2 Flashcards
Which IC space does the superior border of the heart lie on?
2nd IC space
At what vertebral level is the superior border of the right atrium located?
T4-5
Why is the angle of Louis an important landmark?
It’s important because we know that this level marks the level of the intervertebral discs which lies between thoracic vertebra T4 and T5
Where is the angle of Louis an important landmark?
Located at the superior border of R atrium
Which cardiac chamber forms most of the inferior border of the heart?
RIght ventricle
Which vein lies in the posterior mediastinum immediately R lateral to descending thoracic aorta?
Azygous vein
Moving away from the heart, what’s the 3rd branch of the aorta?
3rd – L. common carotid
What are adrenaline and noradrenaline classed as?
Alpha-adrenoceptor agonist
Which structures does the ligamentum arteriosum attach to?
Pulmonary arteries and aorta
What is the ligamentum arteriosum?
A remnant of the foetal ductus arteriosus that allowed passage of blood from the high-pressure pulmonary arteries to the aorta
When does the ductus arteriosus close?
On day 1-2 of life in response to hyperoxia, it undergoes fibrosis to form the ligamentum arteriosum that inserts into the aortic arch opposite the left subclavian artery.
What is the function of alpha-adrenoceptor agonists?
Induces smooth muscle and blood vessel contraction
Which embryonic structure, is the brain derived from?
Neural tube
Isoprenaline use + class
Use: Treatment of bradycardia, heart block, rarely for asthma.
Class: Non-selective beta-adrenergic receptor agonist
Differentiate between: endocardium, myocardium, epicardium, pericardium
Endocardium – lines inside of heart
Myocardium – muscular tissue of the heart
Epicardium – visceral lining of the outside of heart
Pericardium – lines the cavity (one with epicardium)
What endothelial ion change results in release of nitric oxide?
Increased calcium.
Describe NO synthesis + how it affects blood vessels
Vascular endothelial cells produce NO from endothelial nitric oxide synthase (eNOS) in response to raised shear stress from blood flow.
eNOS is activated by a rise in intracellular calcium.
NO then diffuses into vascular smooth muscle cells and causes hyperpolarisation w/ a fall in intracellular Ca2+ in myocytes.
Result: vasodilatation
How is a rise in blood pressure signalled to the CNS?
Increased firing in CN IX afferents from carotid sinus
1st korotkoff sound indicates what?
Systolic blood pressuve
In an ECG what does the P, Q, R, S + T represent?
P – Arterial depolarisation (systole)
QRS – Ventricular depolarisation (systole)
T – Ventricular repolarisation (diastole)
What is the anterior interventricular artery a branch of?
L coronary artery
Which arteries arise directly from the ascending thoracic aorta?
Coronary, brachiocephalic, L. common carotid, L subclavian
What is the thymus gland anterior to?
Aorta, trachea, oesophagus
What are chronotropic, and inotropic agents?
Chronotropic - Change the heart rate.
Inotropic - Modifying the force contraction of muscles.
GIve examples of positive + negative inotropic agents.
+ve = digoxin, insulin, catecholamines (A, NA)
-ve = beta-blockers
What does the P-R interval, S-T segment + Q-T interval on an ECG indicate?
P-R interval – Delay at AVN
S-T segment – interval between ventricular depolarisation + repolarisation
Q-T interval – Total time for ventricular depolarisation to repolarisation (prolongation or shortening increases risk of arrhythmias). It’s inversely proportional to HR
What is a negative chronotrope?
Something that decreases the HR
What class of drug is calcium-channel blockers + what effects does it have?
Negative chronotropic
- Reduces HR
- Vasodilation
Negative inotrope
- Reduce force of contraciton
- Reduce aldosterone production (blocking channels of adrenal cortex) —> decreases BP
What class of drug is digoxin + what affects does it have?
Digoxin is a = +ve inotrope, -ve chronotrope
Increases force of contraction, reduces HR.
What does ACh do to the HR?
Which receptors does it target?
Targets muscarinic (M2) cholinergic receptors and decreases HR.
MoA: inhibition of T-type Ca2+ channels + activation of K+ GIRK channel. K+ efflux
–> hyperpolarised
What causes the 1st heart sound?
atrioventricular valve closure (mitral + tricuspid)
What causes the 2nd heart sound?
semilunar valve closure (aortic + pulmonary)
What does a larger P wave on ECG indicate?
P – Enlargement of atrium
What does a larger Q wave on ECG indicate?
Q – MI
What does a larger R wave on ECG indicate?
R – Enlarged ventricles
What is dromotropy?
Conduction velocity of AVN
What is lusitropy?
Relaxation of myocardium
What does the ‘x’ in the JVP waveform indicate?
Atrial relaxation
What does the ‘a’, ‘c’, ‘v’ + ‘y’ in the JVP waveform indicate?
a – atrial contraction
c – tricuspid bulging
v – filling of atrium
y – emptying of atrium to ventricle
What is stroke volume?
Vol of blood ejected by a ventricle in a single contraction
What is the formula to workout stroke volume (SV)?
SV = EDV – ESV
What is EF?
EF (%) = SV/EDV x100
What is isovolumetric contraction?
Isovolumetric contraction – ventricular volume unchanged, ventricles begin to contract, intraventricular pressure rises sharply.
What is isovolumetric relaxation?
Isovolumetric relaxation – ventricular pressure falls, volume of blood in chamber remains the same.
List the stages in the cardiac cycle + the state of the AV + semilunar valves at each point.
Atrial systole – AV=O, SL=C Isovolumetric contraction – AV=C, SL=C Ventricular ejection – AV=C, SL=O Isovolumetric relaxation – AV=C, SL=C Ventricular filling – AV=O, SL=C
Which nerves supply the mediastinal pleura (parietal + costal) lining of the chest wall + the pericardium?
Parietal – IC nerves + phrenic nerve
Costal – IC nerves
Which nerve is involved in swallowing?
When the swallow response is initiated, this center causes messages to be sent to the glossopharyngeal, the vagus, and the hypoglossal nerves. The glossopharyngeal is considered the major nerve for the swallowing center
A patient with a stab wound to the neck may be unable to maintain ventilation because of injury to which nerve?
Phrenic nerves
What is the cardiac plexus?
Plexus of nerves situated at the base of the heart
Formed by cardiac branches derived from both the sympathetic + parasympathetic nervous systems
What does the phrenic nerve supply?
Where does it originate from?
C3-C5
Innervates mediastinal pleura + diaphragm!!
What structure does the intercostal nerve supply?
Where does it arise form?
Arises from anterior rami of T1-T11
Supplies the intercostal muscles
What structure does the subcostal nerve supply?
Where does it arise from?
Arises from T12.
Innervates the transverse abdominis
What structure does the vagus nerve supply? a.k.a. the pneumogastric nerve
Innervates the heart, lungs + digestive tract.
Parasympathetic control.
What do juxta-glomerular cells synthesis + secrete?
Renin
What do chromaffin cells in adrenal medulla secrete?
Adrenaline, NA, little DA, enkephalin and few other hormones
What is the pattern in AF?
Irregularly irregular.
What is the cardiac plexus?
Plexus of nerves situated at the base of the heart.
Formed by cardiac branches derived from both the sympathetic + parasympathetic nervous systems.
What is SERCA? What is its function?
Sacro-endoplasmic reticulum Ca2+ - ATPase.
Resides in Sacro-ER within myocytes.
Transfers Ca2+ from cytosol of cell to ER by ATP hydrolysis during muscle relaxation.
What structure secretes ADH (vasopressin)?
Posterior pituitary
What structure responds to low blood flow by activation of an endocrine cascade?
Juxtaglomerular kidney cells are stimulated to release renin by signally from the macula densa
Where does adrenaline act on in the heart?
B1-adrenoceptors via cAMP on:
SAN (increase rate), Atrial muscle (increase force), AVN (increase automaticity), Ventricular muscle (increase automaticity + force)
Where does the superficial part of the cardiac plexus lie?
Beneath aortic arch, anterior to R pulmonary A.
At what vertebral level do the renal arteries branch from the aorta?
L1
Where may the dorsalis pedis pulse be palpated?
Lateral to extensor hallucis longus tendon on the dorsal surface of the foot
How does the ultrastructure of a vessel change in atherosclerosis?
Tunica intima thicken;
Little change to the adventitia.
Tunica media thickens, w/ increased elastin + muscle - this adds to the raised resistance.
What is the role of the atrioventricular node?
Delay atrio-ventricular depolarisation
What ventricular ion movements are responsible for the Q-T segment seen on ECG?
Sodium + calcium influx, potassium efflux
What ion movement is responsible for the pre-potential of SAN + AVN?
Na+ influx (leak channels) – are continuously open to allow sodium influx that causes gradual depolarisation
How does parasympathetic stimulation alter ion movements in cardiac pacemaker cells?
Increased potassium efflux.
When ACh from vagus nerve act son muscarinic receotrs
Which ion acts on ventricular contraction?
Calcium
Sympathetic stimulation increases sodium + calcium permeability via B1-adrenoceptor activation
Increased CO2 causes the oxygen-dissociation curve to shift in which direction?
Right (Bohr shift). Hb gives up oxygen more readily.
What is the infundibulum?
Infundibulum (a.k.a. conus arteriosus) – conical pouch formed from the upper + L angle of R ventricle in the chordate heart, from which the pulmonary trunk arises. It develops from the bulbus cordis.
Area proximal to the pulmonary valve.
What are the 2 contractile proteins that make up cardiac muscle?
Actin + Myosin
What does NA do to the heart + how in detail?
Binds to the beta-1-adrenergic receptor
Activates funny sodium channel and T-type calcium channel so sodium and calcium ions enter and depolarise SAN
Which complex is attached to tropomyosin?
Troponin
What makes up cardiac myocytes?
Myofibrils
What is one functional unit of the heart muscle called?
Sarcomere
Where does calcium ions bind on actin for muscle contraction?
TnC subunit of troponin TnI stops inhibiting myosin from binding to actin.
What does phospholamban activate when triggered?
Activates a pump on the sarcoplasmic reticulum (SR) which causes Ca2+ to be taken up by the SR.
Name the 3 subunits of troponin. What are their functions?
TnT – keeps whole complex bound to tropomyosin
TnC – binding site for Ca2+ –> triggers contraction
TnI – inhibits myosin binding to actin
Describe the structure of actin filaments.
Globular actin proteins forming 2 helical strands.
Between strands = rod shaped protein (tropomyosin) cover the binding sites.
Actin = thin filament.
What do myosin heads contain?
2 heads that contain myosin ATPase
What is the hinge + tail region of myosin made up of?
Heavy alpha helix chains
Which is the thin filament + which one is the thick?
Actin = thin, myosin = thick
Why is hydrolysis of ATP necessary to allow actin + myosin to interact forming a cross-bridge?
Hydrolysis of ATP energises the molecule, cocking it as myosin heads move along the thin filament.
ADP + Pi stays attached to thick filament.
Pi is released which cocks the myosin head from 90 degrees to 45 (power stroke)
How does depolarisation of cardiac muscle cells differ from that of other muscle cells?
Repolarisation takes much longer to occur thus cells cannot be stimulated at high frequency.
This prevents cardiac muscles going into tetanus.
Which rod shaped proteins cover the myosin binging sites on the actin filament?
Tropomyosin
Where does Ca2+ come from before they bind to TnC?
Sarcoplasmic reticulum + external environment
What does spirometry measure?
Ventilation (volumes of gases in + out of lungs)
How many branches does are there from the bronchi to alveolar sacs?
23
What is dead space?
Anatomical – bits that don’t exchange gases e.g. conducting zone
Physiological – alveoli that are ventilated by not perfused by oxygen e.g. damaged walls of alveoli
Where does the venous sinus of the heart run along?
In the posterior AV groove
What is the role of 2,3-diphosphoglycerate?
2,3-DPG – by-product of anaerobic metabolism that increases oxygen delivery to tissues by reducing oxygen’s affinity w/ Hb.
Anaerobically respiring tissues produce more 2,3-DG so have greater delivery of oxygen from Hb.
What is the Bohr effect?
Right shift of oxygen dissociation curve
Why is the dissociation curve of HbF a different shape to that of HbA?
Gamma-chains cannot bind 2,3-DPG –> doesn’t reduce oxyhaemoglobin affinity –> Hb has higher affinity for O2.
What globin chains are present in HbF?
2 alpha + 2 gamma
What globin chains are present in HbA?
2 alpha + 2 beta
What is methaemoglobin?
Hb with oxidised iron
What does methaemoglobin reductase do?
Convert iron back to Fe2+ (the reduced state for oxygen to bind to haemoglobin)
What is carboxyhaemoglobin?
Hb with carbon monoxide bound
What is the shape of the myoglobin-oxygen dissociation curve?
Hyperbolic – because there is only one molecule to bind + after that it becomes fully saturated
What is the shape of the haemoglobin-oxygen dissociation curve?
Sigmoidal – because there are 4 oxygen molecules to bind at they show co-operative binding.
How do oxygen saturations change in anaemia?
No change in oxygen saturation.
Anaemia = a reduction in the conc. of haemoglobin per volume of blood. Oxygen carrying capacity reduced.
What is the name given to the process by which oxygen shifts the CO-Hb dissociation curve right?
Haldane effect – describes the relationship between the Hb-CO2
What percentage composition of whole blood, is cells?
45%
What is the haematocrit?
Percentage of whole blood that is RBCs
What is the most prevalent plasma protein + what are its functions?
Albumin – synthesised in the liver
Exerting oncotic pressure to maintain of intravascular volume + binding of substances to aid in their transport.
What is C-RP?
1 of the acute proteins involved in activating complement.
What is blood serum?
Whole blood w/ all cells + clotting factors removed
How are platelets produced?
Budding off megakaryocytes.
What type of tissue is blood?
Connective
What ratio of water to solutes are in blood plasma?
91:9
Define haemopoiesis.
Where does it occur + what is involved?
The formation of blood cells from haemopoietic stem cells in red bone marrow.
What do myeloid stem cells form?
RBCs, platelets, granulocytes, monocytes.
What do lymphoid stem cells form?
Lymphocytes
What is a cord-blood transplant?
In a cord-blood transplant, stem cells from the placenta are removed from the umbilical cord.
Where does the R + L atrium receive blood from?
R – Superior + inferior vena cava + coronary sinus
L – 4 pulmonary veins (oxygenated blood)
Where + what is the fossa ovalis?
On the interatrial septum.
It’s an oval depression, the remnant of the foramen ovale, an opening in the interatrial septum of the foetal heart that normally closes soon after birth
What is the fibrous skeleton of the heart made up of?
Dense connective tissue surrounding + supporting heart valves
In embryonic folding, folding on the horizontal + median plane produces what?
Median – head fold + tail fold
Horizontal – 2 lateral folds
Overall curves embryo into a C shape.
What lies above the developing brain then moves down?
Cardiogenic mesoderm
What is the main force responsible for embryonic folding?
The different rates of growth of various parts of the embryo, especially the rapid longitudinal growth of the neural tube.
On the median plane the neural fold strengths to form what?
The beginning of the CNS.
Where does the oropharyngeal membrane form?
At the head end.
Where does the cloacal membrane form?
At the tail end.
What does the primitive gut differentiate into?
Anterior – foregut, intermediate – midgut, posterior – hindgut
What does the diaphragm develop from?
Septum transversum (central tendon), pleuroperitoneal membranes, dorsal mesentery of oesophagus, muscular components from somites at C3-5 levels.
What is the yolk sac a precursor to?
Umbilical cord
What does the parietal + visceral mesoderm cover?
Visceral – serous membranes covering organs.
Parietal – walls of peritoneal, pleural, pericardial cavities. They are continuous at the roots of each organ in their cavities.
Where is the septum transversum initially located?
Opposite cervical segments C3, C4, C5; muscle cells for diaphragm + phrenic nerve arises from these segments.
What cavities does the diaphragm separate?
The thoracic + abdominal cavities.
What does the specialised bit of mesophilia of gut allow?
Allows gut to move away from the body wall brining the blood vessels with it.
Pericardial + peritoneal cavities communicate via what?
Pericardioperitoneal canal – a tubular space.
What are invaginations of the ventral gut wall cranial to the septum transversum?
Lungs
The septum transversum is incomplete where?
Dorsally
Which nerve(s) innervates the diaphragm?
C3,4,5
What is the respiratory diverticulum (lung bud)?
An embryological structure of endodermal origin that develops into organs of resp system (larynx, trachea, lungs).
How does the thoracic cavity separated into the pleural + pericardial cavities?
Blood vessels + phrenic nerve on either side of diaphragm moves in towards the midline forming pleuropericardial folds.
Lungs expand in which direction when growing.
Laterally + ventrally
What does the respiratory diverticulum form?
Elongates its distal ends + enlarges to form a globular tracheal bud (which gives rise to trachea)
What does the tracheal bud divide into?
The bronchial buds which branch repeatedly + develop w/ bronchi.
At what day/week/month has all major elements of the lungs formed? + what hasn’t?
Day 64
Everything except the respiratory bronchioles, alveolar ducts + alveoli. Foetus can’t survive if born now.
