Week 3 Heart Flashcards
What comes right after diastole?
Systole
What is end diastolic volume?
The volume of blood in the ventricle just BEFORE it starts to contract
What is the largest volume of blood in the ventricle during cardiac cycle?
End diastolic volume
Gotta fill it before pushing it out
What is systolic volume?
Volume of blood in ventricle
- just at the end of ejection
- at the end of systole
- just before heart starts to relax
What is the LOWEST volume of blood in the heart?
Systolic volume
What is stroke volume?
The volume of blood EJECTED from the ventricle in one cardiac cycle
What is the equation definition of stroke volume?
EDV - ESV = SV
What is the difference between EDV and ESV?
The amount of blood you pumped out
What is ejection fraction?
A measure we use to talk about how efficiently the heart is working as a pump
A way of measuring what percentage of the volume of blood that was in the heart was pumped out
How to calculate ejection fraction?
SV divide by EDV X 100
What is P in an equation?
Arterial blood pressure
What is Q in an equation ?
Cardiac output
What is cardiac output?
The volume of blood pumped out by the ventricle over some unit of time
Usually minutes
What is the relatively normal cardiac output ?
5L per minute
What does R stand for in an equation?
Total peripheral resistance
What is the equation to determine cardiac output?
HR X SV = CO
If CO goes up, what happens to pressure?
It will go up
Do CO and BP change in the same direction?
Yes
How do we adjust pressure?
By changing cardiac output
If you change heart rate what changes?
CO and blood pressure changes
If you change CO, what changes?
Arterial blood pressure
If you change SV, what changes?
cardiac output
The chief determinant…
Chief determinant of arterial blood pressure is the amount of blood in the arterial side of circulation
What raises blood pressure?
Anything that helps to put more blood into arterial side of circulation or anything that makes it harder to leave the arterial side of circulation.
What lowers blood pressure?
Anything that makes it harder to get blood into the arterial side of circulation or easier to leave.
How is heart rate controlled?
At the SA node by the balance of sympathetic and parasympathetic activity there
We can adjust things with neurons but what can’t we do with neutrons?
Trigger them
Increase sympathetic activity at the heart tend to what?
Raise heart rate
Increased parasympathetic activity at the heart tend to what?
Lower heart rate
What is in the carotid sinuses?
Baroreceptors
What does baroreceptors measure?
Pressure
The more baroreceptors stretch, the more what?
More indication of high pressure you have
Where do you have baroreceptors in the body?
In the carotid sinuses and aortic arch
What do aortic baroreceptors tell you?
when the pressure coming out of that ventricle is sufficient.
What do the carotid receptors tell you?
if you have enough pressure to profuse the rate and if there’s a difference of pressure on one side of carotids, you may have a blockage.
We have some constant level of autonomic nervous system activity, what are the advantages of that?
Being able to find the control disc and gives us the ability to increase or decrease both sympathetic and parasympathetic
What is dual innervation?
It is innervated by the sympathetic and parasympathetic branches of autonomic nervous system
What is an autonomic reflex?
It control or adjust blood pressure
How does autonomic reflex work?
The aortic/carotid baroreceptors receive a certain amount of stretch. That info is sent to medulla oblongata into an area called cardiac control center.
Where does the cardiac control center take the info if blood pressure is low?
sends it to the cardiac acceleratory center
What does cardio acceleratory center do with the low blood pressure info?
Send signals to SA node to raise heart rate
What if BP is too high?
info from baroreceptors also sends to cardiac control center which integrates info to cardio inhibitory center
Where does cardio inhibitory center send high BP info?
Send signals to SA node to decrease heart rate
If blood pressure is high what is the arrow answer? What is it controlled by?
^BP -> baroreceptor detects -> CCC -> CIC -> down HR -> down Q -> down BP
Negative feedback, stimulus went down
If blood pressure is low what is the arrow answer?
Down BP -> baroreceptor detects -> CCC -> CAC -> ^ HR -> ^ Q -> ^ BP
What’s another reflex that can adjust heart rate for a few moments?
Atrial reflex or Bainbridge reflext
What does the atrial/bambridge reflex do?
When you have a lot of blood going back into the right atrium, it stretches the right atrium and stretches the SA node and that stretch makes HR go up a couple beats so you can pump extra blood out of atrium
What are the hormones that affect heart rate?
Thyroid hormone, epinephrine and norepinephrine.
What is preload?
The amount of TENSION in the wall of ventricle just PRIOR to contraction.
What is the less invasive way to estimate preload?
End diastolic volume
What’s putting tension in wall of left ventricle just before contraction?
Amount of blood in it
What happens to preload when EDV goes up? What happens if it goes down?
Preload goes up
Preload goes down if EDV goes down
What happens to someone’s ejection fraction if someone has a heart failure?
Their ejection fraction goes down (efficiency of pump) and the amount of blood that stays in ventricle continues to rise and the ventricle gets very stretched and it take more work to start contraction
Someone who has high preload, what do we do?
We need to lower blood volume so their EDV can go down
What happens if you get rid of water from some parts of body,
The rest of water I’m body redistributes a lil and some water will leave blood
What is afterload?
The work that the heart has to do to cause ejection
If left ventricle can’t generate that much pressure then what?
You won’t have enough ejection cuz you won’t be able to open aortic valve
What is the less invasive way of estimating afterload?
Arterial blood pressure
What is the problem people when they are hypertensive?
They have high afterload,
heart has to work harder to cause ejection if BP is 160/95, than the person with 120/80 BP
What is Frank-Starling Mechanism/Starling’s Law of the Heart?
When you increase stretch, you increase the force of contraction.
Cardiac muscle contracts the same way as?
Skeletal muscle
You need an overlap of thick and thin filaments or you can’t get any movement
If you put a skinny strip of cardiac muscle and clip a heavy 5 pound on it, what will happen
It won’t move due to an overstretch
If heart contracts more forcefully, what goes up?
Stroke volume
What causes stretch in a heart that’s in a person?
Increased blood right before ejection/contract
What does EDV determine?
The stretch of the heart
If EDV increases, what happens to the force of contraction ?
It will increase
What are you looking for that makes you think this is a starling question?
Look for EDV change and change in stretch, etc
Arrow answer of high EDV
^EDV -> ^stretch -> ^ force of contraction -> ^ SV -> ^Q -> ^BP
Arrow answer for low EDV
Low EDV -> low stretch -> low force of contraction -> low SV -> low Q -> low BP
Where do you see the work of EDV to BP in a normal healthy person
When transitioning from rest to exercise and vice versa.
Cardiac output changes dramatically
What happens to cardiac output in the transition points of rest = exercise
Cardiac output changes dramatically
Can we sow individual neurons back on to SA node?
NO
Normal heart can adjust to force of contraction in many way, what is the main regulation of moment to moment in someone with heart transplant?
Frank starling mechanism
What happens to frank starling mechanism during exercise? And how do we get both ventricles of SV to match up again?
Muscles are working and more blood is coming back to right side of heart and getting pumped out of left side of heart
- More blood coming back , stretches heart and right ventricular SV goes up.
- blood goes through the lungs
- and ultimately into left ventricle which now has a larger SV and it gets stretched so it’s contracting. Within a few beats, SV of both ventricles matched up again.
What if I run home and i sit and rest?
Muscles are not working as hard and not breathing as hard = less blood is going back to the right side of heart
Less stretched means what?
Smaller SV coming out of right ventricle and eventually will have a smaller EDV in left ventricle causing less stretch, causing SV to go down and you match again.
What is the other way to change stroke volume?
Contractility
What is contractility?
A change in the force of contraction WITHOUT a change in stretch
If you’re reading a question on exam and it says “explain how joes CO could change under these conditions and EDV is stable” what does it mean?
If it’s stable or no change in EDV, means no change in stretch
What is the only way you can change SV without change in stretch ?
Contractility
Contractility is about what?
Chemicals
What happens when some chemicals are placed on heart muscle?
- It will make it contract more forcefully cuz that’s what they do
- decrease how forcefully cardiac muscle contracts
- contracts less forcefully
when the hormones make the heart contract more forcefully, what happens to SV?
It increases
What hormones will make heart contract more forcefully?
Epinephrine, norepinephrine, thyroid hormone
Arrow answer of Contractility
Add chemical -> ^ Contractility -> ^ force of contraction -> ^ SV -> ^ Q -> ^ arterial BP
What will change Contractility?
Neurotransmitter and hormones
Once you get to the point where you are about to have the action that changed the SV..
What happens in Frank starling and change of Contractility are exactly the same
The baroreceptors responses are the way that changes what?
Heart rate
The Contractility and starling mechanism are ways that changes what
Stroke volume
What is about heart rate?
Stroke volume mechanisms and baroreceptor responses
When talking about changing stroke volume, what do you leave out?
Leave heart rate out of it
What is the normal stroke volume?
75 ml
