Lecture 8 - Cardiovascular System Flashcards
How does Blood Flow go to the lungs?
DEO blood comes in through the Right Atrium, goes to the Right Ventricle, goes to the pulmonary artery, which leaves to go to the lungs.
How does Blood Flow go to the rest of the body?
Oxygenated blood comes through the left atrium, goes to the left ventricle which goes to the Aorta which leaves to go to the rest of the body
What is a septal defect in the ventricles?
A weakness in the walls between the ventricles which causes a mix of deoxygenated and oxygenated blood.
Why is the amount of work performed by the LV much greater?
Because it needs to supply your whole body with blood
Which ventricle has larger wall?
The LV has a larger wall
What is the size of the LV wall?
8 - 10 mm
What is the size of the RV wall?
2 - 3 mm
What are the ventricles and the atrium separated by?
Atrioventricular Valves (AV)
What do AV valves do?
Prevent the back flow of blood into the atria
What is the AV value called that is between the RA and RV?
Tricuspid Valve (3 flaps)
What is the AV valued called that is between the LA and LV?
Bicuspid or Mitral Valve (2 flaps)
Where are one way semilunar valves located?
At the origin of the Pulmonary Artery (pumping deoxygenated blood to the lungs) and the Aorta (pumping oxygenate blood to the body)
What happens when the ventricles are contracted?
The valves will open so blood can be pumped through them
What happens during ventricular relaxation?
Semilunar valves shut so blood can not flow back into the ventricles
How does the Cardiac cycle start?
Both atria fill with blood, then contract simultaneously to allow blood to enter the ventricles
What happens about 0.1-0.2 seconds later?
The simultaneous contraction of both ventricles where one is sending blood into lungs and other is sending blood to our body
What does contraction of the ventricles during systolic do?
It ejects about 2/3 of the blood they contain
What is your Stroke Volume?
Amount of Blood coming from the ventricle in one heart beat
What is the end systolic volume?
About 1/3rd the initial amount in the ventricles
What is your End Diastolic?
Filling with Blood
What is your End Systolic?
Pumping (ejecting) the blood
What is your Cardiac Output?
How much the heart can pump in one minute
What is your Cardiac Output equal to?
CO = Heart Rate x Stroke Volume
At an average heart rate of 75bpm, what does each cycle last?
0.8 seconds
In the 0.8 seconds, how much time is spent in distole and systole?
0.5 s - diastole (filling with blood)
0.3 s - systole (contracting)
What does Electrical Activity facilitate?
The pumping of the heart
How many regions of the heart can spontaneously generate action potentials?
3
What are the 3 regions of the heart?
- Sinoatrial (SA) Node
- AV Node
- Purkinje Fibres
What is the SA node?
It is known as the Pace Maker
Where is the SA node located?
In the right atrium
What nerve innervated the SA node?
The Vagus nerve which has parasympathetic innervation to adjust heart rate
Where do AP originate at?
At the SA node
How do Action Potentials spread to adjacent myocytes in the RA and LA?
Through gap junctions between cells
What happens to the AP; because the atria and ventricles are separated
They are specialized myocardial cells in the AV node to allow the impulse to move from atrium to ventricle
What is the pathway of the electrical activity of the heart?
Impulse starts at SA nodes, travels to AV Node then descends down the intraventricular septum, divide right and left with Purkinje fibres in the ventricle wall
How does AP spread?
From endocardium (inside heart) to epicardium (outside heart) to cause both the ventricles to contract
What is the timing of the SA node?
Fast Conduction Rate (0.8-1m/s)
What is the timing at the AV node?
Conduction Rate Decreases (0.03 - 0.05m/s)
What is the conduction through the Bundle of His?
Increases
What is the conduction peak through the whole electrical activity of the heart?
5m/s
What does your SA node directly contact?
Atrial Muscle Cells
Why does conduction slow in the AV node?
To allow the atria to contract and fill the ventricles
What are the only connections between the AV Bundle and Node?
AV Bundles and the AV Node
What happens in the Purkinje Fibres?
Conduction rate increases causing rapid conduction
What causes the rapid conduction?
More positive resting membrane potential and many gap junctions
What do the Purkinje Fibres synapse onto?
The ventricular myocytes
What does an Electrocardiogram measure?
Not recording a single action potential - but it does result from the production and conduction of action potential
What is a P wave?
Atria depolarizes and contracts
What is a QRS complex?
Ventricles depolarize and contract
What is a T wave?
Ventricles begin to repolarize and relax
According to WHO, how many people die each year due to CVD?
17 million people
How many patients with HF die within 5 years?
50%
What is Coronary Artery Disease?
When you have a plaque buildup in one of the 3 coronary arteries
In the earliest stages, what can coronary artery disease cause?
Angina (chest pain due to restricted blood flow)
What happens when atherosclerosis is suffiecient enough to interrupt blood flow?
Myocardial Infarction or Heart (death of the heart muscle cells)
What region on an ECG indicates an ischemic stroke?
ST is more elevated then normal
What is bradycardia?
Very slow heart rate (less then 60bpm)
What is tachycardia?
Very fast resting heart rate (greater then 100bpm)
What is Ventricular Fibrillation?
Abnormal heart rhythm in which the ventricles of the heart quiver. It is due to disorganized electrical activity.
What does Ventricular Fibrillation result in?
Ventricular fibrillation results in cardiac arrest with loss of consciousness and no pulse. This is followed by sudden cardiac death in the absence of treatment
What can COVID or the SARS virus do?
Gain entry into the cardiomyocytes via ACE2 (receptor), cause inflammation and scarring which can lead to heart conditions
What are myocardial cells?
Heart Muscle Cells
What are your heart muscle cells?
Striated
What is Striated?
Striated means that the heart appears “striped” when under a microscope
What do myocardial cells contain?
Actin filaments and myosin filaments arranged in the form of sarcomeres
How do myocardial cells contract?
Via a sliding mechanism
What are the striations in cardiac muscle?
Striations in the heart are the stripes that appear in cardiac muscle cells when viewed under a microscope. These stripes are caused by the arrangement of contractile proteins called actin and myosin.
How are myocytes connected?
Via gas junctions that lie at the ends of each myocardial cell
What do these gap junctions permit?
Electrical impulses to be conducted cell to cell
What do the gap junctions “stain” as?
Intercalated Disks
What are the two major organelles myocytes are organized into?
1.) Mitochondria for energy
2.) Sarcoplasmic Reticulum for Calcium Handling
Where do Cardiac AP’s originate in?
The SA node (pacemaker)
What does contraction follow?
Ca2+ induced-Ca2+ released
What is the Ca2+ induced Ca2+ released?
Ca2+ enters into the myocyte cytoplasms via voltage gated ion channels which stimulates the opening of Ca2+ release channels in the SR
What does Ca2+ from the voltage gated channels serve?
A messenger for the Ca2+ release channels
What must happen in order for the heart to relax?
Ca2+ must be pumped from the cytoplasm into the SR
What is the First Step of Excitation-Contraction Coupling in the Cardiac Muscle?
Ca2+ diffuses from Extracellular fluid to cytoplasm
What is the Second Step of Excitation-Contraction Coupling in the Cardiac Muscle?
Ca2+ release channels in the SR open
What is the Third Step of Excitation-Contraction Coupling in the Cardiac Muscle?
Ca2+ related from the SR is going to bind to the sarcomere to stimulate a contraction
What is the Fourth Step of Excitation-Contraction in the Cardiac Muscle?
Ca2+ ATPase is going to pump calcium back into SR
What is the Fifth Step of Excitation-Contraction in the Cardiac Muscle?
Myocardial Cell Relaxes
What are the muscle fibres made ups of?
Thin (actin) filament and a thick (myosin) filament
What are the Myosin and Actin cells arranged into?
Long, rod shaped organelles called myofibrils
What does the myofibrils have?
A distinct striated pattern of alternating light and dark bands and z discs
What are Z discs
Proteins that act as anchors for thin filaments
What do z discs consist of?
A protein called actin
What are myofibrils separated into?
Sections by the Z discs
What is the section of fibre in between two z discs called?
The sarcomere
What lies between the thin filaments (actin)?
Myosin (thicker filament)
How does the muscle contract?
When the z-discs move closer to each other due to the myosin and actin sliding past each other
What does the overlapping of thin and thick filaments give?
The striated pattern of the myofibril
What are the light bands called?
I bands
What are the dark bands caused?
A bands
Where do the Z discs lie?
In the middle of the I band
What is in the centre of the A band?
A narrow light band called the H zone
What do the Thick Filaments - TF (myosin) have?
Made up of rod proteins that have an angular head
What does the angular head do?
It swivels which causes contraction of the muscle
What is Tropomyosin attached to?
Actin
What is troponin?
A complex of 3 subunits attached to tropomyosin
What does the myosin head contain?
Actin Binding Site
ATP Binding Site
What happens when ATP gets hydrolyzed to ADP?
Myosin head becomes activated and changes orientation
What happens to troponin?
Attachment of Ca2+ to troponin which causes movement of the troponin-tropomyosin complex, exposing binding sites of actin
What happens when the binding sites of actin are exposed?
Myosin cross bridge can bind to actin and undergo a power stroke
What is a power stroke?
A “power stroke” refers to the conformational change that occurs within a myosin protein during muscle contraction, where it forcefully pulls the actin filament towards the center of the sarcomere, generating the force needed for muscle contraction
How many differences are there between Cardiac and Skeletal Muscle contraction?
3
What is the first difference?
Skeletal muscles require external stimulation by the somatic motor neurons
Cardiac Muscle produced action potentials automatically by the SA node (pacemaker)
What is the second difference?
Skeletal Muscles are long and fibrous and myocardial cells and Cardiac cells are short, branches and interconnected
What is the structure of myocardial cells?
Tubular in structure and joined to other myocardial cells by electrical; synapse (gap junctions)
What is the third difference?
Skeletal muscles have direct excitation-contraction between the transverse tubules and SR and Cardiac Cells have voltage gated Ca2+ channels in the plasma membrane and the Ca2+ channels in the SR DO NOT INTERACT - Ca2+ induced-Ca2+-release
What do humans not produce?
Taurine and need it in our diet
What do cats produce?
Taurine but also need a well balanced diet so cat food contains taurine
What gives cats heart failure?
Insufficient amount of taurine in their diets
What are Dobermans more likely to be diagnosed with?
60% are more likely to be diagnosed with Dilated Cardiomyopathy
What is Dilated Cardiomyopathy?
Muscle fibres stretched and heart chambers have enlarged
