Unit 3: Cardiovascular Physio Flashcards
Define “circulation”.
the movement of extracellular fluid (plasma, RBC/WBC/platelets) from region to region within the body
Define “internal environment”.
interstitial fluid
environment that our cells are in direct contact with
Describe the major functions of the cardiovascular system.
Transport
~oxygen from lungs to interstitial fluid surrounding cells everywhere in body
~nutrients from digestive tract to interstitial fluid everywhere
~also will pick up metabolic waste and deposit it into interstitial fluid > sites of elimination (Ex) Co2 > lungs). most other wastes removed by kidneys
~also transport of hormones, heat
~Self-repair mechanism (blood clotting)
Identify the three major components of the cardiovascular system and relate each to the major functions described
- Blood- transportation, defense, etc.
- Blood vessels (lymph vessels)- allow blood to travel
- heart- pumping blood
Describe each of the three major types of blood vessels - both anatomically and functionally.
- Arteries/arterioles- resistance vessels
~Thick, muscular tubes that carry oxygen-rich blood from heart > body.
~Act like highways, delivering blood with a strong push from the heart. - Capillaries- exchange vessels
Driving forces: diffusion, filtration, osmosis
~Tiny, thin-walled vessels where blood exchanges oxygen, nutrients, and waste with body cells.
~Act like small bridges, allowing essential substances to pass between blood & cells. - Veins- capacitance vessels
influence how much blood returned to heart (venous return)
~medium tubes carry oxygen-poor blood back to the heart.
~Act like rivers, relying on muscle contractions and valves to keep blood flowing upward.
Diagram/describe the flow of blood through the heart, naming all of the chambers and valves along the way.
Add to your diagram a description of where the blood leaving the heart goes and where the blood entering the heart comes from
Vena cava
right atrium
right AV / tricuspid valve
right ventricle
right semilunar valve
pulmonary trunk
pulmonary veins
left atrium
left AV / mitral valve
left ventricle
left semilunar valve
aorta
> systemic circulation
Arteries, capillaries, veins
Name the blood vessels and describe the oxygen content of the blood in each blood vessel and heart chamber.
vena cava > right atrium = low oxygen
right ventricle > pulm. arteries = low oxygen
exchange Co2 and O2
left atrium > left ventricle = high oxygen
What is the primary function of the heart?
to pump blood to supply oxygen and nutrients to your body’s parts, like muscles and organs, and to carry away waste products.
What is the function of the atria?
Of the ventricles?
atrium- receives blood returning to the heart from blood vessels
ventricle- pumps blood out into blood vessels
What is the function of the valves? What causes the valves to open and close?
to permit blood to flow forward while preventing it from flowing backward
Heart valves open and close in response to changes in pressure within the heart chambers during its pumping cycle.
When the heart contracts, higher ventricular pressure closes the AV valves to prevent blood from returning to the atria; increased pressure forces the semilunar valves to open, enabling blood to exit the heart.
As the ventricles relax, lower pressure causes the semilunar valves to close, preventing backflow from the arteries. This pressure difference leads to the opening of the AV valves, allowing blood to flow from the atria to the ventricles
Describe the microscopic structures that make the heart function as a pump.
Intercalated Discs: Special connections between cells that help them work together.
gap junctions- cells function in unison
Describe the transmission of electrical energy through the conduction system of the heart.
What type of tissue is the conduction system made of?
cardiac muscle tissue
The transmission of electrical energy through the heart’s conduction system begins with the SA node generating an impulse in the atria, causing them to contract. The impulse then travels to the AV node, delaying briefly to allow ventricular filling. It continues through the bundle of His and spreads via Purkinje fibers, triggering ventricular contraction and the pumping of blood. The heart then undergoes repolarization and relaxation before the next cycle begins.
The sinoatrial (SA) node serves as the initial source of the action potential (AP), which subsequently spreads throughout the atrial myocardium, reaching all atrial cells. This propagation activates the atrioventricular (AV) node, prompting the generation of another AP in its cells. After a brief delay, the AP travels down the AV bundle (Bundle of His), which then divides into left and right bundle branches, featuring side branches that allow adjacent cells to depolarize. Near the apex, each branch of the AV bundle ascends along the ventricular walls, stimulating neighboring cells, particularly the Purkinje fibers, to initiate their own action potentials through cell-to-cell communication.
Describe the excitation-contraction-coupling mechanism of myocardial contraction.
Electrical Signal: electrical signal starts in the heart’s natural pacemaker (SA node) and spreads through the heart.
Calcium Release: The signal causes calcium to be released inside heart muscle cells.
Calcium Activation: Calcium activates proteins in the muscle cells, including troponin.
Muscle Contraction: Activated troponin allows actin and myosin (proteins in muscle cells) to interact and cause muscle contraction.
Sliding Filaments: Actin and myosin filaments slide past each other, shortening the muscle cell and causing contraction.
Relaxation: calcium is pumped back out of the cell, and the muscle relaxes.
This process repeats with each heartbeat, allowing the heart to pump blood efficiently. The electrical signal triggers the release of calcium, which then activates the muscle contraction machinery, leading to the rhythmic beating of the heart.
excitation - AP
Ap = membrane
contraction = interaction between thin and thick myofilaments
diffusion of calcium
in myocardial cells, diffusion of Ca originates from SR or extracellular… calcium diffuses until it binds to troponin-tropomyosin complex; shape change ; binding site on actin uncovered, myosin heads can latch on..
Define diastole and systole.
Diastole:
heart’s “relaxation” phase.
During diastole, the heart fills with blood as its chambers relax.
heart “resting” and getting ready to pump blood.
Systole:
heart’s “contraction” phase.
During systole, the heart’s muscular walls contract, squeezing blood out.
heart “working” to pump blood out to the body or lungs
Describe the pacemaker action potential.
What is the mechanism of “autorhythmicity” in the pacemaker tissues?
The ability of myocardial autorhythmic cells to generate AP in absense of input from NS results from their unstable membrane potential (starts at -60 mV and slowly drifts up toward threshold)
This is AKA pacemaker potential, rather than resting membrane potential, bc it never “rests” at a constant value
Whenever pacemaker potential depolarizes to threshold, the autorhythmic cell fires an AP
—3 phases
no resting phase
in between AP = pacemaker potentil [slow depolarization due to sodium funny channels and slow ca channels], voltage gated channels open (2 types- fast Ca cause rapid depolarization to produce AP, as they close, K channels open > repolarization
Describe the different stages of the myocardial action potential.
What ions / ion channels are responsible for the different stages?
How does the myocardial action potential relate to the phases of contraction (twitch)?
Phase 0- depolarization
Na channels open
Phase 1- initial repolarization
Na channels close
phase 2- plateau
Ca channels open; Fast K channels close
Phase 3- rapid repolarization
Ca channels close, Slow K channels open
Phase 4- resting membrane potential
Describe the different waveforms of the electrocardiogram.
What specifically is represented by each waveform?
Identify the points in time when the SA and AV nodes begin to depolarize.
P wave- electrical activity in the atrium
[not a measure of AP, but measures electrical differences between 2 recording electrodes at the time AP are moving through myocardium of atria]
atrial depolarization
P wave- spread of atrial depolarization
initiation p wave - SA node depolarizes
peak to end - spread of depolarization
QRS wave- [complex] - represents electrical excitation within ventricles
[Q wave, large R wave, small S wave]
ventricular depolarization
QRA begining - AV node depolarizes
spread of ventricular depolarization
T wave- return to resting state within ventricles
Ventricular repolarization
Define bradycardia and tachycardia.
bradycardia- abnormally slow heart rate
tachycardia- abnormally fast heart rate
[detectable by ECG or taking pulse]
Define and describe each of the different degrees of AV nodal block (aka heart block).
1st degree- long P-R interval
2nd degree- more than 1 P wave per QRS
3d degree- independent P wave & QRS wave rhythms
Describe the pattern of depolarization known as a circus rhythm.
Explain how a circus rhythm can be generated and sustained.
What pattern would be observed on an ECG.
Fibrillation is a consequence of circus rhymthm
circus rhythm- self-re-generating AP that transits through the myocardium in ventricles or atrium
Pattern: no evidence of P or QRS or T wave.. just irregular wave form; or just may be a flat line
initiation due to ectopic pacemaker and this can be due to hyperexcitability of cells due to hypoxia or excess K, traumatic injury
Cells contracting but not working together..
can be problematic
Describe the forces that lead to “exchange” between
capillaries and interstitial fluid.
Pay particular attention to the “exchange” of oxygen, carbon dioxide and water.
it takes place either by movement between endothelial cells or movement through the cells
Pg. 496
in capillary, there are 2 types of movement - molecular driven by diffusion (concentration gradient)
and water movement driven by 1) pressure / filtration 2) osmosis
these 2 oppose
filtration out of capillary dominates
pressure drops as you move down capillary length
at the venous end, osmotic movement of water into capillary dominates
What factors influence the movement of water between capillaries and interstitial fluid?
What effect would altering any of these factors have on water distribution?
pressure and osmosis
high blood pressure = pressure gradient dominant over osmotic»_space;> water builds up in tissue
high salt diet - water moves into blood until pressure balances it out.
Describe two different ways to determine cardiac output.
[flow]
how much blood is pushed out of the heart
1) MAP / TPR
total peripheral resistance
[diamater of blood vessel is big factor]
2) Stroke volume (SV) x heart rate (HR)
What is the principal regulatory factor contributing to peripheral resistance?
diameter of the blood vessels
[systemic circuit]
Describe the (intrinsic) Frank-Starling law of the heart. How does this phenomenon help increase cardiac output to match increased physical activity?
How does it contribute to maintaining a balanced output from the left and right ventricles?
if venous return increases, this results in increased end-diastolic volume
[volume of ventricle will be greater at the end of the diastolic phase if there is more blood flowing into it]
The ventricle will contract with force proportional to its volume [length-tension relationship]
The heart contracts as forcefully as it needs to eject the volume it receives, in the form of its end-diastolic volume
Describe the innervation of the heart by the parasympathetic and sympathetic systems.
~innervated by both the parasympathetic and sympathetic systems.
~During rest, heart primarily under parasympathetic control, ~During activity or stress, it falls under sympathetic control.
Describe the effect and the mechanism of parasympathetic stimulation on the heart.
Chronotropic effect
slows HR by slowing SA node activity (AP generation)
Describe the effect and the mechanism of sympathetic stimulation on the heart.
~chronotropic: —increases HR by increasing AP generation by SA node
~inotropic effect: affects strength of contraction—increases force of contraction by influencing calcium influx into cell
Describe how blood flow (distribution) is regulated intrinsically by carbon dioxide.
metabolic vasodilation- blood vessels respond intrinsically to metabolic byproducts in their vicinity
Increased skeletal muscle activity during exercise > skeletal muscles generate Co2 as byproduct > Co2 stimulates metabolic vasodilation of blood vessels in the muscle > increased blood flow to muscle
Co2 levels increased > vasodilation
Describe the effect of the parasympathetic and sympathetic regulation of blood vessels.
Sympathetic stimulation : blood vessels within muscles can vasoconstrict (decreases blood flow) in the viscera and vasodilate (enhance blood flow) in the muscle
Parasympathetic Regulation:
Parasympathetic nerves mainly relax blood vessels in specific areas, like the digestive system; helps increase blood flow to those areas, which is useful for digestion, etc
Describe the baroreceptor reflex.
baro = pressure
reflex that helps to regulate blood pressure
If BP drops too low, not enough flow/pressure to keep blood moving
BP always being monitored; if too low, will drive BP up by increasing HR/ Stroke volume/ resistance
predominantly measured within baroreceptors found in carotid sinus; also some in the aorta
[pressure sensitive sensory receptors that will detect stimulus > graded/AP generation > sensory neurons carry info towards CNS]
Describe the different factors that affect venous return to the heart.
Venoconstriction
Venodilation
respiratory pump- decreases pressure in thorax as lungs expand in inhalation; moves blood up from abdomen; at exhalation, there is increased pressure and this pushes blood along in thoracic cavity
~during inhalation, pressure in thoracic cavity decreases, vena cava expands, blood in other veins flow towards vena cava leading to heart. Expiration - slows flow.
Venous return increases during inhalation.
Skeletal muscle pump - skeletal muscles moving/squeezing/ contracting on veins which exert pressure on veins, pushing blood along
~centered around veins having valves , veins squeeze out blood, valves ensure it is squeezed towards heart
Formula for pulse pressure
systolic - diastolic pressure
Formula for MAP (mean arterial pressure)
[pressure difference]
Pulse pressure = systolic - diastolic pressre
MAP = diastolic pressure + 1/3(pulse pressure)
Although many myocardial cells are capable of auto-rhythmicity, 1 group of cells in the right atrium predominates over all others:
SA node (sinoatrial node)
since body fluids contain a high concentration of __________,, they are electrically conductive
electrolytes
Blood flows from high to low concentration/pressure, a pressure difference generated by:
contraction and relaxation of heart
The amount of blood flow, called ____________________, is a product of the balance between pressure differences generated by the heart and resistance generated by blood vessels
cardiac output
Average cardiac output is
5-6 L/min
Specialized exchange vessels are
capillaries
Arteries and arterioles are also known as
resistance vessels
[carry blood away from heart, towards capillaries]
The only portion of the vascular system where exchange between blood and tissues can occur:
capillaries = exchange vessels
The plateau phase of a myocardial cell action potential (indicated by 2 in the image above) is caused by movement of:
calcium ions into the cell
The rapid depolarization phase (indicated by B in the image above) of a pacemaker cell action potential is caused by movement of:
calcium through fast L-type channels
The unique ion channel(s) in the SA node that are responsible for the SA nodes autorhythmicity (segment A) due to its hyperpolarizing threshold:
HCN channel
Slow T-type calcium channel
Sodium “Funny” channel
What’s happening during 0 and 1?
1- Na+ channels open
2- Na+ channels close
What’s happening during 2 and 3?
3- Ca2+ channels open; Fast K+ channels close
4- Ca2+ channels close; Slow K+ channels open
What’s happening during 4?
resting potential
