The Conduction System Flashcards
Cardiocytes
Striated, short thick, branched cells with a central nucleus surrounded by a lot of glycogen
Does cardiac muscle undergo mitosis?
Nope
What happens when cardiac muscle gets damaged?
Scarring occurs
What is the scaring of damaged cardiac muscle called
Fibrosis
Intercalated discs do what
Join cardiocytes by three special features
What are the 3 special features that intercalated discs have that join cardiocytes together
Interdigitating folds, mechanical junctions, electrical junctions
Electrical junctions are also called what
Gap junctions
What do gap junctions do
Allow ions to flow between cells easily
What system does cardiac muscle use to make ATP
Aerobic respiration
What is unique about cardiac muscle
It is rich in myoglobin and glycogen and has a HUGE mitochondria
The cardiac muscle can adapt to different types of fuel very easily. What types of fuel can the heart use?
Fatty acids, glucose, ketones, lactic acid, amino acids
The heart is more likely to run out of ___ than ___
Oxygen rather than nutrients
Does the cardiomyocytes make lactic acid
They shouldn’t
Name the major function of the conductive system
Coordinates the heartbeat
How is the heartbeat coordinated
Through internal pacemaker and nerve-like conduction pathways
What is the first step of sending electrical signals
The sinoatrial node (contains the pacemaker)
What does the pacemaker say your heartbeat should be
100 bpm
Where is the pacemaker
In the right atrium near the SVC
What is the first chamber to get the signal
The right atria
What is the second thing to get the signal
The atrioventricular node
Where is the AV node
Near the bottom r. ventricle by the interatrial septum
What does the AV node do? Its main thing?
It is the electrical gateway between the atria and ventricles
What prevents the electric current from getting out of path
Fibrous skeleton
Where does the AV node send the signal to
The Atrioventricular bundle
What is the AV bundle also known as
The bundle of HIS
The AV bundle forks left and right. What do they go through
The interventricular septum towards the apex
The AV bundle sends signals to the apex of the heart. What in the ventricles of the heart spread the signal to cardiocytes
Purkinje fibers
Where does ventricle contraction start
The base of the heart
Sympathetic system is
Fight and flight
Sympathetic nervous system causes what to happen
HR goes up, muscles need more blood, respiratory rate increases, digestive and urinary slow
Where does the sympathetic pathway originate
The lower cervical to upper thoracic segments of the spinal cord
Where does the sympathetic pathway go after the spine
The sympathetic chain ganglia and cervical ganglia
After the sympathetic pathway starts in the spinal cord and then goes to the sympathetic chain ganglia and cervical ganglia where does it go next
Postganglionic fibers through the cardiac plexus in the mediastinum and goes to heart
The parasympathetic nerves do what
Rest and digest. Slows the heart rate
Where does the parasympathetic pathway begin
The nuclei of the vagus nerves in the medulla oblongata (brain)
Second step of the parasympathetic pathway
Cardiac plexus and then cardiac nerves
For the parasympathetic system, the fibers of the right vagus nerve go where
The SA node
For the parasympathetic nervous sytem the fibers of the left vagus nerve go where
The AV node
The parasympathetic system really does not stimulate what
The myocardium
Sinus rhythm is triggered by the SA node. What is it with adjustments from the parasympathetic system
70 to 80 bpm
What is ectopic focus
A region of spontaneous firing that the SA node did not approve of
Is SA node is damged, ectopic focus may
lead the heart rythem
Is the SA node is damaged, the AV sets the pace. What does the AV node say the heart rate should be
40-50 bpm
Nodal rhythm is set by the av node. What rate is it
40-50 bpm
Ectopic focal rhythms are what temp
20-40 bpm
The SA is different from other cells membranes because why
It does not have a stable resting membrane potential
What is a resting membrane potential
The different in electrical charge from inside and outside the membrane AT REST
The SA node resting membrane potential is
Always changing
The pacemaker cells have an unstable resting potential around what number
-60 mV
The membrane of the SA node slowly depolarizes(gets more positive) until it reaches a threashold for firing what
an action potential
Why is having an unstable resting membrane potentially really good for the heart
It allows it to make its own rhythm without external stimulation
Funny channels allow what to happen in the heart
Slow Na+ influx during diastole (gradually depolarizing it)
Calcium channels are ___ during depolarization
Open
Calcium channels contribute to
Contraction
What is the gradual depolarization called
Pacemaker potential
What is the threshold for the Ca and Na channels to open
-40mV
What happens when the threshold of -40mV is reached opening the Ca and Na channels
Faster depolarization (peaks at o mV)
How does the membrane repolarize
K+ channels open and K+ leaves the cell
When does pacemaker potential start over
When K+ channels close
The sodium potassium pumps works __ the concentration gradient
against
The sodium potassium pump requires
ATP
The sodium potassium pump pumps 3 Na+ out of the cell and 2K+ into the cell. This measn that more positive charges are leave then entering. This creates what
An electrochemical gradient
During polarization Na+ is highest __ the cell
Outside
During polarization K+ is highest ___ the cell
Inside
Ventricular Fibrillation
Heart arrhythmia caused by messed up electrical signals
Valvular insufficiency
Failure of a valve to prevent reflux backwords
A type of valvular insufficiency is called Valvular stenosis. What is that
When the cusps are stiffened and the opening is constricted by scar tissue
What could the scar tissue of valvular stenosis be from
Rheumatic fever, calcium deposits, autoimmuen etc
What does valvular stenosis end up doing to the heart
It has to overwork itself and becomes enlarged
Mitral valve prolapse is when
one or both mitral valve cusps bulge into atria. Not fully closed
What the heck is auscultation
Listening to the sounds of the body
What is the first heart sound caused by
When the AV valves close
What is the second heart sound caused by
The semilunar closing
There is a 3rd sound of the heart. Who is it usually heard in
Children
The cardiac cycle. What is the order of events
Ventricular filling(d), isovolumetric contraction(s), ventricular ejection(s), isovolumetric relaxation(d)
Whats going on during ventricular filling
The ventricle expand and the pressure drops below the atria. AV valve opens and blood flows in.
What are the 3 phases of ventricular filling
-Rapid filling -Diastasis: slower filling(p-wave) –Atrial systole: atria contract (EDV)
What is EDV
End diastolic volume
How do you find EDV (end diastolic volume)
Blood that was passively added during atrial diastole + end-systolic volume + blood added by atrial systole
What is a standard EDV
130 mL
Why would end diastolic volume be the biggest number
Because it is the volume before contraction
What is end systolic volume
The volume after the heart contracts
So you add End systolic volume to passive filling and atrial systole to get
EDV
What is stroke volume
The amount actually ejected by ventricular systole
The right and the left ventricles must eject the same amount of blood. What is it called when they do NOT do that
Congestive heart failure
Why would a side of the heart become weak, resulting in congestive heart failure
If the heart is working too hard (high blood pressure, atheroma etc) then the muscle will be constantly exerting itself with NO rest. This weakens it.
Left ventricular failure leads to what medical condition
Pulmonary edema
Right ventricular failure leads to what medical condition
Systemic edema
When talking about ventricular failure, the fluid buildup occurs in the place where the blood is ______
Coming from
Cardiac output is what
Amount jected by each ventricle in 1 MINUTE
How is cardiac output different from stroke volume
Stroke volume occurs in 1 heartbeat, cardiac output occurs in 1 minute
What is the equation for cardiac output
Heart rate X stoke volume
What is the average amount of blood in the body
4 to 6 L/min
How long does it take a RBC to cycle the body
1 minute
Cardiac output ____ in a trained athlete
Increases
What does it mean to have an increased cardiac output
Your body can move more blood person heartbeat
What is cardiac reserve
The difference between your maximum and resting CO
Why is cardiac reserve so important
You want it to be able to go up higher than your resting because that means your arteries and stuff are clear and working good
What is positive chronotropic agent
Just something that rasies the heart rate
What is a negative chronotropic agent
Something that lowers the heart rate
Without input from cardiac centers, the heart has am intrinsic firing rate of
100 bpm
What is the thing called that lowers the heart rate from 100 bpm
Vagal tone
Vagal tone comes from __ nerves
vagus nerves
Who is the Wizard of Oz for the heart
the medulla oblongata
What are some other centers that influence that heart in the brain
cerebral cortex, limbic system, hypothalamus
The medulla oblongata receives in out from proprioceptors. What does that mean
Proprioceptors are in muscles and joints and when they start working they tell the Medulla in hurry it up
Baroreceptors signal to what
the cardiac center
What are baroreceptors
Pressure sensors in aorta and internal carotid arteries that tell the Medulla what to do with the BP and HR
Is BP increases, cardiac center ___ heart rate
decreases
If BP decreases, cardiac center ____ heart rate
increases
Internal and external carotid arteries talk to who
The brain(medulla oblongata)
Baroreceptors are in the __
Carotid arteries
Chemoreceptors talk to who
The cardiac center
Where are chemoreceptors
Aortic arch, carotid arteries and medulla oblongata
What makes the chemoreceptors upset
pH, Co2, O2 levels
What will the chemoreceptors do when CO2 levels are high
Increase heart rate
What is high CO2 levels called
Hypercapnia
What is hypoxemia
Low oxygen
