CV 1 Flashcards
3 cog wheel depiction of CV and Vascular system
- The 3-cogs represent the connection between the tissues, heart, and airways/lungs.
- If one clog is limited, this impacts the function of others
“heart is composed of 2 parallel pumps”? What does this mean in terms of right and left ventricular stroke volume?
- the right and left sides of the heart are separated by a continuous septum
- they are parallel but separate
- atrias contract in sync and ventricles contract in sync
Where are the valves located in the heart? What is their function?
-tricuspid (right atrium and right ventricle) pulmonary valve (right ventricle and pulmonary artery) mitral valve (between left atrium and left ventricle) aortic valve (left ventricle and aorta) -functions to ensure one way flow
Explain the impact of valvular dysfunction on both upstream and downstream CV physiology and anatomy.
- valvular dysfunction leads to back flow being possible upstream and a reduction of blood flowing through the heart (effects downstream)
- Chronic overfilling will lead to changes in anatomy at that chamber
What is the function of the papillary muscles and when in the cardiac cycle do they contract?
- help keep em CLOSED valves
Layers of the heart
Fibrous layer» parietal pericardium» fluid»> visceral pericarium=epicardium» myocardium»> endocardium
Describe the positioning of the heart in the thoracic cavity.
Medial (behind sternum) on the left
When first touching the heart in your cadaver, what layer are you most likely touching?
Fibrous pericardium
What layers permit the heart to expand and contract with very little friction?
Pericardium cavity (bathed in liquid to reduce the mechanical friction of visceral pericardium on the fibrous pericardium)
Blood cells flowing through the heart would come in contact with what layer of the heart?
Endocardium (innermost layer)
Explain the ramifications of the large aerobic capacity of the heart.
-Cardiac Muscles need a continuous oxygen supply; constant blood flow
Explain how cardiac muscle grade contractile strength and their intrinsic beat rate. During your last heartbeat, how many cardiac muscle cells actively contracted.
- Muscle graded contraction result in either a more rapid or slowed contraction
- All cardiac muscle cells contract during every beat.
How many cardiac myocytes contracted the last time you were suddenly scared? Describe the involvement of the autonomic nervous system in this response.
All of them
SNS: Activity of the SNS increases (increased discharge rate of SA node)
PNS: Activity of Parasympathetic nerves decrease
Define chronotropic
positive vs negative
Chronotropic: Affecting the Heart Rate
+ Chronotropic effects: increases HR→ Sympathetic Nervous System
- Chronotropic effects: decreases HR→ Parasympathetic Nervous System
SA node symp and parasymp
symp nerves - increase HR
para nerves - decreased HR
AV node symp and parasymp
symp nerves - increased conduction rate
para nerves - decreased conduction
Atrial muscle symp and parasymp
symp nerves - increased contractility
parasymp - decreased contractility
Ventricular muscle symp and parasymp
symp nerves - increased contract
parasymp - no sig effect
Assume that a wave of depolarization starts at the SA node. Describe the pathway? What cells conduct this wave in the LV?? What structure allows the signal to move from the atria into the ventricles???
SA Node → AV Node → Bundle of His → R & L bundle branch → Purkinje Fibers
- Purkinje Fibers: In the left ventricle
- AV Node (starts action potential) → allows signal to move from atria to ventricle
Describe the action potential found in cardiac myocytes? What is the absolute refractory period and what is its role in the cardiac cycle??
- The AP are conducted across the whole cardiac muscle due to intercalated disks, allowing it to act as one unit
- absolute refractory period = time when another AP cannot be generated (this period is longer in cardiac muscles compared to skeletal muscles)
- For every minute the heart beats, another beat cannot beat
- There is a maximum Heart Rate (220-age)
What cardiac event is associated with the P, QRS, and T wave
- P-Wave: the SA node discharges and the atria depolarize. Atrial depolarization
- QRS-Wave: depolarization ventricular, atrial repolarization
- T-Wave: Ventricular Repolarization
Define: ventricular systole & diastole EDV ESV isovolumetric contraction
Ventricular Systole -(Contraction): semilunar valves open, AV closed
Ventricular Diastole - (Relaxation): AV open, semilunar open
-EDV (End Diastolic Volume): The amount of blood in the ventricle at the end of diastole (relaxation phase)
- ESV (End Systolic Volume): The amount of blood in the ventricle after ejection (contraction)
- IVC: During the first part of systole, the ventricles are contracting but all valves in the heart are closed and so no blood can be ejected
Briefly describe the vascular system of the heart.
- blood moves when a pressure gradient exists → this gradient is what drives blood through peripheral circulation and returns blood to the heart
- Coronary Vessels: blood supply to the heart
Describe how the autonomic nervous system regulated cardiac function.
Autonomic nervous system regulates the action of the SA node. The SA node is responsible for the initiation of the heartbeat.
Explain the intrinsic heart rate.
Frank-Starling Law describes the intrinsic ability of the heart to adapt to changes in the volume of inflowing blood (venous return or preload) and to automatically accommodate to the blood that comes into it. The heart can regulate its own heart rate because of the SA node.
Calculate CO for a heart rate of 140 BPM and a stroke volume of 80 mls. How hard is this individual working? How does dehydration effect CO???
Cardiac Output=Stroke Volume x Heart Rate
- Volume of R and L heart is should be equal
- CO= 140 (HR over 100) x 80 (avg. SV 72) = CO= 11.2 L per minute
- Yes, b/c this is double the normal CO.
- Dehydration causes decrease in SV and CO and HR would be increased to compensate for the loss in CO
How does preload influence CO?
Preload or end diastolic volume (EDV) is the venous return into the right atria. A higher preload would increase CO.
Describe the relationship between EDV, ESV and SV.
SV = EDV - ESV, increase in end diastolic volume → increase in stroke volume, increase in ESV → decrease in SV
How does afterload influence CO?
- Increasing afterload decreases the shortening velocity of the cardiac muscle. The heart compensates by increasing contractility so that cardiac output can be maintained.
Increase afterload= increased workload of the heart
How does contractility influence CO?
Contractility is the ability of the heart to pump blood out of the Left ventricle into the blood vessels; therefore, the greater the contractility of the heart, the greater the cardiac output
How does the Frank Starling mechanism ensure that the stroke volume is the same for the LV and RV?
The Frank-Starling Law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles before contracting
- -The right will try to match the left. Why we can characterize these pumps as parallel.
- So if the RV receives more blood, the LV will match it’s volume and pump out more blood
How is CO maintained in a patient who is dehydrated? In someone who is hypervolemic?
- Dehydration causes a reduction in stroke volume. In response a higher heart rate is needed to keep the status quo of CO
- Hypervolemia results in a lower heart rate to keep the CO equivalent
How is cardiac contractility increased?
Cardiac contractility is increased by sympathetic (innervation) stimulation, and this results in a reduced ESV (end systolic volume)
Define ejection fraction. How does it relate to SV?
Ejection Fraction:
- (EDV-ESV) / EDV = EF
- Normal EF: about 65%
- Stroke Volume tells you exactly how much blood was ejected.
- Very possible for two people to have same EF, but different SV
Explain the cardiac cycle.
The repeating pattern of contraction (systole) and relaxation (diastole) of the chambers of the heart.
Wiggers diagram summary
Wiggers Diagram Summary:
EKG: electrical pulses from the heart; regulates the rhythm; causes contraction; it brings about contraction of the heart and of the four chambers in a very specific sequence. Brings about synchronicity in ventricles and atria.
Ventricular Volume:
- Ventricular volume increases due to the atria contracting (p-wave) and influences of gravity;
- Now the volume has maxed out we have End Diastolic Volume;
- Then the ventricles contract and you get a decrease of blood volume.
- The change of volume EDV-ESV the difference is Stroke volume
- When divided by EDV you get Ejection Fraction
- Diastolic Filling and the cycle repeats
What drives Blood movement?
Pressure: the pressure gradient; blood moves in response to a pressure gradient and moves from high to low
Change In pressure:
- Pressure Change in Ventricle during diastole: Little Bump in pressure is caused by atrial contraction, movement of blood into the ventricles
- Between Diastole and systole; the pressure increases and is the start of ventricular contraction (ventricular systole)
- In order for the blood to leave ventricle and enter the aorta the pressure will push the valve open; the pressure has to reach a threshold. Once the ventricular pressure exceeds aortic pressure the valve will open and blood will enter the aorta.
Aortic pressure:
