CR EOYS1

Question 1

label A-D

Answer 1

A: moderator band
B: trabeculae carnae
C: chordae tendinae
D: anterior papillary muscle

Question 2

label the heart chambers

Answer 2

Question 3

what do a and b show?

Answer 3

Question 4

Answer 4

Question 5

Answer 5

Question 6

Answer 6

Question 7

Answer 7

Question 8

what does the superior mediastinum mostly contain? [2]

Answer 8

great vessels
nerves

Question 9

where does the phrenic nerve enter the superior mediastinum?

Answer 9

between the subclavian artery and the origin of the subclavian vein

Question 10

what does the phrenic nerve cause during inhalation / exhalation? [2]

Answer 10

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.

Question 11

what are the arrows, arrowheads, A & B?

Answer 11

Question 12

what are the three layers that make up the heart valves?

Answer 12

– 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)

Question 13

what is the function of bundle of his? [

Answer 13

It is a collection of cells that carry electrical signals from the AV node to the to the ventricles of the heart.

Question 14

what does the big arrow point to in this pictutre of cardiac histology? [1]

Answer 14

bundle of His

Question 15

explain how the cardiac conducting system works x

which are the specifc cells that make up this system?

where does it occur (2)?

Answer 15

• 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

Question 16

what are the two types of venules?

how do u distinguish them?

Answer 16

• 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)

Question 17

** which method of calculating HR do you use if the ECG is irregular? **

Answer 17

QRS X 6

Question 18

on ECG, what is small box and large box on x axis?

Answer 18

small box: 40ms
large box: 0.2s

Question 19

what is the J point on ECG?

Answer 19

The J (junction) point in the ECG is the point where the QRS complex joins the ST segment

Question 21

how long should QRS complex usually last?

Answer 21

QRS complex: usually 60-100ms

Question 22

calculate the HR of this ECG

Answer 22

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!!**

Question 23

for each lead (I, II & III), where do you find negative and positve electrodes?

Answer 23

Question 24

chest leads (V1-V6) view heart in which plane?

how do they change (V1-V6)?

Answer 24

horizontal plane !

V1-V6: starts in more downwards and gets more postive

Question 25

what is normal PR interval?

Answer 25

120-200ms

Question 29

what happens as a result of phrenic nerve paralysis?

Answer 29

- results in **elevation of the hemidiaphragm**

Question 30

trachea runs from where to where? at which structures in trachea does the aorta cross over?

Answer 30

trachea: **c6-t4** - aorta arches over **left main bronchus and lung root**

Question 31

where does the oesphagus sit? compared to trachea? how does it incline?

Answer 31

oesophagus: * *- C6-T10** - inclines to the left but compressed by the aortic arch (T4) and root of left lung (left main bronchus: T5-6)

Question 32

where do posterior intercostal arteries 1&2 orginate? where do posterior intercostal arteries 3-12 orginate?

Answer 32

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**

Question 33

the atrioventricular node is supplied by which artery? where do myocardial infarctions predominately occur?

Answer 33

- the atrioventricular node is located close (and supplied by the) right coronary artery . LCA: ~ 60% RCA: ~ 30-40% Circumflex of LCA: ~ 15-20%

Question 34

describe the paths of th coronary arteries - what do they both anastmose with?

Answer 34

**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

Question 35

which ion determines the race of firing of cardiac pacemaker cells?

Answer 35

- the rate of firing of cardiac pacemaker cells is **determined by rate of closure of K channels**

Question 36

what is sinus arrythmia?

Answer 36

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.**

Question 37

what is the effect of sympathetic and parasympathetic on the heart? what NT and receptor used for each? ^

Answer 37

_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

Question 38

calmodulin is assocaited with which type of muscle contraction? [1] tropinin C is associated with which type of muscle contraction? [1]

Answer 38

**calmodulin** is assocaited with **smooth muscle muscle** contraction **tropinin C** is associated with **cardiac muscle muscle** contraction

Question 39

what are NTs and Rs for sym and parasym of bronchiole sm?

Answer 39

parasympathetic: **Ach & M3 muscarinin receptors** sympathetic: **adrenalin / noradrenaline** and **B2 adrenergic receptor**

Question 40

what is the difference between multi and single unit smooth muscle? what are the difference between these? ^ where each found?

Answer 40

* *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 s**ingle 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**

Question 41

how does smooth muscle contraction occur?

Answer 41

## Footnote - **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 contrac**t - ends are pulled towards the centre, causing midsecction to bulge

Question 42

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

Answer 42

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

Question 43

describe what the ventricular AP is like during the depolarisation stage AND during the refractory period (and why)

Answer 43

* *- starts wth normal nerve-like AP with Na influx**, yet a **_prolonged depolarisation occur_**s: 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

Question 44

what do each of Class 1-4 antiarrhythmic drug classes block?

Answer 44

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

Question 45

what is S like on normal ECG for V1-V6? which precoridal leads should T wave be largest on?

Answer 45

S wave: - large on V1 & V2 - progessively smaller to V5 - should be gone by V6 T wave: large on V2 and V3

Question 46

what do QRS seperately show?

Answer 46

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