PBL 4 Flashcards
how does the heart beat?
- the heart has its own pacemaker cells — contract on their own without any external nervous input
- collection of pacemaker cells at top right of atrium = sinoatrial node (SA)
- the electrical impulse generated here will spread throughout both atria and will reach the AV node
- impulse reaches the AV node before the left atrium has finished contracting
- the impulse is slowed down through the AV node, which allows the left atrium to finish contracting
- from the AV node, the impulse goes down the bundle of His and the wave of depolarisation will go down through the left and right bundle branches and then they’ll spread through both ventricles via the Purkinjie fibres.
what effect does the SNS have on the heart?
- increase HR
- increase contraction strength
- dilate coronary arteries to increase myocardial blood flow
what effect does the PNS have on the heart?
decreases HR
what makes up the cardioregulatory centre and where are they?
cardioaccelatory/pressor centre in the upper part of hte medulla oblongata, and the cardioinhibitory/depressor centre in the lower part of the MO
where does the SNS act and where does the PNS act?
SNS = pressor centre PNS = depressor centre
how does the SNS increase HR? PNS?
acts on the SAN to speed up depolarisation rate
PNS does the opposite
what nerve do the sympathetic fibres and parasympathetic fibres run down into the cardiac plexus, from which they enter the heart?
vagus nerve
where do sympathetic and parasympathetic fibres arise and originate from?
sympathetic: superior, middle and inferior cervical ganglia — T1-T4/5 (but originate in MO)
parasympathetic: originate in MO
what is rheumatic fever?
an autoimmune disease in which antibodies produced to fight a bacterial infection also attack the mitral and aortic valves. results from a streptococcal infection
what immunoglobins are most likely to cause rheumatic fever?
IgM
what happens to the heart valves in rheumatic fever?
heart valves are infiltrated with T cells — which are reacting against cardiac myosin, having been activated against the M antigen
what is rheumatic heart disease?
= a chronic condition caused by irreversible damage to the heart as a result of rheumatic fever
- leading cause of heart disease in children and young adults in the developing world
what valve is most commonly affected in rheumatic heart disease (RHD)?
mitral valve
what can the valves suffer from in RHD? are some more severe than others?
any valve can suffer from stenosis, regurgitation or both — mitral stenosis typically causes more severe disease than mitral regurgitation
how can mitral stenosis cause atrial fibrillation? mitral regurgitation?
very high atrial pressure — atrium becomes dilated — becomes very electrically active — irregular HB (fibrillation)
regurgitation: LA can become stretched — more electrically active — etc
what are 2 equations for cardiac output?
CO = mean arterial BP / total peripheral resistance
CO = HR x stroke volume
what is pink sputum a symptom of and how is it caused?
= pulmonary oedema
- fluid and small amounts of blood leak from capillaries into alveoli
what are basal crepitations and why are they a symptom of pulmonary oedema?
- abnormal sounds from the base of the lungs
- due to accumulation of fluid or mucus in the lungs (or failure of parts of lungs to inflate properly)
- sounds more common in inhalation
why is rheumatic fever associated with chronic heart valve damage?
because streptococci trigger production of antibodies that target heart valves
what does high BNP levels indicate?
heart failure
what is LV ejection fraction? what is it like in heart failure and why?
= measures amount of blood being pumped out of the LV in each contraction
- would be low in HF
- harder for the LV to pump blood into the aorta due to the increase in pressure
acute vs chronic HF
acute — often follows an MI. sudden onset of symptoms
chronic — symptoms appear gradually over time and gradually get worse
what kind of drug is furosemide and what does it principally act to do?
loop diuretic that acts principally to reduce fluid overload and relieve pulmonary congestion
what is rust coloured sputum a symptom of?
pneumococcal infection
when does the foetus’s 1st heartbeat occur?
day 22
in the embryologic heart, where is the ostium secondum located?
in the septum premium
what 2 proteins are involved in the pathogenesis of AF?
matrix metaloproteinases and disintegrin
what are aschoff bodies (histological charactersitic of rheumatic fever)?
areas of focal accumulation of macrophages in the hiliar lymph nodes
(nodules on heart in people with RF)
phospholamban regulates what in the process of cardiocytes relaxation?
SERCA pump
what does the 2nd heart sound represent?
aortic and pulmonary valve closure
the pressure in the LV after ventricular diastole is what?
preload
walls of the LV are around __ times thicker than the walls of the RV
3x thicker
what is the approximate weight of an adult male heart?
325g
which embryological event is responsible for left-right asymmetry?
cardiac looping
BNP is released in response to what?
stretching of cardiac muscle
