Cardiovascular 2:Heart Anatomy and Histology
Summary
TLDRDr. Deviant's lecture delves into the cardiovascular system, emphasizing the heart's unique blood supply and the perils of blockages leading to angina pectoris and myocardial infarction. He explains the heart's structure, highlighting the non-dividing nature of cardiac muscles and the formation of scar tissue post-damage. The lecture distinguishes between cardiac and skeletal muscles, focusing on the heart's synchronized contraction and the role of the cardiac conduction system in rhythm regulation. It also touches on the importance of heart valves, the phenomenon of heart murmurs, and the use of pacemakers and defibrillators in treating heart conditions.
Takeaways
- π The heart needs its own blood supply through a capillary network, and any blockage can cause significant issues.
- π Angina pectoris is a thoracic pain caused by temporary deficiency in blood flow, often related to stress or physical demand.
- π¨ Myocardial infarction (heart attack) results from blocked blood flow leading to death of myocardial tissues, with scar tissue replacing the damaged heart muscle cells.
- π Damage to the left ventricle, which pumps blood to the rest of the body, is particularly dangerous.
- π Cardiac muscles resemble skeletal muscles but are shorter and have intercalated discs that help cells connect and function as a unit.
- π Unlike skeletal muscles, cardiac muscles do not require neuron stimulation for contraction, thanks to gap junctions that allow heart cells to contract together as a functional syncytium.
- π« Cardiac muscles do not exhibit sustained tetanic contractions like skeletal muscles, preventing prolonged contraction.
- π‘ The heart's contraction relies on oxygen, and low oxygen levels can lead to cell death, with high calcium and acidity causing gap junctions to close.
- π The heart contracts and relaxes in a coordinated manner (systole and diastole), with the atria and ventricles working together to move blood through the body.
- β‘ The cardiac conduction system controls heart rhythm through pacemakers like the SA node and AV node, with specialized fibers distributing the electrical signal across the heart.
Q & A
What is the importance of the blood supply to the heart?
-The blood supply to the heart is crucial as it provides the necessary nutrients and oxygen to the heart muscle. Any blockage in this supply can lead to serious issues such as angina pectoris or myocardial infarction (heart attack).
What is angina pectoris and what causes it?
-Angina pectoris is a type of chest pain caused by a temporary deficiency in blood flow to the heart. It is often related to stress, increased physical demand, or temporary weakening of the heart muscle.
How does a blockage in the blood supply to the heart lead to a myocardial infarction?
-A blockage in the blood supply, often due to a cholesterol plaque, prevents blood flow to the heart muscle, leading to the death of myocardial tissues, which is known as a myocardial infarction or heart attack.
Why is damage to the left ventricle considered more serious than other parts of the heart?
-Damage to the left ventricle is more serious because it is the thickest and most important chamber of the heart. It is responsible for pumping blood to the aorta and the rest of the body, so damage can significantly impair the heart's ability to circulate blood.
What is the difference between cardiac and skeletal muscles in terms of contraction?
-Cardiac muscles contract autonomously without direct stimulation from neurons, whereas skeletal muscles require innervation from neurons to contract. Additionally, cardiac muscles contract as a unit due to gap junctions connecting each cell, unlike skeletal muscles which contract independently.
What are the three main differences between cardiac and skeletal muscles as mentioned in the script?
-The three main differences are: 1) Cardiac muscles do not require stimulation by neurons to contract, unlike skeletal muscles. 2) Cardiac muscles exhibit functional syncytium, meaning the heart contracts as a whole unit, whereas skeletal muscles contract independently. 3) There is no sustained tetanic contraction in cardiac muscles, which is possible in skeletal muscles.
What is the role of the intercalated discs in cardiac muscle cells?
-Intercalated discs in cardiac muscle cells are specialized structures that facilitate the connection between cells, allowing for the coordinated contraction of the heart muscle as a single unit.
Why are gap junctions important in the heart's function?
-Gap junctions are crucial as they allow the electrical impulse to spread from one cardiac cell to another, enabling the heart to contract in a synchronized manner.
What is the significance of the cardiac conduction system in the heart's function?
-The cardiac conduction system is responsible for generating and coordinating the electrical impulses that regulate the heartbeat. It includes the SA node, AV node, bundle of His, and Purkinje fibers, ensuring the heart contracts in a coordinated and efficient manner.
What happens if both the SA node and AV node fail in the heart?
-If both the SA node and AV node fail, an implantable cardioverter-defibrillator may be used. This device monitors heart rhythms and delivers shocks to the heart to restore normal rhythm when necessary.
What is the difference between a heart murmur and a more serious heart condition?
-A heart murmur is a sound caused by turbulent blood flow, often due to leaky valves, and is common in infants. However, in adults, a heart murmur can indicate valve damage or other serious heart conditions.
Outlines
π Understanding the Heart's Blood Supply and Blockages
In this section, Dr. Deviant discusses the importance of the heart's own blood supply, despite its role in pumping blood. The key issues that arise when there is a blockage in the heart's circulation include angina pectoris, a temporary thoracic pain, and myocardial infarction (heart attack), which is more serious as it leads to the death of myocardial tissues. The inability of cardiac muscle cells to divide results in scar tissue replacing dead cells, which cannot contract. Damage to the left ventricle is particularly dangerous as it impairs the heart's ability to pump blood to the rest of the body. The structure and function of cardiac muscles are compared to skeletal muscles, highlighting features such as intercalated discs and gap junctions that enable coordinated contraction.
π The Unique Contraction Mechanism of the Heart
This part emphasizes the unique functional syncytium of the heart, where all the cells contract as a unit due to the presence of gap junctions. Unlike skeletal muscles, which can sustain long tetanic contractions, the heart cannot, ensuring that the heart contracts and relaxes rhythmically without fatigue. The section also explains the critical role of oxygen in cardiac muscle function, the impact of high calcium levels and increased acidity, and how gap junctions close under stress, preventing the spread of action potentials.
π« Systole, Diastole, and Heart Valve Function
Dr. Deviant explains the pumping mechanism of the heart, detailing the phases of systole (contraction) and diastole (relaxation). He describes how atrial systole and ventricular diastole coordinate to fill the ventricles with blood, and how ventricular systole pushes blood out through the semilunar valves. The proper functioning of heart valves is crucial, and any issues, such as heart murmurs caused by leaky valves, can indicate serious problems. The importance of the correct timing of valve opening and closing during the heart's cycle is also highlighted.
β‘ Cardiac Conduction System and Pacemakers
This segment covers the heart's ability to generate action potentials and contract without neuronal stimulation, emphasizing the intrinsic nature of cardiac muscle contraction. The cardiac conduction system, including the SA node (the primary pacemaker), AV node, bundle of His, and Purkinje fibers, is detailed. The SA node initiates the heartbeat, and if it fails, the AV node takes over. Implantable defibrillators and pacemakers are mentioned as interventions for serious arrhythmias, such as ventricular fibrillation, with defibrillators resetting the heart's electrical activity.
Mindmap
Keywords
π‘Cardiovascular System
π‘Angina Pectoris
π‘Myocardial Infarction
π‘Cardiac Muscle
π‘Mitotic
π‘Left Ventricle
π‘Intercalated Discs
π‘Functional Synchrony
π‘Cardiac Conduction System
π‘Ventricular Fibrillation
π‘Heart Murmur
Highlights
The heart requires its own blood supply through a capillary network.
Blockages in the heart's blood supply can lead to angina pectoris, a thoracic pain due to temporary blood flow deficiency.
Myocardial infarction, or heart attack, is dangerous as it can lead to the death of myocardial tissues due to blocked blood flow.
Cardiac muscles are non-mitotic, meaning they cannot divide, and scar tissue replaces dead cells, which cannot contract.
Damage to the left ventricle is particularly serious as it is the thickest and most important chamber for pumping blood to the body.
Cardiac muscles are striated and resemble skeletal muscles but are shorter and interconnected through intercalated discs.
Cardiac muscle cells are connected by gap junctions, allowing the heart to contract as a unit, a concept known as functional syncytium.
Skeletal muscles contract due to nerve stimulation, unlike cardiac muscles which contract intrinsically.
Cardiac muscles do not exhibit sustained tetanic contractions, unlike skeletal muscles.
Cardiac muscles are dependent on oxygen, and low oxygen levels can lead to cell death.
High calcium levels and increased acidity can cause the gap junctions to close, blocking the action potential from traveling between cells.
The heart's pumping involves systole (contraction) and diastole (relaxation), with atria and ventricles working in coordinated phases.
Valves such as tricuspid, bicuspid, and semilunar play crucial roles in ensuring one-way blood flow during the heart's pumping cycle.
Heart murmurs are common in infants but can indicate valve damage in adults.
The cardiac conduction system, including the SA node, AV node, and Purkinje fibers, is responsible for generating and distributing electrical impulses for contraction.
Implantable cardioverter-defibrillators are used to monitor heart rhythms and can shock the heart to regain normal rhythm in case of fibrillation.
Defibrillators are used to depolarize the entire myocardium in cases of ventricular fibrillation, resetting the heart's electrical activity.
Transcripts
hello this is dr deviant and we are
continuing
with cardiovascular system
all right so we talked about the blood
supply to the heart and we noticed
that the blood supply to the heart which
itself
may be a little confusing because you're
thinking it's pumping blood
so it doesn't need to have its own
circulation but it
absolutely absolutely has to have
this kind of capillary network and
if there is any blockage then that will
create
lots of issues okay so here
what are the issues if there's a
blockage so first is
angina pectoris so this is a thoracic
pain
caused by temporary deficiency in the
blood flow
often it is stress related often it is
increased physical demand
or temporary weakening this is not that
serious okay
now myocardial infarction which is a
heart attack
is dangerous why because here what
happens is
that it leads to the death of myocardial
tissues you are noticing that
there is a cholesterol plaque which is
not allowing the flow of blood
all right which leads to heart attack
now what is the issue the main issue the
cardiac muscles are
a mitotic that means they cannot divide
and what happens is that the scar tissue
the fibrous scar tissues
replaces the dead myocardial cells but
these scar tissues will not have the
ability
to contract so what happens is that
there is
there is an issue now it says damage to
the left ventricle which is more serious
why
because notice what we are saying is
that the
the left ventricle which is the thickest
of all and the most
important chamber because remember it
pumps the blood
to the aorta to the rest of the body all
right so
here what happens is if there is this if
this is damaged
will you supply will you be able to
supply the blood to the rest of the body
the answer is what no yes so here it is
going to be most dangerous
now the cardiac muscles should remind
you
exactly of the skeletal muscles except
that the cardiac muscles are going to be
shorter so they are striated striated
means
they have actin and myosin once again
good time to look
up go back and look at your 201 uh
skeletal muscle fiber nose okay so here
they look very much like the skeletal
muscle fibers
except that they are what that they are
intercalated so here
they look like the ends have
intercalated discs
that means they look like corrugated
cardboard look out here interpolated
disc
right here this is much more obvious and
these cells
are connected to each other by desperate
zones which look like cell snaps
i'm sure you have this i know uh seen
the snap
button on your um shirts oh and how do
they connect with each other
through gap junctions these are pores
through which a cytoplasm is continuous
from one cell into the other
and uh here they have
the cardiac muscles uh muscle cells
they will pull and push against the
skeletal like muscle there's no skeleton
but skeletal like
muscles all right so here
not going into too much of detail but
there are myofibrils
just like the sarcomere they have the t
tbus just like the these skeletal
muscles
and sarcoplasmic reticulum very much
like the
skeletal muscle okay so uh without going
into too much of detail
i definitely want to see what are the
differences
so here what happens the skeletal
muscles contract
because they're stimulated by nerve
ending do you remember
that or if i can show you here so here
is the here is my neuron and my neuron
has endings
and then the neuron ending will fire an
action potential
and this muscle will contract yes now
here
this is a neuron so this is how a
skeletal muscle
um acts now here there is none in a
cardiac muscle
there is no innervation from a neuron
so uh so cardiac muscles they do not
require stimulation by not
important number one in skeletal muscle
there is no spread
of cell impulse from one cell to another
like
so a contraction of your uh biceps
is independent of cons a contraction say
for example
of your pectoralis major they're not
connected are they
absolutely not right so here but what
i'm saying
is that in a heart because of the gap
junctions
each cell is connected to each other so
the heart contracts as a unit this is
important you have to know this
what is it called functional singtion so
what i'm saying is when this contracts
this also contracts this also contracts
this also contracts
the heart will contract as a whole so
this
is difference number two got to know it
number three what's the difference there
is no sustained
technique contraction in the cardiac
muscle so the skeletal muscle
what happens if this is one contraction
let me draw this
and there's another contraction what
happens is
that this contraction and this
contraction can merge and you can have a
sustained
long technique contraction now that does
not happen
in a heart all right so these three
differences just keep in mind i'm not
going to go into
great detail out here all right so
here um the uh uh
t let's go let's go to tissue damage so
tissue damage
is that the cardiac muscles are
dependent on oxygen
and if there is low oxygen
then what happens is that we talked
about there is death right
now there are some defense mechanisms
and what is that
is when there's too much of high calcium
level we'll see why
why high calcium level will cause
a high a surge in the
rate and a rate and
force of contraction so you don't want a
huge
high surge in calcium level but if
there's excessive high calcium level
and increase acidity why increase
acidity because
oxygen is low and so because of lactic
acid production
the gap junctions are going to close so
those gap junctions which connect
one cell to another cell these are going
to to close
and therefore what happens is the the
action potential will be
blocked it will not travel all right so
um
now let's look at pumping of the heart
so pumping of the heart
involves what systole and dye stone
systole is when they contract diastole
is when they relax now both what we are
noticing is that both the atrium
are going to contract at the same time
which is called the
atrial systole and when the atrium
contract
the ventricles are going to relax
together
and that's called ventricle diastole so
when
these two contract these two relax
when these two contract these two relax
all right now let's see when the atrium
are contracting that means they are
going through systole
then what happens is that these valves
what are these valves the tricuspid and
the bicuspid will open
because they are squeezing the blood
from the atrium
into the ventricle you understand that
the ventricles are relaxed
but the blood the semilunar valve which
is going to push the blood from the
ventricles
out this into the lungs and this into
the rest of the body the aorta
will close i repeat when the
atrium contract the tricuspid and the
bicuspid valve open
so that the blood will fill into the
ventricles and the ventricles are nice
and relaxed
they're filling when the winter so
but at the same time these two valves
the semilunar valves are going to be
closed why because we are going to wait
to push the blood out
okay so they're going to be filled in
here
then when the ventricles go into
contraction that means when they're
going to systole
trims relax what's relaxation called
diastole
and when they're going to die a stone
these
two valves what are these two valves the
tricuspid and the bicuspid they will
what
they will close you don't you know and
the
atrium are relaxed ventricles are
contracting squeezing the blood
out so obviously the semilunar valves
will remain open
allowing the blood to be pushed out
through these semilunar valves into the
lungs
in this case and to the aorta in this
case
do we understand this all right
so here the heart sound is loved up
there's a very common heart sound called
the heart murmur
and this is because of the leaky valves
it uh
leaky valves are very common in small
infants
murmur heart murmur is very common but
adults having murmur is not
good and correct and it indicates valve
damage all right now there is the
cardiac conduction system what did we
say
in the last presentation we said that
the
heart muscles are able to
generate an action potential
as well as contract so here unlike
a skeletal muscle there is no neuron
and nerve endings innervating a muscle
all right so here the cardiac muscle
contraction is
intrinsic now there is of course
some control of heart rhythm but it is
generated the contraction
is uh the action potential is generated
within
all right so there are some
non-contractile cardiac muscles which
are specialized
for initiating and distributing all
right
so let's see them so before
uh let's see right here i think
this is good yes so there is the sa node
and from the sa node which is the
default pacemaker of the heart
from the from the sa node there's a
atrial syncium
that goes into the junctional fibers and
the junctional fibers
end up in the av node the av
node is the second fallback
a pacemaker so if sa node fails av node
kicks in
the av node leads into the av bundle
which is also called the bundle of haze
and separates out in the right and the
left branch
goes to the apex of the heart and
becomes
and turns around and goes into the
purkinje fibers you can see the spine
branches
per perkins fibers and these parking g
fibers go into the ventricular syncia
this is the cardiac conduction
system all right so
here is the labeling for you the sa node
here are the the junctional fibers the
av
node here is the the bundle of his
bundle of his going into the right and
left branch
going to the apex of the heart and
finally going into smaller branches
called the parking g fibers
and then going into the ventricular
allowing the ventricular sinks
okay all right
if by chance
both the essay and the av node
the pacemakers of the heart fail
then uh uh you know then uh implantable
cardio what uh uh water defibrillator
this is the one that is a pacemaker is
placed right
and what happens is that it is going to
monitor the heart rhythms
and detect fibrillation so anytime what
happens is it will shock the heart and
cause mycard
myocardium to depolarize we'll see all
that what it means
it will reset all the cell membranes so
it can sa node can regain control
all right now here what happens if there
is
a if there is a ventricular fibrillation
which is very
dangerous and we will see that in the
ekg
then you have to use a defibrillator
and what a defibrillator is i'm sure
you've seen a defibrillator
and you've seen that in all these uh
movies
and tv shows where basically they will
shock your heart
so here it depolarizes the entire
myocardium what is depolarizing
and repolarizing and polarizing again
look at your 201 notes for that okay
it will reset the heart so we'll stop
here we'll continue with our next
presentation
i thank you for listening to me for
questions or concerns
please contact me have a good day
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