Cardiovascular biology Flashcards
what does cardiovascular system consist of?
Heart and blood vessels
Where is the heart located?
Behind sternum ( almost in middle )
1/3 of heart lies to the right of the midline
Part of heart is covered by lungs - sits between lungs
How many pumps does the heart have
2 which distribute blood around
RHS - pumps blood to lung
LHS - pumps blood to body
How many layers are the walls of the heart divided into
3
What are the 3 layers that make up walls of the heart?
- Endocardium - inner
- Myocardium
- Pericardium - outer
What is the function of pericardial fluid?
lubrication to reduce friction between the heart and the surrounding structures , and minimises the friction generated by heart as it contracts
What is the space between pericardium and epicardium
Filled with fluid - pericardial fluid
what is myocardium?
middle layer of heart which serves to pump oxygenated blood around body of wall of heart
Bulk of heart - 95%
what is pericardium?
Dense, fibrous sac which anchors heart in place but still allows movement
Tough connective tissue coat for protection - outer coat
pericardium produces pericardial fluid
what does inflammation of pericardium result in and what is it an example of
Pericarditis Acquired defect ( developed after birth )
What happens in pericarditis
Heart has to beat against high resistance ( inflammation ) = stops pericardium producing pericardial fluid
What is pericarditis brought about by
Viruses, drugs or bacteria
What is endocardium
- Smooth simple endothelium lining which ensures friction less flow of blood
- Going into and coming out of the heart
- Inner lining of heart
- Protect valves and heart chambers
what are the four chambers of heart?
. right atrium
. right ventricle
. left atrium
. left ventricle
What is function of right atrium?
Receives deoxygenated blood from body and pumps to right ventricle
What is function of left atrium?
Receives oxygenated blood from lungs and pumps it to left ventricle
What is function of right ventricle ?
Pumps deoxygenated blood back to lungs
What is function of left ventricle ?
Pumps oxygenated blood to body
What does right side of heart do
Pumps blood to lungs - less force, myocardium smaller
What does left side of heart do
Pumps blood to whole body - more force, thicker
What are the 2 main vessels
Superior vena cava
Inferior vena cava
What does Superior Vena Cava do
Bringing in deoxygenated blood from head and neck
What does Inferior Vena Cava do
Bringing in deoxygenated blood from lower half of body
What does pulmonary circulation do
Circulation from heart to lungs and back
What does systemic circulation do
Circulation from heart to rest of body’s tissues and back
Which is smaller -right or left atrium
Left atrium
How many chambers does heart have
4
Describe what happens in the circulatory system?
- right atrium receives deoxygenated blood from body and pumps to right ventricle
- right ventricle contracts and pushes blood out of pulmonary arteries and deoxygenated blood goes to the lungs
- lung pick oxygenated blood and it comes back to left side of heart into left atrium
- left atrium receives oxygenated blood from lungs and pumps it to left ventricle
- left ventricle contracts and pumps oxygenated blood to the body via aorta
what are the 3 openings of the heart?
Superior vena cava
Inferior vena cava
Fossa ovalis
What is the function of fossa ovalis / coronary sinus?
Brings in deoxygenated blood from heart to right atrium
How does blood leave the heart via the aorta to the rest of body?
- deoxygenated blood arrives at the right atrium
- deoxygenated blood from heart comes to right atrium via fossa ovalis
- when right atrium is full of deoxygenated blood , tricuspid valve opens and lets blood into right ventricle
- right ventricle contracts and closes this valve
- another valve opens ( semi lunar valve)
- SL valve pushes blood out of pulmonary artery which takes blood to lung - picks up O2 - goes back to right atrium
- blood goes to lung and picks up oxygen
- oxygen comes back to right atrium
- left atrium contracts when full and opens bicuspid valve
- blood goes lo left ventricle
- left venticle contracts and open aorta
- oxygenated blood rushes out the aorta
Why is the left side of heart stronger than the right?
The left ventricle is much more developed than the one on the right.
This corresponds to the greater force needed to push blood through the systemic circulation
What is the function of the right and left coronary arteries?
They supply the heart muscle with oxygenated blood - enters aorta
Takes 5% of the hearts daily output - 380L a day
where do the right and left coronary artery branch from? and into what
The aorta
Branch into smaller blood vessels - into dense capillary network
what is the function of aorta?
The main artery that carries oxygenated blood from left ventricle to the heart
what are the two main types of valve in the heart?
. atrioventricular (AV) - mitral and bicuspid
. semi lunar - pulmonary and aortic
how many valves does the heart have?
4
What is the function of the 4 valves of the heart?
They are purely passive = not open and shut by muscles, respond to blood flow
and ensure blood flows around the heart in the correct direction
where is mitral AV located ?
Right of heart
where is bicuspid AV located ?
Left of heart between between atria and ventricle
What happens if right side of heart produces same force as left side
All blood is at high pressure to lungs, not good as lungs delicate
What % will die because of blockage in coronary circulation
70
Where is tricuspid valve found
Right side, AV valve
What happens if AV valves weren’t attached in any way
When ventricle contracts, they will blow valves straight back into atria
How many times do AV valves open and close
2/3 billion
When oxygenated blood comes out of aorta where does it go
Aorta
what does semilunar valve consist of and what does it do
3.5 moon shaped cusps ( of connective tissue )
Guard exits of heart - forms seal
Describe the action of semilunar valve?
- when ventricle is full of blood , ventricle contracts = SL valves open
- pressure rises , blood is pushed up against semilunar valve forcing them open
- ventricles relax , blood flows back down due to gravity, pressure falls , blood flows back from arteries, filling cups of semilunar valve forcing them to close
- semilunar valve stops blood falling back to ventricle
What are valves flattened against
Walls of aorta
What happens to semilunar valves when ventricles contract and relax?
ventricles contract - valve open
ventricles relax- valve close
What are AV valve ?
Flaps of connective tissue which open and shut
Describe the action of AV valve?
- atrium contracts
- AV valve open and blood comes into ventricle
- ventricle contracts - valve shut - blood doesnt flow back into atria
What happens when AV valve opens
- Blood returning to heart fills atria = pressure against AV valves - AV valves open
- As ventricles fill, AV valves flap hang simply intro ventricles
- Atria contracts, forcing additional blood into ventricles
What happens when AV valve closes
- Ventricles contract forcing blood against AV valves cusps
- AV valves close
- Papillary muscle contracts and chordae tendineae tighten preventing valve from entering into atria
What are the muscles attached to AV valves
Tendons
What is chordae tendineae
Attached to pupillary muscles, part of myocardium
Function of chordae tendineae
- hold AV valve in place
. Puts tension on AV valves during ventricular contraction to stop eversion via tendons
what is the main difference between AV valve and semilunar valve?
. AV valve have muscle in them
chordae tendinae which are attached to papillary muscle
What is meant by luvduv sounds
Lub = AV valves close Dub = SL valves close
what are examples of valve defects?
. Stenosis
. Regurgitation
What happens if lubdub sounds not right
Problems with valves
What is Stenosis
Narrowing of valves - don’t open wide enough
What is Regurgitation
Valve doesn’t shut properly
What can you do solve valve defects?
Defective valve can be replaced by using a mechanical valve cause they’re passive.
- Valve replacement surgery - replace with hinged bit of plastic
What are the similarities between skeletal muscle and cardiac muscle?
Both are striated
Both generate a lot of force
What are the differences between skeletal muscle and cardiac muscle?
- Skeletal muscle fibres have several peripheral nuclei , cardiac fibres have only one single central nucleus
- Skeletal muscle fibres don’t branch . cardiac fibres branch
- Cardiac muscles are joined by gap junctions ( intercalated disc ) forming syncitium
Why are cardiac muscles joined by gap junctions and branched
For rapid conduction of action potential - spread rapidly throughout heart
what is syncitium ?
Sheet of muscle where individual cells are connected by gap junctions
Each muscle sheet is syncitium
How many syncitia does cardiac muscle form ?
Two……
One around the atria and another around the ventricles
These are only joined by the bundle of his
How many sheets of muscle over heart
2
What does cardiac muscle contain ?
Myoglobin, many mitochondria
How is cardiac muscle described
Amitotic
What are the two phases of cardiac cycle?
. Diastole ( relaxation )
. Systole ( contraction )
What happens in the two phases of cardiac cycle?
- Blood flows into atria until full - AV valves shut - 72 times a minute ( AV valve shut )
- AV valve opens when atria full and 70% of blood leaves atria passively intro ventricles by gravity
- Remaining blood is squeezed out by atria contracting ( 30% )
- Ventricles contract closing AV valves = so blood not back into atria
- Semilunar valves open and blood leaves ventricles
- ventricles relax , and flow of blood shuts semilunar valve
How many times does heart have to contract in a lifetime
3 billion times
What system controls the heart?
The heart is under the control of ANS
Sympathetic system speed it up - a.p to heart = contracts
Parasympathetic system slows it down
How is the basic rhythm of the heart initiated?
The heart is myogenic meaning it generates its own action potential so the basic rhythm of the heart is initiated within the heart itself independent of ANS
What is meant by myogenic
Generate its own action potential - so brain doesnt have to tell heart to contract - so heart still beats when taken out of body
How is the myogenic rhythm of the heart maintained?
By the Specialised excitatory and conductive muscle system - in heart
What are all parts of this specialised excitatory and conductive muscle system
Modified cardiac muscle and lie amongst the myocardium
what are the parts that make up the specialised excitatory and conductive muscle system?
. SA node (pace maker) - this is where action potential is generated
. SA node is connected to atrioventricular node
. atrioventricular node is connected to bundle of his which bridges the gap between muscle sheet of atria and ventricle
. Bundle of his splits into 2 purkinje fibres ( down middle of ventricles and up outside ) which go down central septum between two ventricles
What is the function of the specialised excitatory and conductive muscle system?
Ensure initiation of each cardiac contraction
and proper coordination of each cardiac cycle
What is structure of Specialised and conductive muscle system
- Below opening in rear wall of heart is superior vena cava
- Below opening of superior vena cava is PACEMAKER - SINOATRIAL NODE
- SA node attached to ATRIOVENTRICULAR NODE - connected to BUNDLE OF HIS
How long and side is Sinoatrial node
3mm wide and 1cm long
What is function of Bundle of His
Bundle of his connects/bridges gap of atrial muscle sheet to ventricular muscle sheet
Where is action potential generated
Pacemaker - SA node
What does the action potential lead to
Cardiac contraction
How does the inside of the SA node become more positive and reach threshold to fire action potential?
The SA node is leaky to sodium , it thus depolarises slowly ( by about 15mv ) , reaches threshold, inside more + and initiates action potential without external nervous output
how does heart beat independent of ANS ?
SA node is leaky to Na ions ( opens Na ions channels )
Describe what happens once action potential has been initiated at SA node?
- action potential is generated at SA node by being leaky to sodium ions
- action potential spreads throughout atria ( due to branching and intercalated discs) causing them to depolarise and gets to AV node and bundle of his
- action potential is delayed at the AV node and bundle of his - makes sure atria contracts before ventricles
- ventricles contract when action potential spreads along purkinje fibres
Why is action potential slowed down at bundle of his?
Action potential is delayed by 0.1 sec at bundle of his to ensure atria contracts before ventricles .
this happens because bundle of his have small diameter so action potential takes a longer . time to get through them
How does inside of SA node become positive
- Leaky to Na+
- Na+ into SA node as it wants to go into neuron
- Depolarises = reaches threshold
- Action potential which spreads rapidly throughout 2 atria as cardiac muscle branches and connected via junctions
Why is heart beat independent of nervous system
SA node is leakly to Na+ ions
What is function of SA node
Depolarises = sends a.p throughout 2 atria
Where is the only place atria muscle sheet and ventricular muscle sheet connected
AV node and Bundle of His
How does cardiac cycle function
Atria has to contract before ventricles
Why do the cells of Bundle of His have a smaller diameter
Makes sure a.p is delayed so atria contracts before ventricles
Examples of Pathology in the excitatory/conductive system
- Cardiac arrhythmias
- Ectopic pacemakers
- Heart block
- Ventricular fibrulation
What do defects in this system result in and what are the two examples
Cardiac arrhythmias ( heart beats too slowly or quickly )
. bradycardia < 60 bpm ( heart is too slow )
. tachycardia > 100 bpm ( heart is too fast )
What is meant by ectopic pacemaker
When another part of system takes over from the SA node as pace maker
‘ ectopic = out of place ‘
What happens during a heart block
There is a complete break in the system ( bundle of his - thin fibres - delicate ) = atria and ventricles beat independently/separately
What is ventricular fibrillation?
Series of very high frequency uncoordinated contractions > 300 bpm where the heart has been likened to a ‘ writing bag of worms ‘ - whole system breaks down
How many american people does ventricular fibrillation kill every year
300,000
What is example of ectopic pacemaker
Ectopic pregnancy - embryo develops in Falopian tube
What happens if heart attack near SA node
It becomes non -functional or other parts of system e.g. Purkynje fibres become hyperleaky to Na+ = another part of system takes over
How can arrhythmias be fixed ?
Artificial pacemakers - battery operated devices that are implanted into thoracic cavity - have leads that go into heart and generate required depolarisation ( 72 times every minute )
How is the heart controlled by the ANS ?
The heart can be slowed by turning sympathetic supply off and by turning parasympathetic system on - control heart by altering Na+/K+ permeability
How does PNS control the heart
Via vagus nerve - Ach causes increase in potassium permeability causing the heart to slow down
How does SNS control the nervous system?
Nor-adrenalin increases sodium permeability so heart speeds up
How does vagus nerve slow down heart
Releases Ach onto SAN = makes it more leaky to K+ = leaks out of SAN = more negative = further away from threshold
what is ECG
Recording representation of electrical conductivity of heart recorded at body surface
what does the gap between P and Q wave mean in ECG ?
Time difference between atria and ventricle contracting - how long it takes a.p to get through Bundle of His
what does S-T mean in ECG ?
How long is ventricle contraction
how is heart block presented in ECG ?
Some P waves are not transmitted . thus QRS and T waves are not present = a.p in atrium but not ventricles
how is congenital long QT syndrome presented in ECG ?
Genetic defect causing sodium channels to stay open
. distance from Q - T is long meaning ventricles stay contracted longer than they should
How many bits is ECG made of
3
P wave
Atrium contracting
Q wave
Ventricle contracting - how long it takes action potential to get through bundle of his
T wave
Ventricle relaxing
What happens during QRS complex
Bigger wave - ventricle contracts
What happens during variable QT interval
Ventricles contracted at varying amounts
