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)
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
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
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
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
