic: higher than 120
Hypotension
90/60 mmHg or lower
Why is the systolic pressure more important?
major indicator of cardiovascular disease
increased stiffness of large arteries
buildup of plaque (atherosclerosis)
Clinical implications of hypertension
aneurysm: bulges in weak blood vessel point
atherosclerosis: build of up lipid deposits
myocardial infarction
stroke
heart failure
Clinical implication of hypotension
blood loss
dehydration
anemia
Why does anemia cause hypotension?
low hemobglobin -> decrease oxygen -> blood vessels swell -> blood pressure lowers
pulse pressure
difference between systolic and diastolic pressure
Wide pulse pressure
greater than 40 mmHg
heart is working harder/ arteries less flexible
physically inactive at risk
indicator of heart disease, heart rhythm disorders, stroke, and other cardiovascular disease complications
Narrow Pulse pressure
less than 40 mmHg
your heart does not pump enough blood
heart failure, heart valve disease, or loss of blood
Mean Arterial Pressure
average arterial pressure throughout one cardiac cycle
= diastolic pressure + (1/3)pulse pressure
Average blood pressure that most influences risk level for?
edema, fainting, atherosclerosis, kidney failure, and aneurysm
Distance from the left ventricle
factor affecting blood pressure
increase distance, decrease blood pressure
due to arterial elasticity and effect of friction against vessel wall
no pulse pressure beyond arterioles
Cardiac output, blood volume, and peripheral resistance
factor affecting blood pressure
resistance hinges on blood viscosity, vessel length, and vessel radius
As you get older what does blood pressure do?
increases
arteries with less dispensable and absorb less systolic force
Peripheral resistance
opposition to flow that blood encounters in vessels away from the heart
What are the 3 variables of peripheral resistance?
blood viscosity
vessel length
vessel radius
How does [RBC and albumin] affect viscosity?
increases it
How do anemia and hypoproteinemia impact viscosity?
decrease it
How do polycythemia and dehydration impact viscosity?
increase it
Polycythemia
abnormal increase of RBCs
The farther liquid travels, the more cumulative friction it encounters. This means pressure and flow xxx with distance?
decrease
What has the most powerful influence over flow?
vessel radius
vasomotion
spontaneous change in vessel radius
rhythmical contraction-relaxation mechanism (oscillation frequency)
independent of heart beat, innervation or respiration
vasoconstriction
muscular effort that results in smooth muscle contraction
vasodilation
relaxation of the smooth muscle
laminar flow
streamline flow, flows in layers
faster in layers, slower near the wall
turbulent flow
does not flow linearly, flow is chaotic
Vessel radius affects
blood velocity
Blood flow is proportional to
r^4
A larger vessel radius leads to what kind of flow
greater average
Why does blood velocity decrease from the aorta to the capillaries?
greater distance; more friction to reduce speed
smaller radii of arterioles and capillaries offers more resistance
farther from heart, number of vessels and their total cross-sectional area becomes greater
Why does blood flow increase from the capillaries to the vena cava?
decreased resistance going from capillaries to veins
large amount of blood forced into smaller channels
never regains velocity of large arteries
What are the most significant points of control over peripheral resistance and flow?
arterioles; they are highly capable of vasomotion
What produces half of the total peripheral resistance?
Arterioles
Why is vasomotion important?
Aids blood flow through tissues by reducing resistance
regulates oxygen, fluid, and nutrient exchange between the vascular system and peripheral tissues
for arterioles and capillaries
Unregulated Vasomotion can lead to conditions such as?
hypoperfuison and hypoxia
What are the three general controls of vasomotion?
local control
neural control
hormonal control
Autoregulation
ability of tissues to regulate their own blood supply
bloodstream delivers oxygen, incr blood flow, removes metabolites, and the constricts vessels
type of local control
Metabolic theory of autoregulation
if a tissue is inadequately perfused, waste accumulates
vasoactive chemicals
substances secreted by platelets, endothelial cells, and perivascular tissue stimulate vasomotion
Histamine, bradykinin, and prostaglandins stimulate?
vasodilation
What do endothelial cells secrete?
prostacyclin
nitric oxide
endothelin
Reactive hyperemia
transient increase in blood flow following brief ischemia
if blood supply is cut off then restored, flow increases above normal
Angiogenesis
growth of new blood vessels
Where does angiogenesis occur?
in regrowth of uterine lining, around coronary artery obstructions, exercised muscle, and malignant tumors
In neural control, vessels are controlled by?
the CNS and ANS
Vasomotor Center of medulla oblongata
exerts sympathetic control over blood vessels
stimulates most vessels to constrict
dilates vessels in skeletal and cardiac muscle
What 3 autonomic reflexes is the vasomotor center the integrating center for?
baroreflexes
chemoreflexes
medullary ischemic reflex
Carotid vessels
supply blood to brain, face and neck
Carotid sinus
structure appearing as a dilation at the proximal end of the internal carotid artery and above the branches of the common carotid artery into the internal/external carotid artery
Baroreflex
automatic, negative feedback response
incr BP detected by carotid sinuses
inhibit sympathetic cardiac and vasomotor neurons; reduces sympathetic town, decreases blood pressure
important in short term regulation of blood pressure
Chemoreceptors
in aortic arch, carotid arteries and medulla oblongata
sensitive to blood pH, CO2, and O2 levels
important in respiratory control
negative feedback loop
Hypercapnia and acidosis stimulate the cardiac center to increase?
heart rate
Medullary Ischemic Reflex
automatic response to a drop in perfusion of the brain
increase heart rate, contraction force, and blood pressure
causes widespread vasoconstriction
Stress, anger, and arousal can increase?
blood pressure
How do hormones influence blood pressure?
through vasoactive effects and regulating water balance
Aldosterone
promotes sodium and water retention by kidneys
increase blood volume and pressure
Atrial natriuretic peptide
increases urinary sodium excretion
reduces blood volume and promotes vasodilation
lowers blood pressure
Antidiuretic hormone
promotes water retention and raises blood pressure
can be a vasoconstrictor at pathologically high concentrations
Epinephrine and norepinephrine can be used in?
hormonal control
What happens during vigorous exercise?
Dilation of arteries in lungs, heart, and muscles
vasoconstriction in kidneys and digestive tract
What is the most important blood in the body?
Capillaries
Capillary Exchange
2 way mvmt of fluid across capillary walls
3 Routes of capillary exchange
through endothelial cell cytoplasm
intercellular clefts between endothelial cells
filtration pores of fenestrated capillaries
What 4 mechanisms are involved in capillary exchange?
diffusion
transcytosis
filtration
reabsorption
Capillary diffusion can only occur if
solute can permeate plasma membrane and find passages large enough to pass through
Capillary Transcytosis
vesicular transport of macromolecules from one side of a cell to the other
important for fatty acids, albumin, and hormones
Blood hydrostatic pressure
drives fluid out of capillary
Colloid osmotic pressure
draws fluid into capillary
What percentage of fluid do the capillaries reabsorb?
85%
What percentage of fluid is reabosorbed by the lymphatic system and returned to blood?
15%
Where does capillary filtration occur?
arterial end
Where does capillary reabsorption occur?
at the venous end
Kidney capillaries
in glomeruli do not reabsorb, devoted to filtration
alveolar capillaries
in lung absorb completely to keep fluid out of air spaces, devoted to absorption
In resting tissue, capillary activity focuses on ?
reabsorption
In active tissue, capillary activity ?
increases in flow
edema
accumulation of excess fluid in a tissue
could be caused by increased capillary filtration, reduced capillary absorption, or obstructed lymphatic drainage
Venous return
flow of blood from the veins back to the right atrium of the heart
blood pressure is the most important part
Gravity drains blood from the head and neck to?
the heart
Where is the skeletal muscle pump and what is it?
in the limbs
contracting muscle squeezed out of the compressed part of the vein
During inhalation what does the thoracic cavity do?
it expands and the diaphragm contracts
blood is forced upward
During exhalation what does the thoracic cavity do?
contracts, pressure increases
circulatory shock
any state in which cardiac output is insufficient to meet the body’s metabolic needs
low venous return
cardiac output is low because too little blood is returning to the heart
hypovolemic shock
most common low venous return
loss of blood
obstructed venous return shock
tumor/aneurysm compresses a vein
type of low venous return
venous pooling shock
long periods of standing, sitting or widespread vasodilation
septic shock
bacterial toxins trigger vasodilation and increased capillary permeability
life-threatening condition, BP drops to a dangerously low level after an infection
anaphylactic shock
severe immune reaction to antigen, histamine release, generalized vasodilation, increased capillary permeability
How does exercise increases venous return?
heart beats faster, harder increasing CO and BP
vessels of skeletal muscles, lungs, and heart dilate and increase flow
increased respiratory rate, increased action of thoracic pump
increases skeletal muscle pump
What are the 6 principle organs of the urinary system?
2 kidneys
2 ureters
the urinary bladder
the urethra
What does the kidney regulate?
blood volume and pressure
osmolarity
renin
EPO
CO2 and acid-base balance
What does the kidney do?
filters blood stream
reabsorbs components
removes toxins, waste, and extra fluid
renal pyramids
structure containing nephrons and tubules
renal columns
extension of the cortex, in-between renal pyramids
lobe of the kidney
renal pyramid and a renal cortex
renal pelvis
funnel-shaped sac, minor calyx, major calyx
renal papilla
apex of a renal pyramid
minor calyx
surrounds renal papilla, collects urine from the pyramid
ureter
tubular continuation of the pelvis and drains the urine down to the urinary bladder
unfiltered blood flows into?
kidneys through renal artery
nephron
filtering unit of kidney
1.2 million per kidney
includes glomerulus and tubule
kidney filtration amount
150 qts/day
Most of the water and other substances filtering through glomeri are returned to the body by the ?
tubules
glomerulus
masss of capillaries around the end of kidney tubule
filter blood
small molecules pass into it, larger ones stay out
Renal corpuscle
glomerulus and a two-layered glomerular
Tubule
long coiled tube that converts the filtrate into urine
Order of fluid flow through tubules
- proximal convoluted tubule
- nephron loop
- distal convoluted tubule
- collecting duct
Renal circulation receives about 21% of ?
the cardiac output
order of blood flow through the kidney
- renal artery
- afferent arterioles
- capillaries
- glomerulus
- efferent arterioles
- peritubular capillaries/vasa recta
2 types of microcirculation in kidney
glomerular capillary system
peritubular capillary system
What can pass through the filter in glomerular filtration?
water
electrolytes
glucose
amino acids
fatty acids
vitamins
urea
uric acid
creatinine
Urine Composition
95% water
2% urea
0.1% Creatinine
0.03% uric acid
electrolytes
Indicators of Kidney function
creatinine
blood urea nitrogen
3 steps of urine formation
- Glomerular Filtration
- Tubular reabsorption and secretion
- water conservation
Net filtration pressure
total pressure that promotes filtration
glomerular blood hydrostatic pressure - colloid osmotic pressure - capsular hydrostatic pressure = this
glomerular blood hydrostatic pressure
blood pressure in glomerular capillaries
push water and solutes in plasma through glomerular filter
Colloid osmotic pressure
prevents net movement of water into a solution containing solutes
Capsular hydrostatic pressure
back-pressure opposing filtration
filtrate is forced into the capsular space
glomerular filtration rate
amount of filtrated formed per minute by the 2 kidneys combined
indicator of kidney disease
normal range 90-120 mL/min/1.73m^2
measured with a blood test to check creatine levels
Indicators to determine renal impairment
GFR
degree of albuminuria
If GFR is less than 60 it indicates
kidney disease
If GFR is less than 15 it indicates
need of dialysis or kidney transplant
Degree of albuminuria
level of albumin present in urea
normal range of albumin to creatine ratio is above 30 mg/mmol
Renal autoregulation
ability of the nephrons to adjust their own blood flow and GFR without external control
regulates glomerular filtraiton
Sympathetic controls
sympathetic nerve fibers innervate the renal blood vessels
under acute conditions sympathetic stimulation and adrenal epinephrine constrict afferent arterioles
regulates glomerular filtration
Renin-Angiotensin-Aldosterone Mechanism
activated by a drop in blood pressure
acts to raise blood pressure
secret renin-> converts angiotensinogen into Angiotensin 1 -> ACE converts it into angiotensin 2, the active hormone
What is most sodium reabsorbed by?
the proximal convoluted tubule
What percentage of water is reabsorbed at the proximal tubule?
65%
What are the two types of capillary systems in the kidney?
Glomerular and peritubular
Vasa Recta
presents in the medullary and is closer to the nephron loop
What is the function of the nephron loop?
generate an osmotic gradient that enables the collecting duct to concentrate the urine and conserve water
sodium and water reabsorption
How do loop diuretics work?
reduce NaCl reabsorption in ascending limb of the loop of Henle
increases urine volume-> reduce the fluid volume of the body and blood pressure
Where is the major place of secretion in the kidney?
Distal convoluted tubule
Angiotensin 2
potent vasoconstrictor
incr blood pressure
hormone
aldosterone
salt retaining hormone
increases blood pressure
atrial natriuretic peptide
made by heart
if high level indicates congestive heart failure
decreases blood pressure
antidiuretic hormone
promotes water retention and raises blood pressure
What makes pee yellow?
urochrome
Pyuria
cloudy, potential indicator of bacterial growth
Hematuria
blood in urine, potential indicator of UTI or kidney stone
Phenylketonuria
mousy odor
Urinary tract infection odor
rotten
polyuria in diabetes mellitus
> 2L per day or urine
Urine volume
1-2 L per day
Renal clearance
volume of blood plasma from which a particular waste is completely removed in 1 minute
Glomerular filtration of waste + amount added by tubular secretion - amount removed by tubular reabsorption
Can you determine GFR from urea excretion?
no
Inulin or creatinine is useful for ?
GFR measurement
How does the female urethra compare to the male urethra?
it’s shorter
Why are women more susceptible than men to bladder infections?
The relatively short female urethra is less of an obstacle for bacteria traveling from perineum to the urinary bladder
What inhibits the release of urine?
urethral sphincters
Internal urethral sphincter
regulates involuntary control of urine flow from the bladder to the urethra
External urethral sphincter
regulate voluntary control of urine flow from the bladder to the urethra
When the bladder is filling the detrusor is xxx and the external urethral sphincter is xxx.
relaxed
closed by somatic fibers
