cardiovascular week 1 Flashcards
Describe cardiac muscle
form an interconnecting network
joined to each other by intercalated disks
central nuclei and regular cytoplasmic cross-striations
highly vascularised
long cylindrical cells with one or at most two nuclei
What are the similarities between cardiac muscle and skeletal and smooth muscle?
skeletal - strong contractions that use large amounts of energy
smooth - the contractions are continuous and initiated by inherent mechanisms although they are moderated by external autonomic and humeral control
What are intercalated disks?
specialised intercellular junctions that provide both mechanical and electrophysiological coupling, allowing cardiac cells to function as a functional syncytium
describe the difference in the way that cardiac cells contract as compared to skeletal muscle
in cardiac muscle there is a slow release of calcium ions from the sarcoplasmic reticulum after recovery from the previous contraction; this causes a succession of autonomic contractions independent of external stimuli
Describe the sarcomeres in cardiac muscle
they form a branching myofibrillar network, continuous in three dimensions throughout the cytoplasm.
The branding columns of sarcomeres are separated by sarcoplasm containing rows of mitochondria and sarcoplasmic reticulum
Describe the composition of the intercalated disks
3 types of membrane to membrane contact;
mainly fascia adherens (FA) - actin filaments - transmit contractile forces
Desmosomes - anchorage for intermediate filaments of the cytoskeleton
Gap junctions - sites of low electrical resistance through which excitation passes from cell to cell
Describe the mitochondria of cardiac cells
elongated or spheroidal and have abundant closely packed cristae rich in oxidative enzyme systems.
The sarcoplasm within and between the sarcomeres is rich in glycogen granules
Give an overview of the coronary circulation of the heart
two coronary arteries arise from the aortic sinuses in the initial portions of the ascending aorta and supply the muscle and other tissue of the heart
They circle the heart in the coronary sulcus, with marginal and interventricular branches, in the inter ventricular sulki, converging toward the apex of the heart
The returning venous blood passes through cardiac veins, most of which empty into the coronary sinus
Describe the coronary sinus
a large venous structure located in the coronary sulcus on the posterior surface of the heart between the left atrium and left ventricle.
The coronary sinus empties into the right atrium between the opening of the inferior vena cava and the right atrioventricular orifice.
What are the branches of the right coronary artery?
sino-atrial node branch
right marginal branch
small branch to AV node
posterior inter ventricular branch
What does the right coronary artery supply?
right atrium and ventricle
sion-atrial and AV nodes
interatrial septum
portion of the left atrium
posteroinferior 1/3 of the inter ventricular septum
a portion of the posterior part of the left ventricle
What are the branches of the left coronary artery?
inter ventricular
circumflex - left marginal artery
What does the left coronary artery supply?
most of the left atrium and ventricle
most of the inter ventricular septum - including AV bundle and its branches
What are the cardiac veins called?
great
middle
small
posterior
Describe the great cardiac vein
begins at apex and agents in the anterior atrioventricular sulcus - often termed anterior inter ventricular vein
greatly enlarges to form the coronary sinus and enters the right atrium
Describe the middle cardiac vein
begins at apex and ascends in the posterior inter ventricular sulcus towards the coronary sinus
Describe the small cardiac vein
begins in the lower anterior section of the coronary sulcus between the right atrium and ventricle
accompanies the right coronary artery
Describe the posterior cardiac vein
lies on the posterior surface of the left ventricle just to the left of the middle cardiac vein.
What are the phases of cardiac muscle action potential?
phase 0 - depolarisation
phase 1 - initial repolarisation
phase2 - plateau
phase 3 - rapid repolarisation
Describe phase 0
depolarisation
voltage gated sodium channels open to permit sodium to rapidly flow into the cell and rapidly depolarise it
the membrane potential reaches about +20mV before the sodium channels close
Describe phase 1
the sodium channels close
the cell begins to depolarise
potassium ions leave the cell through open potassium channels
describe phase 2
voltage gated calcium ion channels open slowly during phases 1 and 2 and calcium enters the cell
potassium channels close
decreased potassium efflux and increased calcium influx causes action potential to plateau
Describe phase 3
closure of the calcium ion channels
increased potassium ion permeability
cell membrane returns to resting action potential of -90mV
Describe the heart cycle
the atria functions as a primer pump for the ventricles
the ventricles fill with blood during diastole
outflow of blood from ventricles during systole - period of isovolumic contraction
period of ejection
period of isovolumic relaxation
Describe the heart sounds
S1 - lub - AV valves closing
S2 - dub - semi-lunar valves closing
S3 - lub dub ta - movement of ventricles
S4 - ta lub dub - pre systolic gap
What is a functional heart murmur?
may also be referred to as innocent
when blood rushes through the heart quickly during normal function
may occur when heart beats more quickly than normal for example in fever, anaemia, hyperthyroidism and pregancy
What can cause heart murmurs?
congenital valve abnormalities valve stenosis valve regurgitation valve sclerosis valve prolapse endocarditis
Describe an ECG
visual representation of the electrical activity of the heart
abnormalities of rhythm, conduction and depolarisation
critical in heart attacks
Describe chest xray
cardiac silhouette - size, position pulmonary vasculature great vessels pulmonary oedema pleural effusions
Describe echocardiography
gross anatomy of the heart
see valve structure and function
look at muscle size and contraction
assess ejection fraction
echo doppler - direction and speed of blood flow
3D echo - multiple plains
contrast echocardiography
transoesophageal
pros - cheap, available, portable, no radiation
cons - requiere good acoustic window, user dependent
Describe functional stress testing
exercise stress
nuclear stress
echo stress
imaging for ischaemia
Describe coronary angiogarphy
gold standard investigation for coronary artery disease
pros - option to treat, availability
cons - radiation, risks, contrast reaction, bleeding to death
Describe cardiac MRI
still images
very clear gross anatomy
contrast MRI - tissue characterisation
CMR cine images
Pros - gold standard LV assessment, reproducible, no radiation
cons -cost, availability, claustrophobia, pace makers
