CR EOYS1 Flashcards
label A-D
A: moderator band
B: trabeculae carnae
C: chordae tendinae
D: anterior papillary muscle
label the heart chambers
what do a and b show?
what does the superior mediastinum mostly contain? [2]
great vessels
nerves
where does the phrenic nerve enter the superior mediastinum?
between the subclavian artery and the origin of the subclavian vein
what does the phrenic nerve cause during inhalation / exhalation? [2]
The motor innervation activation will cause the diaphragm to contract with inspiration, resulting in a flattened diaphragm and increased intrapleural space.
During exhalation, the diaphragm relaxes and returns to the dual dome shape.
The phrenic nerve also provides touch and pain sensory innervation to the mediastinal pleura and the pericardium in addition to the intercostal nerves.
what are the arrows, arrowheads, A & B?
what are the three layers that make up the heart valves?
– Fibrosa: forms the core of the valve -DIC.
– Spongiosa: LCT on atrial side (loose collagen/elastic fibres), as shock absorber. has bubble morphology (looks like a sponge)
– Ventricularis: Adjacent to ventricular surface of the valve. DCT with elastic fibres. Forms the _chordae tendineae (_fibrous cords covered with endothelium).
(on picture - first arrow: Fibrosa, middle, spongiosa, last - ventricularis)
what is the function of bundle of his? [
It is a collection of cells that carry electrical signals from the AV node to the to the ventricles of the heart.
what does the big arrow point to in this pictutre of cardiac histology? [1]
bundle of His
explain how the cardiac conducting system works x
which are the specifc cells that make up this system?
where does it occur (2)?
- specialised myocytes
- contraction is synchronised by specialised conducting cells
- *location**
i) found in sub-endocardial layer: Purkinje Fibres (convey signals 4x faster thatn muscle fibres - larger & less densely stained)
ii) SA & AV node (smaller)
big arrow in picture points towards: Bundle of His
what are the two types of venules?
how do u distinguish them?
- Postcapillary venules collect blood from the capillary network and are characterized of pericytes (contractible cells wrapped around the endothelial cells). Made up of endothelial, basal lamina and pericytes.
- Muscular venules can be distinguished by the presence of tunica media. Distal to the postcapillary venules and have one to two SMC layers.
(picture on right = postcapil, on left; muscular venules)
** which method of calculating HR do you use if the ECG is irregular? **
QRS X 6
on ECG, what is small box and large box on x axis?
small box: 40ms
large box: 0.2s
what is the J point on ECG?
The J (junction) point in the ECG is the point where the QRS complex joins the ST segment
how long should QRS complex usually last?
QRS complex: usually 60-100ms
calculate the HR of this ECG
methods: Heart rate (bpm) = 300 / RR interval in large squares HR = 300/4.1 = **73 bpm**
OR
the rhythm strip should be 10seconds long, so can calculate HR as
- R waves in rhythm strip x 6
- HR = 11 x 6 = **66 bpm
- use this method if irregular!!**
for each lead (I, II & III), where do you find negative and positve electrodes?
chest leads (V1-V6) view heart in which plane?
how do they change (V1-V6)?
horizontal plane !
V1-V6: starts in more downwards and gets more postive
what is normal PR interval?
120-200ms
what happens as a result of phrenic nerve paralysis?
- results in elevation of the hemidiaphragm
trachea runs from where to where?
at which structures in trachea does the aorta cross over?
trachea: c6-t4
- aorta arches over left main bronchus and lung root
where does the oesphagus sit?
compared to trachea?
how does it incline?
oesophagus:
- *- C6-T10**
- inclines to the left but compressed by the aortic arch (T4) and root of left lung (left main bronchus: T5-6)
where do posterior intercostal arteries 1&2 orginate?
where do posterior intercostal arteries 3-12 orginate?
where do posterior intercostal arteries 1&2 orginate: costocervical trunk (branch that comes off subclavian arteries)
where do posterior intercostal arteries 3-12 orginate: desecending aorta
the atrioventricular node is supplied by which artery?
where do myocardial infarctions predominately occur?
- the atrioventricular node is located close (and supplied by the) right coronary artery .
LCA: ~ 60%
RCA: ~ 30-40%
Circumflex of LCA: ~ 15-20%
describe the paths of th coronary arteries - what do they both anastmose with?
RCA: anastomoses with circumflex branch of LCA: gives rise to posterior interventricular artery
LCA: loops around apex and branches into left anterior descending (LAD). anastamoses with posterir interventricular artery
which ion determines the race of firing of cardiac pacemaker cells?
- the rate of firing of cardiac pacemaker cells is determined by rate of closure of K channels
what is sinus arrythmia?
Sinus arrhythmia refers to a changing sinus node rate with the respiratory cycle, on inspiration and expiration. This is quite common in young, healthy individuals and has no clinical significance. The heart rate increases with inspiration, due to the Bainbridge reflex, and decreases with expiration.
what is the effect of sympathetic and parasympathetic on the heart?
what NT and receptor used for each? ^
sympathetic: increaeses HR and force of contraction. secretion of noradrenalin and activation of B1 adrenoreceptor
parasympathetic: decreases HR. secretion of ACh and activation of muscarinin (M2) receptors
calmodulin is assocaited with which type of muscle contraction? [1]
tropinin C is associated with which type of muscle contraction? [1]
calmodulin is assocaited with smooth muscle muscle contraction
tropinin C is associated with cardiac muscle muscle contraction
what are NTs and Rs for sym and parasym of bronchiole sm?
parasympathetic: Ach & M3 muscarinin receptors
sympathetic: adrenalin / noradrenaline and B2 adrenergic receptor
what is the difference between multi and single unit smooth muscle?
what are the difference between these? ^
where each found?
- *multi-unit smooth muscle:**
- each smooth muscle cell recieves synpatic input.
- little electrical coupling
- each SMC can contract independently of neighbour: fine control
- (similar to motor unit in skeletal muscle)
- location: intrinsic muscles of eye & SM of larger BV
- *single-unit smooth muscle:**
- autonomic NS innervates a single cell within a sheet or bundle
- AP is propogated by gap junctions to neighboring cell: whole bundle contracts as a functional syncytium
- slow, steady contractions (allow food substances to move around body)
- location: walls of all viseceral organs
how does smooth muscle contraction occur?
- thin filaments slide past the thick filaments, pulling on the dense bodies (connected to the sarcolemma)
- dense bodies pull on the intermediate filaments’ networks through the sarcoplasm
- causes entire muscle fibre to contract - ends are pulled towards the centre, causing midsecction to bulge
how long delay occurs at AVN?
AV node does not start to transmit action potentials down into the Bundle of His in the ventricles until HOW MANY MS after the start of the SA node action potential
delay - 60 ms
AV node does not start to transmit action potentials down into the Bundle of His in the ventricles until 120ms after the start of the SA node action potential
describe what the ventricular AP is like during the depolarisation stage AND during the refractory period (and why)
- *- starts wth normal nerve-like AP with Na influx**, yet a prolonged depolarisation occurs: the plateau
- the plateau is from prolonged entry of calcium into the cell, which comes from extracellular space
THEN
- get a long refractory period before a new AP
- this prevents the muscle contracting prematurely and keeps cells synchronous
what do each of Class 1-4 antiarrhythmic drug classes block?
Class 1: Na+ channel blocker
Class II: B blocker - e.g. Propranolol
Class III - Potassium-channel blockers
Class IV - Calcium-channel blockers. e.g Verapamil
what is S like on normal ECG for V1-V6?
which precoridal leads should T wave be largest on?
S wave:
- large on V1 & V2
- progessively smaller to V5
- should be gone by V6
T wave: large on V2 and V3
what do QRS seperately show?
Q wave representing interventricular septal depolarisation
R wave representing ventricular depolarisation
S wave representing depolarisation of the Purkinje fibres / signifies the final depolarization of the ventricles, at the base of the heart
