Chapter 12 (Midterm 2) Flashcards
Why does the left side of the heart have more myocardium tissue than the right side?
it needs more pressure to move blood throughout the body and maintains the same flow rate as the right side
What differentiates the arterioles from the other microcirculation vessels?
covered in smooth muscle cells = regulates pressure and controls where blood flows
What differentiates the venules from the other microcirculation vessels?
covered in of connective tissue = can stretch more
What differentiates the capillaries from the other microcirculation vessels?
purely consists of endothelial cells = site of exchange
What are the two advantages of parallel blood flow?
allows the control of blood flow to each organ, deO2 blood/waste are not traveling from one organ to another
What is the importance of parallel blood flow?
to make sure that each of the peripheral organs and tissues receives only a fraction of the blood pumped by the left ventricle
What drives blood flow?
resistance from the vessels and the pressure from the heart
What is hydrostatic pressure?
pressure exerted by any fluid
What is resistance (R) to flow?
how hard it is for blood to flow between two points at any given pressure difference
What is resistance controlled by?
the vessels
What is pressure controlled by?
the heart
What is the equation for blood flow?
the difference in high and low pressure (from the heart) divided by the resistance (from the vessels)
What is the myocardium?
middle layer of the heart muscle
What is the myocardium composed of?
cardiac muscle and forms the bulk of the heart mass
What is the function of myocardium?
the layer of the heart that contracts = generates force to pump blood out of the heart
What are the important features of cardiac muscles that are unique?
many large mitochondria, high resistance to fatigue, few wide T-tubules, no triads
What is the advantage of having a high resistance to fatigue for cardiac muscles?
no relaxation stage = constant beating
What are intercalated discs?
connecting junctions between cardiac cells
What do intercalated discs contain?
desmosomes and gap junctions
What is an advantage of having an increased number of desmosomes?
heart increases in surface area
What is the function of desmosomes?
holds the cardiac cells together and prevents them from separating during contraction = allows for a unison beating
What is the function of gap junctions?
allows ions to pass from electrically coupled adjacent cells
What does functional syncytium mean?
to be a single coordinated unit
What allows the heart to be a functional syncytium?
gap junctions
What is the purpose of functional syncytium for a heart?
allows for even blood flow
What is the sinoatrial (SA) node?
a small group of conducting cells
What is the pacemaker for the entire heart?
the SA node
What determines heart rate?
the discharge rate of action potentials released from the SA node
What is the atrioventricular (AV) node?
the link between the atrial and ventricular depolarization
What does laminar flow mean?
normal blood flow through the valves and vessels, makes no sound
What does a stenotic valve mean?
a narrowed valve, doesn’t fully open
What is an insufficient valve?
a leaky valve that can cause backflow
What does a stenotic or insufficient valve indicate?
turbulent flow
How can a doctor diagnose a patient whose blood flow is turbulent?
listen for a heart murmur
What is the internodal pathway?
low resistance conducting-cell pathway connecting the sinoatrial and atrioventricular nodes of the heart
Where in the heart does the action potential must pass through for contraction to begin?
the apex (apex means bottom)
What are the bundle of His?
conducting system fibers, also known as AV bundle
What are the left and right bundle fibers?
conducting fibers that separate at the bottom (apex) of the heart and enter through the walls of both ventricles
What are the Purkinje fibers?
large-diameter conducting cells that rapidly transmits the impulse through the ventricles
What ions are permeable to the plasma membrane of myocardial cells?
K, Na, and Ca(21)
What is different between skeletal and cardiac muscles cells in terms of calcium permeability?
cardiac muscle is more permeable to calcium than skeletal muscle is
What type of calcium channels does cardiac muscle use?
L-type Ca2+ channels
What is the unique about the specialized calcium channel?
opens slower than Na+ channels do but remain open for a prolonged period
What is the purpose of the specialized calcium channel?
maintains the depolarization of the membrane and creating a balance between the potassium going out and calcium flowing in
What are the four ion channels that contribute to the pacemaker potential?
potassium, F-Type (Na+) channels and T-type Ca2+, and L-type Ca2+ channel
What are F-type channels?
“funny” sodium conducting channel mainly responsible for the inward flow of positive current in autorhythmic cardiac cells
What are T-type Ca2+ channels?
open temporarily (T) but contributes to the inward movement of Ca2+ ions and acts as a final depolarizing boost to the pacemaker potential
What are the only electrical connections between the atria and ventricles?
AV node and Bundle of His
How do the Purkinje fibers help prevent backflow?
must transmit action potentials to the papillary muscles in order to contract before the rest of the ventricle contracts
What is stroke volume?
amount of blood heart fills per contraction
Are there any electrical events during the period of isovolumic relaxation?
No, this phase is in between heartbeats
What are arrhythmias?
uncoordinated atrial and ventricular contractions
What is fibrillation?
a rapid irregular heartbeat where the SA node no longer controls the heart rate
What is defibrillation?
the procedure in which an electrical current passes through the heart to try to stop the fibrillation
Why do we have a plateau phase in some action potentials? (between cardiomyocytes and skeletal muscle cells)
cardiomyocytes need that plateau phase in its APs to maintain depolarization
What role does calcium play?
maintains depolarization and increases frequency of action potentials
What is the electrocardiogram (EKG)?
tool for evaluating the electrical events that happen within the heart
What causes a P wave on an EKG?
atrial depolarization
What causes the QRS complex in an EKG?
ventricular depolarization
What causes a T wave in an EKG?
ventricular repolarization
Why isn’t there a wave for atrial repolarization?
it occurs at the same time as the QRS complex
What is an ectopic pacemaker?
controls ventricular contraction at a different rhythm
What is cardiac output?
amount of blood pumped out of each ventricle in one minute
What are the Frank-starling forces?
relationship between the end-of-diastole volume and stroke volume
What is end-diastole volume?
the blood returned from the venous vessels || also called venous return
What is end-of diastole pressure?
the preload
How can venous return increase?
when there is an increase in the blood flow through peripheral organs to veins
What is arterial pressure?
the afterload that affects stroke volume
What is hypertension?
a high pressure in the arteries decreases stroke volume
What causes high blood pressure?
capillary damage due to clotting at the capillaries
What is blood pressure?
force exerted by the blood against the vessel wall
What is mean arterial pressure (MAP)?
average pressure during the cardiac cycle
How is blood returned to the heart?
increase in arterial pressure = increase pressure gradient throughout vasculature = increase blood flow (venous return)
How does an increase in resistance affect blood flow?
decreases blood flow
What is the major factor in determining the resistance of a vessel?
the diameter of the vessel
How does the structure of veins make blood being returned to the heart possible?
arteries are thick, muscular highly elastic = can change diameter and control pressure
What are baroreceptors?
receptors that sense arterial pressure and use negative feedback to keep MAP at set point
Where are baroreceptors located?
aorta and carotid arteries
What controls the blood flow to the organs?
arteriolar resistance
What is the driving force of venous return to the heart?
pressure gradient between peripherial veins and the right atrium
How does the body control which organs will receive blood?
through arteriolar dilation or contraction
What is the role of smooth muscle in the control of blood flow to organs?
responsible for contracting to make arterioles contract
What are the two horomonal receptors on the smooth muscles of arterioles?
alpha and beta-2
What effect does the beta-2 receptor have on blood flow to organ? Which organs does it work prevalently at?
increases flow to organ; skeletal muscles, brain, heart and lungs
What effect does the alpha receptor have on blood flow to organ? Which organs does it work prevalently at?
decreases flow to organ; GI tract and kidneys
What else contributes to the return of blood to the heart?
skeletal muscle pump and respiratory pump
What is a skeletal muscle pump?
(during muscle contraction) venous diameter decreases = increase venous pressure = force flow of blood to heart
In skeletal muscle pumps, why does the pressure only force the flow of blood to the heart? What prevents the backflow?
the decrease in venous pressure forces the valves in the veins to close = prevents backflow due to the veins’ one-way valves
What makes venous return unique since it is a low pressure difference system?
one-way valves, the skeletal muscle and respiratory pumps
What are one-way valves?
valves are curved in a way that when it opens, material only flows one way; what they look like: closed valve = (JL) | open valve = (J L)
What is the respiratory pump?
venous return is enhanced via inspiration; increases the pressure differences between the peripheral veins and the heart
What is the role of sodium channels in setting the heart rate?
helps depolarize the membrane potential as it only opens when membrane potential is negative
What can change the heart rate in terms of the SA node?
PNS signalling of APs
How does the SA node work as a pacemaker?
the one that initiates the APs for the heart to contract
What role does the sympathetic/parasympathetic nervous system have in the changes of total peripheral resistance?
can adjust all arteriole resistance by affect changes to their diameter and size, etc.
What is the autonomic nervous system?
all of the internal organs such as blood vessels, stomach, intestine, liver, kidneys, heart, etc.
What are the two branches of the autonomic nervous system?
sympathetic and parasympathetic
What is the sympathetic nervous system?
fight/flight response - prepares body for intense physical activity
What is the parasympathetic nervous system?
relaxes body, inhibits/slows high energy functions
In terms of the Frank-Starling Mechanism, how does it affect the quantity of blood the heart moves and the pressure generated?
an increase in amount of blood heart moves = increase in Frank-starling = increase contraction = increase in pressure generated
In terms of the Frank-Starling Mechanism, what will the cardiac muscles do if the stroke volume and the end-diastole volume both increase?
muscle will contract
In terms of the Frank-Starling Mechanism, what will the cardiac muscles do if the stroke volume and the end-diastole volume both decrease?
muscle will relax
In terms of the Frank-Starling Mechanism, what is the affect if the sympathetic nervous system is activated?
heart rate will increase = increase heart contraction = increase in blood volume heart moves = increase in pressure
