cardiovascular biology Flashcards
what does cardiovascular system consist of?
heart and the blood vessels
where is the heart located?
the heart is located behind sternum
1/3 of heart lies to the right of the midline
2/3 lies to the left
part of heart is covered by lungs
how many pumps does the heart do ?
2 pumps which distribute blood around
RHS - pumps blood to lung
LHS - pumps blood to body
how many layers are in the wall of heart?
the walls of the heart are divided into 3 layers
what are the 3 layers that make up walls of the heart?
. epicardium - external layer - tough outer protective composed of connective tissue
. myocardium - bulk of the heart - cardiac muscle tissue - responsible for pumping oxygenated blood around body cardiac muscle
. endocardium- inner layer - smooth endothelium , simple squamous epithelium ,continuous with major blood vessels entering and leaving the heart which ensures frictionless flow of blood
protect valves and heart chambers
what is pericardial cavity/pericardium ?
. outer coat of heart which protects the heart and big blood vessels
what is the space between pericardial cavity and epicardium ?
space between pericardial cavity and epicardium is filled with pericardial fluid which is formed by pericardium
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
-If cavity dries up- pericarditis- acquired defects.
what is pericardium?
the heart is enclosed by pericardium
pericardium produces pericardial fluid
-There to anchor the heart is place but still give it freedom to move
what does inflammation of pericardium result in?
decreased secretion
this is example of acquired defect
what is the lining of heart made of ?
simple endothelium
what are the four chambers of heart?
. right atrium
. right ventricle
. left atrium
. left ventricle
function of right atrium?
.receives deoxygenated blood from body via 2 vessels superior and inferior vena cava and pumps to right ventricle
what is the function of right ventricle?
. pumps deoxygenated blood back to lungs
what is the function of left atrium?
. receives oxygenated blood from lungs and pumps it to left ventricle
what is the function of left ventricle?
. pumps oxygenated blood to body
describe what happens in the circulatory system?
- heart has 4 chambers
- right atrium receives deoxygenated blood from body and pumps to right ventricle
- right ventricle contracts and pushes blood out pulmonary arteries and deoxygenated blood goes to the lungs
- lung pick oxygenated blood and oxygenated blood goes to left side of heart
- left atrium receives oxygenated blood from lungs and pumps it to left ventricle
- left ventricle contracts and pumps oxygenated blood to the body
what are the 3 openings of the heart?
superior vena cava
inferior vena cava
fossa ovalis ( coronary sinus )
what is the function of superior vena cava?
The superior vena cava is the large vein which returns
deoxygenated blood to the heart from the head and neck
what is the function of inferior vena cava ?
the inferior vena cava returns deoxygenated blood to the heart from lower body
what is the function of fossa ovalis / coronary sinus?
brings deoxygenated blood from heart to right atrium via fossa ovalis
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)
- blood is pushed out pulmonary artery and pulmonary artery takes blood to lung
7.blood goes to lung and picks new oxygen - new oxygen comes back to left atrium through pulmonary veins
- there are 4 openings from lungs to right atrium
2 left and 2 right - left atrium contracts when full and opens bicuspid valve
- blood goes lo left ventricle
- left ventricle 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 blood
they branch off the aorta where it emerges from the heart taking about 5% of the heart’s daily output
where do the right and left coronary artery branch from?
the left and right coronary artery branch off the aorta
what is the function of aorta?
the main artery that carries oxygenated blood from left ventricle to the body
what are the two main types of valve in the heart?
. atrioventricular (AV) ( associated with opening between atria and ventricles -
bicuspid (left )and tricuspid ( right )
. semi lunar ( associated with exit from heart )- pulmonary and aortic
how many valves does the heart have?
. heart has 4 valves
what is the function of the 4 valves of the heart?
. they are purely passive and ensure blood flows around the heart in the correct direction
where is tricuspid AV located ?
between the right atrium and right ventricle
where is bicuspid AV located ?
bicuspid is located on the left of the heart between atria and ventricle
what does semilunar valve consist of ?
semilunar valve consist of 3.5 moon shaped cups
describe the action of semilunar valve?
- when ventricle is full of blood , ventricle contracts
- pressure rises , blood is pushed up against semilunar valve forcing them open
- ventricles relax , blood flows back down due to gravity , filling cups of semilunar valve forcing them to close
- semilunar valve stops blood falling back to ventricle
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
describe the action of AV valve?
- atrium contracts
- pushes AV valve open and blood comes into ventricle
- ventricle contracts papillary muscle contracts and chordae tendineae tighten preventing valve from everting into atria
what is the main function of chordae tendinae?
. hold AV valve in place
. tension is put on AV valves during ventricular contraction to stop eversion by the chordae tendinae
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 lub and dub ?
lub - AV valve shut
dub - semilunar valve shut
what are examples of valve defects?
. stenosis ( narrowing )
. regurgitation ( valve doesn’t shut properly )
what can you do solve valve defects?
. defective valve can be replaced by using a mechanical valve
what are the two phases of cardiac cycle?
. diastole ( relaxation )
. systole ( contraction )
describe what happens in the two phases of cardiac cycle?
- blood flows into atria until full ( AV valve shut )
- AV valve opens and 70% of blood leaves atria passively
- remaining blood is squeezed out by atria contracting
- ventricles contract shutting AV valves
- semilunar valves open and blood leaves ventricles
- ventricles relax , and flow of blood shuts semilunar valve
how do nerve cells ( neurons ) and muscle fibres transmit messages ?
. in the form of small electrical signals known as action potential
. these electrical messages are usually transmitted to adjacent neurons or muscle cells by the release of neurotransmitter
how are some nerve cells joined to other neurons/muscles ?
by gap junction which allows action potential to spread more rapidly
what muscle does somatic nervous system supply ?
skeletal muscle
what muscle does autonomic nervous system supply ?
cardiac and smooth muscle
what are the similarities between skeletal muscle and cardiac muscle?
. both are striated by regular arrangement of actin and myosin
. 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
what is syncitium ?
. sheet of muscle where individual cells are connected by gap junctions
how many syncitia does cardiac muscle form ?
. cardiac muscle forms two syncitia one around the atria and another around the ventricles
. these are only joined by the bundle of his
what does cardiac muscle contain ?
. myoglobin , many mitichondria
what system controls the heart?
the heart is under the control of ANS
sympathetic system speed it up
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
how is the myogenic rhythm of the heart maintained?
by the specialised excitatory and conductive muscle system
where do the parts of the specialised excitatory and conductive muscle system lie?
. all the parts of the system are 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 which go down 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
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 , reaches threshold and initiates action potential without external nervous output
how does heart beat independent of ANS
SA node is leaky to sodium ions
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 2 atria ( due to branching and intercalated discs) causing them to depolarise
- action potential is delayed at the AV node and bundle of his- to ensure atria contracts before ventricle
- action potential spreads along purkinje fibres and then ventricles contract
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
what is the function of bundle of his?
bundle of his connects atrial muscle sheet to ventricular muscle sheet
what is ECG
recording representation of electrical conductivity of heart recorded at body surface at the limb or chest with electrodes
what does ECG contain ?
. p wave which is positive deflection this is where atrium depolarisation occurs followed by atrium contracting
. QRS complex - complicated wave
. T wave - another positive deflection
this is where ventricular repolarisation occurs - ventricle relaxing
what does the interval between P and QRS wave mean in ECG ?
how long it takes action potential to get through bundle of his
what does S-T mean in ECG ?
how long is ventricle contraction
what is delay between QRS and T wave mean ?
length when ventricle are contracting
