Exam 2 Flashcards
arteries
carry blood away fro heart
veins
carry blood toward the heart
capillaries
exchange with air sacs in the lungs and system cells
the hearts 4 chambers
left and right atrium
left and right ventricles
left atrium and right atrium
superior chambers that receive blood and send it to ventricles
left and right ventricles
inferior chambers that pump blood away
which side of the heart has oxygenated blood
left
which side of the heart has deoxygenated blood
right
function of heart valves
prevent back flow to ensure one way blood flow
atrioventricular valves
right (tricuspid) and left (mitral, bicuspid) AV valve are between atrium and ventricle
semilunar valves
pulmonary and aortic semilunar valves are between a ventricle and an arterial trunk
entierity of CV system circulations
- right atrium passes deoxygenated blood from head and neck region forcing valve to open entering into right ventricle
- right ventricle contracts, pulmonary semilunar valve opens sending deoxygenated blood to each lung where gas exchange occurs
- oxygenated blood returns through pulmonary veins into left atrium which contracts causing left AV valve to open and send blood into ventricle
- ventricle contracts sending blood to aortic semilunar valve and through to systemic cells and tissues in the body where more gas exchange occurs causing blood to become deoxygenated again and heads back to right atrium
pulmonary circulation
transports blood from right side of heart to the alveoli of the lungs for gas exchange and back to the left side of the heart
steps of pulmonary circulation
- deoxygenated blood enters right atrium from SVC and IVC and coronary sinus
- blood passes through right AV valve
- enters the right ventricle,
- passes through pulmonary semilunar valve, and
- enters the pulmonary trunk
- blood contrinues through the right and left pulmonary arteries to both lungs, and
- enters pulmonary capillaries of both lungs for gas exchange
- blood is now oxygenated, enters right and left pulmonary veins and is returned
- to the left atrium of heart
systemic circulation
transports blood from left side of heart to the systemic cells of the body for nutrient and gas exchange and back to right side of heart
systemic circulation steps
- oxygenated blood enters the left atrium
- blood passes through left AV valve,
- enters the left ventricle,
- passes through aortic semilunar valve, and
- enters the aorta.
- this blood is distributed by the systemic arteries, and
- enters the systemic capillaries for nutrient and gas exchange
- this blood which is now deoxygenated, ultimately drains into the SVC, IVC, and coronary sinus, and
- enters the right atrium
pericardium
refers to the three layer of the heart
fibrous pericardium
outer layer of pericardium
contains fibrous connective tissue
serves for protection, stabilization of heart, prevention of overfilling of ventricles
serous pericardium
internal layers beneath fibrous pericardium that contains visceral layer, parietal layer, and pericardial cavity
visceral layer
innermost layer
lines and covers the viscera
parietal layer
layer beneath fibrous pericardium
pericardial cavity
filled with cardiac fluid
used for lubrication for pumping of blood consistently
heart wall thickness
ventricle have thicker walls than atria
left ventricle has thicker wall than right
- left must generate high pressure to force blood through systemic circulation; right must pump to nearby lungs
three layers of heart wall
epicardium
myocardium - cardiac muscle
endocardium - continuous w endothelial lining
histology of cardiac muscle
striated muscle
short and branching
intercalated discs
why are cardiac muscles striated
due to arrangement of contractile proteins and overlapping nature of thick and thin filaments
intercalated discs
desmosomes:
proteins that serve to connect two adjacent cells
projections of desmosomes become embedded in cell membrane
gap junctions:
rest on folded sarcolemma and function as proteins that have an opening in the center, ions pass through opening and serve an important role in contraction and activation of muscle, provide electrical current
sarcoplasmic reticulum is a
storage site for calcium
metabolism of cardiac muscle
high demand for energy (extensive blood supply, numerous mitochondria, myoglobin and creatine kinase)
able to use different types of fuel molecules (fatty acids, glucose, lactic acid, amino acids, and ketone bodies)
relies mostly on aerobic metabolism (makes it susceptible to failure when O2 is low, interference w blood flow can cause cell death)
creatine kinase helps
transfer P to give it to ADP creating ATP to combine with creatine
fibrous skeleton
dense irregular connective tissue
-provides structural support at boundary of atria and ventricles
-forms fibrous rings to anchor valves
-provides framework for attachment of cardiac muscle
-acts as electrical insulator preventing ventricles from contracting at same time as atria
coronary circulation
delivers blood to heart’s thick wall
coronary arteries transport oxygenated blood to heart wall
coronary veins transport deoxygenated blood away from heart wall toward right atrium
arteries involved in coronary circulation
right coronary artery
posterior IV artery
right marginal artery
left coronary artery
circumflex artery
anterior IV artery
conduction system
initiates and conducts electrical events to ensure proper timing of contractions
-specialized cardiac muscle cells that have action potentials but do not contract
-its activity is influenced by autonomic nervous system
sinoatrial nodes
SA or pacemaker
tissue in posterior wall of right atrium that
sets pace for generating action potential
atrioventricular node
AV node
impulse is conducted along IV septum where it reaches AV bundle (bundle of His) and then along bundle it splits into right and left AV bundles and travels down to the apex of heart and follows right and left AV bundles as they become Purkinjie fibers
cardiac center of medulla oblongata
contains cardioacceleratory and cardioinhibitory centers
recieves signals from baroreceptors and chemoreceptors in CV system
sends signals via sympathetic and parasympathetic pathways
modifieds cardiac activity (doesn’t initiate it)
-influences heart rate and force of contraction
parasympathetic innervation and heart rate
decreases
sympathetic innervation and heart rate
increases heart rate and force of contraction
physiologic processes associated with heart contraction
conduction system
1. initiation : SA node initiates action potential
2. spread of action potential : an action potential is propagated throughout the atria and the conduction system
cardiac muscle cells
1. action potential : action potential is propagated across the sarcolemma of cardiac muscle cells
2. muscle contraction : thin filaments slide past thick filaments and sarcomeres shorten within cardiac muscle cells
SA node cellular activity
RMP of -60 mV
Na/K pumps and Ca2+ pumps along membrane of nodal cell help actively transport sodium out of cell and potassium into cell so concentration of sodium is greater outside than inside
activity of SA node
- RMP at -60mV DEPOLARIZATION (becomes more positive)
- increase in mV ^ depolarization
- -40mV for threshold voltage (repolarization)
- when cell is negative enough it causes action potential
steps in generating action potential of SA node
- reaching threshold
- slow voltage gated Na+ channels open, inflow of Na+ changes MP from -60mV to -40mV - depolarization
- fast voltage gated Ca2+ channels open, inflow of Ca2+ changes MP from -40mV to just above 0 - repolarization
- fast voltage gated Ca2+ channels close. voltage gated K+ channels open allowing K+ outflow. MP returns to RMP -60mV and K+ channels close
initiation and spread of action potential through cardiac conduction system
- action potential is generated at SA node. it spreads via gap junctions between cardiac muscle cells throughout the atria to the AV node
- action potential is delayed at AV node before it passes to the AV bundle within the interventricular septum
- the AV bundle conducts the action potential to the left and right bundle branches and then to the purkinje fibers
- the action potential is spread via gap junctions between cardiac muscle cells throughout the ventricles
cardiac muscle cells RMP
-90 mV
at RMP potential in cardiac muscle cells, which pump remains closed
all pumps remain closed so concentration gradient for ions remains stable
electrical events of cardiac muscle cells
- depolarization - starts at -90mV and then has rapid increase to +30mV
- plateau - almost no change for that period of time until cell repolarizes it is refractory to further stimuli, want to delay to prevent hazard from normal synchronous behavior of heart
- repolarization
steps of electrical events of cardiac muscle cells
- depolarization: fast voltage gated Na+ channels open and Na+ rapidly enters the cell, reversing the polarity from negative to positive (-90mV to +30mV). these channels then close.
- plateau: voltage gated K+ channels open and K+ flows out of cardiac muscle cells. Slow voltage gated Ca2+ channels open and Ca2+ enters the cell with no electrical change and the depolarized state is maintained
- repolarization: voltage gated Ca2+ channels close, voltage gated K+ channels remain open and K+ moves out of the cardiac muscle cell, and polarity is reversed from positive to negative (+30mV - -90mV)
electrocardiogram
ECG/EKG
skin electrodes detect electrical signals of cardiac mucles cells
common diagnostic tool
p wave
reflects electrical changes of atrial depolarization originating in SA node
QRS complex
electrical changes associated with ventricular depolarization
atria simultaneously repolarizing
t wave
electrical change associated with ventricular repolarization
what two segments of ECG correspond to plateau phase of cardiac action potentials
P-Q segment and S-T segment
p-q segment
associated with atrial cell’s plateau
atria are contracting
s-t segment
associated with ventricular plateau
ventricles are contracting
P-R interval
time from beginning of P wave to beginning of QRS deflection
from atrial depolarization to beginning of ventricular depolarization
time to transmit action potential through entire conduction system
Q-T interval
time from beginning of QRS to end of T wave
reflects the time of ventricular action potentials
length depends upon heart rate
cardiac cycle
all events in heart from the start of one heart beat to start of the next
- systole (contraction) and diastole (relaxation)
contraction _______ pressure; relaxation _______ it
increases;decreases
blood moves down pressure gradient (high to low)
valves ensure blood flow is forward (closes to prevent backflow)
what is the most important driving force in cardiac cycle
ventricular activity
ventricular contraction
raises ventricular pressure
AV valves pushed closed
semilunar valves pushed open and blood ejected to artery
ventricular relaxation
lowers ventricular pressure
semilunar valves close (no pressure from below keeping them open)
AV valves open (no pressure pushing them closed)
phases of cardiac cycle
- atrial contraction and ventricular filling
- isovolumetric contraction
- ventricular ejection
- isovolumetric relaxation
- atrial relaxation and ventricular filling
atrial contraction and ventricular filling (1)
atria CONTRACT , ventricles RELAX
ventricular pressure is less than BOTH atrial pressure and arterial trunk pressure
AV valves OPEN , semilunar valves CLOSED
isovolumetric contraction (2)
atria RELAX , ventricles RELAX
ventricular pressure is greater than atrial pressure but NOT greater than arterial pressure
AV valves CLOSED , semilunar valves CLOSED
ventricular ejection (3)
atria RELAX , ventricles CONTRACT
ventricular pressure is greater than BOTH atrial pressure and arterial pressure
AV valves CLOSED , semilunar valves OPEN
isovolumetric relaxation (4)
atria RELAX , ventricles RELAX
ventricular pressure greater than atrial pressure but NOT arterial trunk pressure
AV valves CLOSED , semilunar valves CLOSED
atrial relaxation and ventricular filling (5)
atria RELAX , ventricles RELAX
ventricular pressure is LESS than BOTH atrial pressure and arterial trunk pressure
AV valves OPEN , semilunar valves CLOSED
cardiac output
amount of blood pumped by a SINGLE ventricle in one minute (L/min)
measure of effectiveness of CV system
increases in healthy individuals during exercise
determined by HR (bpm) and stroke volume (SV - amount of blood ejected per beat)
HR x SV = CO
stroke volume
amount of blood ejected in one beat from ONE ventricle
influenced by venous return, inotropic agents, and afterload
venous return
volume of blood returned to the heart
directly related to stroke volume
determines amount of ventricular blood prior to contraction (end-diastolic volume (EDV))
volume determines preload
- pressure stretching heart wall before shortening
frank starling law (starlings law)
as EDV increases, the greater stretch of heart wall results in more optimal overlap of thick and thin filaments
heart contracts more forcefully when filled with more blood so SV increases
venous return may be increased by
increased venous pressure or increased time to fill
-venous pressure increases during exercise as muscles squeeze veins
-time available to fill increases with slower heart rate (high-caliber athletes w strong hearts)
venous return steps
volume of blood return to heart per unit time
1. increased venous return (occurs w greater venous pressure or slower heart rate)
2. increases stretch of heart wall (preload), which results in greater overlap of thick and thin filaments within the sarcomeres of the myocardium
3. additional corssbridges form, and ventricles contract with greater force
4. stroke volume increases
opposite occurs in smaller venous return (rapid heart rate , hemorrhage
what variable influence stroke volume
venous return
inotropic agents
afterload
inotropic agents
substances that act on myocardium to alter contractility
1. positive inotropic agents (e.g., stimulation by sympathetic nervous system)
2. increased Ca2+ levels in sarcoplasm results in greater binding of Ca2+ to troponin of thin filaments within sarcomeres of myocardium
3. additional crossbridges form, and ventricles contract with greater force
4. stroke volume increases
oppositive is seen w negative inotropic agents (e.g. calcium channel blockers)
afterload
resistance in arteries to ejection of blood
1. atherosclerosis, which is deposition of plaque on the inner lining of arteries, is typically only a factor as we age
2. arteries become more narrow in diameter
3. increases the resistance to pump blood into the arteries
4. stroke volume DECREASES
chronotropic agents
alter SA node and AV node activity
positive and negative agents
positive -increase HR
negative - decrease HR
increase or decrease in HR directly impacts cardiac output
venous return is directly correlated with
stroke volume which directly affects cardiac output
inotropic agents contain
positive agents - increase SV
negative agents - decrease SV
increase or decrease in stroke volume impacts CO
afterload is INVERSELY correlated with
stroke volume which is directly correlated with CO
fetal vs neonatal circulation
foramen ovale passes most of blood through right atrium to left
some falls into right ventricle and then oxygenated blood will go to pulmonary trunk and pass through ductus arterioles
ductus arteriosis connects aorta and pulmonary trunk
deliver oxygen to developing lung tissue
three types of blood vessels
arteries
capillaries
veins
tunica intima
consists of endothelium and subendothelial layer
endothelium- single layer of endothelial cells
subendothelial - loose connectie tissue containing collagen fibers
tunica media
composed of smooth muscle (thick layer)
as they contract, it influences diameter of lumen
contains elastic laminae, and elastic fiber to stretch and recoil
tunica externa
primarily loose connective tissue
small network of vessels is called vasa vasorum with represent blood supply to components of the vessel
artery branching
brnach into smaller vessels extending from heart
decrease in lumen diamter
decrease in elastic fibers
increase in relative amount of smooth muscle
composed of : elastic arteries, muscualr arteries, arterioles
capillary characteristics
small vessels connecting arterioles to venules
average length = 1mm; diameter = 8 to 10 micrometers
rouleau
wall consists of endothelial layer on basement membrane
thin wall and small diameter are optimal for exchange between blood and tissue fluid
three types: continuous, fenestrated, and sinusoid
continuous cappilaries
endothelial cells form a continuous lining
tight junctions connect cells but don’t form a complete seal
-intercellular clefts are gaps between endothelial cells of capillary wall
-large particles (cells and proteins) cannot pass but smaller molecules (glucose) can