CVS Physiology Flashcards
what is a cardiac myocyte
cardiac muscle cells
how does a cardiac myocyte get its nutrients, o2, and eliminate waste?
intracellular fluids and extracellular fluid help with removing waste within the body and help with life-sustaining exchanges
revision : what is homeostasis
active and passive transport process to help maintain a relatively stable internal environment
maintaining homeostasis
- detect deviations from normal ranges
- integrate information with other information
- make adjustments accordingly to restore it back to normal
Negative feedback example: Body temp high, integrate information, adjust to lower body temp
function of the heart
provides metabolic need for tissues by providing o2 and nutrients
factors affecting nutrient exchange with tissues
adequate exchange of fluids at the capillaries
- sufficient pressure and output from the heart
- integrity of vessels
what is contractile cells and its other variation
cardiac muscle cells that provide the mechanical work of pumping blood
autorhythmic cells/pacemaker cells
what do pacemaker cells do
initiate and conduct action potentials responsible for contraction of working cells
what is the route for the action potential of the heart
Sinoatrial node > atrioventricular node > bundle of his > purkinje fibers
What is the SA Node located, and what is it’s purpose
Main pacemaker of the heart
Right atrium wall, near opening of the superior vena cava
Location and purpose of AV Node?
Acts as a junction between atria and ventricles
near opening of coronary sinus
Bundle of his location and purpose
specialized tract originating from the AV Node and travels down the interventricular septum (separates left and right ventricle)
Location and purpose of purkinje fibers
terminal fibers spreading through the myocardium like tree branches
location and purpose of internodal pathway
connects the SA node and AV node to allow transmission of the signal from the SA node
impulse conduction through the heart
SA node activates and atrial activation begins
Stimulus spread through the atrial surfaces and reaches AV node
100ms delay at AV node, atrial contraction begins
Impulse travels along interventricular septum through the bundle of his to the purkinje fibers and by the moderator band, to the papillary muscle of the right ventricle
Impulse distributed by purkinje fibers, relayed to the ventricular myocardium, atrial contraction is completed and ventricular contractor begins
What is an action potential
electrical signal
rate of action potential of all 4 pacemakers
SA node = 70-80 AP/min
AV node = 40-60 AP/min
BH and PF = 20-40 AP/min
what happens if the SA node fails/not functioning properly?
AV node takes over as the main pacemaker of the heart
how is efficient cardiac function achieved?
atrial contraction and excitation is completed before ventricles contraction
tldr: atrials are coordinated, ventricles are coordinated, simultaneously contract/relax
what controls the HR?
autonomic nervous system
- parasympathetic
- sympathetic
some things that affect the HR
Resting - P predominates
Epinephrine/temperature - acts on the SA node directly, independent of the ANS
Pain, chemoreceptors, respiratory center, baroreceptor - acts on the cardiovascular control center
how does the 2 autonomous nervous system affects HR (Increase or decrease)
Sympathetic - increase HR
parasympathetic - decrease hr
what does an ECG measure, and from where?
electrical events in the heart FROM the surface of the body (does not measure the heart directly)
what does an ECG tell you?
overall spread of electrical activity throughout the heart during depolarization and repolarization
how many ECG leads and where are they located?
12 leads
6 on the heart
right arm to left arm
right arm to left leg
left arm to left leg
left leg (goes up straight from left leg) (aVF)
left arm (across body) (aVL)
right arm (across body) (aVR)
AV = augmented voltage
what is the purpose of having these leads in an ECG
viewing electrical events in the heart from a unique vantage point to identify if there is any anomaly
explain what causes the P, QRS, and T wave within a LEAD II ECG
P - atrial depolarisation
QRS - ventricular depolarisation (atrial repolarisation is here too but it is overshadowed by VD)
T - ventricular repolarisation
why are the P wave smaller than the QRS complex
atria got smaller muscle mass than ventricles
what 3 occasions within a LEAD II ECG is there no electrical activity
P-R = AV node delay
S-T = ventricular completely depolarises, cardiac cells undergoing plateau phase
Passive filling of the ventricles
What happens during the P-R interval
signal from SA node travels to AV node, then out to the bundle of his
majority of time taken is the AV node delay
How to identify the respiratory rate within a LEAD II ECG
time taken between the peak of two R complex within the QRS complex
each square is 0.2seconds or 200ms, one small square is 0.04seconds or 40ms
why is there a plateau phase of the action potential
to prevent tetanic contraction, where the heart contracts repeatedly
during the plateau phase, there cannot be another action potential
what is the benefit of having calcium entry from the extracellular fluid (ECF)
induces a much larger Ca2+ release, with slow Ca2+ removal to allow for long period of cardiac contraction, this increased contraction ensure enough time for all the blood to be ejected out of the heart
kahoot
the normal pacemaker of the heart is?
SA node
Kahoot
blood returning to the heart from the systemic circuit first enters the?
right atrium
kahoot
what is range of the Action Potentials/min in the AV node
40-60 APs/min
kahoot
what is the parasympathetic system’s influence on the SA node
lowers HR
kahoot
the P wave of the ECG is a signal from (in terms of heart, not nodes)
atrial depolarisation
kahoot
depolarisation of the ventricle is represented on the ECG by
QRS
kahoot
which of the 12 LEAD ECG indicates the apex of the left ventricle?
LEAD II
kahoot
what interval helps you calculate the heart rate?
RR interval
what is the pacemaker ability?
slowly depolarises the membrane potential (mV) from -60 to -40 (threshold potential)
what is required for the pacemaker ability to function?
Funny channel allows sodium ions to cross the membrane, sodium is essential for the slow, depolarizing pacemaker potential
what happens once the membrane potential crosses the threshold potential?
you get your self-induced action potential
what happens to the action potential after it’s self-induced and hit its peak of depolarisation?
the action potential is spread throughout the heart
mechanical movements of the heart in the cardiac cycle
systole and diastole
contraction and relaxation
what happens in the first part of the cardiac cycle?
all chambers are relaxed
AV valves open
passive feeling completed
Atrial systole begins, forcing small amounts of blood into the relaxed ventricle
what happens in the second part of the cardiac cycle
Atria begins to relax after contracting (atria diastole)
ventricles start to contract (ventricular systole)
AV valves are close
The semi-lunar valves are also close, as there is not enough pressure to open them
isovolumetric contractions to increase pressure
describe ventricular systole second phase within the cardiac cycle
semilunar valves open
blood is contracted and goes out of the ventricle
describe the ventricular systole within the cardiac cycle
ventricles start to relax, back flowing back pushes against the semi-lunar valves and force them shut
all chambers relax, AV valves open and passive feeling occurs
overview of cardiac cycle just go see your notes (Part 2 pg11) the damn big graph will all the aortic pressure left ventricular pressure etc etc
GO SEE THE DAMN NOTES
what gives rise to the first and second heart sounds?
1st - closure of the AV valves
2nd - closure of the aortic/pulmonary
valve
what is cardiac output and how do you calculate it?
Volume of blood pumped out by each ventricle per minute
Cardiac output = heart rate x stroke volume
HR = beats per min
SV = amount of blood pumped from ventricles per beat
kahoot
what is the second heart sound associated with?
Closure of semi-lunar valves/aortic valve
kahoot
ventricular diastole refers to the contraction of the ventricles. True or False?
False
kahoot
what is the state of the heart valves during isovolumetric ventricular relaxation
all closed
kahoot
depolarization of the atria is represented on an ECG by which feature
P wave
Effect of ANS on HR
SA Node*
parasympathetic - decrease rate of depolarsation to threshold, decrease HR
sympathetic - increase rate of depolarisation to threshold, increase HR
effect of ANS on HR
AV Node
parasympathetic - decreases excitability, increase AV node delay
Sympathetic - increases excitability, decreases the AV node delay
effect of ANS on HR
Ventricular conduction pathway
Sympathetic - increases excitability, hastens conduction through the bundle of his and purkinje fibres
Effect of ANS on HR
Atrial muscles
parasympathetic - decreases contractibility, weakens contraction
sympathetic - increases contractibility, strengthens contraction
Effect of ANS on HR
Ventricular muscle*
Sympathetic - increases contractibility, strengthens contraction
Effect of ANS on HR
Adrenal medulla
Sympathetic - promotes secretion of epinephrine
Effect of ANS on HR
Veins*
Sympathetic - increases venous return, which increases strength of cardiac contraction via intrinsic pathway
2 controls components of stroke volume, and what each component is related to
intrinsic control - related to the extent of venous returns
extrinsic control - related to the extent of sympathetic stimulation of the heart
can you explain the frank-sterling law of the heart?
Intrinsic relationship between end-diastolic volume and stroke volume
higher diastolic volume = higher stroke volume
more blood in ventricles, more blood can be pumped out
how does increase diastolic filling result in greater contractions?
higher diastolic filling = increased EDV = stretching of the heart = increase length of cardiac muscle fibers before contraction = more force on subsequent cardiac contractions = increase stroke volume
what is stroke volume and what is its equation
amount of blood pumped from ventricles per beat
EDV - ESV
what is ejection fraction and how do you calculate it
what is its normal range
fraction of blood ejected from a ventricle with each beat
SV/EDV x 100%
normal range = 55%-75%
how does sympathetic and parasympathetic activity influence cardiac output
parasympathetic activity increase = lower HR = lower CO
Sympathetic activity increase = higher HR = higher CO
Intrinsic control - sympathetic activity increase = increase venous return = increase EDV = increase stroke volume = increase CO
Extrinsic control - sympathetic activity decrease = decrease stroke volume = decrease CO
factors affecting cardiac output
preloading (volume of passive and active filling), heart contractibility and rate, afterload (peripheral resistance) (part 3 of cardiac physiology)
how does the body compensate for systolic heart failure
sympathetic stimulation
kidneys retains salt and water to maintain blood volume as much as possible
how does the heart get majority of its blood supply
through coronary circulation during diastole, blood flow is adjusted based on the heart’s o2 requirement 70%
systole is the other 30%
opening found on the side of the aortic valve when it is closed, opening closes partially when the aortic valve opens
whats the process of the heart’s coronary acquiring more o2
increase metabolic activity = increase adenosine = vasodilation of coronary vessels = blood flow to cardiac muscle cells = increase oxygen availability to meet oxygen needs
Describe angina pectoris, acute myocardial infarction, and coronary artery disease (CAD)
angina pectoris - sensation of chest pains arising from myocardial ischemia
acute myocardial infarction - heart attack
CAD - blockage of the lumen with plague, resulting in reduced blood flow
what is a thrombus, embolus, and thromboembolism
embolus - abnormal particle floating in the blood vessels
thrombus - abnormal clot in the vessel wall
thromboembolism - thrombus that broke away and obstruct blood vessel elsewhere
using endothelium, smooth muscle, collagen fibres, and elastin fibers
state from lowest to highest abundance within large arteries, arterioles, capillaries, and large veins
large artery - endothelium, collagen fibers, elastin fibers, smooth muscles
elastin fibers - endothelium/collagen fiber, smooth muscle
capillary - endothelium
large vein - elastin fibers, endothelium, collagen fiber, smooth muscle
name 3 examples of blood reconditioning organs and what they do
- kidney - eliminate waste, adjust water and electrolytes
- digestive tract - pick up nutrient supplies
- skin - regulation of temperature
define flow rate
volume of blood passing through per unit of time
proportional to pressure gradient, and inversely proportional to resistance
define blood pressure
force exerted by blood against a vessel
define pressure gradient
pressure difference from the start and end of the blood vessel
name a type of resistance to affect flow rate
friction between blood and vascular wall
what is the order that blood flows within the body
blood flow is parallel
each major organ has their own artery, its not a lung > heart > organ > organ > organ > back to heart, more like a lung > heart > specific organ > heart again
describe more about arteries and them being pressure reservoirs
arteries have the ability to distend, which often happens when the heart contracts. Capillaries unable to flow as fast as the heart pumps, so the artery distend. During diastole, when the heart relaxes, blood still flows due to the elastic force that drives the blood along, even though there is no blood flow
factors that affect blood pressure
volume of blood within the vessel
distensibility of the blood vessel
2 types of blood pressure, and their definitions
systolic and diastolic
systolic - maximum pressure when blood is ejected into the arteries
diastolic - minimum pressure when blood is draining in the rest of the vessels during diastole
what is the formula for pulse pressure
systolic pressure - diastolic pressure
Define mean arterial pressure, and its purpose. What is the formula?
Average pressure driving blood forward.
Formula can either be
= 2/3 diastolic + 1/3 systolic
OR
= diastolic + 1/3 pulse pressure
complications if blood pressure is too high or too low
too high = blood vessels cannot support the high BP
too low = tissues do not get enough blood
describe capillaries
site of exchange between blood and tissues
very thin walled, extensive branching, proximity of almost every cell to a capillary
RBC moves in a single file, slow blood velocity which benefits gaseous exchange
high cross-sectional area together with slow velocity of blood flow maintains the constant flow rate
what are some important features within the capillaries
water-filled pores - allows small water soluble substances to pass through
phospholipid bilayer - allows lipid-soluble substance to pass through
As capillaries do not have smooth muscles, what do they utilise to control blood flow? what does it get stimulated by?
pre-capillary sphincters
stimulated by increase in metabolic activity = sphincters relax = more open capillaries = increase blood flow to active tissues
kahoot
how is mean arterial pressure determined?
2/3 diastolic + 1/3 systolic
OR
diastolic + 1/3 pulse pressure
kahoot
what is systolic blood pressure?
the maximum pressure exerted on the blood vessels during contraction
kahoot
which of the following is a reconditioning organ?
kidney
skin
digestive tract
kahoot
which of the following is an important characteristic of capillaries?
high surface area
low blood flow velocity
presence of pre-capillary sphincters
thin-walled so exchange is very quick
how is blood flow distribution regulated?
local control of arterioles, depending on demands for blood
vasoconstriction and vasodilation of vessels
what causes vasoconstriction or vasodilation of the vessel
(intrinsic control)
vasoconstriction - high o2, low co2, high endothelin, high sympathetic stimulation vasopressin and angiotensin II
vasodilation - low o2, high co2, high nitric oxide, low sympathetic stimulation histamine
what is the result in relation to sympathetic activity changes (extrinsic control)
increase sympathetic activity - all arterioles vasoconstrict
decrease sympathetic activity - all arterioles vasodilate
sympathetic fibers supply arterioles smooth muscle everywhere but the brain, as it requires constant supply of blood
which takes over control, intrinsic or extrinsic?
list the riding bicycle as an example
local control overrides sympathetic vasoconstriction
ride bike = sympathetic activity = everything vasoconstrict = metabolic activity in leg = vasodilate in leg (local so it overrides) = more blood to leg = less blood to other places
what is responsible for extrinsic control?
cardiovascular control centre - control sympathetic output
adrenal hormones - norepinephrine and epinephrine
norepinephrine - generalised constriction
epinephrine - local vasodilation mechanisms
Potent vasoconstrictors
vasopressin - maintains water balance
angiotensin II - regulates salt balance
revision - what two factors affect blood pressure, and 2 components each
cardiac output
- HR
- Stroke volume
total peripheral resistance
- arteriole radius
- blood viscosity
features of veins
low resistance, less elastic recoil, less smooth muscle
slow transit time
blood storage as blood being pumped is faster than blood flow
what affects the venous capacity
distensibility of the veins
external pressure such as skeletal muscles compressing it
sympathetic innervation of the venous return
vasoconstriction in veins = lower capacity = higher pressure = faster flow
skeletal muscle effect on venous return
large veins reside between skeletal muscles in arms and legs
when muscle contracts, veins compress
reduces venous capacity, increase venous pressure, increase venous return
effect of gravity on venous returns
vessels below heart subjected to gravity
veins are more distensible, resulting in increase capacity
reduces venous returns, reducing cardiac output
