cardiovascular week 1

Question 1

Describe cardiac muscle

Answer 1

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

Question 2

What are the similarities between cardiac muscle and skeletal and smooth muscle?

Answer 2

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

Question 3

What are intercalated disks?

Answer 3

specialised intercellular junctions that provide both mechanical and electrophysiological coupling, allowing cardiac cells to function as a functional syncytium

Question 4

describe the difference in the way that cardiac cells contract as compared to skeletal muscle

Answer 4

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

Question 5

Describe the sarcomeres in cardiac muscle

Answer 5

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

Question 6

Describe the composition of the intercalated disks

Answer 6

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

Question 7

Describe the mitochondria of cardiac cells

Answer 7

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

Question 8

Give an overview of the coronary circulation of the heart

Answer 8

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

Question 9

Describe the coronary sinus

Answer 9

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.

Question 10

What are the branches of the right coronary artery?

Answer 10

sino-atrial node branch
right marginal branch
small branch to AV node
posterior inter ventricular branch

Question 11

What does the right coronary artery supply?

Answer 11

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

Question 12

What are the branches of the left coronary artery?

Answer 12

inter ventricular

circumflex - left marginal artery

Question 13

What does the left coronary artery supply?

Answer 13

most of the left atrium and ventricle

most of the inter ventricular septum - including AV bundle and its branches

Question 14

What are the cardiac veins called?

Answer 14

great
middle
small
posterior

Question 15

Describe the great cardiac vein

Answer 15

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

Question 16

Describe the middle cardiac vein

Answer 16

begins at apex and ascends in the posterior inter ventricular sulcus towards the coronary sinus

Question 17

Describe the small cardiac vein

Answer 17

begins in the lower anterior section of the coronary sulcus between the right atrium and ventricle
accompanies the right coronary artery

Question 18

Describe the posterior cardiac vein

Answer 18

lies on the posterior surface of the left ventricle just to the left of the middle cardiac vein.

Question 19

What are the phases of cardiac muscle action potential?

Answer 19

phase 0 - depolarisation
phase 1 - initial repolarisation
phase2 - plateau
phase 3 - rapid repolarisation

Question 20

Describe phase 0

Answer 20

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

Question 21

Describe phase 1

Answer 21

the sodium channels close
the cell begins to depolarise
potassium ions leave the cell through open potassium channels

Question 22

describe phase 2

Answer 22

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

Question 23

Describe phase 3

Answer 23

closure of the calcium ion channels
increased potassium ion permeability
cell membrane returns to resting action potential of -90mV

Question 24

Describe the heart cycle

Answer 24

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

Question 25

Describe the heart sounds

Answer 25

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

Question 26

What is a functional heart murmur?

Answer 26

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

Question 27

What can cause heart murmurs?

Answer 27

congenital
valve abnormalities
valve stenosis
valve regurgitation
valve sclerosis
valve prolapse
endocarditis

Question 28

Describe an ECG

Answer 28

visual representation of the electrical activity of the heart
abnormalities of rhythm, conduction and depolarisation
critical in heart attacks

Question 29

Describe chest xray

Answer 29

cardiac silhouette - size, position
pulmonary vasculature
great vessels
pulmonary oedema
pleural effusions

Question 30

Describe echocardiography

Answer 30

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

Question 31

Describe functional stress testing

Answer 31

exercise stress
nuclear stress
echo stress
imaging for ischaemia

Question 32

Describe coronary angiogarphy

Answer 32

gold standard investigation for coronary artery disease
pros - option to treat, availability
cons - radiation, risks, contrast reaction, bleeding to death

Question 33

Describe cardiac MRI

Answer 33

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