Cardiovascular Physiology I (EXAM III) Flashcards
The three principal components of the circulatory system are:
- The heart
- The blood vessels
- The blood
The pump:
The pipes:
The fluid to be moved:
Heart
Blood vessels
Blood
Cardiovascular function is regulated by ____ & _____ and strongly impacted by _______
Endocrine factors & autonomic nerves
Renal function
Number one cause of death worldwide
Cardiovascular disease
____ & _____ are the most common cardiovascular diseases
Atheroscerosis
HTN
Cardiovascular disease affects many organs including:
Brain, Eyes, kidneys
Multiple risk factors for cardiovascular disease include:
Smoking
Obesity
DM
Genetics
Build-up of plaque on the wall of the vessel causing narrowing of the lumen
Athersclerosis
The beats to generate ____ to push the blood through the vessels
Pressure
The heart beats to ultimately allow blood to reach the _____
Capillary system
Exchange at the capillary system occurs between
Plasma & interstitial fluid
Supplies O2 and nutrients to the tissue & removes waste
Systemic circulation
Adds O2 and removes CO2
Pulmonary circulation
Blood always enters the heart through the:
Atria
Blood always exits the heart through the:
Ventricles
Blood vessels that return blood to the heart:
Veins
Blood vessels that carry blood away from the heart:
Arteries
Blood vessels attached to the atria, returning blood to the heart
Veins
Blood vessels attached to the ventricles, carrying blood away from the heart
Ventricles
What is the pump for systemic circulation:
Left ventricle
What is the ultimate goal of systemic circulation:
- supply O2 and nutrients to tissues
- removes waste
Describe the path of systemic circulation
The left ventricle pumps the blood out into systemic vessels & then into systemic capillaries & then to systemic veins. The systemic veins then bring the blood back to the right atrium (end of systemic circulation)
What is the pump in pulmonary circulation?
Right ventricle
Describe the pathway of pulmonary circulation:
The right ventricle pumps blood into vessels that will it to the pulmonary capillaries, from here, the pulmonary vein will bring it back to the left atrium (this ends pulmonary circulation)
What are the ultimate functions of pulmonary circulation:
Add O2 and remove CO2
Function to keep blood flowing in one direction
Heart valves
Heart valves open and closed due to:
Changes in pressure
When we see vessels color-coded red, what type of vessels are these and describe the blood within them:
Systemic arteries
Blood is high in O2 low in CO2
When we see vessels color-coded blue, what type of vessels are these and describe the blood within them:
Systemic veins
Blood is high in CO2 and low in O2
What is the one artery that is carrying blood low in O2 and high in CO2:
Pulmonary artery
What is the one vein that is caring blood high in O2 and low in CO2:
Pulmonary vein
The blood flow out of the left ventricle into systemic circulation is _____ compared to the blood that is pumped out into the right ventricle into pulmonary circulation
Is EQUAL
Unequal blood flow (between pulmonary and systemic circulation) would result in:
Blood pooling
Oxygen is loaded & CO2 is unloaded in the:
Pulmonary capillaries
Oxygen is unloaded & CO2 is loaded in the:
Systemic capillaries
Veins attached to the left atrium:
Pulmonary veins
Large systemic artery attached to the left ventricle:
Aorta
Large vein attached to the right ventricle:
Pulmonary trunk
The pulmonary trunk will branch into:
Right and left pulmonary arteries
Attached to the right atrium (returns blood to the right atrium):
Vena cava
Valves are not _____ and are considered _____
Muscle
Passive structures
Passive structures that open and close based on pressure gradients & function to keep blood flowing in one direction
Heart valves
Valves found between the atria and their respective ventricles:
Atrioventricular valves (AV)
What are our two AV valves?
- Tricuspid valve
- Mitral/Bicuspid valve
Where is the Tricuspid valve located:
Between right atrium & right ventricle
Where is the Mitral/bicuspid valve located:
Between the left atrium & left ventricle:
Valve located between the right atrium & right ventricle:
Tricuspid
Valve located between the left atrium & left ventricle:
Mitral/Bicuspid
If P(A)>P(V)=
Open
If P(A)<P(V)=
Closed
Valves located between the ventricles and their respective arteries:
Semilunar valves
Valve located between the right ventricle & pulmonary trunk:
Pulmonary valve
Valve located between the left ventricle & the aorta:
Aortic valve
Where is the pulmonary valve located:
Between the right ventricle & pulmonary trunk
Where is the aortic valve located:
Between the left ventricle and the aorta
If P(V)>P(art)=
Open
If P(V)<P(art)=
Closed
When semilunar valves are open, the blood will be:
Ejected out into the arteries
Prevents the back flow of blood into the ventricles when ventricular pressure falls
Closing of the semilunar valves
Once we get blood from the atria into the ventricles we don’t want:
Once we get the blood from the ventricles into the arteries we don’t want:
Backflow
Backflow
Two loops in the cardiovascular system:
Systemic loop & pulmonary loop
Loop that carries oxygen rich blood to the systemic capillaries and oxygen poor blood back to the heart:
Systemic loop
The systemic loops carries oxygen rich blood to the ____ & oxygen poor blood ____
Systemic capillaries; back to the heart
The systemic loop carries ___ blood to the systemic capillaries and ___ blood back to the heart
Oxygen rich
Oxygen poor
Loop that carries oxygen poor blood to the lungs and oxygen poor blood back to the heart
Pulmonary loop
The pulmonary loop carries oxygen poor blood to the ____ and oxygen rich blood ____
Lungs; back to the heart
The pulmonary loop carries ____ blood to the lungs and ____ blood back to the heart
Oxygen poor
Oxygen rich
What occurs between the plasma and interstitial fluid at the capillaries
Exchange
Exchange occurs between the ___ & ____ at the ____
Plasma & interstitial fluid; capillaries
How is blood supply to tissue arranged:
Parallel
The cardiovascular system is considered a ____ system
Closed
What considered “bad” due to the cardiovascular system being a closed system?
Leaks
A bleeding paper cut would be considered a _____ in the cardiovascular system
Leak
What repairs leaks in the cardiovascular system?
Hemostasis
Vessels and capillary beds have a ____ arrangement
Parallel
Why is it significant that all capillaries in systemic circulation are arranged in parallel?
Allows body to selectively change blood flow to a certain tissue without affecting the blood flow to another area
There is around ______ of blood moving through the body every minute at rest:
5 liters
Each tissue gets a different amount of blood because you can regulate how much blood goes into each tissue and this is due to the:
Parallel arrangement
During strenuous exercise where might the body increase blood flow to?
Brain, heart, skeletal muscle, skin
During strenuous exercise where might the body decrease blood flow to?
Kidneys, abdominal organs, etc.
List the types of arteries:
- Elastic arteries
- Muscular arteries
- Arterioles
The largest arteries that are attached to the heart:
Elastic arteries
Muscular arteries may also be called:
Distribution arteries
Type of artery that branches off the aorta and functions to distribute blood to & around different organs of the body:
Muscular artery (Distribution artery)
Represent the end of arteries:
Arterioles
Smallest arteries, connected to the capillaries
Arterioles
Blood flows out of the arteriole system into the ____ through _____
Capillaries
Arterioles
Function to carry blood to tissue capillaries from the heart
Arteries
What is responsible for regulating blood pressure?
Arterioles
What are the three types of veins?
- Large veins
- Medium sized veins
- Venuoles
Large veins are attached to the:
Heart
What are some examples of large veins?
Vena cava & pulmonary vein
Medium-sized veins are considered our ____ veins
Collection
Collect blood from different tissues that the muscular arteries delivered it to:
Medium-sized veins (Collection veins)
Smallest of veins, that capture the blood that flows out of the capillaries:
Venules
Represent the beginning of the venous system:
Venules
Venules collect into ______
Medium-sized veins
Carry blood to the heart from tissue capillaries:
Veins
The process of carrying blood to the heart from tissues capillaries is referred to as:
Venous return
Veins serve as:
A reservoir of blood
Veins have a very high compliance and can hold a large volume of blood with very little change in pressure and this can be referred to as:
Peripheral venous pool
Describe what peripheral venous pool means:
The ability of veins to act as a reservoir of blood
At rest how much of our blood volume is contained within the veins?
Around 60%
The aorta is an example of an:
Elastic artery
The aorta is attached to the:
Heart
Describe blood flow through an aorta:
Blood is ejected out at a forceful pressure
Muscular arteries branch off of the:
Aorta
Example of muscular arteries:
Renal artery & celiac artery
Muscular arteries enter into the _____ and get smaller & smaller until they become _____
Organs
Arterioles
_____ will end with capillaries and this is where exchange will occur:
Arterioles
After exchange occurs in the capillaries this blood will be picked up by the:
Venules
For every artery we have a ____ component to it
Venous
The force exerted by fluid in a tube:
Pressure (Hydrostatic pressure)
Force exerted by a fluid in a tube:
Pressure (Hydrostatic pressure)
Pressure is measured in:
mmHg
In the cardiovascular system what pressure are we measuring?
Pressure of blood in blood vessels
The volume of fluid moved in a given amount of time:
Flow
Flow is measure in:
mL/min
How difficult it is for blood to flow between two points at any given pressure difference:
Resistance
Resistance is a measure of:
Friction that impedes flow
Ohms law =
F= Change in Pressure/Resistance
Flow is directly related to _______
Flow is inversely related to ____
Pressure gradient
Resistance
What is the unit for resistance?
Poiseuille
If the change in pressure is constant and the resistance increases, flow:
Flow decreases
The driving force to move blood through the cardiovascular system:
Pressure gradients generated by the heart
From a mechanistic standpoint, which one would be better to alter to change blood flow to specific tissues?
1) increase in pressure
2) decrease in resistance
Reduce resistance to flow bc the driving pressure is your blood pressure and we don’t want to alter that too much
Flow will be regulated by ______ and NOT _____
regulating resistance
changing pressure
As the blood flows through systemic circulation (aorta to arteries to arterioles to capillaries to venues to veins to vena cava) what happens to the pressure and why?
Pressure decreases due to friction as you move away from the heart
Where is pressure the highs in the CV system?
Immediately outside the left ventricle
Where is the biggest pressure drop in systemic circulation?
Through the arterioles
The biggest pressure drop occurs in the arterioles due to:
Most resistance/friction there
What are the three factors that contribute to cardiovascular resistance?
- Blood viscosity (n)
- Total blood vessel length (l)
- Blood vessel radius (r)
Resistance is directly related to:
Resistance is indirectly related to:
Blood viscosity, Blood vessel length
Blood vessel radius
How thick the blood is=
Viscosity
Viscosity is determined by:
Hematocrit
The percentage of RBCs per unit of whole blood:
Hematocrit
The more red blood cells present per unit of whole blood =
Higher viscosity
How much tubing is needed:
Total blood vessel length
The longer the blood vessel the ____ the resistance
Greater
What determines blood vessel length?
Genetics
Vasodilated blood vessels increase ____ and decrease ____
Radius; resistance
Vasoconstricted blood vessels decrease ____ and increase ____
Radius, resistance
What is the main contributor to minute-to-minute control of resistance in the vascular system?
Blood vessel radius
Small changes in blood vessel radius lead to:
Big changes in resistance
If we want to increase blood flow to an area, we can _____ the blood vessel
If we want to reduce blood flow to an area, we can ____ the blood vessel
Dilate
Constrict
What is Poiseuille’s law?
Resistance = 8(n)(l) / pi(r^4)
n= viscosity
l= length
r= radius
By combing Poiseuille’s law and Ohm’s law we get:
Q=P(pi)(r^4) / 8(n)(l)
Hagen-PoiseuIlle’s Equation
Regarding pressure & flow in vessels, its not the _____ of the pressures that is important rather the _______
Absolute value
Difference between them
Diameter of the vessel is a major determinant of:
Flow
A two fold increase in radius will lead to a:
16 fold increase in blood flow
Describe the effects the following have on flow:
- Increased radius
- Decreased radius
- Increased tube length
- Decreased tube length
- Increased flow
- Decreased flow
- Decreased flow
- Increased flow
What is the equation for velocity regarding blood flow through vessels:
V= Q/A
V= Velocity
Q= blood flow
A= total cross sectional area
How something happens:
Mechanistic explanation
Why something happens:
Teleological explanation
The velocity of blood flow is slowest through the capillaries, what is the mechanistic explanation of this:
Greatest total cross sectional area leads to lowest velocity
(One aorta= low cross sectional area compared to many capillaries= highest cross sectional area)
(V=Q/A)
The velocity of blood flow is slowest through the capillaries, what is the teleological explanation of this:
We want velocity to be slow at the capillaries to allow time for maximum exchange to occur
Describe the following at the aorta:
- Total cross-sectional area
- Velocity of blood
- Blood pressure
- Low cross-sectional area
- High velocity of blood flow
- High blood pressure
Describe following at the capillaries:
- Total cross-sectional area
- Velocity of blood
- Blood pressure
- Large cross-sectional area
- Low velocity of blood flow
- Low blood pressure (but higher than in the venules, veins & vena cava)
Connective tissue cords that are attached to the AV valves on one end and papillary muscle (inside the ventricles) on the other end:
Chordae tendonae
What does the chordae tendonae connect to?
AV valves and papillary muscle
The walls of the atria are _____ compared to the walls of the ventricles
Thinner
What is the mechanistic explanation to the walls of the atria being thinner than the walls of the ventricle:
Walls of the atria are thinner because the atria only have to contract to push blood into the ventricles (not a ton of work)
Compare the walls of the right ventricle to the left ventricle:
Wall of the left ventricle is much thicker
What is the mechanistic explanation of the left ventricle wall being thicker than the right ventricle wall:
Left ventricle is responsible for systemic circulation meaning that it has to forcefully contract to get blood all the way to the toes (a lot of work)
Separates the right ventricle from the left ventricle
Interventricular septum
List the AV valves and where they are located:
- Tricuspid (right atrium-right ventricle)
- Bicuspid/mitral (left atrium-left ventricle)
The AV valves are supported by ___ when closed
Chordae tendonae & papillary muscles
When the AV valves are open, the semilunar valves are:
Closed
When are all valves open at the same time?
Never
When the AV valves are open, blood is flowing into the:
Ventricles
Describe the chordae tendonae when the AV valves are open:
Lots of slack, not drawn tight
When the AV valves are closed, the semilunar valves are:
Open
Describe the chordae tendonae when the AV valves are closed:
Chordae tendonae stretched tight and supported by papillary muscle
The function of the chordae tendonae is to:
Prevent backflow
What would happen if the chordae tendonae were not functioning?
Valve prolapse
Caused by weakened/stretched chordae tendonae & can be due to HTN
Valve prolapse
Valve dysfunction creates:
Heart murmurs
Valves open and close due to:
Pressure gradients
Valves function to:
Keep blood flowing in one direction
Which valve is considered the tricuspid?
Right AV valve
Which valve is considered the bicuspid?
Left AV valve
Cardiac myocytes may also be called:
Cardiocytes, cardiac muscle cells
There are two types of cardiac myocytes found in cardiac muscle, these include:
- Conductive muscle fibers (autorhythmic cells/AR cells, pacemaker cells)
- Contractile muscle fibers
Conductive muscle fibers may also be called:
Autorhythmic cells (AR cells)
Pacemaker cells
Makes up 1% of cardiac myocytes:
Conductive muscle fibers
Spontaneously generate AP that leads to heart beat:
Conductive muscle fibers
______ stimulates an excitation (AP) which stimulates _____
Conductive muscle fibers; Contractile cells
Type of cardiac myocyte that contract very weakly:
Conductive muscle fiber
Conductive muscle fibers are located:
In conduction system of heart
99% of myocytes in the heart:
Contractile muscle fibers
Contract & generate heartbeat:
Contractile muscle fibers
What are the two types of contractile muscle fibers:
- Atrial myocytes
- Ventricular myocytes
Cardiac muscle cell that contracts in response to the electrical signal that is generated by conductive muscle cells:
Contractile muscle cells
Contractile muscle cells located in the atria
Atrial myocytes
Contractile muscle cells located in the ventricle
Ventricular myocytes
What stimulates a SKELETAL muscle to contract?
Action potentials in somatic motor neurons
What are the steps (simplified_ to stimulating a SKELETAL muscle to contract?
- Action potential in somatic motor neuron
- Release of acetylcholine
- Acetylcholine binds to nicotinic receptors on motor end
- Excitation leading to calcium entry for contraction
Compare the cause of heart contraction to skeletal muscle
No outside electrical stimulus is needed for heart muscle to contract
Where does the electrical signal that leads to heart contraction come from?
From WITHIN the heart
Why enables the heart to beat outside the body?
Internal stimulation from conductive muscle fibers
The appearance of cardiocytes can be described as:
Striated
What is the functional unit of a cardiocyte?
Sarcomere
The ______ & ______ of cardiac muscle is similar to skeletal muscle
Anatomy & function
Cardiac muscle can be described as a:
Syncytium
A group of cells that function as one:
Syncytium
What feature of cardiocytes allows them to function as a syncytium:
Intercalated discs
Specialized connections between one cardiac muscle cell & another:
Intercalated discs
Intercalated discs are composed of:
- Interlocking plasma membrane
- Gap junctions
- Desmosomes
Describe the interlocking plasma membrane of intercalated discs inc cardiac muscle:
Little hooks locking the plasma membrane together
Describe the function of the gap junctions found in intercalated discs in cardiac muscle:
Allows for rapid movement of ions from one cell to the next
Describe the function of desmosomes found in intercalated discs in cardiac muscle:
Structural support cell connections
Why is it so important that the desmosomes are found in the intercalated discs of cardiac muscle:
Allow the cells to stay together under the extreme pressure of the heart
In what ways are cardiac muscle cells linked?
- Mechanically
- Chemically
- Electrically
What are the two syncytium in the heart?
- Atrial
- Ventricular
The atrial syncytium & ventricular syncytium function:
Separate from each other
If the atrial syncytium is contracted, the ventricular syncytium is:
Relaxed
The arteries supplying the myocardium are the:
Coronary arteries
The blood flowing through the coronary arteries:
Coronary blood flow
Coronary arteries exit from behind the _____
Aortic valve cusps
Coronary arteries exit from behind the aortic valve cusps and lead to a branching network of:
Small arteries, arterioles, capillaries, venues and veins
Describe the drainage of most of the cardiac veins:
Most of the cardiac veins drain into a single vein- the coronary sinus
After the cardiac veins drain into the single coronary sinus, this empties into the:
Right atrium
Coronary circulation is a part of:
Systemic circulation
Because coronary circulation is part of systemic circulation, it functions to:
Provide oxygen & nutrients to tissues of the body including the heart
Systemic blood flow to the heart, providing fresh oxygen & nutrients to the cells
Coronary circulation
What does the coronary circulation bypass?
Vena Cava
The coronary sinus dumps directly into the:
Why is this unique?
Right atrium
Because it bypasses the vena cava
The very first branch off of the aorta is the:
Coronary artery
The coronary artery branches into:
Right & left coronary arteries
(travel around the heart)
Lack of blood supply to the left ventricle=
Widowmaker
What is the artery involved in the “widow-maker”
Left anterior descending
(coronary??)
What the is the thing that does not use the vena cava to dump blood back into the heart?
Coronary sinus
Contraction =
Systole
Relaxation =
Diastole
Atrial contraction =
Atrial relaxation =
Ventricular contraction =
Ventricular relaxation =
Atrial systole
Atrial diastole
Ventricular systole
Ventricular diastole
What is the term describing the events that makeup a single heart beat?
Cardiac cycle
The events of the cardiac cycle include:
- Atrial systole
- Ventricular systole/atrial diastole
- Ventricular diastole
What must occur before systole can happen?
What muscle occur before diastole can happen?
Heart muscle must depolarize before systole can happen & repolarize before diastole can happen
What is the order of depolarization in the heart/conduction system:
- SA Node
- Internodal pathways
- AV node
- Bundle of HIS
- DOWN bundle branches
- UP Purkinje fibers
The SA node will generate AP which travel via gap junctions along ______ to the _____
Internodal pathways; AV node
The AP is held up for 0.1 seconds in the _____ node. This is known as the _____
AV node
AV delay
What is the teleological explanation for the AV delay?
The atria needs to contract before the ventricles fill with blood
What is the mechanistic explanation for the AV delay?
The conduction velocity through the AV node is slower than elsewhere along the conduction system
The action potential travels from the AV node ____ the bundle of HIS, _____ bundle branches, _____ Purkinje fibers
Down, Down, Up
The Purkinje fibers also supply the _____
Papillary muscles
Contracts during ventricular contraction to tighten chordae tendinae and prevent AV valves from prolapsing into the atria
Papillary muscles
When do the papillary muscles contract?
Ventricular contraction
The pacemaker cells with the ____ drive the heart
Fastest rate of discharge
In general pacemaker cells have high ______
What is an exception to this?
Action potential conduction velocities
AV node (due to AV delay)
The reason that the AP is held up for a fraction of a second at the AV node is because it has ________ which causes the AP to take longer to move through this area
Very slow conduction velocity
The speed at which the action potential moves:
Conduction velocity
The number of action potentials the pacemaker cells can generate in a given amount of time:
Rate of discharge
Why does the SA node drive the heart?
Because it contains the pacemaker cells with the fastest rate of discharge
Describe an ectopic focus:
Abnormal pacemaker cells (hijackers)
If contractile cells convert into AR cells (like after a long viral infection) these cells will be considered an:
Ectopic focus
Describe the events that occur when the AP takes the internodal pathways:
- Depolarization of atria
- AV delay
- Atrial contraction
Describe the events that occur when the AP is sent DOWN the bundle branches and UP Purkinje fibers:
- Depolarization of ventricles
- Contraction of ventricles
Atrial repolarization occurs at the exact same time as ____.
Describe the wave of atrial repolarization on an ECG:
Ventricular depolarization
Because it is the same time as ventricular depolarization it is dominated (bc the ventricles are bigger) and therefor is absent on an ECG
Name the wave that is characterized by the following actions:
- Atrial depolarization
- Ventricular depolarization/atrial repolarization
- Ventricular repolarization
- P wave
- QRS complex
- T wave
The P wave itself does NOT represent atrial ______ but it instead represents atrial _____
Contraction
Depolarization
Does the QRS complex represent atrial repolarization? Why?
No- it represents ventricular depolarization although atrial repolarization does occur at this time (just not represented on ECG)
The AV delay occurs during the PR interval.
If AV delay is longer than normal= ________
If AV delays is shorter than normal= _____
Longer PR interval
Shorter PR interval
When would the Q wave show up on an ECG:
Not normally, only on patient with previous cardiac event
AR cells do not have a:
Steady resting membrane potential
Describe the resting membrane potential of AR cells:
Unsteady
Depolarization to threshold in AR cells
Pacemaker potential
What are the two channels of pacemaker potential?
F-type channels
T-type channels
F-type channel=
Voltage-gated sodium channel (funny channel)
T-type channel=
Transient voltage-gated calcium channel
What are the two channels of AP:
L channel
K+ channel
L channel=
Long lasting voltage gated calcium channel
Once the membrane potential hits the resting potential that will be the stimulus for:
Opening of F-type channel
What occurs when the F-type channel opens?
Sodium influx into the cell leading to depolarization to 3/4 the threshold
At resting potential sodium permeability is ____. But as soon as the F-type channel opens, _____.
Low
Sodium permeability increases
At 3/4 the way up to threshold what occurs?
Transient voltage-gated calcium channels open
Why do we call them “transient” voltage-gated calcium channels?
Because they only open briefly
The calcium flowing in due to the transient voltage-gated calcium channels allows for:
Depolarization to threshold (the final 1/4)
What work together to get the cells to threshold?
F-type channel + Transient voltage-gated calcium channel
Once we reach threshold what occurs?
L-type calcium channel opens, calcium flows in = spike of depolarization
Describe the opening of the L-type calcium channel:
Long lasting opening at threshold
At peak of depolarization the L-type calcium channel _____ and the permeability of calcium _______
Closes
Goes down
When the L-type calcium close, _____ opens
Voltage gated potassium channels
The increased permeability to potassium (opening of K+ channels leads to:
Repolarization to rest
As soon as repolarization to rest occurs what happens?
The process starts over with F-channels opening
In skeletal muscle & neurons the depolarization is due to ____ while in cardiac muscle the depolarization is due to _____
Sodium moving into cell
Calcium moving into cell
Describe what neurotransmitters are involved in sympathetic control of AR cells:
Epinephrine & Norepinephrine
Describe what neurotransmitters are involved in parasympathetic control of AR cells:
Acetylcholine
What receptor do norepinephrine & epinephrine bind to?
Beta-1 adrenergic
What receptors do acetylcholine bind to?
Muscarinic
Desribe the effects of norepinephrine & epinephrine binding to Beta-1 adrenergic receptors to control AR cells
- Increase in probability of opening of F-type channels & Transient calcium channels
- Decrease in time to threshold
- Increase in HR
The aspects sympathetic control on AR cells are considered:
+ Chronotropic agents
Describe the effects of ACH binding to muscarinic receptors to control AR cells:
- Decrease in probability of opening of F-type channels
- Increase in probability of opening of K+ channels
- Hyperpolarization of membrane
- Increase in time to threshold
- Decrease in HR
The aspects of parasympathetic control on AR cells are considered:
- Chronotropic agents
Agents that function to increase heart rate
Agents that function to decrease heart rate
+ Chronotropic agents
- Chronotropic agents
Facilitated diffusion rate of ion =
(equation)
(Change in concentration)(Temperature)(#channels)
______________________________________________________
Probability the channels are open
_______ we need to be able to change the heart rate based on the needs of the body
Teleologically
SA node spontaneous rate =
Normal resting heart rate =
Meaning the heart is under _______ NS control
100 bpm
80 bpm
parasympathetic
Contractile Cell Depolarization Events:
Phase 4=
Caused by:
Resting membrane potential
Sodium channels reset gate & are ready for next AP
Contractile Cell Depolarization Events:
Phase 0=
Caused by:
Spike of depolarization
Due to sodium entry through the fast voltage-gated sodium channel
- Activation/inactivation gates are open here
Contractile Cell Depolarization Events:
Phase 1=
Caused by:
Partial repolarization
Fast gated sodium channels close
Contractile Cell Depolarization Events:
Phase 2=
Caused by:
Plateau
Transient potassium channels close
L-type calcium channels open
Contractile Cell Depolarization Events:
Phase 3=
Caused by:
Repolarization
L-type calcium channels close
Slow potassium channels open
Unlike AR cells, contractile cells have:
Resting membrane potential
Plateau phase is unique to:
Contractile cells (does NOT occur in NS or skeletal muscle)
During this phase of contractile cell AP, the number positive charges entering the cell is equal to the number of positive charges exiting the cell:
Plateau phase
Atrial cell contraction corresponds to what wave on an ECG?
P wave
Ventricular depolarization corresponds to what wave on an ECG?
QRS complex
Ventricular repolarization corresponds to what wave on an ECG?
T wave
The _____ cells have the action potential with the pacemaker potential while the ____ cells have the action potential with the plateau
AR cells
Contractile cells
What are located in the membrane of T-tubules in contractile cells?
DHP L-type calcium channels
What stimulates the DHP L-type channels to open?
Stimulated to open when AP reaches them
What are the two ways to reduce cytosolic calcium following contractile cell contraction?
- Calcium ATPase in SR membrane (primary active uniporter)
- Secondary active antiporter in PM (sodium in, calcium out)
Excitation Contraction Coupling in Cardiac muscle
Excitation (depolarization) of the PM leads to
Opening of plasma membrane L-type calcium channels in T-tubules
Excitation Contraction Coupling in Cardiac muscle
Following the opening of plasma membrane L-type calcium channels in T-tubules what occurs?
Flow of calcium into the cytosol from the ECF (10%)
Excitation Contraction Coupling in Cardiac muscle
After calcium flows into the cell from the cytosol what occurs?
Calcium binds to calcium ryanodine receptors on the outter membrane of the SR
Excitation Contraction Coupling in Cardiac muscle
After calcium binds to the ryanodine receptors of the SR, what occurs?
Flow of calcium out of the SR into the cytosol (90%)
When calcium from outside the cell causes calcium from inside to the SR to be released in to the cytosol this is known as:
Calcium-induced calcium-release
Excitation Contraction Coupling in Cardiac muscle
Once the bulk calcium (90%) flows into the cytosol from the SR with the addition of the other 10% of calcium from the ECF this ultimately causes:
Increase in cytosolic calcium concentration, crossbridge cycling & contraction
In both skeletal muscle & cardiac muscle contraction _____ is required
Calcium
In both skeletal muscle & cardiac muscle contraction, _______ begins once calcium binds to troponin
Cross-bridge cycling
In both skeletal muscle & cardiac muscle contraction a ______ pumps calcium back into the ______
Primary active uniporter
SR
A difference between cardiac & skeletal muscle contraction is that in addition to the primary active uniporter, cardiac muscle uses a ______ in the membrane to pump calcium into the _____
Secondary active antiporter
ECF
In skeletal muscle all the calcium form contraction comes from the _______ while in cardiac muscle, some calcium comes from _____ and the rest comes from _____
SR
ECF & SR
In skeletal muscle, the AP is very quick and is over before the contractile event even begins and can allow for:
Summation & tetanus to occur
What aspect of the cardiac muscle contractile events causes the AP to be longer?
Plateau phase
In cardiac muscle contraction, the contractile event occurs simultaneously with the:
Electrical activity in the cell
In cardiac muscle contraction, by the time the muscle has returned to its resting state, the _____ is already over
Because of this what _____ & ____ cannot occur
Contractile event
Summation & tetanus
What is the mechanistic explanation of cardiac muscles inability to go into summation & tetanus:
Because the duration of the absolute & relative refractory periods is so long that by the time you can actually generate another AP the muscle has relaxed
What is the teleological explanation of cardiac muscles inability to go into summation & tetanus:
We do not want our heart to go into summation & tetanus, we want our heart to contract & relax between beats so that we can fill our heart with blood & pump it out to the body
Where does the electrical signal for skeletal muscle contraction come from?
What stimulate contractile cells to contract?
Somatic motor neurons
AP from the AR cells
In skeletal muscle, contractile response to a single AP is:
All or none
Graded is opposite of:
All or none, may happen differently every time
Because skeletal muscle contractile response to a single AP is all or none, the calcium released saturates ______ and contraction strength is _____
Troponin
Maximal
In cardiac muscle, contractile response to a single AP is:
Gradede
In “resting” state, AP-induced sarcoplasmic release of calcium in cardiac cells does NOT:
Saturate troponin sites
The strength of contraction in cardiac muscle is dependent on:
Concentration of calcium inside the cell
The amount of intracellular calcium is adjusted to:
Change or increase the strength of contraction
Substances that alter the force of contraction of cardiocytes by changing the cytosolic calcium concentration are termed:
Inotopic agents
Inotropic agents change the ____ of the heart
Contractility
+ inotropic agents _____ the force of contraction
- inotropic agents _____ the force of contraction
Increase
Decrease
Inotropic agents work via:
Voltage-gated calciu channels
Under sympathetic influence, describe what happens to heart contraction:
More forceful and shorter duration
When epinephrine & norepinephrine bind to _____ which are GPCRs these activated ______
Beta-1 adrenergic receptors
cAMP second messenger system
When epinphrine & norepinephrine bind to Beta-1 adrenergic receptros causing activation of camp this results in what two events:
- Phosphorylation of voltage-gated calcium channels
- Phosphorylation of phospholambin
When cAMP causes the phosphorylation of voltage-gated calcium channels, this causes the voltage-gated calcium channels to _______ resulting in _____
Stay open longer resulting in increased calcium entry from ECF
Because phosphorylation of the voltage-gated calcium channels allows them to stay open longer and bring more calcium into the cell from the ECF this leads to what three actions:
- increased calcium stores in SR
- Increased calcium release from SR
- more forceful contraction
cAMP phosphorylating phospholamban increases the activity of _____ in the SR
Calcium-ATPase
The increased activity of the calcium-ATPase in the SR (caused by phosphorylation via cAMP on phospholambin leads to:
- Increased calcium stores in the SR
- Faster calcium removal from cytosol
The chain events of phosphorylation of phospholambin that ultimately increase the calcium ATPase activity which increases calcium stores in the SR, and causes calcium to be removed from cytosol more quickly leads to:
- increased calcium release from SR leading to a more forceful contraction
- Shortens calcium-troponin binding time leading to a shorter duration of contraction
Ultimately under sympathetic influence on contractile cells, you get:
- More forceful contraction
- Quicker duration of contraction
Pressure Atria < Pressure veins
Pressure Atria > Pressure Ventricles
Pressure Ventricles < Pressure arteries
Between beats
Describe the atria & ventricles between beats:
Both relaxed in diastole
Between beats, the pressure of the Atria is less than the pressure in the veins therefore:
Blood will flow into the atria
Between beats, the pressure in the atria is greater than the pressure in the ventricles therefore:
The AV valves is open so blood is flowing into the ventricles
Between beats, the pressure in the ventricles is less than the pressure in the arteries therefore:
Semilunar valves are shut
Between beats, the blood returning to the right atrium is from the:
Between beats, the blood returning to the left atrium is from the:
Systemic circulation
Pulmonary circulation
Between beats is the period of ________
Meaning that:
Period of passive filling
80% of blood for contraction is loaded into the ventricles at this time
Pressure of atria is elevated
Pressure Atria > Pressure Veins
Pressure Atria > Pressure Ventricles
Pressure Ventricles < Pressure Arteries
Atrial systole
During atrial systole:
- The pressure of the atria is greater than the pressure of the veins therefore:
- The pressure of the atria is greater than the pressure of the ventricles therefore:
- The pressure of ventricles is less than the pressure of the arteries therefore:
- Potential backflow into the veins may occur
- AV valves are open
- Semilunar valves are shut
As the atria contracts, blood will travel into the:
Ventricles
Atrial systole is the period of ______
Meaning that:
Period of active filling
20% of blood for contraction is loaded into the ventricles at this time
Pressure of atrium is decreased
Pressure of ventricles is elevated
Pressure atria < Pressure veins
Pressure atria < Pressure of ventricles
Pressure ventricles < Pressure arteries
Atrial diastole/ Early ventricular systole
In atrial diastole/ early ventricular systole:
- The pressure of the atria is decreased because:
- The pressure of the ventricles is increased because:
- The pressure of the atria is less than the pressure of veins therefore:
- The pressure of the atria is less than the pressure of the ventricles therefore:
- The pressure of the ventricles is less than the pressure of the arteries therefore:
- the atria are relaxed
- the ventricles contract
- blood will start flowing back into the atria
- AV valves will shut
- semilunar valves are shut
We have filled the bag with blood and have now closed all entrances & exits and we start to squeeze causing a rapid rise in pressure in the ventricles
What stage of the cardiac cycle does this describe?
Atrial diastole/ early ventricular systole
During atrial diastole/ early ventricular systole is the period of _____
Meaning that:
Period of isovolumetric contraction
Pressure in ventricles rises rapidly
Pressure atria < Pressure veins
Pressure atria < Pressure ventricles
Pressure ventricles > Pressure arteries
Late ventricular systole
During late ventricular systole:
- The pressure of the atria is less than the pressure of the veins therefore:
- The pressure of the atria is less than the pressure of the ventricles, therefore:
- The pressure in the ventricles is greater than the pressure in the arteries, therefore:
- Blood will be flowing into atria
- AV valves are shut
- Semilunar valves are open & blood is ejected into the arteries
During late ventricular systole is the _________
Meaning that:
Ejection phase
Equal volume of blood ejected into both circulations
During the ejection phase where is blood ejected into:
The aorta on the left side or pulmonary trunk on the right side
Pressure of ventricles is decreased
Pressure atria < Pressure veins
Pressure atria < Pressure ventricles
Pressure ventricles < Pressure arteries
Early ventricular diastole
During early ventricular diastole:
- Pressure of ventricles is decreased because
- Pressure of atria is less than the pressure of the veins therefore:
- Pressure of the atria is less than the pressure of the ventricles therefore:
- Pressure of the ventricles is less than the pressure of the arteries therefore:
- ventricles are relaxing
- blood will be flowing into atria
- AV valves will be shut
- Semilunar valves are shut
We have emptied this bag of atleast half its volume, closed entrances & exits, and have allowed it to relax.
This describes what stage of the cardiac cycle?
Early ventricular diastole
During early ventricular diastole is the period of _____
Meaning that:
Isovolumetric relaxation
Meaning that the pressure of the ventricles falls rapidly
Pressure atria < Pressure veins
Pressure atria > Pressure ventricles
Pressure ventricles < Pressure arteries
Late ventricular diastole
During late ventricular diastole:
- The Pressure of the atria is greater than the pressure of the ventricles therefore:
- The pressure in the ventricles is less than the pressure of the arteries therefore:
- AV valves are open - we start to fill the ventricles again
- Semilunar valves are shut
During late ventricular diastole, the period of _____ begins
Passive filling (again)
The volume of blood that is in the ventricle before it contracts (at the end of ventricular diastole)
End diastolic volume (EDV)
EDV=
End diastolic volume
The average EDV=
135 ml
The volume of blood that is in the ventricle at the end of ventricular systole (the minimum amount of blood after contraction)
End systolic volume (ESV)
ESV=
End systolic volume
What is the average ESV?
65 ml
Volume of blood that is ejected per beat:
Stroke volume (SV)
Stroke volume (sv) =
(equation)
EDV-ESV
An average stroke volume is around:
70 ml per beat
Fraction of EDV ejected per beat:
Ejection fraction
Equation for ejection fraction:
SV/EDV
The average ejection fraction is _____ at rest
52%
Heart sounds are due to:
Valve closures
What causes the first heart sound:
Closure of AV valve
What causes the second heart sound:
Closure of semilunar valve
Abnormal heart sounds due to valve dysfunction
Heart murmur
Heart murmur caused by failure of valves to open completely
Stenosis
Lub-Shh-Dub
Heart murmur caused by failure of valves to close properly
Insufficiency or prolapse
Lub-Dub-Shhh
Compare the pressure changes in pulmonary circulation to the pressure changes in systemic circulation:
Pressure changes in pulmonary circulation are much smaller
The amount of blood pumped out of eat ventricle in one minute:
Cardiac output
Equation for cardiac output:
CO= HR x SV
Normal resting CO=
70 bpm x 70 ml/beat = 5 L/min
During intense exercise CO can:
Elevate (to 30-35 L/min)
CO is regulated to match:
Demands of tissues
What factors can increase CO?
Physical activity
Metabolic status
Drugs
What factors can decrease CO?
Blood loss
Heart disease
How can we control CO?
By changing HR & SV
Factors that increase heart rate:
Positive chronotropic agents
Factors that decrease heart rate:
Negative chronotropic agents
HR is mainly controlled by:
Input from the nervous system
_____ increases the HR (AR & Contractile cells)
_____ decreases the HR (AR cells only)
SNS
PNS
If we want to affect the heart rate we we need to change the function of ____ cells, NOT ____ cells
AR cells; contractile cells
In order to increase heart rate we need to (2):
- Increase speed at which APs are generated by the SA node
- Increase the speed at which the APs travel through the conduction system
Factor that increases the speed at which the AP moves through the myocardium:
What NTs might do this?
Positive dromotropic agent
Epinephrine & Norepinephrine
Factor that reduces the speed at which the AP moves through the myocardium:
What NTs might do this?
Negative dromotropic agent
Acetylcholine
To increase the heart rate we need to increase the activity of the ______ & decrease the activity of the ______
Sympathetic NS
Parasympathetic NS
Equation for stroke volume (SV):
SV= EDV-ESV
SV is altered by:
- Change in the preload (EDV)
- Change in the afterload (BP)
- Change in the contractility (force of contraction)
At rest, cardiac muscle sits at a length that is:
Less than optimum
_____ EDV: ______ stretch of myocardium: moves resting cardiocyte length toward _____: ______ SV
Increased; increased; optimum; increased
Starling’s law of the heart states:
Increased EDV leads to increased SV
Anything that increases EDV increases what two other things?
- Force of contraction
- SV
Stroke volume is an index of:
The force of contraction
EDV is an index of:
Resting fiber length
EDV is _____ to venous return (VR)
Directly related to
Rate at which blood is returned to the heart from the veins
Venous return
Flaccid vessels with high compliance & can hold up to 60% of the total blood volume:
Veins
Can expand to hold more blood without a change in pressure:
Veins
The change in pressure to return blood to the heart from the capillaries is:
Very small
______ facilitates blood movement back to the heart (venous return)
One-way valves
Factors that increase VR that are dependent on one-way valves & veins:
- increase in skeletal muscle pump
- increase in thoracic pump
- increase venoconstriction via sympathetic nervous system
The increase in venoconstriction via the sympathetic nervous system increasing venous return is due to what receptors?
Alpha-1 adrenergic receptors
What is one factor that increases VR that is NOT dependent on one-way valves in veins:
Extremely high heart rate (tachycardia) because this causes a drop in EDV which leads to a drop in CO leading to a lower stroke volume
Increasing thoracic pressure against a closed glottis used during defecation reflex:
Valsalvas maneuver
Valsalvas maneuver functions to _____ venous return because it creates a large increase in thoracic pressure which _____ VR, _____ EDV, ____SV, _____CO
Decreases (all)
How is heart rate related to SV?
Indirectly related
How is cardiac output related to HR? (at a NORMAL HR)
Directly related
______ has a greater affect on CO than _____ under normal conditions
HR; SV
When you increase HR, you increase CO, however past ____ increasing HR will lead to a decrease in CO and this is because:
200 BPM; you do not have enough time to fill the ventricles with blood reducing EDV, SV, & CO
The pressure that the ventricles must overcome to force open the pulmonary & aortic valves
Afterload
Anything that increases systemic or pulmonary pressure can _____ the afterload
Increase (hypertension)
Increase in after load causes a ______ in stroke volume
Decrease
_______ is not a major factor in healthy subjects
Afterload
Peak pressure in ventricle:
Systolic BP
Pressure at which the semilunar valves open; minimum pressure in the aorta
Diastolic BP
At BP of 130/90 what pressure is needed to open the semilunar valves?
90
If the heart has to work harder to open the valves (increased BP for example) the will ______ and this will lead to _____
Grow; Left ventricular hypertrophy
Anything that increases the afterload on the heart will lead to a ______ in SV
Reduction
The ability of the heart to contract at any given resting fiber length:
Contractility
The ventricles are never completely empty of blood (ejection fraction) so a more forceful contraction will:
Expel more blood with each pump
Contractility is varied by controlling the amount of ____ that enters the contractile cell via ______ gated channels
Calcium
L type Voltage gated Ca++ channel
Because the amount of calcium that enter the cell via the L type voltage gated calcium channels determines the contractility of the muscle this is considered what type of contraction?
Graded contraction
What affects does a + inotropic agent have on contractility & ejection fraction
Increase in contractility
Increase in ejection fraction
Give examples of + inotopic agents:
Sympathetic stimulation & epinephrine
What affects does a - inotropic agent have on contractility & ejection fraction
Decrease in contractility
Decrease in ejection fraction
Give example of - inotropic agents:
Beta-1 Blockers
Ca++ channel blockers
Adrenergic effects on cardiac contractility:
- Increase force
- Increase speed
Adrenergic effects on cardiac muscle contractility:
The SNS releases epi & norepi which bind to:
Beta-1-adrenergic receptors
Adrenergic effects on cardiac muscle contractility:
When epi & norepi bind to beta-1-adrenergic receptors in the contractile cell membrane this activates:
The inactive cAMP-dependent protein kinase
Adrenergic effects on cardiac muscle contractility:
When the cAMP-dependent protein kinase becomes activated, what affects are seen in the contractile cells (3)
- VG L-type calcium channel gets phosphorylated
- Myosin heads get phosphorylated
- Calcium-ATPase activity in SR membrane is increased (indirect)
Adrenergic effects on cardiac muscle contractility:
Further explain the effects of the VG L-type calcium channel following phosphorylation:
-This increases the FDR (rate calcium ions enter cell because the probably that the channel will open is greater)
The increased FDR results in more calcium release from the SR, which leads to a greater calcium spike, more troponin bound to calcium & ultimately MORE FORCEFUL CONTRACTION
Adrenergic effects on cardiac muscle contractility:
Further explain what happens when the myosin heads get phosphorylated by cAMP-dependent protein kinase:
Myosin heads get phosphorylated, causing myosin heads to cycle faster
Ultimately will GENERATE TENSION MORE QUICKLY
What aspect of the SNS effects on contractile cells is considered the “Contractility effect”
Voltage-gated calcium channels getting phosphorylated causes a more forceful contraction
Adrenergic effects on cardiac muscle contractility:
Further explain what happens to the activity of the calcium ATPase:
This occurs indirectly through phospholambin- when the calcium-ATPase gets phosphorylated, its activity increases therefore the rate of calcium removal from the cytosol is increased so the cell can relax faster
Under the effects of the SNS on the contractile cells:
- The overall amount of tension will go up
- The speed of tension development will be quicker
- Muscle will relax more quickly
What are each of these due to?
- Due to increased amount of calcium released from SR (Contractility effects_
- Due to phosphorylation of myosin heads
- Due to increased activity of calcium-ATPase
Starling’s Law of the heart states that:
Anything that increases EDV will increase SV
Sympathetic motor neurons & epinephrine through Beta-1-receptors act on ______ to do _____
Atria & Ventricles
To increase BOTH HR & SV
Parasympathetic nervous system releases acetylcholine that will bind to muscarinic receptors on the _____ that will ONLY effect:
Atira
HR
Describe parasympathetic NS effects on stroke volume:
NO effect
At rest the amounts of _____ > ______ meaning that at rest the heart is under ______ influence
Acetyolcholine>NE
Parasympathetic
Receptors on the atria are for the influence of:
HR
Receptors on the atria are for the influence of:
Receptors on the ventricles are for the influence of:
HR
SV
Cardiac output is the function of ____ & _____
HR & SV
What is the functional unit of cardiac muscle?
What is the functional unit of skeletal muscle?
Sarcomeres
Because sarcomeres are the functional units of both skeletal & cardiac muscle, they both have a _____ relationship
Length/tension
What does having a length/tension relationship mean?
That there is a resting fiber length where you will optimum tension
What happens if you move away from the resting fiber length?
You decrease the tension that the muscle can generate
The stimulus for cardiac muscle is _____ while the stimulus for skeletal muscle is ______
Intrinsic
Extrinsic
Describe the calcium release in skeletal muscle:
Describe the calcium release in cardiac muscle:
100% SR
90% SR 10% ECF
Contractile response to a single AP:
Muscle twitch
Describe the muscle twitch in cardiac muscle:
Graded
What is the preferred drug of choice for dysrhythmia?
Beta-Blockers
Describe the effects of each on CO:
- Increasing sympathetic activity
- Increasing parasympathetic activity
- Increasing movement
- Decreasing HR
- Increasing resting sarcomere length
- Increasing BP
- Increase CO
- Decrease CO
- Increase CO
- Decrease CO
- Increase CO
- Decrease CO
Explain why increasing movement would increase CO:
Due to skeletal muscle pump, which increases venous return, that will increase EDV & therefore increase SV
Explain why increasing resting sarcomere length with increase CO.
What would happen if we decreased resting sarcomere length?
Cardiac muscle sits at a less than optimum length so by increasing resting sarcomere length we are getting closer to optimum.
Because we are already at a less than optimum length, this would move it further away from optimum
Explain why decreasing BP would increase CO:
Bc BP is the afterload on the heart. Anything that will decrease the load that the heart has to contract against will increase SV.
